Safety Document Group 3

Occupational Safety Training Document for Mechanical Work

Posted on by LÊ THẾ QUÝ
Occupational Safety Training Document for Mechanical Work
03
Apr
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LABOR SAFETY TRAINING MATERIALS FOR THE MECHANICAL INDUSTRY (English version)

The materials for the occupational safety training course in the mechanical industry equip workers with safety knowledge and prevention of hazards when operating mechanical machines and being in close contact with moving parts.

Table of Contents

PART 1: GENERAL INTRODUCTION TO MACHINE TOOLS AND MECHANICS

A. TYPES OF MACHINE TOOL EQUIPMENT USED IN ACTUAL PRODUCTION

1. Lathe in mechanical safety documents

  • Requires that workpiece clamping fixtures such as chucks, tailstocks, etc., must be securely fastened to the machine.
  • When turning parts, if the machine rotates quickly, the tailstock center must be a live center.
  • If the workpiece is long, a steady rest must be used to prevent the part from flying out due to centrifugal force.
  • If the workpiece is too long and protrudes behind the gearbox, a support stand must be used to prevent the workpiece from bending.
  • Using a file to deburr the sharp edges of a part while it is being turned is not allowed, as it can slip, lose momentum, causing the hand holding the file to slide into the rotating workpiece and cause an accident.
  • To ensure that chips do not become too long, the turning tool should have an appropriate chip breaker angle.

Mechanical safety document

2. Milling machine in mechanical safety documents

  • For milling machines, the cutting speed is lower than lathes, but safety issues must also be carefully considered.
  • Screw heads on the milling table, dividing head, and other potential snagging points should be well-guarded.
  • When installing or removing milling cutters, a specialized clamping fixture should be used.
  • Do not put your hands in the cutter’s operating area while the cutter is running.
  • The flywheel braking mechanism of the milling machine must be in good working order, sensitive, and ensure safety.

Mechanical safety document

3. Drilling machine in mechanical safety documents

  • For drilling machines, the drill bit holder must clamp the drill bit tightly and ensure it is concentric with the main spindle.
  • Workpieces must be clamped securely, either directly or through a fixture, to the drill table.
  • Never use your hands to hold the workpiece, and do not wear gloves while drilling.
  • If chips get wrapped around the drill bit and the drill chuck, do not use your hands to remove them directly.

Mechanical safety document

4. Grinding machine in mechanical safety documents

  • General characteristics of a grinding machine are:
  • Grinding machines have high speeds (20-30) [m/s]; high-speed grinding can reach 50 [m/s].
  • A grinding wheel is a hard material, made from fine powder by pressing and bonding, but it is brittle and cannot withstand vibrations and impact loads. Do not stack grinding wheels on top of each other or place other heavy objects on them to avoid cracks.
  • Humidity also greatly affects the strength of the wheel; it must be stored in a dry place, away from acidic environments and other corrosive substances.
  • Grinding wheels using magnesium-based bonding agents should not be used if the storage period exceeds one year because the bonding agent is no longer guaranteed.
  • Operating characteristics:
  • The choice of grinding wheel must be based on the technical requirements of the machining process to select the correct type of wheel.
  • When installing and adjusting the wheel, do not use a steel hammer to tap the grinding wheel.
  • When installed, the grinding wheel must be clamped evenly between two identical flanges. A layer of elastic material must be placed between the wheel and the clamping flange. When the wheel diameter decreases and the distance between the wheel and the clamping flange is less than 3 [mm], the wheel must be replaced.
  • After installation, the wheel must be dynamically balanced and tested for mechanical strength by running it at no load with a speed greater than 1/2 of the working speed:

Table 4.5. Mechanical strength test of grinding wheel.

Test condition with wheel diameter, [mm] for a duration, [minutes]
run the wheel at no-load with a speed greater than 1/2 of the working speed > (150-175) 5
> (300-475) 7
> 500 10

 

  • If the permissible rotational speed of the wheel is unknown, it must be tested at a speed 60% higher than the working speed for 10 minutes.
  • When in operation, the grinding wheel must have a fully enclosed guard, and the operator must not stand in the unguarded area.
  • When rough grinding or finishing by the dry method, which generates a lot of dust, a dust extraction system is required.

Mechanical safety document

5. Planing machine in mechanical safety documents

  • All planing machines need to have a control for the travel range of the cutting tool. The gear mechanisms, racks, and movement mechanisms must be guarded.
  • Absolutely do not set up or adjust the workpiece while the machine is running.
  • Do not cross in front of the machine’s path of motion while it is running.

Mechanical safety document

B. STRUCTURE AND OPERATING PRINCIPLE OF EACH TYPE OF EQUIPMENT

1. Lathe in mechanical safety documents

a. Lathe Structure

This section on lathe structure refers to the model of a common “high speed” lathe we often see.

Mechanical safety document

Here I divide it into 4 main parts:

  • Part 1: The machine base: this part can be divided into two sections. One part is on the left from the chuck down, and the other part is on the right.
    • The left base often has a recess for the main spindle motor, the remaining space can be part of the gearbox: containing gear clusters, oil compartment.
    • The right part has an empty space for a chip pan to collect chips during machining, this part has a foot pedal for braking and stopping the main spindle motor, the rest is the right support base. The outermost base also often has a compartment for the feed motor for large types like the 1M65.
  • Part 2: In fact, this part can be cast as one piece with or separate from Part 1. This is the gearbox for selecting the machining speed: spindle speed, feed rate for normal machining and threading. We can see on the model that this part is often divided into 2 sections separated by a line passing through the machine bed.
    • The part above the bed is the working area: the levers in front are for selecting the spindle speed. Usually there is a High speed and Low speed mode lever, the other lever is for selecting the corresponding cutting speed. On the surface of this part, there is also a spindle speed chart, often like a clock face located below the lever.
    • The part from the bed down: this part contains a portion of the gearbox, these gearbox parts are for selecting the machining mode. The front levers are for selecting the feed rate. Similar to selecting the spindle speed, it has a lever for fast and slow feed rates, and a lever for selecting normal machining and threading modes. (For each type, these levers are in different positions but their function is mostly the same.)
    • The part below the bed is the slideway, the part that transmits motion from the gearbox to the carriage: includes 2 motion shafts: one for plain turning mode, one for threading. The bottom shaft is a support, guide, and a lever to control the opening and closing of the spindle.
  • Part 3: The carriage: This is the part that moves along the machine bed, on top of which is the tool post. This post can move transversely, longitudinally, and rotate as controlled by the user.
  • Part 4: The tailstock: This is a component that can move along the machine bed. The tailstock is used with a dead center or live center to support long workpieces to increase the rigidity of the workpiece.

The above is a brief overview of a lathe according to my analysis. This division is not intended to provide a deep understanding of the detailed structure of the lathe but is a division in terms of application during machining operations, helping the reader to gradually become familiar with the features of each part and have a more general view when working with a lathe.

b. Operating Principle of the Lathe.

The operating principle of a lathe is based on the general machining principle of materials: Using the main motion, which is the rotary motion of the workpiece, and the feed motion, which are the transverse and longitudinal movements along the machine bed. Therefore, the operating principle of the lathe is the principle of controlling the rotary motion of the workpiece and the principle of controlling the feed motion.

On a lathe, the workpiece is mounted on a chuck (there are 3-jaw self-centering types and 4-jaw types). For long workpieces (about 200 mm or more), a center is often used to increase rigidity with a center drill (there are two types: dead center and live center) located on the tailstock.

  • The rotational movement of the main spindle (of the workpiece) is the movement of the chuck according to the following diagram:
    • Motor —> Gearbox —-> Chuck
    • The motor of a lathe (manual lathe) is usually located at the base behind the machine. This motor has different power and speed depending on the type of machine used. The rotational motion of the motor is transmitted to the gearbox by a belt drive. In the gearbox, there are gear clusters that can mesh in pairs to deliver motion to the chuck at different speeds. The speed is selected by the speed levers on the speed box.
  • The movement of the tool is the movement of the carriage according to the following diagram:
    • Motor —> Gearbox —-> Transmission Shaft ——-> Carriage.

The principle of motion and speed of the carriage is similar to that of the main spindle. The motor, in addition to providing rotational motion to the main spindle, also provides motion to the carriage through gear sets that divide the motion and speed levels in the speed box. Because the carriage is far from the speed box and must move flexibly in both longitudinal and transverse directions of the bed, it uses a longitudinal and transverse transmission shaft drive. The speed level of the carriage is adjusted by the gears in the speed box. The speed selection and motion tables are attached to the body of the speed box.

2. Milling machine in mechanical safety documents

a. Milling Machine Structure:

Depending on the type of milling machine, the structure varies, but a milling machine usually has the following main parts:

    • Machine base.
    • Machine body (column).
    • Knee (if it is a knee-type milling machine).
    • Cross slide (saddle).
    • Table.
    • Overarm (if it is a horizontal milling machine).

–

  • Arbor (if it is a horizontal milling machine).
  • Arbor support (if it is a horizontal milling machine).
  • Slideways for vertical, cross, and longitudinal movement.
  • Leadscrews for vertical, cross, and longitudinal movement.
  • Handwheels for vertical, cross, and longitudinal movement.
  • Clutch levers for vertical, cross, and longitudinal movement.
  • Main motor.
  • Spindle gearbox.
  • Spindle.
  • Auxiliary motor (if any).
  • Auxiliary motor gearbox.
  • Switch box.
  • Coolant pump.
  • Limit switches for longitudinal, cross, and vertical movement.
b. Principles of Using a Milling Machine:

Starting and stopping the machine must follow this sequence:

  • When starting the machine:
    • Check and apply lubricating oil to necessary locations, such as the slideways, tool head, etc.
    • Check that all clutch mechanisms are in the neutral position, meaning they are not engaged.
    • Start the machine without a load (only turn on the electric motor). If the main motor makes an unusual noise, stop the machine and notify a maintenance technician to inspect it.
    • Check the direction of cutter rotation, start the machine at the lowest speed, if normal, adjust to the required speed.
    • Engage the clutch lever for automatic table feed in the longitudinal, cross, and vertical directions. If normal, return it to the neutral position.
    • Do not change the spindle speed or feed rate while the machine is operating.
  • When stopping the machine:
    • Move the clutch lever to the neutral position to stop automatic feed.
    • Move the cutter slightly away from the workpiece.
    • Turn off the main spindle.
    • If the machine is stopped for a long time, turn off the main switch as well.

3. Drilling machine in mechanical safety documents

a. Technical Specifications of a Rock Drill:

The rock drill is a machine manufactured and supplied to order by Asia Consulting Limited. This is a relatively modern Japanese drill with many superior technical features compared to some other types of rock drills currently used in Vietnam. The drill drive head is designed and manufactured using a hydraulic-driven rotary percussion method with a fairly high drilling speed and high impact frequency, resulting in high drilling productivity. All drilling mechanisms, control mechanisms, air compressor, hydraulic pump, and other components are arranged on a crawler chassis.

Technical specifications of the rock drill:

  • Drill bit diameter is F76
  • Drill rod length is 3157 mm.
  • Drive head weight is 185 (Kg), impact frequency is 2250 – 2500 times/minute, rotation speed is 0 – 250 rpm.
  • The drill rod changing system can hold 5 + 1 (initial rod) drill rods, thus it can drill a hole up to 18.9 m deep without stopping the machine.
  • The swing angle of the drill rig right/left is 30o/30o.
  • The rotation angle of the drill rig (horizontally) is 60o
  • The lift/lower angle is 40o/20o.
  • The tilt angle of the drill rig (rotating vertically) is 90o.
  • The engine has a power of 215 Kw, speed of 2500 rpm.
  • Air compressor capacity is 8.1 m3/minute, pressure is 8 atm.
  • The total length of the machine is 7800 mm.
  • The length of the drill rig support frame is 6750 mm
  • The travel length of the drill head on the frame is 4200 mm
  • The sliding travel length of the frame is 1500 mm
  • The total width of the machine is 3490 mm.
  • The total height of the machine is 3730 mm.
  • The crawler vehicle has a ground clearance of 520 mm, a travel speed of 0 – 3.1 Km/hour, and can travel on roads with a slope of up to 30o.
  • The total weight of the machine: 15200 kg
b. Operating Principle of a Rock Drill

The rock drill operates on the principle of hydraulic-driven rotary percussion drilling. The movements of the mechanisms are driven by a system of hydraulic cylinders and hydraulic motors. Below is a general schematic of the machine’s operation:

The structure and operating principle of the rock drill can be divided into 4 main parts:

  1. Drill Drive Head Assembly: This assembly performs the main task of the drilling machine, which is to drive the drill rod to perform the drilling process by creating rotational motion and impact frequency on the drill rod. The drill drive head is designed for the machine to operate using the rotary percussion drilling method, including a hydraulic cylinder that creates the impact force and frequency on the drill bit, combined with a hydraulic motor that rotates the drill rod.
  2. Rod Changer and Drill Head Guide Assembly: This assembly is responsible for changing the drill rod when the machine has drilled the full length of a rod and guiding the drill drive head to move linearly up and down to drill to the required hole depth. The rod changer and guide assembly includes a system of hydraulic cylinders, rod supports, a hydraulic motor, a chain drive system, etc. The rod support can hold 5 drill rods, so the rod changing system allows the machine to operate with reduced auxiliary time, leading to increased productivity.
  3. Drill Bit Positioning Assembly: This assembly includes hydraulic cylinders, support frames, intermediate force transmission mechanisms, and other auxiliary parts. This assembly is responsible for lifting, lowering, and moving the entire drill rig to different positions, and rotating the drill rig to different angles in various coordinate planes, thus allowing the machine to drill holes at different locations and angles.
  4. Crawler Vehicle: This includes a crawler chassis on which all important parts are arranged, such as the internal combustion engine that drives the entire machine, the oil pump, the air compressor, the control cabin, the hydraulic control systems, fuel tanks, etc. The crawler vehicle allows for easy movement on rough and complex terrain.

The movements of the mechanisms such as the drill drive head, the clamping mechanism, the rod changer assemblies, and the drill rig positioning assembly are all performed by hydraulic cylinders. These hydraulic devices are operated by a high-pressure oil source at an appropriate pressure and are controlled by control valves (directional control valves – here we use a 5/3 valve). The high-pressure oil energy is obtained thanks to a high-pressure oil pump (using two piston pumps). Oil from the reservoir is drawn by the high-pressure pump through a filter, then passes through a one-way valve and goes to the drive mechanisms through a pressure reducing valve and a control valve. Depending on the specific movement that requires oil at different pressure levels, we have oil lines that are divided to pass through pressure reducing valves. Then we will get oil lines with appropriate pressures passing through the control valves to control the movements of the mechanisms. Because the mechanisms when moving are driven by hydraulic cylinders and hydraulic motors, and each hydraulic device requires a different oil pressure, we need to choose an oil pump so that the pressure after the pump is the highest required pressure and the flow rate is sufficient to supply all mechanisms operating at the same time. The one-way valve after the pump has the effect of only allowing oil to flow in one direction from the oil pump to the mechanisms. When the pump operates with a flow rate and pressure sufficient to overcome the spring force of the one-way valve, the one-way valve allows oil to pass through to the mechanisms. When the pump is not operating (for example, when the machine is at rest), the one-way valve closes, preventing high-pressure oil from flowing back to the reservoir. Thus, the one-way valve has the effect of preventing the high-pressure oil flow from returning to the reservoir, thus saving energy from being lost when the machine stops operating. The pressure of the outlet oil line after the pump is controlled by a pressure gauge and is limited by a safety valve (relief valve). When the pressure is less than or equal to the permissible value, the safety valve closes, and high-pressure oil from the pump passes through the one-way valve to the hydraulic drive mechanisms for the mechanisms to operate. When the pressure and flow rate are greater than or equal to the permissible value or when the mechanisms stop operating while the pump is still running, the safety valve opens, and the pumped oil flows through the safety valve back to the reservoir. One of the very important devices in the hydraulic system used to control the direction of the oil lines, and thus control the direction of movement of the moving mechanisms, is the control valve (directional control valve). Here we use a 5/3 directional control valve:

This valve has the characteristic that when the spool is in the middle position, all ports of the valve are closed, which means the oil inlet and outlet lines are also closed, and therefore the oil in the hydraulic cylinders is maintained at the same pressure as when it was operating. Thus, it can withstand the lifting force while it does not need to be supplied with oil. When the spool of the directional valve is in the left position, the directional valve allows oil to go up through port 1 through port 3.2 to the hydraulic devices, the return oil line goes from the hydraulic devices to port 3.1 of the valve, passes through the valve out at port 2.1 through the return oil line and back to the reservoir. Conversely, when the spool of the directional valve is in the right position, the valve allows oil to go up from port 1 through the valve and out through port 3.1 to the hydraulic mechanisms, the return oil line goes through port 3.2 through the valve to port 2.2 to the return oil line and back to the reservoir. Thus, corresponding to each left and right position of the spool of the directional valve, we have oil going up through each different line, thus controlling the mechanisms to move in a different direction. And when you want to keep the mechanism stationary, you control the spool of the control valve to be in the middle position. The two ends of the spool 2 have two springs that keep the valve always balanced in the middle position. The process of controlling the position of the spool of the control valve is performed by the control valve 5. This valve has 5 ports, in which the oil inlet port a is taken from the high-pressure oil pump of the system, the two oil lines b1 & b2 are led to the two ends of the spool 2 to control the position of the spool. The two ports c1 & c2 lead oil from valve 5 to the return oil line to the reservoir. When the knob 6 is in the position as shown in the figure, oil from port a goes through valve 5 through the two ports b1 & b2 and up to the two ends of the spool 2, because the oil pressure at the two ends of the spool 2 is equal, it is kept in the middle position, the control valve closes, not allowing high-pressure oil to the operating mechanism. When the knob 6 is turned clockwise by a certain angle, the control oil will go through port a through the control valve 5 up to port b2 and into the right end of the spool 2, oil from the left chamber of the spool 2 goes through port b1 through the valve and through port c1 to the return oil line to the reservoir, because the oil pressure in the chamber at the right end of the spool 2 is higher than at the left end, it pushes the spool 2 to move to the left, opening the control valve 4 to let oil enter port 1 through the valve and out port 3.2 to the operating mechanism. When you want to reverse the direction of motion of the oil motor or hydraulic cylinder, you just need to turn the knob 6 of the control valve 5 counterclockwise, then the control oil will go into port a through the control valve 5 out port b1 up to the left end of the spool 2, oil from the right end of the spool 2 enters port b2 through the valve and out port c2 to the return oil line to the reservoir. At this time, the oil pressure at the left end of the spool 2 is higher than at its right end, so it pushes it to move to the right, causing the control valve 4 to open to let high-pressure oil enter port 1 through the valve and out port 3.1 and up to the oil motor or hydraulic cylinder to perform the reversal of the mechanism’s motion. To stop the motion, you just need to turn the knob 6 to the middle position (as shown in the figure), then the control valve 5 will control the spool 2 of the control valve 4 to be in the middle position, closing the oil line to the oil motor or cylinder, causing it to stop operating.

Concrete drill – an indispensable specialized tool for piercing through hard concrete layers. To help customers better understand the structure and operating principle of a handheld concrete drill, let’s look at the following diagram.

Mechanical safety document

Internal structure of a Bosch concrete drill

Parts of a Bosch handheld concrete drill.

  1. Machine body
  2. Carbon brush set
  3. Drill motor rotor (Moving part)
  4. Motor stator (Stationary part)
  5. Cooling fan
  6. Intermediate motion transmission part
  7. Drill shaft drive part
  8. Drill shaft gear set
  9. Shaft bearings.
  10. Drill bit chuck.

Operating principle of a Bosch concrete drill.

When plugged in, power is supplied to the carbon brush set, causing the motor to rotate and transmit torque to the intermediate shaft. The intermediate shaft creates the hammer impulse and generates torque that is transmitted to the drill shaft through the gear set. Therefore, the drill rotates and creates a strong impact force on the drill shaft, allowing it to drill quickly and powerfully through concrete layers.

4. Grinding machine in mechanical safety documents

Mechanical safety document

There are two main types of grinding machines: Cylindrical grinders and surface grinders. There are also other machines such as: centerless grinders, groove grinders, cutting grinders, gear grinders, etc. Usually, a grinding machine has a workhead or table, on which the workpiece is clamped, and a grinding wheel head, which holds the main spindle with the grinding wheel. Both heads are placed on the machine bed. A diagram representing the grinding technology is shown in Figure 1.2.

There are two types of cylindrical grinders: external cylindrical grinders (fig 2a) and internal cylindrical grinders (fig 2b). On a cylindrical grinder, the main motion is the rotation of the grinding wheel; the feed motion is the linear movement of the wheel head along the axis (longitudinal feed) or the linear movement in the transverse direction (infeed) or the rotational movement of the workpiece (circular feed). Auxiliary motions include the rapid traverse of the wheel head or workpiece, etc.

  • a) External cylindrical grinding
  • b) Internal cylindrical grinding
  • c) Surface grinding with the periphery of the wheel
  • d) Surface grinding with the face of the wheel (rectangular table)
  • e) Surface grinding with the face of the wheel (circular table)

Mechanical safety document

  1. Workpiece
  2. Grinding wheel
  3. Main motion
  4. Longitudinal feed motion
  5. Transverse feed motion.

There are two types of surface grinders: grinding with the periphery of the wheel (figure 2c) and with the face of the wheel (figure 2d). The workpiece is clamped on a circular or rectangular machine table. In grinding with the periphery of the wheel, the grinding wheel rotates and moves linearly across the workpiece, while the machine table carrying the workpiece moves back and forth. The rotation of the wheel is the main motion, the feed motion is the movement of the wheel (transverse feed) or the movement of the workpiece (longitudinal feed). In grinding with the face of the wheel, the table can be circular or rectangular, the rotation of the wheel is the main motion, the feed motion is the transverse movement of the wheel (transverse feed) or the reciprocating movement of the table carrying the workpiece (longitudinal feed).

An important parameter of the grinding mode is the cutting speed (m/s):V= 0.5d.ωđ.10-3

where d – grinding wheel diameter, [mm]; ωđ – rotational speed of the grinding wheel, [rad/s]

Usually v = 30 ÷ 50 m/s.

5. Planing machine in mechanical safety documents

Shaper (horizontal planer)

The shaper is the most common type of planing machine used for machining parts that are not too large. This type of machine is often used in manufacturing or repair workshops.

The shaper’s main motion is the reciprocating straight-line motion performed by the cutting tool, and the feed motion is an intermittent motion performed by the workpiece.

Planer (vertical planer)

The planer is a type of planing machine used for machining large and heavy parts such as machine bases, machine bodies, lathe beds, etc. Planers are often used in large and heavy machinery manufacturing plants.

The planer’s main motion is the reciprocating straight-line motion performed by the workpiece, and the feed motion is performed by the tool.

Planers can be divided into two types: single-column planers and double-column planers.

To increase productivity, planers are equipped with two to four tool holders. When the machine is operating, the cutting tools mounted on these tool holders can participate in cutting simultaneously.

Slotter (vertical shaper)

The slotter is a machine used for machining flat surfaces, shaped surfaces, internal and external grooves, keyways, splines (in holes), etc.

The slotter’s main motion is the vertical reciprocating straight-line motion of the slotting tool, and the feed motion is an intermittent motion performed by the workpiece.

  • Main parts:

The basic part of the machine is the body, which has a slideway (dovetail) for the ram to move back and forth (the main motion of the planer). The ram carries the tool holder for mounting the planing tool.

The machine body is a box-shaped casting made of cast iron. On the outer and front surfaces of the body, there are flat slideways to guide the sliding motion of the machine table (feed motion). Inside the machine body are the gearbox and the crank and slotted lever mechanism.

The planing machine table moves in two directions, vertical and horizontal, thanks to the guiding slideways on the front part of the machine body.

The movement of the machine table is carried out by a screw-nut mechanism (leadscrew-nut transmission).

The table support increases the rigidity of the machine table.

The workpiece is mounted on the machine table and clamped securely by bolts fitted into the T-slots on the table. The main reciprocating motion of the ram is performed by an electric motor, through the gearbox and the crank and slotted lever mechanism. In addition to this method of motion, in some planing machines, the ram performs the main reciprocating motion by a hydraulic mechanism.

  • Crank and Slotted Lever Mechanism

The crank and slotted lever mechanism consists of a gear with a pin, a slider, and a slotted lever.

The slider slides in the slot of the lever. The upper end of the lever is connected to the slider in the ram.

When the gear rotates, due to the action of the slider, the lever will oscillate around the center of the slider which is mounted on the machine base, and transmit reciprocating linear motion to the ram.

  • Feed Mechanism

The horizontal and vertical feed motions of the machine table are intermittent. They are performed at the end of the return stroke of the ram.

The feed mechanism of a shaper often uses a ratchet and pawl mechanism (see figure).

The feed amount is changed by adjusting the number of teeth of the ratchet wheel each time the pin pushes the ratchet wheel.

Mechanical safety document

C. SOME RULES, STANDARDS, AND REGULATIONS FOR OWNERS, USERS, AND OPERATORS IN THE PROCESS OF MANAGING AND USING EQUIPMENT

NATIONAL TECHNICAL REGULATION ON SAFE WORK OF HAND-HELD MOTOR-OPERATED ELECTRIC TOOLS – QCVN 09: 2012/BLĐTBXH

1. General provisions in mechanical safety documents

a. Scope of application

This regulation applies to hand-held electric tools driven by an electric motor or by a magnet, with a rated voltage not exceeding 250 V for single-phase AC or DC hand-held electric tools and 440 V for three-phase AC hand-held electric tools (hereinafter referred to as hand-held electric tools).

Hand-held electric tools, which can be mounted on a support or stand for use as a stationary tool without any modification of the tool itself, also fall within the scope of this regulation.

This regulation does not apply to:

  • Hand-held electric tools designed for use in places with special environmental conditions such as the presence of flammable or explosive substances (dust, vapor, or gas);
  • Hand-held electric tools used for preparing and processing food;
  • Hand-held electric tools used for medical purposes;
  • Heating tools mentioned in TCVN 5699-2-45 (IEC 60335-2-45).

Hand-held electric tools designed for use on means of transport, in addition to complying with the provisions of this regulation, must also have additional requirements from the competent authority on labor safety when used.

b. Subjects of application

This regulation applies to:

  • Organizations and individuals that manufacture, import, circulate, and use hand-held electric tools (hereinafter referred to as manufacturers, importers, sellers, and users of hand-held electric tools).
  • State management agencies and other relevant organizations and individuals.
c. Explanation of terms

In this Regulation, the terms and definitions of the National Standard TCVN 7996-1:2009 (IEC 60745-1:2006) Hand-held motor-operated electric tools – Safety – General requirements and the TCVN 7996-2 series (IEC 60745-2) are used.

2. Technical regulations in mechanical safety documents

  • Hand-held electric tools subject to the scope mentioned above must ensure the safety technical characteristic requirements for motor-operated hand-held electric tools in TCVN 7996-1: 2009 (IEC 60745-1: 2006).
  • For each specific type of hand-held electric tool, in addition to meeting the general safety technical requirements for motor-operated hand-held electric tools mentioned above, they must also meet the specific safety technical requirements for each type of hand-held electric tool (if any) in the TCVN 7996 Part 2 series (IEC 60745-2).
  • In case the aforementioned TCVNs are changed or supplemented, the latest provisions shall be applied.

PART 2: BASIC TECHNICAL CHARACTERISTICS OF EACH PIECE OF EQUIPMENT

A. BASIC TECHNICAL CHARACTERISTICS OF MACHINE TOOL EQUIPMENT: CHISELS, DRILLS, COMPACTORS, GRINDERS, POWER TROWELS, VIBRATORS, CONCRETE MIXERS, ETC.

General structure of construction machinery – There are many types of machinery used in various economic sectors. Each sector has specialized equipment to improve efficiency and labor productivity. This is achieved thanks to the outstanding capabilities of humans. In particular, the construction industry. The types of machines serving construction projects are very diverse and abundant.

Mechanical safety document

General structure of construction machinery

Although each piece of construction machinery has different functions and uses, in general, they all consist of the following parts:

  • Power equipment: The power equipment of construction machinery is usually an internal combustion engine or an electric motor
  • Control system
  • Transmission system
  • Travel system
  • Working mechanism
  • Slewing mechanism of construction machinery
  • Machine frame and body
  • Auxiliary equipment such as: safety devices, lighting, and warning signals…

In construction work, a large volume of sand, gravel, and stone is used annually. A large part of this material is used to produce concrete. In addition, road construction also requires a very large volume of stone. Sand and pebbles are extracted from natural geological layers by mechanical or hydraulic methods, while crushed stone is extracted by blasting, after which it must go through a processing stage at crushing and screening plants or stations.

Stone processing machinery includes various types of machines for crushing, screening, and washing stone.

Due to the specific nature of the School, in this section, we will only mention the combined crushing-screening machine, while other stone processing machines and equipment will be mentioned later if conditions permit.

1. Combined Crushing and Screening Station in mechanical safety documents

The combined crushing and screening station is used for combined crushing and screening of stone, and they are widely used on construction sites, especially in road and bridge construction sites, and the station can be mobile. Crushing is done two or three times in different types of machines. After each crushing stage, a portion of the obtained material reaches the required size; this material is removed before being sent to the next crushing stage to prevent the material from being over-crushed and to reduce the power consumption of the machines in the subsequent stages. Therefore, after each crushing stage, it is necessary to arrange screening machines.

The crusher in the final stage usually works in a closed circuit with the vibrating screen placed after it.

Then, the material that is still larger than the product size will be returned to the crusher for re-crushing.

2. Concrete production machines and equipment in mechanical safety documents

Concrete is formed from a binder (cement), water, and aggregate (sand, stone, or gravel). Concrete, like other building materials, has a most important property which is strength.

Nowadays, permanent structures are often built with concrete and reinforced concrete because of their durability, aesthetics, and good fire resistance. Concrete work includes preparing the mixture (batching, mixing), transporting, pouring, and compacting the concrete.

There are many types of machines and equipment for concrete and reinforced concrete construction, but the main ones are concrete mixers, concrete transport and pumping machines, concrete vibrators, and various types of rebar processing machines…

3. Concrete mixer in mechanical safety documents

A concrete mixer is used to produce a concrete mixture from components that have been batched according to a specified mix design. Compared to manual mixing, machine mixing saves cement, ensures high productivity and quality. The main technical characteristic of a batch mixer is the production capacity Vprod of the mixing drum, which is the volume of materials loaded for one batch. The geometric volume of the mixing drum is usually 1.5 – 2.5 times the production capacity. In construction, mixers with production capacities of 100, 250, 500, 1200, 2400, and 4500 liters are commonly used.

Mixers are often named after the production capacity of the mixing drum.

A mixer consists of the following main parts: a mixing drum, a working mechanism and drive system, a loading and discharging device for concrete, and in addition, there are other batching and safety devices…

Concrete mixers are classified according to operating conditions, working mode, and mixing method.

According to the working mode, there are batch type and continuous type. Most mixers work in batches, consisting of the operations of preparing, mixing, and discharging the concrete, which are performed in the sequence of one batch. Their productivity is calculated in liters of concrete per batch. Continuous mixers have the processes of loading materials, mixing, and discharging concrete occurring continuously. The technical characteristic of this type is productivity calculated in m3/h.

According to the mixing method, there are free-fall mixing and forced mixing.

In a free-fall mixer, the mixing drum has mixing blades attached. When the drum rotates, the mixing blades will carry the concrete mix upwards and then let it fall, so they fall freely. Thanks to the drive of a pair of spur gears, the tilting frame will rotate, causing the drum to tilt down, discharging the mixed material. This type discharges concrete very quickly and relatively cleanly.

Currently, machines similar to the one in Figure 5.4 are commonly used but with 2 separate motors, one of which is connected to a reduction gear unit placed on the tilting frame to drive the rotation of the mixing drum, and another motor through a coupling and a worm gear reduction box to drive the loading skip. In this type of machine, the mixing drum 2 is rotated and suspended cantilevered on the tilting frame through a set of straight gear and bevel gear reduction boxes or a planetary reduction box attached to the bottom of the mixing drum.

a. Mixer Productivity
  • Productivity of a batch mixer
    • The productivity of a batch mixer is calculated by the formula: Q = Vprod . f . m . ktime, m3/h
    • Where: Vprod: production capacity of the mixing drum or the material holding capacity of the drum for effective mixing, m3
    • f: output factor, equal to the ratio of the mixed concrete Vc to the production capacity Vprod of the mixing drum (f = Vc/Vprod). The output factor is 0.65 ÷ 0.70 when mixing concrete, f = 0.75 ÷ 0.85 when mixing mortar.
    • ktime: time utilization factor
    • m: number of concrete batches mixed in 1 hour.
  • Productivity of a continuous forced mixer
    • The productivity of a continuous forced mixer is calculated by the following formula: Q = 3600 . A . V, m3/h
    • impulse transmitted to the concrete right inside them. The flexible shaft immersion vibrator is widely used thanks to its advantages: compact, lightweight, and high energy transfer efficiency.
    • Flexible shaft immersion vibrators are divided into: eccentric immersion vibrators, internal oscillating immersion vibrators, and external oscillating immersion vibrators.
    • The shaft through a coupling transmits to the shaft with an eccentric mass that acts on the surface of the part installed inside the vibrator casing. The eccentric mass creates a circular vibration, causing the vibrator head to vibrate.
    • The main disadvantage of the flexible shaft vibrator is the very large friction between the shaft and the casing, which leads to a loss of engine power and the vibration cannot be transmitted far.
b. Surface Vibrator
  • There are usually 3 types of surface vibrators: plate compactors, vibrating screeds, and electromagnetic vibrators. Electromagnetic vibrators are less used than the other 2 types because the vibration is not uniform, resulting in low efficiency.
  • They are often used to compact large concrete areas such as: house floors, roadbeds…
  • The vibrating part is a squirrel-cage motor with a casing 1, the two ends of the rotor shaft are tightly fitted with 2 eccentric masses 4, the shaft rests on two bearings 6. When the rotor rotates, the eccentric mass rotates with it, causing a circular vibration that is transmitted to the vibrating plate. By being able to change the center of gravity of the eccentric mass, the moment and vibrating force can be changed.
  • In many cases, technological requirements call for directed linear vibration, for example: vibrating hammers, vibrating screens… Because the eccentric masses have the same mass and size, are symmetrically mounted along the axis, and rotate at the same speed in opposite directions, the horizontal component of the centrifugal force balances out, the exciting force changes in value and has a direction acting on the vibrator casing. Thanks to two identical gears, the rotational speed of the eccentric masses is balanced.

B. BASIC TECHNICAL CHARACTERISTICS OF MECHANICAL MACHINERY: SAWS, PUNCHES, STAMPERS, LATHES, MILLING MACHINES, PLANERS, GRINDERS, DRILLS, ETC.

1. Lathe in mechanical safety documents

a. working principle
  • The motor, through a belt drive, rotates the shaft to create the main motion, which combines with the feed motion to create the cutting motion.
b. technological capabilities
  • Turning is mainly used to machine surfaces of revolution such as external cylindrical surfaces, internal cylindrical surfaces, external conical surfaces, internal conical surfaces, face surfaces, shaped surfaces of revolution, internal threads, and external threads.
  • The accuracy of turning machining depends on factors such as:
    • the accuracy of the lathe,
    • the rigidity of the technological system,
    • the cutting tool.
    • the skill level of the worker

2. Drilling machine in mechanical safety documents

a. working principle
  • From the motor, it is transmitted to the belt drive to rotate the drill bit spindle, while the workpiece is mounted on the machine table. The feed motion, along with the rotational motion of the main spindle, creates the cutting motion.
b. technological capabilities
  • Drilling is often used to machine holes in solid workpieces (workpieces without pre-existing holes or workpieces that already have holes). When drilling, a twist drill bit is usually used as the tool.
  • Drilling can machine holes with diameters from 0.1 to 80 mm, most commonly holes with diameters of 35mm or less. For larger holes, a very high-power machine is required. For holes that are too small, the drill bit does not ensure rigidity. The machining accuracy of drilling is low, only reaching accuracy grade 12-13 and Ra = 3.2-12.5µm. For holes that require high accuracy, drilling is the roughing machining step.
  • Drilling machines come in the following types: – a bench drill is the simplest type, small in size, usually placed on a workbench, the largest hole it can drill is 12mm, – a vertical drill is a type of drilling machine whose main spindle only moves along its axis. It can machine holes with a diameter ≤ 50mm, – a radial drill is a machine whose tool spindle, in addition to being able to move along its axis, can also move up and down, in and out, and rotate around the machine column. With these movements of the tool-carrying spindle, it can drill holes at any coordinate. It is suitable for machining large, bulky parts. – a multi-spindle drill is a machine capable of drilling multiple holes thanks to a tool head with multiple drill bits. This type of machine is suitable for mass production.
  • a deep hole drilling machine is a specialized machine, with a horizontal main spindle used for machining holes with great depth.

3. Milling machine in mechanical safety documents

a. working principle
  • From the motor, through a belt drive, it rotates the main spindle which has a milling cutter attached. The workpiece/part is mounted on the machine table, which moves up and down, longitudinally, and transversely to create the cutting motion.
b. technological capabilities
  • Milling can machine many different types of surfaces; however, below we will only study two types of surfaces in detail: flat surfaces and splines.
  • Small grooves or steps are often machined using a side milling cutter or an end mill. Keyways and splined shafts often require high machining accuracy to ensure the proper fit of the key or spline joint. Depending on the type of key, the keyway can be machined with a three-sided milling cutter or by using an end mill.
  • When milling a splined shaft, a three-sided milling cutter can be used by milling the two side faces with two side milling cutters, then using one milling cutter for the cylindrical part of the spline. Splined shafts are also often machined with a form milling cutter.

4. planing, slotting machines

a. working principle
  • From the motor, through a belt drive, it rotates the crank and slotted lever mechanism, leading to the reciprocating linear motion of the ram which carries the cutting tool. The workpiece is mounted on the machine table via a clamping mechanism. The table moves up and down, and transversely/longitudinally to create the cutting motion.
b. technological capabilities
  • Planing is mainly used to machine flat surfaces, but it can also machine shaped surfaces with straight generatrices. Planing can achieve a maximum accuracy of grade 8 to grade 7 and a surface finish of Ra = 2.5µm. Slotting is mainly used to machine internal surfaces, keyways in pipes, on gears, etc.

5. Reaming

a. working principle
  • Reaming is a finishing operation for holes that have been drilled or bored. Accuracy can reach grade 7 to 9, and the surface finish can achieve Ra=6.3µm.
  • Reaming can be performed by forced reaming or floating reaming.
  • Forced reaming is when the reamer is rigidly mounted to the machine spindle. This method can cause hole enlargement, the reasons being misalignment between the tool axis and the machine spindle axis, poor tool grinding, built-up edge appearing on some cutting edges, and non-uniform material on the hole wall.
  • Floating reaming is when the tool is connected to the machine spindle with a floating holder, which eliminates the error between the machine spindle axis and the tool axis. To overcome the phenomenon of the tool wearing down from repeated grinding, a type of floating reamer with the ability to self-adjust its diameter can be used.
  • Depending on the quality and size requirements, a suitable tool should be chosen. Reamers often have multiple cutting edges, which are parallel or inclined at a very small angle to the tool axis. grinding machine: a-working principle: from the electric motor through a transmission, it rotates the main spindle which has a grinding wheel mounted. The workpiece is mounted on the machine table.
b. technological capabilities
  • Grinding can machine many different types of surfaces such as flat surfaces, internal cylindrical surfaces, external cylindrical surfaces, conical surfaces, shaped surfaces, etc. Depending on the type of surface to be machined, we divide it into the following methods: – external cylindrical grinding, – internal cylindrical grinding, – surface grinding, – form grinding.

C. HAZARDOUS AND HARMFUL FACTORS WHEN WORKING WITH EACH MACHINE AND PIECE OF EQUIPMENT

1. Accidents in mechanical safety documents

In mechanical machining, common accidents can be divided into several types as follows:

  • Tripping, falling – Collapse, impact
  • Burns from chips – Electric shock
  • Punctures – Clothing, hair caught in the machine,
  • Machine rolling, clamping, cutting – Chips flying into eyes…

2. Causes in mechanical safety documents

The causes of accidents:

  • Unsafe machine guards,
  • Lack of safety devices or safety devices are broken or not functioning correctly,
  • Damaged machine controls,
  • Violation of standards, regulations, and safe machine operating procedures,
  • Violation of the safety rules of the workshop or factory,
  • Poor sanitary conditions such as: insufficient lighting, poor ventilation, noise exceeding permissible standards…
  • Disorganized workshop layout, inconvenient traffic within the workshop…
  • Untidy and disorganized arrangement of raw materials, finished products, and semi-finished products…

D. Principles to ensure occupational safety for users, operators, and maintenance personnel in the mechanical industry.

1. General principles in mechanical safety documents

Must fully comply with the current occupational safety and health requirements from the design, manufacturing, installation, use, and management of machines and equipment according to specific safety technical regulations, standards, and the requirements in the machine’s documentation from the manufacturer;

Specifically identify hazardous areas and the risks of occupational accidents during the use of machines and equipment;

Fully implement appropriate safety measures;

The workshop layout must be organized in accordance with safety conditions:

  • Choose a suitable position and location;
  • Arrange the workshop, warehouses, and transport routes logically and conveniently;
  • Install equipment in the workshop ensuring safe conditions;

2. Safety principles for using machines and equipment

  • No one except the person in charge is allowed to start or control the machine;
  • Before starting the machine, check the safety devices and standing position;
  • Before leaving for other work, turn off the machine; do not leave the machine running unattended;
  • Turn off the power switch in case of a power outage;
  • To adjust the machine, turn off the motor and wait for the machine to stop completely; do not use your hands or a stick to stop the machine;
  • When operating the machine, wear appropriate personal protective equipment (do not wear clothes that are too long, do not wear scarves, gloves, etc.);
  • Inspect the machine regularly and before operation;
  • A “Machine Out of Order” sign must be hung on a broken machine.

3. Rules to make machines safer and more productive

  • Choose and purchase machinery where all operating procedures are completely safe;
  • Moving parts are fully guarded;
  • There is an automatic stop device or two-hand control at the operating level;
  • Use safe material loading and unloading devices to increase productivity and reduce dangers caused by the machine;
  • Fully guard the hazardous parts and areas of the machine: the guard must:
    • Be firmly fixed to the machine;
    • Guard the moving parts of the machine;
    • Not interfere with the machine’s operation and the worker’s visibility;
    • Be removable when machine maintenance is needed;
    • Maintain the machine properly and regularly;
    • Use appropriate personal protective equipment;
    • Have a complete system of signs for dangerous places and hazardous areas;
    • Ensure a safe electrical system;
    • Fully implement fire prevention and fighting measures.

PART 3: OPERATING PROCEDURE

A. EQUIPMENT INSPECTION BEFORE OPERATION. PREPARATION WORK

1. Operating Procedure

Mechanical safety document

 

Establish a procedure to control the following situations:

An authorized person removes a machine guard or deactivates a machine safety device.

Operating the machine for testing purposes without a guard or safety device.

There will be situations where maintenance work needs to be performed on a moving machine. This work may not require guards and/or safety devices. To ensure the safety of the person performing this work, the machine must be isolated and locked out before removing the guard.

Remember that in this case, the requirements of the Fatality Prevention element regarding isolation and lockout must always be followed.

Also be aware that there are cases that require the machine to be operated for testing or calibration purposes with the guard removed or the safety device not in use. In these cases, a formal procedure must be established that defines the means to protect workers from accidental contact with mechanical parts during testing. The procedure must be approved by a competent person and the person responsible for safety in the area where the work will be performed.

Below is a summary of methods considered as notification and protection for workers in this type of activity. These methods should be used in combination.

Method Advantages Limitations
Temporary Barrier

 

 Creates a physical barrier between the exposed part of the machine and workers in the area. Requires clearance around the exposed machine area and its parts.
Barrier Tape

 

 Easy to set up and creates a visible boundary area around the exposed machine part. Barrier tape is not a physical barrier; this method requires a minimum distance of 2m from the machine part.
Sentry/Spotter

 

 Provides immediate warning to everyone and safety in the area where workers might ignore the requirement to stay outside the restricted area. Cannot secure a large area, especially if parts of the exposed machine are hidden from the sentry’s view by other structures.
Signage Easy to position and provides immediate information about the hazard in the area. Does not provide protection, only a source of information.

 

Supporting Documentation

All records and logs related to surveys and procedures must be retained until the machine is no longer being tested and is not put into operation.

It is important that all supporting documentation and information related to machine guarding are retained as they are a reference source used in the following ways: to prove that all machines have been assessed and all types of guards have been installed. It can be used to identify hazards and guarding requirements if similar machinery is purchased. It is the basis for identifying guarding requirements for the regular inspection program.

Selection, Training, Competence, and Authority

Knowledge to Conduct a Guarding Survey

The person conducting the guarding survey must be instructed as below and assessed as proficient in:

describing machine hazards and the types of guards and devices available.

how to determine if a machine guard or safety device is sufficient for protection.

deciding what information needs to be recorded in the survey and how to proceed with corrective actions.

A person is considered proficient to conduct a machine guarding survey after receiving formal training on the Fatality Prevention element and related instructions. At a minimum, the training and competency assessment of the person conducting the machine guarding survey must indicate the following details:

Has an understanding of the types of machines used in Holcim’s operations/facilities.

Can describe the machine components and potential hazardous movements/operations.

Understands the principles of machine guarding including the different types of machine guards and their general design and construction requirements.

Identifies the different types of safety devices used to protect workers, including how they operate.

It is generally expected that supervisors will be the ones presenting and/or conducting the machine guarding survey.

Hazard Awareness

All workers required to work near or on moving machinery must be instructed on hazard identification related to moving machinery at the point of operation.

Because Holcim Equipment is highly mechanized, it is emphasized that the majority of workers at the point of operation/facility will be required to perform work in areas where there is moving machinery. Therefore, it is important that all workers are informed of the hazards and safety requirements while working near or around moving machinery. The following outlines the areas that need to be addressed.

Mechanical safety document

Hazards associated with moving machinery.

Safety requirements for machine guards

Personal protection requirements (loose clothing, long hair, etc.)

Actions to be taken when it is identified that a machine guard or safety device is missing or damaged.

Communication and Awareness

Awareness Information and Guidance

Awareness information and promotional campaigns will be conducted regularly to enhance knowledge and understanding of the following issues:

types of hazards associated with moving machinery

types of machine guards and safety precautions when working near moving machinery, i.e., restricting access to moving parts, wearing loose clothing. measures when a machine guard is missing or damaged.

Information or instructions should be provided regularly to workers, the purpose of which is to:

  • maintain focus and a high level of awareness on key risk areas such as the hazards of moving machinery.
  • inform workers of the requirements if they must work on machinery with guards removed.
  • enhance workers’ interest and understanding of the safety requirements for machine guarding by discussing findings from area safety inspections, incidents, safety monitoring, etc.

The information is provided in a form that workers at the point of operation can understand. Methods are established so that workers and contractors, regardless of language and literacy level, are provided with appropriate information. This can be achieved by using verbal methods (safety meetings, pre-shift talks) or visual methods (posters, monthly banners, and short films).

It is recommended that the following topics on machine guarding be disseminated to anyone who comes into contact with moving machinery.

Principles of Machine Guarding – by explaining the concept behind the design, i.e., preventing accidental access to hazardous motion or preventing materials or objects from being ejected.

Personal Protection and Behavior – emphasizing the risks associated with issues like wearing loose clothing and leaning over moving machinery, i.e., long hair should be tied back, etc.

Take corrective action when a guard is found to be missing or damaged.

Planning

To help ensure regular communication of information, planning is necessary. Pre-start talks or safety meetings (example below) will provide an opportunity to raise awareness by using established information sets. It is important that awareness among contractors is also addressed. Planning and keeping records of the presentation makes it easy to track what has been presented and to plan future meetings.

Notification of Interlocking Devices

When an interlocking device is installed in place of a machine guard, a sign must be placed at each access point to identify that the machine has been safely guarded through the use of an interlocking device.

To avoid unplanned machine shutdowns due to workers inadvertently entering a hazardous area, signs should be placed at each access point connected to an interlocking device.

When a guard is installed in conjunction with an interlocking device, this requirement is not necessary but should be considered as a form of additional protection.

Design, Procurement, Manufacturing, Installation, and Commissioning

Design Requirements

Design standards must be established for the types of machine guards and safety devices used at the point of operation. The design standards must specify the following details:

Guards must be easy to remove and replace (lifting points, handles, covers, etc.).

Guards should only be removed with a tool or used in conjunction with an interlock.

Use good quality and durable materials to prevent access and/or the ejection of materials or objects.

Position the guard so that there is sufficient distance between the hazard and the reach point of the protected body part.

Machine guards must be clearly distinguished from other structures, i.e., through color coding or signage.

As described above in the hazard identification, risk assessment & control section, there are three main parts of a moving machine that need to be guarded:

The point of operation

The power transmission apparatus

Other moving parts

Machine guards should be designed to prevent workers from accidentally touching them or getting their clothes caught, for example, between belts and pulleys, chains and sprockets, cables and sheaves or drums or rollers. As a general guide, when guards are not removed for inspection or maintenance, they must be securely fastened in place so they cannot be removed without tools. In all cases, the following properties should be included in the design standards:

Considered as a permanent part of the machine or equipment;

Designed for the specific job and specific machine, with provisions for oiling, inspection, testing, adjustment, and repair of machine parts;

The guard must be made of sturdy material, mesh, or similar construction and prevent access to the hazardous moving area (danger zone) during operation;

If the guard is placed so that a person can climb or sit on it, it must be able to support the weight of a person (75kg) placed at any position.

When guards and covers need to be removed, there must be lifting handles or pins to help remove or open the guard cover safely.

Identifiable through a standard color code different from the color of the machine;

When there is a possibility of particles being ejected from inside the machine, the guard must be durable and of strong enough construction to withstand impact.

The guard itself must not pose a hazard.

Guarding Hazardous Parts

Machinery is designed and procured with machine guards or other safety devices (interlocks) to prevent accidental contact with hazardous parts of the machine and risks such as:

  • in-running nip points, shearing, crushing, cutting, stabbing or piercing hazards;
  • impact hazards;
  • rotating parts that can cause entanglement;
  • hot/cold surfaces; and
  • flying objects (as a result of normal operation or failure), etc.
  • Inspect each machine to ensure all machine hazards are adequately controlled and the machine guarding survey form is updated to reflect the findings from this inspection before the machine is commissioned.

Most manufacturers and/or suppliers of single-purpose machines will provide point of operation and power transmission guards as standard equipment. However, this is not always the case, so it is necessary to ensure that all stationary and mobile moving machines are inspected before being put into operation, and the inspection must be recorded for each machine.

Refer to Appendix D for an Example of a General Checklist for Machine Guarding

Adjusting Machine Guards

Adjustments to machine guards must be approved by a designated person who is deemed competent to determine if the adjustment will create a hazard (i.e., Maintenance Manager, Engineer) before any adjustments begin.

Adjustments to machine guards should be addressed through the Management of Change block in the Holcim safety tower. This helps the company ensure that a person with appropriate knowledge regarding the design and function of the machine guard can assess the impact of the change, specifically ensuring the proposed adjustment does not lead to:

compromising the integrity of the machine guard or the machine.

reducing the level of protection required while ensuring the machine can operate as designed.

creating new hazards.

B. WORK PERFORMED WHILE EQUIPMENT IS OPERATING

Work Methods and Condition Control

Accessing Moving Machinery

It is prohibited to remove machine guards or disable safety devices unless the following is done:

  • Isolation and lockout are applied and the machine is tested – i.e., the machine is de-energized (refer to the Fatality Prevention element on isolation and lockout)
  • The removal of the machine guard or disabling of the safety device has been approved.

When working on stationary moving machinery or mobile hand tools, it is important to apply the isolation and lockout procedure. This is achieved by following the requirements in the Fatality Prevention element on isolation and lockout.

In cases where the machine is operated with the guard removed and/or the safety device disabled, a formal risk assessment must be conducted to ensure that safety precautions are established to minimize the risk of injury. In addition, the person responsible for the safety of the workers (Manager in charge) in the area where the work is performed must review and approve the proposed procedure before the work begins.

Missing Guard

When a machine is found operating with a missing or damaged guard or safety device. The machine should be shut down and an out-of-service tag should be attached (refer to the Fatality Prevention element on isolation and tagging).

The absence of a machine guard or safety device increases the risk of injury; an operating standard must be established to address this risk. The most appropriate method for this situation is to instruct all workers that when they encounter a machine without a guard or with a damaged guard that allows them to come into contact with parts of the machine (hazardous area), they must stop the machine immediately, isolate it, and attach an out-of-service tag. The situation must be reported immediately to the person responsible for the relevant machine.

Personal Measures to Prevent Entanglement

Persons working near or on moving machinery must take the following safety precautions to avoid entanglement in the machine:

  • Long hair must be tied back or covered by a hat.
  • Do not wear loose-fitting clothing, i.e., shirts tucked in, sleeve cuffs buttoned or sleeves rolled up, etc.
  • Do not wear jewelry when working with machinery.

The design and construction of machine guards are usually intended to protect body parts from coming into contact with machine parts. In most cases, guards are constructed of steel mesh or perforated sheets to reduce total weight. This design may allow personal items such as hair or clothing to become entangled in the machine. Therefore, it is important that basic personal protective measures are applied by those working near moving machinery. These measures include:

Long hair must be tied back or covered by a hat or hard hat.

Clothing must be buttoned, tucked in, or be close-fitting.

Do not wear jewelry near machinery, especially items like necklaces and bracelets.

When using power tools with grinding or sanding functions, such as grinders, in addition to strictly complying with the occupational safety regulations for hand-held power tool products, special attention should be paid to the following instructions:

  1. Do not use an angle grinder for polishing. Using the machine for a function it was not designed for can cause danger or bodily injury.
  2. Use genuine accessories from the manufacturer to ensure the tool operates safely and has a long service life.
  3. Do not operate the machine beyond the speed indicated on the angle grinder. When running beyond the rated speed, accessories can fly off, leading to machine damage and danger to the user.
  4. Do not use a hand-held power tool if it shows signs of damage; it should be inspected before each use.
  5. Always wear protective equipment when working to protect the operator from injury. Depending on the type of work, use a face shield, goggles, or safety glasses. It is appropriate to wear a dust mask, hearing protection, gloves, and protective clothing capable of preventing stone dust or workpiece fragments from flying out.
  6. Note to only hold the power tool by the insulated gripping surfaces, when operating the machine in a place where the cutting tool may contact hidden wiring or its own cord.
  7. Do not let the power cord get near the rotating tool; the cord can be cut or get entangled in the rotating device.
  8. Only put the tool down when the device has stopped rotating completely.
  9. Do not operate the power tool while holding it at your side.
  10. Regularly clean the ventilation slots of the device.
  11. Do not operate a grinding tool near flammable or explosive materials as the friction during grinding produces sparks that can cause fire or explosion.
  12. Do not use accessories that require liquid coolants, as this can lead to electric shock.
  13. Always operate the grinder in the most stable position and always use the auxiliary handle to have maximum control over kickback or torque reactions during operation.
  14. Do not place your hands near the rotating tool.
  15. When working on corners, be careful to avoid the accessory bouncing or getting jammed, which can lead to loss of control of the rotating accessory.
  16. Do not attach a saw chain, woodcarving blade, or toothed saw blade to the tool, as these accessories often create kickback and loss of control of the tool.
  17. Only use the type of disc recommended for the grinder and the guard designed specifically for the selected disc type.
  18. The surface of a depressed center wheel must be mounted below the plane of the guard lip.
  19. The guard must be securely attached to the tool and positioned for maximum safety.
  20. Only use the disc for its recommended applications.

C. STOPPING THE EQUIPMENT

1. Safety Risks in mechanical safety documents

  • Production parts and mechanisms: Moving mechanisms, shafts, drive couplings, fixtures, reciprocating parts.
  • Ejection: Fragments of tools, work materials flying out such as cutting tools, grinding wheels, chips, workpieces, burrs when cleaning parts…
  • Electric shock: from exposed electrical wires, electrical contact with the machine casing, from wires, circuit breakers, electrical outlets…
  • Burns: Hot metal, materials heated by friction.
  • Poisoning: Industrial toxins entering the human body through handling, contact…
  • Industrial dust: Causing mechanical injuries, toxic or poisonous dust causing occupational diseases, causing fire or explosion, or electrical moisture causing short circuits…
  • Explosion hazard: Chemical and physical explosions.
  • Collisions: Screw heads on milling tables, dividing heads, and protruding parts causing entanglement and injury.

2. Technical Safety Conditions in mechanical safety documents

Article 1: Comply with labor safety regulations when using machine tools.

Article 2: Only workers who have been trained and have a certificate are allowed to install and adjust grinding wheels. When selecting a wheel for machining, it must be in accordance with the requirements of the grinding technology.

Article 3: Before starting the machine, check the wheel, wheel mounting bolts, work rest, guard, and the direction of rotation of the wheel to see if they are safe.

Article 4: It is forbidden to use a grinding machine without a wheel guard and without a work rest; the guard must be sturdy. The gap from the edge of the wheel to the edge of the work rest: ≤3mm.

The height of the work rest surface should be such that when the workpiece is placed on it, the point of contact is ≤ 10mm relative to the wheel spindle plane in the horizontal plane.

Article 5: It is forbidden to use a steel hammer to tap or adjust the grinding wheel. When the grinding machine is working, do not stand opposite the open part of the wheel guard. It must be tested for at least 1 minute before operating the machine and at least 3 minutes after changing a grinding wheel. It is forbidden to let the machine run beyond the specified speed.

Article 6: Grinding wheels must be stored in a dry place, not to be stored in the same warehouse as acids and corrosive substances.

Article 7: In case the grinding machine does not have a dust shield, work is allowed but it is mandatory to wear white safety glasses.

Article 8: It is forbidden to use a chipped, cracked, or worn wheel, and the remaining part of the wheel is < 3mm from the edge of the flange on a two-wheel grinder. It is forbidden to grind when there is only 1 wheel on the machine. It is forbidden to grind on the two sides of the wheel.

Article 9: Do not press the workpiece too hard when grinding, do not grind at one point. Make contact slowly, do not allow strong impacts between the workpiece and the machine. It is forbidden for two people to grind on the same wheel.

Article 10: It is forbidden to grind soft metals such as copper, aluminum, and wood, rubber on a two-wheel grinder.

Article 11: On surface grinders and crankshaft grinders, the workpieces must be clamped securely.

Article 12: When grinding parts that produce a lot of dust, dust prevention measures for workers must be taken, such as using suction or blowing equipment.

Modern machines have been developed to replace a large part of human labor. Many types of machines can be easily transported and handheld, which engineers and technicians love for their compactness and convenience, such as handheld grinders, screwdrivers, paint spray guns…. Despite being so convenient, if you don’t know how to use them or pay attention to small details while working, it can easily lead to accidents. The following notes will help you use a grinder safely.

  • Some accidents that can occur when using a grinder
    • During the use of a grinder, metal dust or stone dust can be ejected, which can be dangerous for the eyes or respiratory system.
    • While grinding by hand, the worker’s hand may touch the grinding wheel, causing injury.
    • Fragments of the grinding wheel can cause injury to the worker who is grinding or people working nearby.
  • Notes for safe use of a grinder
    • If there is an unusual phenomenon when using the grinder, contact the technical support department for inspection and guidance.
    • Prevent accidents due to grinding wheel breakage during machine operation; fragments of the grinding wheel can fly out and cause injury to workers.
    • To prevent accidents from metal filings and grinding wheel particles, the following factors must be complied with and paid attention to: machine placement; Wheel selection; Wheel installation; Work rest and the gap between the wheel and the work rest; Grinding posture;
    • The local lighting voltage must be less than 36 Volts.
    • The machine must be placed in an area with little foot traffic, away from flammable materials because sparks can be ejected during operation that can easily catch fire.
    • The open part of the wheel should face the wall; A suitable grinding wheel must be chosen.
    • Before grinding, recheck the grinding wheel guards and the parts of the machine that can easily cause accidents; check the balance of the wheel and that it is securely clamped.
    • Let the grinder run stably for 3-5s before starting to grind; When grinding, introduce the workpiece slowly, do not press hard, move it evenly. For large workpieces, do not use a small wheel to grind, do not grind on the two cylindrical faces of the wheel.
    • Workers must wear full protective equipment such as glasses, masks, etc., and not stand opposite the wheel when grinding to ensure the safety of the worker from dust or material chips flying out.
    • For a two-wheel bench grinder, the diameter of the two wheels should not differ by more than 10%. When the wheel is worn down close to the clamping flange, 2 to 3 mm from the edge of the flange, a new wheel must be replaced.
    • The grinder must have a sturdy work rest and wheel guard. The gap between the wheel and the side wall of the guard should be between 10 -:- 15 mm. The gap between the wheel and the work rest should not be greater than 3 mm. The opening angle of the guard should be as small as possible.
    • On both sides of the wheel, there must be clamping flanges with the same thickness and diameter. Between the wheel and the clamping flange, there must be an elastic washer (thick paper, cardboard, or leather).
    • The work rest must be adjustable to ensure that the workpiece lies in the horizontal plane passing through the center of the grinding wheel or slightly higher, but not more than 10 mm.
    • When grinding with cooling water, the water must be poured over the entire working surface of the wheel. When stopping work, the cooling must be stopped and the wheel must be dried.
    • Only workers who have been trained and have a certificate are allowed to install and adjust grinding wheels. When selecting a wheel for machining, it must be in accordance with the requirements of the grinding technology.
    • Before starting the machine, check the wheel, wheel mounting bolts, work rest, guard, and the direction of rotation of the wheel to see if they are safe.
    • It is forbidden to use a grinding machine without a wheel guard and without a work rest; the guard must be sturdy. The gap from the edge of the wheel to the edge of the work rest: ≤3mm. The height of the work rest surface should be such that when the workpiece is placed on it, the point of contact is ≤ 10mm relative to the wheel spindle plane in the horizontal plane.
    • It is forbidden to use a steel hammer to tap or adjust the grinding wheel. When the grinding machine is working, do not stand opposite the open part of the wheel guard. It must be tested for at least 1 minute before operating the machine and at least 3 minutes after changing a grinding wheel.
    • It is forbidden to let the machine run beyond the specified speed; run it at the speed indicated on the machine to ensure it is not overloaded and has a long service life.
    • Grinding wheels must be stored in a dry place, not to be stored in the same warehouse as acids and corrosive substances, which can damage the grinding wheel.
    • It is forbidden to use a chipped, cracked, or worn wheel, and the remaining part of the wheel is < 3mm from the edge of the flange on a two-wheel grinder. It is forbidden to grind when there is only 1 wheel on the machine. It is forbidden to grind on the two sides of the wheel.
    • Do not press the workpiece too hard when grinding, do not grind at one point. Make contact slowly, do not allow strong impacts between the workpiece and the machine. It is forbidden for two people to grind on the same wheel.
    • It is forbidden to grind soft metals such as copper, aluminum, and wood, rubber on a two-wheel grinder.
    • On surface grinders and crankshaft grinders, the workpieces must be clamped securely.
    • When grinding parts that produce a lot of dust, you should use additional equipment with dust suction or blowing functions, such as a vacuum cleaner.

PART 4: SOME SAFETY RULES ACCORDING TO TCVN (VIETNAM NATIONAL STANDARDS)

A. COMMON INCIDENTS, REPAIR AND MAINTENANCE METHODS FOR EQUIPMENT

OCCUPATIONAL ACCIDENTS AND COMMON CAUSES OF OCCUPATIONAL ACCIDENTS IN THE MECHANICAL INDUSTRY

1. Accidents in mechanical safety documents

In mechanical machining, common accidents can be divided into several types as follows:

  • Tripping, falling – Collapse, impact
  • Burns from chips – Electric shock
  • Punctures – Clothing, hair caught in the machine,
  • Machine rolling, clamping, cutting – Chips flying into eyes…

2. Causes in mechanical safety documents

The causes of accidents:

  • Unsafe machine guards,
  • Lack of safety devices or safety devices are broken or not functioning correctly,
  • Damaged machine controls,
  • Violation of standards, regulations, and safe machine operating procedures,
  • Violation of the safety rules of the workshop or factory,
  • Poor sanitary conditions such as: insufficient lighting, poor ventilation, noise exceeding permissible standards…
  • Disorganized workshop layout, inconvenient traffic within the workshop…
  • Untidy and disorganized arrangement of raw materials, finished products, and semi-finished products…

In essence, mechanical engineering technology provides the result of the process – the product. However, the final product can only be created if the technology provides all the necessary requirements such as primary materials and energy.

The basic classification of engineering technology is shown in Figure 2; the technology is divided into:

  • Production of semi-finished products
  • Machining of components
  • Product assembly

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Classification of mechanical technology

The production of semi-finished products is further divided into:

  • Production with a change in shape without breaking the material’s bonds
  • Production with a change in material properties

The machining of product components is divided into:

  • Machining with a change in material properties
  • Machining with a change in shape by breaking bonds

IDENTIFYING HAZARDS DURING MACHINING

When identifying risks, the most important first step is to identify the source. The source of a hazard is each element that is the root cause of one or more hazards. The nature of the source is the danger, where some sources have their own inherent hazardous nature, and some only become hazardous after an external energy supply.

To identify the risks in machining, the sources were selected in two ways. First, in general, as a source applicable to the entire machining job, and then sources applicable to each specific stage. An overview of the sources is given in Table 1.

General sources of risk Sources from types of machine tools
Workstation Turret lathe
Work environment (sound, vibration, spray, etc.) Vertical lathe
Cutting fluid Revolving lathe
Electrical equipment Drilling machine
Operation Planing machine
Machining center
Milling machine
Grinding machine
Material cutting machine

Table 1: Sources of Risk

In the following tables are general examples of sources as well as impending risks, possible consequences, and appropriate safety measures.

Source Risk Consequence of risk Preventive measures
Workstation Improper machinery layout Crushing, getting trapped, falling from a height, broken bones Adjust steps, stairs, exits with handrails, flooring
Noise Noise exceeding the permissible threshold Lack of concentration and attention at work Assemble machinery according to manufacturer’s instructions, insulate, use noise protection equipment
Lighting Reduced visibility Machine operator enters an unsafe area, gets caught in the machine, falls Position machinery in a location with the most suitable natural light conditions, establish an area with adequate and appropriate artificial lighting
Spray nozzle Removing spray Hand injuries Use brushes, filters
Cutting fluid Overflow, coolant spray Slips and falls, groundwater contamination, impact on the working and living environment Install protective covers, adjust coolant nozzles, suitable collection system
Electrical equipment Machinery operating without a switch Unintentional disconnection of the machine from all energy sources Install a main switch
Dust Dispersion of dust particles Impaired respiratory system function, affects vision, damages moving parts of machinery Install a separate device on the machinery to extract contaminated air from the machining area

Table 2: Identifying risks from general sources

Source Risk Consequence of risk Preventive measures
Turret lathe Friction in the contact surfaces of the lathe turret Loosening of the workpiece, entanglement of the person Regular lubrication according to the manufacturer’s instructions
Drilling machine Spindle self-travels to a lower position Damage to machinery and equipment, entanglement of the person Balance the spindle lift
Planing machine Table exceeds the limits of the bed Impact with a person Protective fences, railings, expand the space dimensions
Milling machine Rotating shaft end at the back Entanglement of clothing and hair Install a protective cover

Table 3: Identifying risks for machine tools

CONCLUSION

Working with machine tools can be considered very dangerous, because every human activity associated with a complex machine or piece of equipment is more dangerous than the possibility of human error combined with technology. Every machine or piece of equipment, designed and created by humans, is made with the idea of reducing human labor. With each such new technology comes many new potential threats to humans. In machining, this trend is decreasing, because in new machine tools, the safety control equipment is fully digital, and the risk of accidents is significantly eliminated. However, the risks are never completely eliminated, because the role of the human still plays an important part. Timely identification of possible hazards and implementation of subsequent safety precautions are very important. Human health is always the most precious thing that a person can have.

B. RULES AND PROCEDURES FOR HANDLING COMMON INCIDENTS

In mechanical engineering, there are many technological fields, typically:

  • Cold working.
  • Machining.
  • Hot working.
  • Cold working

Currently, cold working is mainly done manually, with only a part of it being done on automatic and semi-automatic machines.

The main causes that can lead to accidents in cold working are:

Hand tools (such as hacksaws, files, chisels, …) can easily strike the worker.

Simple machines (small-sized presses, bench drills, grinding machines, …) have structures that are not durably built, are not synchronized, and lack safety mechanisms, …

Careless use of damaged hand tools by workers, such as hammers with loose handles, wrenches of the wrong size, wrench jaws that are deformed and no longer parallel, …

Careless or improper clamping of parts on a vise, improper arrangement of workbenches, lack of protective screens between opposing vises.

Improperly balanced mounting of grinding wheels on machines, lack of protective shields, or a standing posture while grinding that does not avoid the direction of the grinding wheel’s rotation, grinding heavy objects with strong pressure, …

Sheet metal work involves cutting and stamping operations before forming. Accidents often occur in the form of cuts to hands and feet. When operating punching and stamping machines, carelessness can lead to crushed hands, severed fingers, or even a crushed entire hand. There can also be physical exhaustion, hearing loss, headaches, dizziness, …

Incorrect posture while sawing, filing, chiseling, … in general during cold working can lead to scoliosis.

Machining

Among machining tools, lathes account for a high proportion (40%) and are used quite commonly.

The machine operates at high speed, producing a lot of continuous chips that wind into long strands and fly around. High-temperature chips and small fragments can fly into people standing opposite, causing accidents.

When operating rotating machines, with transmission mechanisms like gears, belts, …, female workers must tie their hair up neatly or cut it short to avoid it getting caught in the machine.

During drilling, the drill can slip, a loosely installed drill bit can fly out, a loosely clamped fixture can cause the workpiece to fall, … leading to accidents.

When grinding, hot metal chips can fly onto people if they are not standing in the correct position, the grinding wheel can break, an insecure grip or a short hand-holding distance can cause the grinding wheel to come into contact with the worker’s hand.

Workers’ clothing that is not the right size, is not neat, … can get caught in the machine and cause an accident.

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Hot Working

Casting Technology

At high temperatures, in addition to thermal radiation, molten iron and steel also emit high-energy ultraviolet rays.

Contact with high-energy radiation sources can cause eye inflammation and skin burns.

A common accident is being burned by molten metal splashing onto the body or because objects in contact with the molten metal are not dry, or because the casting mold has not been dried, so the moisture on these objects is rapidly vaporized by the steel, causing it to splash and burn the worker.

When removing burrs from castings, it is also easy to get scrapes on hands and feet from the rough and sharp edges.

Welding Technology

In electric welding, electrical equipment is mainly used. Arc welding usually has a very high temperature (several thousand degrees). The welding environment contains many toxic gases and dust.

In electric welding, the risk of electric shock is the most dangerous to human life.

During welding, liquid metal can splash and easily cause skin burns to the welder and those nearby.

Arc welding has strong radiation, which can easily burn the skin, cause eye pain, …

The welding arc can cause fires and explosions of surrounding objects, so the welding area should be located far from flammable and explosive materials.

The working environment of welders contains many toxic gases and dust generated from the burning of welding rods, such as CO2, F2, manganese dust, zinc oxide dust, … which are very harmful to the respiratory system and the health of workers when welding in difficult positions such as inside pipes, in cramped, damp places, at heights, …

In gas welding, using compressed gas cylinders, grease stains, and flammable substances on hoses, gas valves, … can easily cause fires, leading to cylinder explosions or fires.

Forging/Pressure Working

The workpiece in forging is processed at a high temperature (can be over 1000°C).

Accidents can occur due to high temperatures, from tools and forged parts, hot iron scales, …, flying out.

At the end of processing, the forged part is still hot, around 700°C. Accidentally touching it can cause burns.

Unsafe forging tools (hammers, tongs, …) such as a hammer with a loose handle can fly off when swung, tongs for removing the workpiece from the furnace not clamping tightly or not being held securely, … causing the hot object to fall, which can lead to an accident.

Heat Treatment Technology

Easy to get burned from contact with objects at high temperatures.

Easy to be poisoned by the heat treatment environment: sodium cyanide (NaCN), potassium cyanide (KCN), substances commonly used in carburizing and nitriding.

Electroplating Technology

In electroplating, electrolytes are used, and the chemical environment contains many harmful substances such as chromium oxide (CrO3), caustic soda (NaOH), acids, …; the workshop has a lot of electrical equipment (power supply equipment, electrolysis tanks, …)

The effect of electrolytic solutions can cause skin burns, skin damage, …

The air environment is contaminated with harmful chemical vapors.

Attention must be paid to electrical safety when operating and using high-current electrolysis equipment.

C. PRINCIPLES TO ENSURE OCCUPATIONAL SAFETY FOR USERS, OPERATORS, AND MAINTENANCE PERSONNEL IN THE MECHANICAL INDUSTRY

1. General principles

  • Must fully comply with the current occupational safety and health requirements from the design, manufacturing, installation, use, and management of machines and equipment according to specific safety technical regulations, standards, and the requirements in the machine’s documentation from the manufacturer;
  • Specifically identify hazardous areas and the risks of occupational accidents during the use of machines and equipment;
  • Fully implement appropriate safety measures;
  • The workshop layout must be organized in accordance with safety conditions:
    • Choose a suitable position and location;
    • Arrange the workshop, warehouses, and transport routes logically and conveniently;
    • Install equipment in the workshop ensuring safe conditions;

2. Safety principles for using machines and equipment

  • No one except the person in charge is allowed to start or control the machine;
  • Before starting the machine, check the safety devices and standing position;
  • Before leaving for other work, turn off the machine; do not leave the machine running unattended;
  • Turn off the power switch in case of a power outage;
  • To adjust the machine, turn off the motor and wait for the machine to stop completely; do not use your hands or a stick to stop the machine;
  • When operating the machine, wear appropriate personal protective equipment (do not wear clothes that are too long, do not wear scarves, gloves, etc.);
  • Inspect the machine regularly and before operation;
  • A “Machine Out of Order” sign must be hung on a broken machine.

3. Rules for making machines safer and more productive

  • Choose and purchase machinery where all operating procedures are completely safe;
  • Moving parts are fully guarded;
  • There is an automatic stop device or two-hand control at the operating level;
  • Use safe material loading and unloading devices to increase productivity and reduce dangers caused by the machine;
  • Fully guard the hazardous parts and areas of the machine: the guard must:
    • Be firmly fixed to the machine;
    • Guard the moving parts of the machine;
    • Not interfere with the machine’s operation and the worker’s visibility;
    • Be removable when machine maintenance is needed;
    • Maintain the machine properly and regularly;
    • Use appropriate personal protective equipment;
    • Have a complete system of signs for dangerous places and hazardous areas;
    • Ensure a safe electrical system;
    • Fully implement fire prevention and fighting measures.

D. LABOR SAFETY MEASURES FOR SOME COMMON MACHINES AND EQUIPMENT

Group 1: Safety for hot working and pressure processing trades

  1. Safety for forging and stamping trades
    • Harmful factors and common accidents in forging and stamping trades:
      • Toxic gases: CO, SO2;
      • Heat: Heat emitted from furnaces can reach 400-450°C;
      • Flying objects:
    • Hot iron oxide scales on the workpiece surface flying in all directions causing burns,
    • Broken tool fragments, workpieces flying out causing accidents.
      • The machine’s transmission parts cause pulling, rolling, clamping, cutting.
    • Measures to ensure safety in forging and stamping trades:
      • Organize the workplace reasonably;
      • Safely use equipment, mechanisms, and tools for forging and stamping (Hand hammers, forging tongs, power hammers, stamping machines, presses…: Interlocks, clutches, two-hand control mechanisms, guarding of moving parts…)
  1. Safety for the casting trade
    • Hazardous and harmful factors in the casting trade:
      • Temperature: very high at metal melting points, mold drying, removing castings…
      • Radiation from infrared and ultraviolet rays;
      • Dust: When casting with sand molds, it often contains quartz sand dust (SiO2 – free silica oxide);
      • Various toxic gases: CO, SO2…
      • Noise: from iron breaking machines, cleaning machines;
      • Radioactive rays: to determine the level of molten metal in furnaces, the height of the material column, or to detect defects in castings…
    • Measures to ensure safety in the casting trade (dust control, heat and burn protection, toxic gas protection, safety during furnace repair…).

Group 2: Safety for the welding trade in mechanical safety documents

  1. Causes and occupational accidents that occur in electric arc welding
    • Causes:
      • Electric shock: due to electricity leaking to the machine casing, damaged insulation of electrical wires;
      • Burns: from molten metal particles flying in all directions;
      • Infrared rays, ultraviolet rays;
      • Radiation from the electric arc: causing flash burns to the eyes, retinal detachment, reduced vision…
      • Toxic gases and vapors: CO, CO2, NO2 and very small metal dust particles such as iron oxide, manganese oxide, silica…
    • Safety measures:
    • Safety measures for arc welding (must wear welding goggles when working, implement ventilation, use leather or canvas gloves…);
    • Safety measures to avoid electric shock (transformers, electrical wires, electrode holders…);
    • When welding in metal tanks (cisterns), boilers, attention must be paid to: insulation, wearing full personal protective equipment, using a handheld lamp with a voltage not exceeding 12V, implementing ventilation and extraction measures…
  1. Causes and accidents in gas welding
    • Causes:
      • Explosion of a C2H2 generator, explosion of an oxygen cylinder;
      • Burns: From molten metal splashing onto a person or touching a still-hot workpiece; Poisoning from toxic gases: CO, SO2…
    • Safety measures:
      • Explosion prevention, protection against toxins and other hazards
    • Safety measures when storing and using a C2H2 generator:
      • Before use, ensure there is no air in the C2H2 cylinder to avoid forming an explosive mixture;
      • The C2H2 gas generator must be placed at least 10 m away from heat sources;
      • Be extremely careful when removing and loading calcium carbide into the generator, do not throw it forcefully to avoid causing an explosion;
      • Always monitor the water temperature in the generator and its pressure. The water level in the generator must be level with the check valve’s level and the water temperature must not exceed 80°C; the pressure must not exceed 1.5 KG/cm2;
      • The safety devices of the generator must be in good working order and accurate;
      • After finishing work, the C2H2 generation must be stopped;
      • To check for gas leaks, use soapy water; it is forbidden to use a flame for inspection;
      • After each shift, check the flashback arrestor; if water is low, it must be replenished. The water level must always be level with the check nozzle.
    • Safety measures for the welding torch:
      • The connection between the torch and the rubber gas hoses must be tight and secure, with no bulges or cracks;
      • Before lighting, slightly open the oxygen valve to blow out dust from the torch, then close the valve and open the C2H2 valve first, then open the oxygen valve. When not in use, the procedure is reversed.
      • If a pop occurs at the torch tip while welding, it indicates that the torch is too hot or a flashback is occurring. The worker must immediately close the C2H2 and oxygen valves and dip the torch tip in cold water.
      • During welding, molten metal or weld spatter can clog the torch tip. A copper wire must be used to clear it, not a hard steel wire. The C2H2 and oxygen valves must be closed when clearing the torch.
      • When welding, do not swing the lit torch forcefully or throw it hard on the ground, as this can cause an explosion or fire.
      • It is strictly forbidden to climb a ladder holding a lit torch or to weld parts near flammable structures without fire prevention measures.
    • Safety measures when using gas and oxygen cylinders:
      • When transporting or using, do not roll cylinders on the ground or carry them on your shoulder; a cart with rubber wheels must be used;
      • Do not leave oxygen cylinders in the sun or near high-temperature sources (oxygen cylinders have high pressure >150at and are prone to explosion due to increased pressure). Within a 10 m radius of the cylinder, no work that generates sparks is allowed;
      • Do not apply oil or grease to the valve threads, and if your hands are oily, do not open the pressure reducing valve;
      • At the welding site, a maximum of only two cylinders are allowed (one for use, one in reserve);
      • When welding, the oxygen cylinder should be tilted at a certain angle, not laid flat on the ground.
    • Safety measures when using a safety valve:
      • The safety valve used on pressure vessels is usually a spring-loaded type, which automatically releases when the pressure inside the vessel exceeds the specified limit. The safety valve must be sensitive and accurate to release in time when necessary. Workers must check the safety valve once a day, and once a week, recheck the pressure setting of the valve and clean it, but avoid breaking the seal as the safety valve has been adjusted to the correct pressure for the vessel.

Group 3: Safety when using machine tools in mechanical safety documents

  1. Safety for lathes
    • Common accidents on lathes: Chips flying into the eyes, burns from chips, cuts on hands and feet from chips; inhaling metal dust; clothing and hair getting caught in the machine, electric shock…
    • Safety measures when operating a lathe:
      • Preventing accidents from chips;
      • Preventing accidents from setup and inspection;
    • Safety for operations on a lathe:
      • Preventing hair, clothing from being caught by the machine…;
      • Local lighting voltage must be less than 36 volts.
    • Safety measures to note:
      • Ensuring safety when machining long parts:
      • When machining long and slender parts, under the effect of centrifugal force, the workpiece can be loosened, fly out of the clamping device, or bend like a spinning steel whip, thus potentially injuring the worker, chipping the cutting tool, or damaging parts of the equipment.
      • Therefore, if long parts on a lathe are bent, they must be straightened. If the length L/D > 12, a steady rest must be used.
      • Long bar stock turned on a turret lathe or automatic lathe up to 3 meters long must have a stock tube (guide tube). However, the guide tube does not protect the entire bar stock because the feed mechanism obstructs it. The part of the bar stock not covered by the tube protruding outwards must be covered by an auxiliary device.
    • On a lathe without a stock tube, the length of the bar stock is only allowed to protrude 0.3 meters from the back of the main spindle. If it protrudes further, it must also be safely guarded.
      • Clamping and holding the workpiece securely: 3-jaw chuck, 4-jaw chuck, and self-centering chuck, etc. Devices used to hold and support the workpiece are live centers, dead centers, and steady rests.
  1. Safety for drilling machines
    • There are many types of drilling machines: Vertical drills, radial drills, horizontal drills, multi-spindle drills, center drills, etc.
    • Common accidents on drilling machines:
      • The fast-rotating parts of the drilling machine such as the spindle, chuck, and drill bit can all entangle hair, clothing, or cut a worker’s hands;
      • When drilling ductile materials, stringy chips will appear. These chips, rotating with the drill bit, can fly into the face or scratch the worker’s hands.
      • If the workpiece is not clamped tightly, it will fly out and hit the worker.
    • Safety measures for workers when drilling:
      • Guard the moving parts;
      • When operating a drilling machine, the worker must wear neat personal protective equipment, sleeves must be buttoned, a hat must be worn, and absolutely no gloves should be worn when drilling;
      • Carefully check the Morse taper of the drill bit; if the taper is scratched or worn, it must be discarded because when installed, the taper will not be clamped tightly, and the drill bit can easily fly out, causing an accident;
      • When drilling ductile materials, stringy chips will form. These chips divide into two strands rotating around the drill bit at the same speed as the drill bit. These chips have sharp edges and can easily fly into the face or hands of the worker. Do not get your eyes close to check the machined surface, and do not put your hands in the turning radius of the stringy chips. Measures must be taken to break the chips. When drilling, occasionally stop the drill feed to break the chips or grind chip-breaking grooves on the drill bit beforehand;
      • When drilling small parts, a vise must be used to clamp them tightly or specialized fixtures must be used. Do not use your hands to hold the part being drilled;
      • Before drilling, check the stability and clamping force of the workpiece. If not, during drilling, the part will be loosened, shift, and rotate with the drill bit. On the other hand, if you hold the part with your hands, your hands are likely to be injured, or if you hold the workpiece tightly, the drill bit may break and the workpiece may fly out, causing an accident;
      • Local lighting voltage must be less than 36 Volts.
  1. Safety for milling machines
    • Common accidents on milling machines:
      • When milling, the milling cutter rotates while the workpiece moves in a straight line. The danger when working on a milling machine is caused by the milling cutter and the chips created when the machine is working; milling machine operators are often injured in the hands. When high-speed milling, workers can be injured in the eyes and sometimes even burned because the stream of chips has a very high velocity and high temperature, flying in all directions.
    • Safety measures for workers when operating a milling machine:
      • Preventing accidents from chips;
      • Preventing accidents from the milling cutter;
      • Preventing accidents from the machine’s transmission parts;
      • Preventing accidents from setup.
      • To prevent the above accidents, the guards must satisfy:
    • Preventing the worker from coming into contact with the hazardous area of the machine,
    • Ensuring that chips operate freely,
    • Allowing for the convenient use of various types of milling cutters without complex machine adjustments,
    • Not causing difficulties in changing the cutter,
    • Allowing for easy and convenient observation of the working cutter,
    • Not obstructing the application of coolant.
      • Local lighting voltage must be less than 36 volts.
  1. Safety for planing machines
    • There are many types of planing machines: planers and shapers. Safety conditions on a planing machine depend on the layout of the equipment and the organization of the workplace. If not arranged correctly, a shaper can crush a worker against a wall or column or hit them in the head, causing injury. Therefore, when arranging and installing the machine, it must be ensured that the distance from the most protruding point of the machine (at the end of the longest stroke) to the wall or column of the workshop is still sufficient for the worker to walk around easily. This distance must be at least 500mm. At the end of the machine table’s stroke, a movable stop painted bright red must be placed.
    • Planers and shapers must have travel limit stops. It is forbidden to cross in front of the machine’s path of motion.
    • Safety measures for workers when operating a planing machine:
      • Preventing accidents from chips;
      • Preventing accidents from the planing tool;
      • Preventing being clamped by the machine and during operations while the machine is running;
      • Local lighting voltage must be less than 36 volts.
  1. Safety for grinding machines
    • Grinding machines are divided into 2 main types: universal grinders and specialized grinders. Universal grinders include external cylindrical grinders, internal grinders, surface grinders, and centerless grinders. Specialized grinders include gear grinders and cutting tool grinders.
    • The use of a grinding machine can machine parts with high accuracy and surface finish and with little material waste. Grinding can machine hardened steel and relatively hard materials.
    • Characteristics of a grinding machine are:
      • The rotational speed of the machine is very fast, reaching up to 50m/s;
      • A lot of dust is generated during grinding;
      • Grinding wheels are made of very small, hard material particles, bonded together with adhesives. The compressive strength of the wheel is very good, but the tensile strength is too weak, making it easy to break. Grinding wheels cannot withstand vibration and impact loads. Humidity and temperature also affect the strength of the wheel.
    • Common accidents on grinding machines:
      • Metal dust and wheel dust flying in all directions can get into the worker’s eyes or pollute the air, easily entering the lungs and leading to pneumoconiosis;
      • While grinding by hand, the worker’s hand may touch the grinding wheel, causing injury;
      • Fragments of the grinding wheel can cause injury to the worker who is grinding or people working nearby.
    • Safety and hygiene equipment on a grinding machine includes:
      • Wheel guard;
      • Work rest, dust shield;
      • Dust extraction equipment.
    • Safety measures for workers when operating a grinding machine:
      • Preventing accidents from grinding wheel breakage;
      • Preventing accidents from metal filings and wheel particles:
    • Machine placement;
    • Wheel selection;
    • Wheel installation;
    • Work rest and the gap between the wheel and the work rest;
    • Grinding posture;
      • Local lighting voltage must be less than 36 Volts.

Specific safety measures:

  • The machine must be placed in an area with little foot traffic, away from flammable materials. The open part of the wheel should face the wall;
  • A suitable grinding wheel must be chosen;
  • Before grinding, recheck the grinding wheel guards and the parts of the machine that can easily cause accidents; check the balance of the wheel and that it is securely clamped;
  • Let the machine run without load for 3 to 5 seconds; when the machine is running stably, then start grinding;
  • When grinding, introduce the workpiece slowly, do not press hard, move it evenly. For large workpieces, do not use a small wheel to grind, do not grind on the two cylindrical faces of the wheel;
  • The rotational speed of the wheel should not exceed the speed indicated on the wheel. If the speed is too high, the wheel will vibrate strongly, the centrifugal force will be large, and it will be easy to break the wheel;
  • Workers must wear full protective equipment such as glasses, masks, etc., and not stand opposite the wheel when grinding;
  • For a two-wheel grinder, the diameter of the two wheels should not differ by more than 10%. When the wheel is worn down close to the clamping flange, 2 to 3 mm from the edge of the flange, a new wheel must be replaced;
  • The grinder must have a sturdy work rest and wheel guard. The gap between the wheel and the side wall of the guard should be between 10 -:- 15 mm. The gap between the wheel and the work rest should not be greater than 3 mm. The opening angle of the guard should be as small as possible;
  • On both sides of the wheel, there must be clamping flanges with the same thickness and diameter. Between the wheel and the clamping flange, there must be an elastic washer (thick paper, cardboard, or leather);
  • The work rest must be adjustable to ensure that the workpiece lies in the horizontal plane, passing through the center of the grinding wheel or slightly higher, but not more than 10 mm;
  • When grinding with cooling water, the water must be poured over the entire working surface of the wheel. When stopping work, the cooling must be stopped and the wheel must be dried./.

E. REGULATIONS FOR OWNERS, USERS, AND EQUIPMENT MANAGERS ACCORDING TO VIETNAMESE REGULATIONS AND STANDARDS

QCVN 09: 2012/BLĐTBXH – National Technical Regulation on Occupational Safety for Hand-held Motor-Operated Electric Tools

1. Regulations on labor safety management in the production, import, circulation, and use of hand-held electric tools.

  • Regulations ensuring the safety of hand-held electric tools in production and import before being placed on the market.
  • Manufacturers and importers of hand-held electric tools must implement the following quality management requirements:
    • Apply a quality management system to ensure the quality of the hand-held electric tools they produce or import conforms to the declared applicable standard.
    • Declare the applicable regulation.
    • The manufacturer or importer shall self-declare the basic characteristics, warning information, and the number of the applicable standard on the hand-held electric tool or in one of the following forms:
      • On the tool’s packaging;
      • On the tool’s label;
      • In the documentation accompanying the tool.
  • Regulations ensuring the safety of hand-held electric tools circulating on the market
    • Comply with the corresponding technical standards during the circulation of hand-held electric tools;
    • Self-apply quality control measures during the circulation of hand-held electric tools.
  • Regulations ensuring the safety of hand-held electric tools in use
    • Storage and transportation
      • Must be stored in a dry place and according to the storage conditions stated in the hand-held electric tool’s documentation.
      • The storage place for hand-held electric tools must have shelves or racks to place the machines. It is forbidden to stack hand-held electric tools on top of each other without packaging.
      • When transporting hand-held electric tools, attention must be paid to protective measures to avoid damaging the tools.
    • Preparing hand-held electric tools before work
      • Each time a hand-held electric tool is handed over to a user, the person handing it over and the user must check the following items together:
        • Check the completeness and the tightness of the joints, attachments, and connections of the hand-held electric tool’s parts.
        • Visually inspect the external parts of the machine (check the power cord, cord protector, plug, insulation of the casing, handle, carbon brush covers…).
        • Check if the circuit breaker works decisively.
        • Check the no-load running.
        • For Class I hand-held electric tools, the protective grounding circuit of the machine must also be checked.
    • Do not issue or put into use hand-held electric tools that are found to have even minor damage, do not meet safety standards, or have passed their periodic inspection date.
  • Regulations ensuring safety when operating hand-held electric tools.
    • Only persons who have been trained in electrical safety and the use of hand-held electric tools, and have been issued a safety card, are allowed to use the tools.
    • Only operate hand-held electric tools that meet the provisions of this regulation.
    • Each hand-held electric tool must have its own logbook. The person responsible for the storage and repair of the tool must record the results of periodic inspections, maintenance, and repairs.
    • Keep the workplace tidy and well-lit while using hand-held electric tools.
    • Do not operate hand-held electric tools in flammable or explosive environments (environments with flammable liquids, gases, dust, or environments containing substances that can damage the insulating structural parts of the tool).
    • In environments with dripping water, or outdoors during rain or fog, do not operate tools that are not of a splash-proof or water-resistant design.
    • Do not allow children and unauthorized persons to come near when operating a hand-held electric tool.
  • Regulations ensuring electrical safety
    • The plug of the hand-held electric tool must fit the socket. The plug must not be modified in any way. Do not use any adapter plugs for earthed hand-held electric tools.
    • When operating Class II hand-held electric tools, additional personal protective equipment must be used (insulating gloves, insulating boots, insulating mats..).
    • Do not let your body come into contact with earthed or grounded surfaces.
    • Do not misuse the power cord. Do not use the power cord to carry, pull, or unplug the hand-held electric tool. Keep the power cord away from heat, oil, sharp edges, or moving parts.
    • When operating a hand-held electric tool outdoors, use an extension cord suitable for outdoor use.
    • If it is necessary to operate a hand-held electric tool in a damp location, a residual current device (RCD) must be used to protect the power supply.
    • Attention must be paid to protecting the flexible cable supplying power to the hand-held electric tool to avoid abrasion of the insulation, and to prevent the cord from getting oily or coming into contact with hot objects.
    • The connection of electrical equipment serving the hand-held electric tool (such as transformers, frequency converters…) to the power grid and their disconnection from the grid must be carried out by a person with electrical expertise.
    • Periodic tests must be conducted for hand-held electric tools and their accompanying accessories (transformers, frequency converters, protective circuit breakers, power cords…) at least once every 6 months. The content of the periodic test includes:
      • External examination.
      • Measurement of insulation resistance with an insulation resistance tester; the insulation resistance must not be less than 2MΩ.
      • Checking the protective circuit.
  • Regulations ensuring safety against mechanical hazards
    • The use of stimulants is prohibited while operating a hand-held electric tool.
    • Use appropriate personal protective equipment when operating a hand-held electric tool, such as a dust mask, non-slip safety shoes, a hard hat, hearing protection, and eye protection.
    • Be careful to prevent unintentional starting of the hand-held electric tool. Ensure that the switch is in the off position before connecting to the power source for use.
    • Ensure that all wrenches or repair tools have been removed from the hand-held electric tool before operating it.
    • Do not overreach when using a hand-held electric tool. Keep your body in a balanced position at all times during operation.
    • If the equipment is fitted with provisions for connection to a dust extraction and collection facility, ensure that they are connected and used correctly.
    • For hand-held electric tools with a mass greater than 10kg, a device must be provided for lifting and suspending the tool during work.
    • Do not force a hand-held electric tool to perform a job it was not designed for. Use the correct hand-held electric tool for each job.
    • Do not use a hand-held electric tool if the switch does not turn it on and off.
    • Disconnect the power source before making any adjustments, changing accessories, temporarily stopping work, or storing the hand-held electric tool.
    • Store hand-held electric tools out of the reach of children, and do not allow persons untrained in the safety of hand-held electric tools to operate them.
    • Only use the hand-held electric tool, accessories, and parts of the tool for jobs that are consistent with the tool’s function and according to the manufacturer’s instructions, taking into account the working conditions and the job to be performed.
    • When using a hand-held electric tool, pay attention to the requirements stated in the tool’s user manual, maintain the tool carefully, do not let it be subjected to impact, overload, or the effects of dirt, grease, and do not allow dripping water, rain, or other liquids to splash onto tools that do not have moisture protection.
  • Repair and Maintenance
    • The user of a hand-held electric tool must regularly inspect, maintain, and keep a record of the work the machine has done. If it is damaged, the hand-held electric tool must be repaired before use; the tool must be cleaned after use. After repair, each tool must be re-tested according to the corresponding standard of the TCVN 7996 part 2 series (IEC 60745-2).
    • Hand-held electric tools must be maintained by a trained repair person and only identical replacement parts should be used.

PART 5: EQUIPMENT MAINTENANCE AND SERVICING REGULATIONS

In modern construction conditions, which are characterized by an increasingly high level of mechanization of technological processes, the correct determination of the required number of vehicles and machines is of great significance because the conditions of use, the volume of work, and the construction schedule often change and depend on many different factors.

When determining the need for vehicles and machines, attention should be paid to the possibility of enhancing synchronized mechanization; the potential of existing vehicles and machines must be fully utilized, and the efficiency of construction and installation must be increased.

In the following cases, we need to determine the demand for vehicles and machines:

when preparing the annual synchronized mechanization plan for general corporations or construction companies

when preparing the investment plan for mechanization enterprises

to ensure supply for subsidiary enterprises;

when preparing the construction plan for each specific project.

The principle for determining the demand for vehicles and machines is the same in all the above cases, but in the last case, the given data for calculation must be consistent with the specific conditions of the project and the volume of work within a specified period. In other cases, norms and practical experience can be used depending on the scale of the calculation.

The demand for vehicles and machines depends on a series of factors: the concentration level of the construction project, the volume and duration of construction, the method of construction organization, construction conditions, weather and climate conditions, the condition of the vehicles and machines, the structure of the machine fleet, the level of maintenance and repair, the professional level of the operating workers…

The average annual productivity of a machine, Nyr, is calculated based on its hourly productivity and the number of working hours in a year.

Nyr = Nhr . T

Where: T – the actual useful working time of the machine

Nhr – hourly productivity.

Calculating the number of additional vehicles and machines by each type for an operating fleet is based on the formula:

M1 = ( M – M2 ) k + M3 + M4

Where: M1 – the number of additional machines needed

M2 – the number of existing machines at the time of calculation

M3 – the average number of machines retired annually due to wear and tear M4 – the number of machines to be replaced due to obsolescence

k – a coefficient that accounts for the regular supply of vehicles and machines throughout the year.

Labor safety in the use of construction machinery

Labor safety is of great significance in protecting human lives, machinery, construction progress, and labor productivity. Mechanized construction, in some respects, already implies a concern for labor safety because people are not in direct contact with the construction objects (earth, rock, heavy lifted materials…), so fewer accidents occur. However, this does not mean that labor safety techniques should be disregarded when using construction machinery. Practice has shown that safety incidents involving construction machinery have led to more severe consequences than those in manual construction. Sometimes, they result in the loss of hundreds of lives, cause billions of dong in damage, and sometimes even lead to the suspension of entire construction projects in progress.

Labor safety must be considered in all stages, from managing the construction plan, and organizing the construction, to operating, maintaining, and repairing the machinery.

In general, when designed and manufactured, machinery has been calculated with a certain durability, stability, reliability, and lifespan, and is also equipped with many safety devices for the mechanisms and the entire machine, such as height limits, maximum load limits, speed limits, working travel limits, etc. However, in reality, due to a lack of understanding of the technical features of the machinery or disregard for safety procedures and regulations in machine operation, damage is caused to people and machines. Therefore, it is necessary to constantly educate and remind machine operators to strictly adhere to the following general labor safety regulations:

  1. All machinery, whether new or old, must be thoroughly inspected for its technical condition before being put into use, according to the requirements stated in the user manual. Special attention should be paid to safety mechanisms such as brakes, self-locking mechanisms, travel limit mechanisms, etc. If there are any damages, they must be repaired promptly before the machine is brought to the construction site.
  2. Only workers who have been trained in schools and have sufficient certificates, licenses, skill levels, a relatively good understanding of the features and structure of the machine, and have been trained in safety techniques for using the machine are allowed to operate it. Drivers who are found to be working carelessly or unsafely should be replaced immediately.
  3. Machine operators and assistant operators must be fully equipped with personal protective equipment for each trade and each machine, such as glasses, helmets, clothing, gloves, boots, and other safety tools.
  4. All other moving parts of the machine, such as rotating shafts, chains, belts, clutches, etc., need to be carefully guarded in positions where they could cause accidents to people.
  5. Regularly inspect, clean the machine, apply oil and grease, and make minor adjustments and repairs to parts, especially safety parts, to eliminate the possibility of machine damage.
  6. The machine must be operated and tasks performed according to the designated construction route, the sequence of construction, and other technical safety regulations set forth by the construction and labor safety engineers.
  7. During breaks, the possibility of the machine starting automatically must be eliminated. The starting mechanism should be locked and braked. The machine should be parked in a safe place, and it is necessary to chock the wheels to prevent it from rolling or tipping over.
  8. Stationary machines need to be installed securely and reliably on a machine base and on the ground where the machine stands. The place where the machine stands must be dry, clean, and not slippery, to prevent labor accidents.
  9. Machines operating at night or in bad weather with fog must use their own lighting in the front and back with a system of headlights and signal lights, even if there is a general lighting system.
  10. When moving the machine over a long distance, safety regulations for moving machinery must be adhered to, such as securely tying the machine to a trailer, ensuring road conditions, clearance, etc.

The above are general safety regulations for construction machinery. In addition, each machine has specific, detailed regulations that must be fully implemented when the machine is put into use.

For officials in charge of managing vehicles and machines, the organization of vehicle and machine management must also comply with the following provisions:

  1. To ensure safety at work, all vehicles, machines, and means of transport must be in good condition and their technical condition checked before use. For lifting and transport machinery, air compressors, and boilers, they must be approved by the state inspectorate. Vehicles and machines must be accepted according to rules and regulations before being put into use.
  2. When designing the construction technology organization, the workplace must be prepared in a way that fully ensures safety at work. Any practice of chasing productivity or simple planning without paying attention to safety must be prohibited, stopped in time, and strictly handled.
    • At all dangerous places on the construction site and in the factory, there must be warning signs.
    • Every workplace must be prepared so that workers are not threatened by the moving parts of machines, materials, and from other machines working together.
    • The driver’s seat or workplace must be convenient, stable, easy to observe, protected from rain and sun, have sufficient lighting, and a wiper system. The workplace must be guarded, sufficiently wide, and have handrails.
  3. Before putting a machine into operation, it is necessary to determine the travel route, parking place, position, grounding method for electrical machines, and establish a method of communication by signals between the driver and the signal person.
    • The meaning of the signals during work or when the vehicle is moving must be communicated to all persons involved in the machine’s work.
    • Moving, parking, and working near foundation pits, trenches, ditches… with unstable slopes must be within the permissible distance specified by the construction plan.
  4. Technical maintenance may only be carried out when the engine has completely stopped, the pressure from the pneumatic and hydraulic systems has been released, and in cases specified by the manufacturer.

When maintaining electrically driven machinery, electrical safety measures must be applied. At the switch boxes, a sign must be hung that reads: “Do not close the switch – electrician at work,” at which time the fuse in the electric motor circuit must be removed.

Machine assemblies that can move under their own weight must be chocked or placed on supports during maintenance.

Do not use open flames in the fueling area, nor use machinery that is leaking oil or fuel.

The disassembly and assembly of the machine must be carried out under the supervision of a responsible person and must follow the manufacturer’s instructions.

The disassembly (assembly) area must be cordoned off or marked with safety signs accompanied by warning signs.

During the organization, management, and use of construction machinery, the provisions in the “Vietnam Standard on safety in the use and repair of machinery” (TCVN – 4587 – 85) must be fully implemented. Only by doing so can the legality of organizing construction and maintaining construction machinery be ensured.

To select a more reasonable method or plan for mechanizing a project, it is necessary to compare the economic and technical indicators of using different mechanization means under given conditions. The criteria for evaluation include cost, labor consumption per product, and construction pace.

To determine the above efficiency indicators, the following sequence should be followed:

  1. Determine the primary machine for construction.
  2. Determine the type and quantity of auxiliary machines to ensure the synchronized execution of a given volume of work within the planned period.
  3. Establish the necessary data to determine the efficiency indicators of the machine’s performance:
    • a) composition of the worker team serving the machine
    • b) labor costs for disassembling and assembling the machine
    • c) necessary data to determine the cost of one machine-hour, one machine-shift
    • d) the operational productivity of a surveyed machine set.

PART 6: Further Reference

1. Safety training service for group 3 certification

Occupational Safety Training for Group 3

Occupational Safety Training for Group 3

99,000 ₫

2. Group 3 labor safety test

3. Price list for labor safety training services

4. Download document

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