Escalator malfunctioned and I was trapped for several hours. Netizens asked: Why can't I go?

Review expert: Tian Lianfang, professor of the School of Automation Science and Engineering, South China University of Technology

With the continuous development of economy, various infrastructure construction in cities is becoming more and more perfect. In the past, we could only see elevators, escalators and other equipment in big cities, but now, we can see them even in supermarkets in small towns.

However, in recent years, we often hear about accidents involving escalators, such as pedestrians being injured due to sudden stops of escalators. Using escalators seems to have become particularly dangerous. Why is this so? What should we do when an escalator breaks down?

Source: Wikipedia

Before answering this question, let's first understand how escalators work.

1 The principle of escalator

At present, the escalators on the market are mainly traction escalators, whose structure consists of two parts: a mechanical system and an electrical system.

Among them, the mechanical system is based on the step structure for mechanical transmission . The mechanical transmission of the escalator consists of two parts, namely the transmission of the step chain and the handrail belt. The step chain transmission means that the driving wheel drives the step chain to operate, and the step chain then drives the step rails layer by layer to operate, forming a closed motion loop.

The components involved in the transmission process mainly include trusses, step chains, guide rail systems, steps, apron plates, etc.

Source: "Technological Development and Trends of China's Elevator Industry", Building Science, 2018

Among them, the truss is used to support and install various components of the escalator, and bear various loads such as the escalator's own weight and passenger loads.

The steps of the escalator are made of metal materials, and each step has a wheel set connected to the step chain so that it can run with the step chain. The handrail belt drive is driven by the driving wheel through friction drive.

Source: Mitsubishi Electric official website

In the national standard "Safety Specification for the Manufacture and Installation of Escalators and Moving Walkways" (GB 16899-2011), the definition of escalators is " escalators are machines and cannot be used as fixed stairs even when not in operation ." From the operating principle of escalators mentioned above, it can be seen that the design principle of escalators is mechanical design, which is completely different from traditional stairs.

The slope of the escalator is relatively high and it is not suitable for walking. When it is not in operation, walking on the escalator as if it were a staircase can also bring great danger. When the escalator stops running, it is usually due to a malfunction and needs to be repaired by the maintenance staff. At this time , the escalator may appear to be stationary on the outside, but it may still be running inside. If you walk on it at this time, the brakes may fail, causing the step pedal to collapse and the passengers to be sucked into the internal space , with disastrous consequences.

In addition, the escalator may stop running temporarily due to insufficient power supply. If you walk on it and the escalator suddenly resumes running, it is very likely to cause a fall, trampling and other chain reactions. The sudden stop of the escalator relies on the braking function of the escalator host to maintain the escalator's stopped state. This is a power-off brake function of the motor. If there are many people walking at this time, the pressure on the escalator exceeds the braking force of the motor, causing the brake to fail, and the escalator pedal will slide down, causing casualties.

2What are the dangers of escalators?

The common sources of danger during the use of escalators are mainly the following: First, the handrail belt is underspeed.
The handrail of an escalator is designed to run in the same direction and speed as the steps. The national standard "Safety Specifications for the Manufacture and Installation of Escalators and Moving Walkways" stipulates that when the speed of the handrail deviates from the actual speed of the steps, pedals, and belts by more than 15% and lasts for more than 15 seconds, the escalator will stop running. In other words, if the handrail only slips for a short time, it will not stop running. At this time, if passengers (especially elderly passengers) cannot adjust their handholding position in time, they will easily be knocked down by the escalator and fall.

The second is the problem of standing on the escalator steps.

When taking an escalator, there are corresponding yellow frames between the steps. The frames are the safe areas for standing. When taking the escalator, you should be careful to keep your feet inside the frames and avoid stepping on the junction of the steps to prevent falling.

Source: Wikipedia

The third is the gap between the escalator steps and the apron plate.

The brushes on both sides of the escalator are called apron plates. Under normal circumstances, the gap between the apron plate and the escalator steps is very small, not exceeding 4mm. However, when the escalator works for a long time, various parts will wear out, and the gap will become larger, making it easy for long objects such as shoelaces to be caught. Therefore, pay special attention to these items when riding the escalator to prevent them from being pinched.

Source of gap between steps and apron plate丨MTR Inspection

Fourth, broken teeth appeared at the joints of the escalator entrance and exit.

The part at the entrance and exit of the escalator is called the comb plate. Normally, the ends of the comb plate are intact and fit closely with the steps, which is highly safe. However, after long-term use, the comb plate is prone to broken teeth and deformation, and a gap of 1 to 3 mm will form between the comb plate and the steps, which can easily clamp thin and soft items such as trouser legs and shoelaces, which is very harmful.

Broken teeth appear at the joint of the escalator entrance and exit Source: See watermark

3 How to deal with escalator failure

There are two reasons for escalator failures, one is the product itself , and the other is the use problem . For the escalator itself, the relevant departments need to do a good job in product safety testing and daily maintenance and repair of the escalator to ensure the safety of citizens and passengers; from an individual perspective, if we want to avoid escalator safety accidents, we need to develop good escalator riding habits and strictly follow the rules of riding. When taking the escalator on a daily basis, please do not run, play, lean on the escalator. Whether adults or children, they should stand alone, keep their center of gravity stable, and never extend other parts of their body out of the escalator.

Playing on the escalator (dangerous action, please do not imitate) Source: Qingdao Youshenghuo

Children can stand hand in hand with adults, while infants and young children are recommended to take the escalator. Families with baby strollers should not bring them on escalators, as they can easily flip over and the wheels can easily get stuck in the brushes on both sides of the escalator, which can easily cause various accidents. When riding an escalator, you should also stay focused, stand with both feet in the yellow frame of the steps, and lift your feet in time when entering and exiting the comb plate; it is also recommended to hold the handrail tightly. If the handrail and the steps are out of sync, adjust the position of the handrail in time.

Stand with your feet in the yellow frame of the steps Source: Danyang News

** In addition, escalators also have a "life-saving" button, namely the "emergency stop button",** which is usually located at the bottom of one side of the escalator and is a red button. Some of them are not obvious in appearance, but they are usually accompanied by text prompts, which can be seen with a little attention. If an escalator accident is found, people around can quickly find this button and press it to stop the escalator immediately, which may save a life.

Escalator "help" button source丨Dongguan News

But please note that this button cannot be pressed casually. When the escalator is operating normally, if the button is pressed casually, causing the escalator to suddenly stop, it may cause passengers on the escalator to fall, and in serious cases, a stampede may occur, endangering the lives of passengers.

With the development of productivity, my country has become the world's largest escalator user. Escalators have an increasingly greater impact on people's lives. Once a safety accident occurs, it will seriously affect people's normal travel and the safety of life and property. Therefore, from a social perspective, it is urgent to strengthen the safety maintenance of escalators and pay attention to the promotion of escalator safety knowledge; as individuals, we should also establish a good sense of escalator safety and protect our lives.