Take a look at the recent serious elevator accidents, most of which are related to the elevator landing door. There are many reasons such as the awareness of the elevator users, the negligence of the technical staff for maintenance, repair, inspection and even objective technical errors related to the elevator.
On July 16, 2022, at Children's Hospital of Ho Chi Minh City, there was an elevator accident in Can Tho that killed one person. Specifically, Mrs. P used her hand to block the elevator door so that the landing door opened and then stepped inside. However, at this time, the elevator cabin had moved upwards, so Mrs. P fell into the pit leading to her death. (Read more: Another person died in an elevator accident)
On April 21, 2022, VHD (4 years old, living in Trung Van ward, Nam Tu Liem district, Hanoi) leaned on the elevator door on the 6th floor, when the door opened inside, causing the baby to fall from the 6th floor into the shaft, but luckily entangled in a steel nail on the 4th floor and was rescued.
In 2015, at the Maritime University (Hai Phong), a DYT student fell into the elevator door, the door burst in, causing the unfortunate student to fall straight from the 5th floor to the bottom of the elevator and died on the spot.
The scene of the elevator accident in Trung Van ward, Nam Tu Liem district, Hanoi
According to statistics, about 60% of serious elevator accidents are related to elevator landing doors. The cause is due to poor quality elevator doors, missing or damaged safety devices, jobs to ensure safe operation for elevators such as inspection, maintenance, and repair are not of good quality, not in accordance with regulations, procedure, technical staff are not qualified, have no experience, …
The price to pay is very high, which is human life.
Dr. Nguyen Duc Hanh, Director of Vietnam Institute Lift Engineering Application (VILEA), affirmed that the operating mechanism of the landing door and the elevator cabin are closely related. According to the general design, when the cabin stops at the floor level and landing door – car door operator works, this door will open. In any case, when the landing door is open, the cabin will not move for safety. If the cabin is moving, for whatever reason the landing door opens, the elevator will stop working.
According to engineer Pham Ba Toan - Head of Maintenance Department Gama Service, the elevator door is composed of 2 layers of doors, the inner door layer is the cabin door and the outer layer is the landing door. These two doors operate according to a strict process according to two basic factors: mechanical and electrical system. Regarding the mechanical system, the landing door has a closed hook-shaped latch that normally cannot be opened. If you want to open it forcibly, you need a dedicated key. According to the operating procedure, when the cabin stops at the floor, door coupler will push the latch of the landing door, then the door motor on the roof of the cabin will be activated so that the two doors will open together.
There is one thing that many people may not know, the "infrared safety curtain" system is usually located at the cabin door, not at the landing door. In other words, only when the cabin stops at the floor level, both the cabin and the floor door open, the infrared curtain system will take effect.
Mechanical latch of elevator landing doors
The electrical system, landing doors and elevator cabin doors, even if they are designed to open to one or two sides, can only be opened when both the landing door and the cabin door are in the same position (on the floor level). If the landing door opens naturally, it will cut off the safety circuit and the whole elevator system will stop working because the processor understands that the elevator is not safe enough to operate.
The elevator, when installed correctly, will not work if one of the contacts is not fully closed (then the circuit is open). Because of this principle, the elevator is designed with an interlock system to ensure that the landing door will not be able to open if the cabin has not stopped at the right position on that floor.
First, about the mechanical system:
Because the floor door and the cabin door are two devices with high operating frequency, the latch and door lock will wear out over time, possibly to the point of no longer having the effect of locking the door. This situation would be very dangerous if it happened.
Low quality of elevator doors can be caused by improper production of standards and regulations, along with the installation, inspection, maintenance, repair, and replacement of components that are sloppy or not in accordance with the process and time. It also does not exclude the possibility that during installation, maintenance, inspection ... unqualified technical staff do not detect wear and tear, damage should ignore errors leading to unfortunate consequences.
Second, about the electrical system:
According to elevator experts, due to the importance of the elevator structure, there are quite a few safety devices installed at the door and cabin. In addition to ensuring the normal operation of the landing doors and cabins, these devices also send out warning signals when there is damage or loss of safety. For high-quality elevators, manufactured and imported in accordance with regulations and standards and implemented in accordance with regulations, maintained and tested in accordance with the process, highly qualified and experienced technical staff with valid certificates, all kinds of elevator doors operate smoothly, rarely damaged.
When in a static state, the landing door can only be opened with a dedicated key
Expert Pham Ba Toan said that for cheap elevators, the safety circuit system is not guaranteed or error messages must be repaired continuously, causing interruption in use. Unfortunately, to handle this situation, some technicians disabled or "turned off" the safety device, causing the door interlock system to be disabled. That is, the cabin can still operate even if the landing door is still open. This is a trick of unscrupulous, inexperienced or poorly aware technical staff… This behavior can completely endanger the life of elevator users.
Many experts also pointed out that due to the lack of pre-testing due to the lack of specialized technical "labs", the lack of equipment and human resources, etc., only the first inspection can be performed. This makes many types of elevators, components, equipment of poor quality, and death lurking, waiting inside the "fake" elevators.
Through the continuous serious elevator accidents that have taken place in recent times, the issue of training to improve professional and ethical qualifications for the workforce of the elevator industry has become more urgent than ever end. We need to soon develop a National Occupational Skills Standard for the elevator industry, standardize the curriculum framework in the national vocational education system for formal training of workers in this industry. Improving professional ethics and having solutions for human resource management in the industry also need to be carried out in parallel, ... in order to improve the safety factor for elevators, progressing towards sustainable development of the domestic elevator industry with longer-term goals./.
