As the New Year approaches, there is a rush to meet deadlines and accelerate progress, resulting in a high incidence of accidents! 119 Rules for Construction Safety
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As the New Year approaches, there is a rush to meet deadlines and accelerate progress, resulting in a high incidence of accidents! 119 Rules for Construction Safety 1: Scaffolding 1. What is the function of the diagonal bracing on a scaffold? Answer: It prevents longitudinal deformation of the scaffold and enhances its overall stiffness. 2. What are the safety regulations when there are external power lines on the outside of the scaffold? Answer: It is strictly prohibited to construct ramps for ascending and descending the scaffold on the side where external power lines are present. 3. Can the scaffold be connected to the unloading platform? Answer: No, the unloading platform should be installed separately. 4. Which steel pipes are not allowed to be used in the construction of scaffolds? Answer: Steel pipes that are severely corroded, crushed, bent, or cracked. 5. Which types of fasteners must not be used? Answer: Those with cracks, deformation, shrinkage, or loose threads must not be used. 6. What sign should be hung on the unloading platform? Answer: A sign indicating the maximum load capacity. 7. What is the general maximum height at which a portal scaffold should be erected? Answer: It should not exceed 45 m. 8. Is it correct to state that when extending the load-bearing steel wire rope and the safety rope of a hanging basket, no fewer than three rope clamps should be used? Answer: No, because neither of these two types of steel wire ropes should be extended for use. 9. What are the safety requirements for the overall lifting frame during lifting? Answer: It is strictly prohibited to stand on the frame body during lifting. 10. What are the main safety devices of an overall hoist? Answer: Fall prevention devices and overturning prevention devices. 11. What safety devices must a suspension basket scaffold be equipped with? Answer: brakes, travel limits, safety locks, anti-tilt devices, and overload protection devices. 12. What are the requirements for the counterweights of suspension basket scaffolds? (1) Appropriate counterweights must be installed on the suspension mechanism of the suspension basket or on the roof trolley ； (2) The counterweights shall be installed accurately and firmly at the designated positions, and sufficient mass of counterweights shall be used as specified in the drawings; they must be verified by a safety inspector before the suspension basket can be put into use ； (3) The overturning resistance coefficient is equal to the ratio of the counterweight moment to the forward tipping moment, and this ratio shall be not less than 2. 13. How much above the roof surface should the top of the scaffold poles be? Answer: The top of the poles should be 1 meter above the upper edge of the parapet wall, and 1.5 meters above the upper edge of the eaves. 14. Can a scaffold made of a combination of steel and bamboo be used? Why? Answer: It cannot be used. The basic requirement for scaffolding is that it remains stable, without shaking or deforming, under overall stress. The joints of the members are crucial for force transmission; however, in mixed-type scaffolds, the lack of reliable binding materials leads to loose joints, causing the scaffold structure to deform and failing to meet the stress requirements of a scaffold. 15. At which stages should the scaffolding and its foundation be inspected and accepted? (1) After the foundation is completed and before the scaffolding is erected ； (2) Before applying a load on the working layer ； (3) After each erection to a height of 10–13 m ； (4) After severe winds of force 6 and heavy rain, in cold regions once thawing begins ； (5) After reaching the designed height ； (6) Out of service for over a month. 16. What protective equipment should personnel involved in scaffolding construction wear? Answer: Wear a safety helmet, use a safety belt, and wear anti-slip shoes. 17. During the use of the scaffolding, which members must not be removed? Answer: (1) The longitudinal and transverse horizontal bars at the main joints, as well as the longitudinal and transverse ground bars ； (2) Wall connectors. 18. What qualifications are required for those who work on scaffold construction? Answer: Persons involved in scaffold construction must be professional scaffolders who have passed the assessment in accordance with the current **standard, namely the ‘Rules for the Safety and Technical Assessment of Special-Type Workers’. Those working in this field should undergo regular medical examinations, and only those who pass such examinations may work with a valid certificate. 19. What are the requirements regarding the installation of diagonal bracing for portal steel tube scaffolds as specified in the \"Safety Technical Specifications for Portal Steel Tube Scaffolds in Building Construction\"? (1) When the height of the scaffold exceeds 20m, diagonal bracing should be installed continuously on the outside of the scaffold ； (2) The inclination angle of the diagonal bracing bars relative to the ground should be between 45 degrees and 60 degrees, and the width of the bracing bars should be between 4 and 8 meters ； (3) The diagonal bracing should be fastened to the vertical members of the frame using fasteners ； (4) If lap joints are used to extend the diagonal braces, the lap length should not be less than 600 mm, and the lap joint should be secured with two fasteners. 20. What are the requirements regarding the deviations in the overall verticality and levelness of a portal scaffold during its installation? Answer: The allowable deviation for verticality is 1/600 of the scaffold’s height plus or minus 50 mm ； The allowable deviation for levelness is 1/600 of the scaffold length plus or minus 50 mm. 21. What are the requirements regarding the loads on building scaffolds and decorative scaffolds? Answer: The load on building scaffolds should not exceed 270 kg/m2, while that on decorative scaffolds should not exceed 200 kg/m2. 22. What anti-slip measures should be taken for A-frame ladders? Answer: They should have sturdy hinges and straps to prevent them from spreading open, and anti-slip measures must be employed when using them on slippery surfaces. 2. Foundation pit support 1: At what depth does a foundation pit require a specialized support design? Answer: 5m. 2. What are the regulations regarding loads at the edge of the excavation site during its construction? Answer: Generally, it is required that the height of the loads at the edge of the excavation does not exceed 1.5 m, and the distance from that edge should be greater than 1.2 m. 3. What should be done in case someone suffers poisoning during work underground? Answer: People on the surface must not descend to carry out rescue efforts; instead, air must first be supplied underground. Those who go down for rescue need to wear personal protective equipment, and someone should inform the site supervisor as well as the relevant health authorities. If the conditions at the scene are not suitable for rescue, it is necessary to call 119, 110, or 120 immediately for help. 4. What are the factors that affect slope stability? Answer: (1) The type of soil has an impact ； (2) Effect of soil moisture level: When the soil contains a lot of water, the slope is prone to instability ； (3) The influence of the climate makes the soil soft ； (4) The effect of additional external loads on the slope. 5. What is the sequence for manual earth excavation? Answer: It should be carried out in layers from top to bottom; the method of excavating under the base is prohibited. When piling soil and materials at the edges of ditches and pits, they should be kept at least 1.2 meters away from the edge, with a height not exceeding 1.5 meters. 6. What are the main causes of collapse accidents during foundation pit excavation? Answer: (1) Insufficient slope gradient for foundation pit excavation ； (2) Overloading at the top of the foundation pit slope or landslides caused by vibrations ； (3) The application method is incorrect, and the excavation procedure is wrong ； (4) Excessive high excavation ； (5) Incorrect installation or removal of supports ； (6) Inadequate drainage measures. 7. When multiple machines are used to dig foundation pits simultaneously, what distance of 10 meters should exist between them to ensure safety? Answer: It should be 10 meters. 8. When excavating soil, should the excavation be carried out from top to bottom or from bottom to top? Answer: Excavation should be done from top to bottom. 9. When digging soil manually, what should be the spacing between workers? Answer: When digging soil manually, the horizontal spacing between workers should be more than 2 meters, and the vertical spacing should be more than 3 meters. 10. How many common slope protection methods are used during construction, and what are the various forms of support used for slope walls? Answer: To ensure the safety of earthwork operations, the common slope protection methods include covering, netting, and soil bag stabilization. Common support forms for pit walls include lining plate type, cantilever type, tie-rod type, bolt type, and diagonal bracing type. 11. What necessary investigations and surveys should be carried out before carrying out earthwork? Answer: Geological, hydrological conditions, as well as underground cables, pipes, and other facilities. 3. Protection for “three treasures” and “four openings”1. For buildings taller than how many meters should a double-layer protective shed be erected? Answer: Greater than 24m. 2. How often should a seat belt be checked after several years of use? Answer: Two years. 3. What do “the Three Treasures” and “the Four Families” refer to? Answer: The “three treasures” refer to safety helmets, safety belts, and safety nets ； “The “four openings” refer to stairways, elevator shafts, reserved openings, and passageways. 4. What precautions should be taken when using it safely? (1) The length of the safety belt used by scaffolders is limited to 1.5–2 meters. (2) It should be hung vertically, with the higher part used for lower-level applications ； When used in a horizontal suspension position, be careful of swinging collisions ； It’s not advisable to use it in a position that requires too much effort ； Ropes should not be knotted for use ； To prevent the knot from breaking under stress ； The hook should not be attached directly to unstable objects or to non-metallic ropes, in order to prevent the rope from being cut. 5. Which types of shoes are prohibited for working at heights? Answer: Shoes with hard soles or nails that cause slipping are prohibited. 6. What kinds of diseases prevent a person from engaging in work at heights? Answer: Those suffering from hypertension, heart disease, anemia, epilepsy, or other conditions that make them unsuitable for working at heights shall not engage in such work. 7. How to make good use of the three essential safety tools? (1) Upon entering the construction site, one must wear a standard-compliant safety helmet and fasten the chin strap ； (2) Anyone working at a height of more than 2 meters must first fasten their safety belt. (3) A close-mesh safety net shall be hung on the outside of the scaffolding, and a safety net shall be installed in the elevator shaft every 2 floors or at intervals of no more than 10 m. 8. **What are the three permanent markings required for safety helmets according to standards?** Answer: (1) Manufacturer’s name and trademark, model number ； (2) Year and month of manufacture ； (3) License number. 9. What does working at heights refer to? Answer: Any work carried out at a height of 2 meters or more above the reference level for falling (including 2 meters), where a fall is possible, is referred to as work at height. 10. When the height is 15m, what is the falling radius in meters? Answer: 3m. 11. What protective measures should be taken for work at openings? (1) For holes smaller than 1.5m×1.5m, a continuous steel rebar mesh should be embedded or a fixing cover plate should be installed. (2) For openings larger than 1.5m×1.5m, two protective railings must be installed around them, and a safety net must be laid beneath the opening. (3) Protective railings or fixed gates shall be installed at the elevator shaft openings, and safety nets shall be installed in the elevator shaft every two floors or at intervals of no more than 10 m. (4) A safety shelter should be erected above the access routes at the construction site. 12. What facilities must be installed at construction sites in public areas? Answer: Clear signs and safety fencing must be installed. 13. **Which colors are the designated safety colors?** Answer: The safety colors are: red, blue, yellow, green. 14. What climate conditions prohibit outdoor work at heights? Answer: Outdoor work at heights is prohibited in conditions of winds above level 6, thunderstorms or heavy rain, snowstorms, and fog. 15. What components does a safety helmet consist of? Answer: Hat shell, hat lining, chin strap. 16. When carrying out bitumen pouring work, what is the minimum distance in meters that the bitumen pouring station should be from roads frequented by pedestrians? Answer: 5m. 17. What measures should be taken at the openings left in concrete floor slabs to prevent accidents caused by the collapse of such openings? Answer: Solid covers, protective railings, safety nets, or other fall prevention measures must be installed. 18. In situations with a tight deadline and heavy workload, can non-electricians connect wires by themselves? Answer: No. 19. What are the “five edges” in construction work? Answer: “Five edges” refer to: the perimeter of balconies that still lack railings, the perimeter of levels without external scaffolding protection, the perimeter of floors where framing work is being carried out, the sides of upper and lower runways as well as ramps, and the sides of material unloading platforms. 20. What are the requirements for wearing a safety helmet? Answer: (1) A safety helmet consists of a lining and a shell; the lining and the shell should not be in close contact with each other – there should be a certain gap between them. When materials fall on the helmet’s shell, the lining can act as a buffer, preventing damage to the cervical spine. (2) The lower chin strap must be fastened tightly; when a person falls, the safety helmet, being worn on the head, provides protection for it. 21. What measures should be taken at night in hazardous areas of the construction site? Answer: A red light should be installed as a warning. 22. What precautions should be taken when using tools during work at heights? Answer: Tools used for working at heights should be placed in toolboxes or tool bags. Commonly used tools should be attached to the body with straps, while necessary materials or other tools must be transferred using strong and sturdy ropes; it is forbidden to throw them back and forth by hand to avoid them falling and causing injury. After the work is completed, all tools used should be counted and taken back to prevent them from being left at the work site and potentially causing harm. 23. During building installation, if work is being carried out on both upper and lower floors simultaneously, what measures must be taken to allow workers to work below the same vertical line? Answer: A dedicated protective panel or other isolation measures must be installed between the upper and lower layers.
4 Vertical Mechanical Transportation 1: What safety protection devices should an external elevator have? Answer: Brakes, speed limiters, door interlock devices, upper and lower limit devices. 2. What signs should be displayed on outdoor elevators? Answer: Signs indicating the load capacity and number of passengers should be displayed. 3. What safety protection devices should an overhead material lift have? Answer: Safety stop device, rope break protection device, over-height limit device, lower limit switch, buffer, overload limiter. 4. What should be the maximum free height at the top of the derrick lifting frame structure in meters? Answer: It must not be greater than 6m. 5. What is the minimum number of wire rope clamps required for the derrick wire rope? Answer: It must be no less than 3. 6. What safety signs should be hung next to the derrick? Answer: A warning sign that reads “Passenger carrying is strictly prohibited.” 7. How many turns should the wire rope have on the drum? Answer: Not less than 3 rounds. 8. What types of safety protection devices should a derrick hoist have? Answer: (1) Safety anchoring device ； (2) Floor entrance protection door ； (3) Safety door of the suspension basket ； (4) Feeding port protection canopy ； (5) Upper limit limiter ； (6) Emergency power-off switch ； (7) Signal device. 9. What are the requirements for the foundation of low-rise elevators? Answer: (1) The bearing capacity of the compacted soil layer is not less than 80 MPa ； (2) Pour C20 concrete with a thickness of 300 cm ； (3) The base surface should be flat, with a levelness deviation of no more than 10 cm. 10. What should be the safety buffer distance for material lifters? Answer: 3m. 11. What should be the distance between the first guide pulley of the derrick and the winch? Answer: For winches with slotted drums, the width is 15 times that of the drum ； For winch drums that are grooveless, the diameter is 20 times the width of the drum. 12. What is the “Ten No-Lifts” principle? Answer: (1) Lifting is not permitted if the weight of the load exceeds the range allowed by the mechanical properties of the equipment ； (2) Do not lift if the signal is unclear or inaccurate ； (3) Lifting is not allowed if there are people standing under the load ； (4) No one is allowed to stand on the lifted load ； (5) Items buried underground must not be lifted ； (6) Tensioning and pulling devices shall not be used for lifting ； (7) If the scattered items are not securely tied, lifting is not allowed ； (8) Loose items must not be lifted without being placed in containers ； (9) Lifting is not permitted if the weight of the load is unknown or if the lifting gear does not meet the specified requirements ； (10) Lifting is not permitted in conditions of strong winds of level 6 or above, heavy fog that impairs visibility, or heavy rain and snow. 13. What are the categories of command signals for lifting operations? Answer: Gesture signals, flag signals, and sound signals. 14. By what percentage of the original height should the wear at the cross-section where the hook is attached to the rope be before it needs to be discarded? Answer: Anything exceeding 10% of the original height should be scrapped. 15. What are the key items to check before operating a tower crane? Answer: (1) The appearance of the mechanical structure – all transmission mechanisms should be in normal condition ； (2) The oil levels in each gearbox and hydraulic tank shall meet the standards ； (3) The connection bolts in the main areas should not be loose ； (4) The wear condition of the steel wire rope and its winding around the pulley shall comply with the regulations ； (5) The power supply cable shall be free of damage. 16. Can a crane lift an object over a person’s head? Answer: No, it is prohibited to lift objects so that they pass over a person’s head. 17. What are the main responsibilities of a signalman for lifting equipment? Answer: During the lifting process, provide appropriate signal instructions to the operator to ensure the lifting work proceeds smoothly. 18. What are the “four limits and two safeguards” for the safety devices of tower cranes? Answer: Four types of limits: torque limit, overheight limit, luffing limit, and traveling limit devices. Two types of safety devices: hook safety device and drum safety device. 19. What are the causes of tower crane accidents? Answer: (1) Operating without a license ； (2) Overload operation ； (3) Incorrect command signals, resulting in erroneous operations ； (4) Pulling at an angle or lifting unevenly ； (5) Failure of safety devices ； (6) The track and mounting fixtures are not installed properly; (7) The maintenance and inspection procedures are not followed, resulting in faults not being resolved in a timely manner ； (8) Underestimation of climate change, especially when strong winds occur at night when no one is working, causing the rail clamps to fail to hold. 20. When the tower crane escalator is installed inside the structure, under what circumstances can a guard ring be omitted? Answer: When the clear distance between the escalator and the structure is less than 1.2 m, a guard rail is not required. 21. How are the longitudinal and transverse irregularities of the tracks of tower cranes specified? Answer: Neither shall be greater than 1%. 22. Under what circumstances should a steel wire rope be replaced? Answer: If the number of broken wires in the steel wire rope exceeds 10% of the total number of wires within one lay length, and if the diameter of the rope is worn by 40%, it should be replaced with a new rope. 23. The Safety Technical Regulations for Building Installation Projects specify at what wind force levels it is prohibited to carry out lifting work and high-altitude operations outdoors? Answer: Strong winds of force 6 or above. 5 Construction Tools 1. What are the safety devices for a surface planer? Answer: It should have hand protection devices as well as protective covers for the moving parts. 2. Which types of equipment shall not have their power cords extended arbitrarily or have their plugs replaced? Answer: Handheld power tools. 3. Which type of hand-held power tool requires the use of insulating equipment as per regulations? Answer: Class I hand-held power tools. 4. What are the safety requirements for the steel bar cold drawing area? Answer: Protective barriers must be installed, warning signs should be in place during cold drawing, and unauthorized personnel are strictly prohibited from staying there. 5. What safety devices should an oxygen cylinder have? Answer: It should have shock-absorbing rubber rings and a safety cap. 6. What are the safety requirements for using submersible pumps? Answer: When using submersible pumps, it is necessary to install a leakage protector with a leakage current threshold of less than 15 milliamps and a response time of less than 0.1 seconds, and proper protective grounding or bonding must be ensured. 7. What electrical safety devices should be installed on a welding machine? Answer: A leakage protector and a secondary no-load voltage reduction protector should be installed. 8. What is the maximum length of the primary wire of a welding machine in meters? Answer: It cannot be more than 5 meters. 9. What are the “four key tasks” for mechanical operators? Answer: Cleaning, lubrication, adjustment, and tightening; as well as corrosion prevention. 10. Why must a grinding wheel be equipped with a guard? Answer: To effectively prevent broken pieces of the grinding wheel and abrasive debris from flying out and causing injury. 11. What potential accident hazards need to be prevented in welding operations? Answer: (1) Prevent the harm caused by arc light radiation to the human body ； (2) Prevent metal splashing, burns caused by electrode tips, and fires ； (3) Prevent poisoning by harmful gases and dusts; pay attention to dust removal and ventilation ； (4) Preventing explosions caused by welding pressure vessels ； (5) To prevent falls from heights, safety measures must be in place ； (6) Prevent electric shock accidents by ensuring proper insulation protection. 12. Indicate separately what the standard colors are for oxygen cylinders, acetylene cylinders, hydrogen cylinders, and liquefied petroleum gas cylinders. Answer: Oxygen cylinders: sky blue cylinder with black writing ； Acetylene cylinder: white cylinder with red letters ； Hydrogen cylinder: green cylinder, red text ； LPG cylinder: silver-gray cylinder with red letters. 13. What precautions should be taken when operating a concrete vibrator? Answer: 1) The power cable must be a weather-resistant flexible cable with a rubber insulated copper core ； (2) Good insulation with reliable neutral or ground protection ； (3) The leakage protector at the power supply must be sensitive and reliable ； (4) The vibrator cable must not be dragged across the rebar mesh to prevent damage and electrical leakage; its length should not exceed 30 m ； (5) The operator should wear rubber-soled shoes (boots) and insulated gloves ； (6) The power supply must be cut off when the vibrator needs maintenance. 14. What precautions should be taken when operating a frog-type rammer? Answer: (1) A directional switch must be used for the rammer’s operation switch; reverse switches are strictly prohibited, and the power inlet should be equipped with a protective rubber ring ； (2) Insulating material must be installed on the handle ； (3) Each rammer must be operated by two personnel: one to operate the rammer and another to tidy up the cables as needed ； (4) When operating the rammer, it is necessary to wear rubber-soled shoes and insulating gloves; when moving the rammer, the power supply must be turned off by switching off the circuit breaker ； (5) When shutting down, the power must be cut off and the switch box locked. Ensure the motor is protected from moisture and water. 15. What precautions should be taken when operating woodworking machinery? Answer: (1) Woodworking machinery must be under the supervision of a designated person ； (2) Safety protection devices must be complete and reliable; they must not be removed during operation ； (3) Gloves are not allowed to be worn during operation; maintenance, refueling, cleaning, and adjustments must not be carried out while the device is running ； (4) Iron nails and dirt must be removed thoroughly before processing old wood ； (5) At the end of each working day, the site must be cleaned thoroughly, power supply must be cut off, and the switchbox must be locked ； (6) The use of multi-functional woodworking machines that combine a saw, planer, and drill is strictly prohibited. 16. What precautions should be taken when operating rebar machinery? Answer: (1) The machinery should be under the supervision of a designated person. Before use, it is necessary to check the electrical system, the grounding of the aircraft body, and ensure that the leakage protection devices are sensitive and reliable; the safety protection devices must also be in good condition ； (2) When using a straightening machine, a steel pipe about 1 meter in length should be used; the rebar to be straightened must first pass through this steel pipe, and then through the guide tube and the straightening cylinder, to prevent the end of the rebar from coming out and causing injury ； (3) When using a cutting machine, hold the rebar firmly; as the cutting blade retracts, feed the rebar into the blade. Use pliers to feed the material that needs to be cut short, in order to avoid injury ； (4) When bending rebar using a bending machine, it is necessary to straighten the rebar first; for longer rebars, a dedicated person should be assigned to hold them steady ； The person holding the rebar and the operator must coordinate their movements; pulling arbitrarily is not allowed ； (5) When using steel bar cold drawing equipment, the cold drawing area must be enclosed for protection, and it is strictly prohibited for people to enter this area ； The operating position of the winch should be perpendicular to the direction in which the rebar is being pulled, to prevent injury in case the rebar breaks ； (6) Once the work is completed, turn off the power by pulling the switch and lock the switch box. 17. What precautions should be taken when operating a concrete mixer? Answer: (1) The driver operating the mixer must have received professional safety training, passed the relevant examinations, and hold a valid license; it is strictly prohibited for persons other than drivers to operate it ； (2) When the hopper lift is in use, it is strictly prohibited to work or pass under the hopper. When cleaning the hopper pit, the double safety hooks of the hopper must be securely fastened before cleaning begins ； (3) It is not allowed to use tools to reach into the mixing drum to remove material while it is in operation ； (4) After class, clean the inside and outside of the mixer thoroughly, raise the hopper, secure it with double safety hooks, turn off the power, and lock the electrical control box ； (5) Maintenance is strictly prohibited during operation. To maintain the mixer, it is necessary to turn off the power supply, lock the switch box, place a sign stating \"Do not close the switch while someone is working\", and assign a dedicated person to supervise the process. 18. What precautions should be taken when operating a mortar mixer? Answer: (1) Before starting the machine, check whether all components are in good condition and whether the protective devices are complete and functional; only after confirming that there are no abnormalities can testing operation begin ； (2) It is strictly prohibited to insert tools into the mixer barrel while it is in operation to remove material ； (3) Maintenance is strictly prohibited while the machine is in operation. In case of any abnormality, the machine must be stopped first, the power supply cut off, and the switch box locked before attempting to resolve the issue. 19. What precautions should be taken when operating a motorized dump truck? Answer: (1) The driver must receive specialized safety training, pass the relevant examinations, and work with a valid license. No passengers are allowed while in motion ； (2) When pouring material at the edge of the trench, the speed should be reduced, and a wheel stop must be installed at a distance of 0.8–1 m ； (3) The engine must be turned off and the handbrake pulled when performing maintenance or cleaning the vehicle after work. 20. What precautions should be taken when performing welding work? Answer: Welding is a type of special operation, and welders must work with a valid certificate ； Power control should use automatic switches; manual switches are not permitted ； I. Primary and secondary circuits must be equipped with shock protection devices ； The length of a single wire should not exceed 5m; it cannot be used for mopping ； The length of the secondary wire should be less than 30 m; the connections must be securely pressed together, and a protective cover should be installed ； The wire for the welding torch should use a dedicated cable, with two wires in place; there must be no joints, and the insulation must not be damaged ； Metal scaffolding, tracks, and structural rebar must not be used as return ground wires. 21. Why is it necessary to install a secondary electric shock protection device on welding machines? Answer: Since the no-load voltage of AC welding machines can reach 50–90 V, this is unsafe, and injuries resulting from such situations can be quite serious. To prevent such accidents, GB10235-88 stipulates that in addition to installing leakage protectors on the primary side, electric shock protection devices must also be installed on the secondary side. This device can reduce the no-load voltage to below 35–24V, thus completely preventing electric shock accidents. 22. What are the “four understandings and three skills” for machinery operators at construction sites? Answer: Understand the principles, performance, structure, and applications; be able to operate the machinery, carry out maintenance, and troubleshoot faults. 23. What should be done after the installation of small and medium-sized machinery is completed? Answer: It is necessary to check whether all components, protective devices, brakes, limiters, steel cables, safety chains, etc., are intact and reliable, whether lubricant has been applied, and only after a trial run shows normal performance can the machinery be put into use. 24. What should be the minimum working distance between oxygen cylinders and acetylene cylinders? What is the distance required between various gas cylinders and open flames? Answer: 5 meters and 10 meters respectively. 25. When storing gas cylinders, should they generally be placed horizontally or vertically? Answer: Vertically. 26. After the mixer is started, what rotational speed should the mixing drum reach before feeding material? Answer: Stable rotational speed. 27. Why is it necessary to clear away combustible materials around the work area before carrying out welding and cutting operations? Answer: Because welding and cutting involve open flames and high temperatures; metal melts and sparks are generated. If combustible materials are not removed from the work area, it can lead to fire accidents. 28. What are the protective requirements for personnel operating rotating mechanical equipment? Answer: They should wear work clothes that are “three-tight” – with tight cuffs, a tight hem, and tight trouser legs ； Gloves and scarves are not allowed ； Women workers’ buns must be tucked inside their work hats and must not protrude outside. 29. What precautions should be taken when using hand-held power tools? Answer: (1) Before using the tool, it should be checked by a qualified electrician to ensure that the wiring is correct, in order to prevent accidents caused by incorrect connection of the neutral wire and the live wires ； (2) Tools that have been left unused for a long time or have become damp should have their insulation resistance measured by an electrician to determine whether it meets the required standards before use ； (3) The soft cable or wire included with the tool shall not be extended; when the power source is located at a distance from the work site, a mobile power box should be used to address this issue ； (4) The original plug of the tool must not be removed or replaced arbitrarily; it is strictly prohibited to insert the wire directly into the socket without using a plug ； (5) If it is found that the tool’s housing or handle is broken, use should be stopped and it should be replaced. (6) Part-time personnel shall not disassemble or repair tools without authorization ； (7) The rotating parts of hand tools should be equipped with protective devices ； (8) Operators shall wear insulating protective equipment as required ； (9) A leakage protector must be installed at the power supply. 30. When a bulldozer pushes soil horizontally on a slope, what is the maximum slope angle allowed? Answer: 30 degrees. 31. What are the safety requirements for using handheld electric tools in wet areas? Answer: Class II or Class III tools should be used in wet areas. If Class I tools are used, a leakage protector with a rated leakage operating current of not more than 30 milliamps and an operating time of not more than 0.1 seconds must be installed. 32. What safety measures should be taken when using hand-held power tools in confined spaces such as boilers, metal containers, and pipes? Answer: Class III tools should be used in such locations. If Class II tools are used, a leakage protector with a rated leakage operating current of not more than 15 milliamps and an operating time of not more than 0.1 seconds must be installed. 33. What regulations must be followed when using gas cylinders? Answer: (1) Knocking or colliding with them is prohibited to avoid damaging the gas cylinders ； (2) When the bottle valve freezes in winter, it should be thawed using hot water or other safe methods; direct heating with an open flame is not allowed, as this may degrade the mechanical properties of the gas cylinder material and increase the pressure inside the cylinder ； (3) Gas cylinders must not be placed near heat sources. Cylinders containing flammable or assisting gases should generally be kept at a distance of at least 10 meters from open flames ； (4) Prevent exposure to sunlight in summer ； (5) The gas in the bottle must not be used up completely; there must be some residual pressure. The residual pressure for combustible gases and oxidizing gases should be maintained at around 0.49 MPa (5 kg/cm²); for cylinders containing other gases, the residual pressure can be lower ； (6) Electromagnetic cranes must not be used to move gas cylinders, to prevent them from falling from a great height in the event of a power failure, which could cause damage or explosion to the cylinders ； (7) Cylinders containing gases prone to polymerization reactions must not be placed in areas with radioactive radiation. 34. What is the inspection cycle for various types of gas cylinders? Answer: (1) Gas cylinders containing corrosive gases shall be inspected every two years ； (2) Cylinders containing ordinary gases shall be inspected every three years ； (3) Liquefied petroleum gas cylinders that have been in use for no more than twenty years shall be inspected every five years ； For those over twenty years old, inspection is required every two years ； (4) Gas cylinders containing inert gases shall be inspected every five years. When severe corrosion or damage is detected in the gas during use, or if there are doubts regarding its reliability, inspections should be carried out in advance. 35. What should be included in the safety operating procedures for gas cylinders? (1) Filling process parameters and requirements for gas cylinders ； (2) Filling methods and operating procedures, precautions ； (3) Key items and areas to inspect when using gas cylinders, possible abnormal conditions during use, and preventive measures ； (4) Methods of sealing and maintenance when gas cylinders are out of use. 6 Demolition operations
1. In the demolition operations at a construction site, what sequence must be strictly followed for demolishing layer by layer? Answer: From outside to inside, from top to bottom. 2. What are the requirements for removing formwork? Answer: (1) A concrete strength report must be obtained to verify the structural strength before removing the formwork ； (2) Set up a sturdy operating platform for work at heights of over 3m ； (3) Set up barriers and supervisors in the demolition area. 3. What are the requirements for demolishing buildings? Answer: (1) When carrying out demolition work, workers should operate from specially erected scaffolding or other stable structural elements ； (2) Remove the fences installed around it, hang warning signs, and assign personnel to supervise; unauthorized persons are strictly prohibited from staying there ； (3) When demolishing a building, it should be carried out from top to bottom in sequence; simultaneous demolition of multiple floors is prohibited. When removing a certain part, it is necessary to prevent the other parts from collapsing ； (4) During the demolition process, the on-site lighting must not use the wiring from the building being demolished; separate lighting should be installed. 4. What issues should be considered when supporting or removing formwork at a construction site? Answer: (1) Formwork support must be carried out in accordance with the specified procedures; the next stage of work shall not begin until the formwork is secured ； (2) It is strictly prohibited to climb up and down on the connections and supports, and it is also strictly prohibited to assemble or disassemble formwork on the same vertical plane ； (3) When the erection height is above 3m, diagonal braces must be installed around it along with an operating platform ； Scaffolding braces can be used for heights below 3m ； (4) The cantilever formwork must have a stable base ； To set up supports for the temporary template at the airport area ； Scaffold or staging ； There are pre-existing openings in the template, which should be covered after installation ； Guardrails should be installed at the edges that are formed after form removal. 5. What preparations should be made before dismantling the scaffolding? Answer: (1) A comprehensive inspection should be carried out to verify whether the fastener connections, wall bracing elements, and support systems of the scaffold meet the required construction standards ； (2) The sequence and measures for demolition in the construction organization plan should be completed based on the inspection results, and implementation is only permitted after approval by the competent authorities ； (3) The person in charge of the individual project shall provide safety technical instructions for the demolition ； (4) Debris on the scaffolding and obstacles on the ground should be removed
1. In the demolition operations at a construction site, what sequence must be strictly followed for demolishing layer by layer? Answer: From outside to inside, from top to bottom. 2. What are the requirements for removing formwork? Answer: (1) A concrete strength report must be obtained to verify the structural strength before removing the formwork ； (2) Set up a sturdy operating platform for work at heights of over 3m ； (3) Set up barriers and supervisors in the demolition area. 3. What are the requirements for demolishing buildings? Answer: (1) When carrying out demolition work, workers should operate from specially erected scaffolding or other stable structural elements ； (2) Remove the fences installed around it, hang warning signs, and assign personnel to supervise; unauthorized persons are strictly prohibited from staying there ； (3) When demolishing a building, it should be carried out from top to bottom in sequence; simultaneous demolition of multiple floors is prohibited. When removing a certain part, it is necessary to prevent the other parts from collapsing ； (4) During the demolition process, the on-site lighting must not use the wiring from the building being demolished; separate lighting should be installed. 4. What issues should be considered when supporting or removing formwork at a construction site? Answer: (1) Formwork support must be carried out in accordance with the specified procedures; the next stage of work shall not begin until the formwork is secured ； (2) It is strictly prohibited to climb up and down on the connections and supports, and it is also strictly prohibited to assemble or disassemble formwork on the same vertical plane ； (3) When the erection height is above 3m, diagonal braces must be installed around it along with an operating platform ； Scaffolding braces can be used for heights below 3m ； (4) The cantilever formwork must have a stable base ； To set up supports for the temporary template at the airport area ； Scaffold or staging ； There are pre-existing openings in the template, which should be covered after installation ； Guardrails should be installed at the edges that are formed after form removal. 5. What preparations should be made before dismantling the scaffolding? Answer: (1) A comprehensive inspection should be carried out to verify whether the fastener connections, wall bracing elements, and support systems of the scaffold meet the required construction standards ； (2) The sequence and measures for demolition in the construction organization plan should be completed based on the inspection results, and implementation is only permitted after approval by the competent authorities ； (3) The person in charge of the individual project shall provide safety technical instructions for the demolition ； (4) Debris on the scaffolding and obstacles on the ground should be removed
These contents should be memorized by managers and safety officers, who must use them as a reference for inspections