Summary of Precautions for the Installation and Production of Elevators

Elevators are indispensable construction equipment for vertical transportation in building projects. In recent years, serious accidents involving construction elevators have occurred from time to time. The fundamental reason lies in the inadequate and unscientific management measures, which are the root cause of potential accident hazards in construction elevators. Taking the SC-type construction elevator as an example, several issues that require attention are presented here.

The fall arrestor is a crucial component on the construction elevator. It is relied upon to prevent cage fall accidents and ensure the safety of passengers. Therefore, the factory tests of the fall arrestor are extremely strict. Before leaving the factory, the legal inspection unit measures its torque, critical speed, and spring compression. Each unit comes with a test report. After being assembled onto the construction elevator, a drop test under the rated load is carried out. Moreover, the elevators in use on construction sites must undergo a drop test every three months. For fall arrestors that have been out of the factory for two years (marked with the date of manufacture on the fall arrestor), they must be sent to the legal inspection unit for testing, and then be inspected once a year. So far, very few people send them for inspection. Some construction sites even fail to conduct the drop test every three months, thinking that their fall arrestors have no problems. However, once an accident occurs, it will be too late to regret. Why not conduct regular tests and send for inspection as required? The user units blindly assume that if it’s not broken, it’s fine. In fact, the quality of the fall arrestor can only be judged through tests and inspections. It’s impossible to determine whether it’s in good condition during daily operation. For those fall arrestors that have been in use for too long, it is advisable to send them for inspection and conduct regular tests earlier. Only by having a clear understanding can major accidents be prevented.

The safety switches of the elevator are designed according to safety requirements, including fence door limit switches, cage door limit switches, top door limit switches, limit switches, upper and lower limit switches, counterweight anti-rope-breaking protection switches, etc. On some construction sites, in order to save trouble, some limit switches are deliberately removed, short-circuited, or not repaired in time after being damaged. This is equivalent to removing these safety barriers and sowing the seeds of potential accidents. For example, when long items need to be loaded into the cage and cannot fit inside but have to protrude outside, the door limit or top door limit is removed artificially. Under such circumstances where the safety facilities are incomplete or not in good condition, people and goods are still carried, which is extremely irresponsible behavior that endangers lives. To avoid potential accidents, it is hoped that the leaders of user units will strengthen management and strictly require the maintenance and operation personnel of the elevator to regularly check the safety and reliability of various safety switches to prevent accidents.

The construction environment on construction sites is harsh, and it’s impossible to completely remove cement, mortar, and dust. The gears and racks keep grinding against each other, and some are still in use even when the teeth are worn sharp, which should arouse attention. As we all know, the tooth profile is like a cantilever beam. When it is worn to a certain size, the gear (or rack) must be replaced. So, when should it be replaced? A 25 – 50 mm common normal micrometer can be used for measurement. When the common normal length of the gear is worn from 37.1 mm to less than 35.1 mm (for two teeth), a new gear must be replaced. When the rack is worn, measured with a tooth thickness caliper, when the chord height is 8 mm and the tooth thickness is worn from 12.56 mm to less than 10.6 mm, the rack must be replaced. However, many “ancient” elevators with severely worn gears and racks are still in use on construction sites. For safety reasons, new parts must be replaced.

Elevators on construction sites operate frequently with a high utilization rate. However, the intermittent working system of the motor, that is, the issue of duty cycle (sometimes called load duration factor), has to be considered. Its definition is FC = working cycle time/load time × 100%, where the working cycle time is the sum of load time and downtime. Some elevators on construction sites are rented from leasing companies. People always want to make full use of them without considering the motor’s duty cycle (FC = 40% or 25%). No wonder the motors get overheated. Some are even still in use when emitting a burnt smell, which is extremely abnormal operation. If the transmission system has poor lubrication, excessive running resistance, is overloaded, or undergoes frequent starts, it’s like using a small horse to pull a big cart. Therefore, every driver on the construction site must understand the concept of duty cycle and act in accordance with scientific laws, because this kind of motor is designed for intermittent operation.

The buffer on the construction elevator is the last line of defense for elevator safety. First, it must be installed. Second, it must have sufficient strength to withstand the impact of the elevator’s rated load and play a buffering role. However, on many construction sites, although some are installed, they are not strong enough to buffer effectively. Some sites don’t even have buffers at all, which is extremely wrong. It is hoped that user units will pay attention to inspection and not neglect this last line of defense.

Each landing floor of the construction elevator should be equipped with a landing safety protection door. Obviously, if not installed as required, construction workers waiting at a height are prone to accidental fall accidents. When installing the landing safety protection door, the height of the safety protection door should be no less than 1.8 m, and the floor door should have an interlocking device so that the protection door cannot be opened when the cage has not reached the landing position, ensuring the safety of workers. Currently, on construction sites, it is common that people waiting for the construction elevator can open the safety protection door at any time, which is very dangerous and should be taken seriously.

According to the provisions of GB 10055, “The base fence should be equipped with mechanical interlocks or electrical interlocks. The mechanical interlock should ensure that the base fence door can only be opened when the cage is at the specified bottom position. The electrical interlock should make the cage stop and not start after the protective fence is opened.” There are quite a number of construction elevators. When the cage approaches the fence door, the bottom of the cage presses down on a beam and runs downward, and through the wire rope of the reversing pulley, the fence door is opened upward, which is not allowed and may easily cause harm to people near the fence.

According to the provisions of GB 10055, “A control box for maintenance or disassembly should be installed on the top of the cage, and it should only be allowed to run at a speed of no higher than 0.65 m/s under various speed conditions. When using the control box on the top of the cage, other operating devices will not function. At this time, the safety devices of the cage still play a protective role. The control on the top of the cage should be operated by constant pressure buttons or bistable switches. A non-self-resetting emergency stop switch should be installed on the top of the cage, which can cut off the circuit at any time and stop the movement of the cage.” This mainly applies to SC-type construction elevators. Few enterprises’ products can meet the five requirements of this article simultaneously, including those designed by some well-known design units. What are the disadvantages of not meeting these five requirements? It may cause safety accidents due to misoperation by installation and maintenance personnel. It is hoped that relevant user units will conduct a comparative inspection of construction elevators, especially for old products. If they do not meet the above requirements, active measures should be taken for modification.

The overvoltage, undervoltage, and phase-failure protection devices will act when there are voltage drops, overvoltages, or phase-failure and wrong-phase faults in the electrical circuit, causing the construction elevator to stop running. On some construction sites, the maintenance personnel of the construction elevator do not promptly eliminate the faults that cause the overvoltage/undervoltage and phase-failure protection devices to act. Instead, they remove or short-circuit the protection devices, leaving potential accident hazards for the equipment. Some early products do not have such protection devices at all, and it is recommended that they should be equipped. The construction elevator should only carry passengers and goods when the overvoltage/undervoltage and phase-failure protection devices are reliable and effective.

In addition to these key points, comprehensive safety management for elevator installation and production encompasses a much broader scope. For the installation process, the foundation construction is of prime importance. The foundation needs to bear the entire weight of the elevator, along with dynamic loads during operation. It must be level, and the strength of the concrete used should meet strict engineering standards. Any unevenness or weakness in the foundation can lead to misalignment of the elevator structure, increasing wear on components and potential instability.

During production, the quality control of raw materials is crucial. High-strength and durable metals should be used for key components like gears, racks, and shafts. The manufacturing process also demands precision. For example, the machining of gears requires strict control of tooth profiles, pitch, and surface finish to ensure smooth meshing with the rack. Any deviation can lead to abnormal noise, increased wear, and reduced efficiency.

Staff training is another integral part. Installation workers need to be proficient in following installation manuals, understanding how to align components accurately, and properly connect electrical and hydraulic systems. Operators should not only be familiar with basic operating procedures but also trained in emergency response. They need to know how to handle situations like sudden power failures, abnormal noises, or stuck cages.

Regular maintenance schedules should be formulated based on the manufacturer’s recommendations. This includes daily visual inspections to check for loose parts, leaks, or abnormal wear. Weekly and monthly inspections can be more in-depth, involving lubrication checks, electrical system tests, and functional tests of safety devices. By covering all these aspects comprehensively, the overall safety and reliability of construction elevators can be significantly enhanced.