MENU

Analysis and Preventive Measures of the Causes of Elevator Squatting and Russing to the Top

2024-05-14

author:

Page view:


Analysis and Preventive Measures of the Causes of Elevator Squatting and Russing to the Top

Traction elevator is driven by the traction machine, relying on the friction between the traction wheel and the wire rope to drive the car along the vertical track of special equipment. The safe operation of the elevator has always been a subject of concern in the process of elevator development, although with the elevator technology is increasingly updated, although the elevator has been equipped with electrical and mechanical and other multi-bearing safety devices to ensure safety, however, the effectiveness of the safety device has a direct impact on the safe operation of the elevator.
 
Therefore, this paper analyzes the relationship between the effectiveness of safety protection devices and the phenomenon of squatting and rushing to the top, and puts forward preventive measures from the perspective of strengthening elevator inspection and maintenance, which is helpful to improve the work efficiency of elevator inspection and maintenance personnel and reduce the possibility of elevator squatting and rushing to the top.
 
1, the elevator squatting bottom and top reasons
Elevator squatting at the bottom refers to the phenomenon that the elevator cannot effectively stop and collides with the bottom pit when it goes down the full bottom end station. The top of the elevator refers to the phenomenon that the elevator cannot effectively stop and continues to rush to the top of the hoistway when it goes up the full top end station. There are several reasons for the bottom and top of the elevator:

1.1 brake failure or insufficient braking force
The brake mainly plays an effective role in stopping the elevator. According to the requirements of 687588-2003((Safety Code for Elevator Manufacturing and Installation ", when the car is running up and down with l25% rated load, the brake can make the car stop reliably, and the average deceleration is smaller than 9. If the brake fails or the braking force is small enough, there is a danger of the elevator rolling. The main reasons for the failure of the brake or the small braking force are as follows:

(1) Brake spring brake is loose and broken;

(2) The electrical contacts of the brake are adhered or not kept open, resulting in the failure of the brake electromagnet to release;

(3) The brake clearance is too large;

(4) The friction between the brake shoe and the brake wheel causes the brake shoe and the brake wheel to overheat, resulting in a decrease in braking ability, brake sticking, brake arm, axle pin fracture and other faults that cause the brake to close effectively.

1.2 end station protection switch failure
The end station protection is equipped with three kinds of protection switches, such as forced speed change, limit and limit switch, also known as over-range protection switch, which is used to prevent the elevator from exceeding the top or bottom end station due to the failure of the control party. If the car overruns due to rope slippage, brake failure or small braking force, the end station protection switch is powerless.
 
The forced speed change switch is mainly used to control the deceleration effect before the whole end of the elevator. The limit switch is used to cut off the direction relay or contactor circuit in the elevator control system when the forced deceleration switch fails to decelerate and stop the elevator. However, at this time, it is only to prevent the elevator from running in a dangerous direction, and the elevator can still run in a safe direction. The limit switch is the third protection against overstepping. When the elevator cannot stop running after the limit switch is activated, the limit switch is triggered to cut off the circuit, causing the drive host and brake to lose power, and the elevator stops running.

The failure of the end station protection switch usually shows the following situations:
 
(1) The failure of the forced speed change switch is mainly due to the loosening of the iron-touching device installed on the car or the wheel-touching phase of the speed change switch and the non-release of the electrical contact bonding.
 
(2) The failure of the limit switch is mainly manifested in the looseness of the touch plate installed on the car frame and the slow adhesion or release of the contactor in the contact direction, resulting in the time lag of the small brake or the brake, making the limit switch unable to act in time.
 
(3) failure of limit switch: it is often manifested as loosening of limit switch wheel or iron, resulting in failure of limit switch when small energy is effectively decelerated and stopped.

If all three protections fail, the overspeed operation of the elevator will inevitably lead to the consequences of squatting at the bottom or rushing to the top. If the forced deceleration switch fails to slow down the elevator, the elevator cannot stop before reaching the buffer even if the limit switch is effective after crossing the exit station position and the limit switch fails, and the elevator has the possibility of squatting at the bottom or rushing to the top; if the limit switch and limit switch fail, even if the forced speed change switch is effective, the elevator may still squat or rush to the top under the condition of brake failure.
 
Insufficient 1.3 traction capacity
The traction elevator is driven by the traction machine, relying on the friction between the traction wheel and the wire rope to drive the car to run along the vertical track, the lack of traction force can not ensure the normal lifting of the car and produce a slip state. So easy to cause squat bottom. The main factors of the elevator drag gravity are as follows:
 
(1) The traction sheave groove is worn or the diameter of the traction rope is reduced. As the friction force is not a constant in the whole service life of the elevator, with the continuous friction between the traction rope and the wheel groove during the operation of the elevator, the static of the rope is continuously reduced, and the traction rope gradually approaches the bottom of the groove, so that the clamping force of the traction rope and the rope groove cutting point (for the V-shaped traction rope groove) is gradually reduced, resulting in insufficient friction force and reduced traction capacity.

(2) The balance coefficient does not meet the requirements of the standard. The balance coefficient is the proportion of the load change of the load balance car on the bearing side. According to GBl0058 requirements, the balance coefficient of heterogeneous elevators should be 40% ~ 50%. The small value of the balance coefficient only affects the quality of the bearing and the small balance load of the elevator, and also affects the tension of the wire rope on both sides of the traction wheel. The size of the tension will have an impact on the specific pressure of the traction wire rope in the rope groove. The greater the tension, the greater the specific pressure, and the stronger the traction capacity provided by the traction wire rope. Therefore, the value of the balance coefficient not only determines the unbalanced load, but also affects the traction capacity of the elevator. When the maximum unbalanced load is greater than the maximum traction force of the elevator, the traction wire rope will slip in the rope groove, increasing the possibility of the elevator crouching.

(3) Wear of transmission and deceleration mechanism: The transmission mechanism mainly refers to the main shaft, bearing, gear, worm and other mechanical parts of the traction machine. Due to the long-term use of these moving parts, or insufficient lubrication and other reasons, excessive wear and aging, resulting in a serious decline in traction.
 
1.4 speed limiter and safety gear failure
The speed limiter-safety clamp system is a safety device that protects the elevator from overspeed and rope breakage. The speed limiter is a device that limits the overspeed operation of the elevator. When the elevator overspeed reaches the set electrical action speed, it will cut off the safety circuit of the elevator through the electrical switch, and then cut off the system power supply. If the elevator continues to overspeed due to bearing force or inertia, the mechanical action device of the speed limiter will be triggered to stop the movement of the speed limit wire rope, thus lifting the safety gear. Safety gear is a kind of mechanical device that makes the car or the bearing stop running. It acts on the guide rail and relies on the friction between the wedge and the guide rail to make the car stop.
 
(1) The speed limiter does not operate: the GB7588-2003 stipulates that the operating speed of the elevator speed limiter shall not be less than 115% of the rated speed. If the elevator safety circuit fails or the operating speed of the speed limiter does not meet the requirements, the speed limiter will not operate. When the elevator overspeed, the control circuit can not open, the brake can not hold the brake.

(2) Although the speed limiter action, but the small can control the car safety gear action. The reason is that the speed limiter wheel groove wear, reduce the friction between the rope wheel and the speed limit rope, when the elevator overspeed, although the speed limiter electrical switch action, but the speed limit rope tension is not enough to make the safety gear work.
 
(3) Failure of the linkage switch of the car top safety gear: At present, the safety gear switch is generally used as a travel switch, which is prone to adhesion of electrical contacts. When the speed limiter rope lifts the safety gear, the electrical switch fails. After the elevator overspeeds, the control The circuit is not disconnected and the brake is not locked.
 
(4) The safety gear cannot reach the effective action position after installation or maintenance. Due to the test and adjustment after installation and maintenance, the action is not in place, or the curved side of the safety clamp is not synchronized. That is, there is a sequence between the safety gear on one side of the car blocking the guide rail and the safety gear on the other side of the car blocking the guide rail, or the gap between the safety gear wedge on one side of the car and the side of the guide rail is too large, and the safety gear on this side does not stop the car, causing the car to fall.
 
(5) The surface friction coefficient of the sliding wedge of the safety gear is reduced. If the actual friction force between the wedge of the safety gear and the side of the guide rail after the action is less than the force required to act on the guide rail during the action of the safety gear; The dirt and rust on the safety gear cannot be repaired and cleaned in time, causing the machine to be stuck and unable to move. This situation makes the safety gear play a role as small as stopping the car.

1.5 elevator overload
According to GB -7588-2003 "Safety Code for Elevator Manufacturing and Installation", the so-called overload refers to exceeding 10% of the rated load and at least 75kg. In case of overload, there should be sound and (or) luminous signals in the car to notify the users and the power-driven automatic door should be kept in the fully open position. When the elevator stops for a long time or the movable contact of the overload protection device located at the bottom of the car is rusted due to the damp and mixing in the hoistway and pit environment. When the elevator is overloaded, the overload device does not operate, thus the safety circuit cannot be disconnected, and the car cannot stop and squat at the bottom.
 
1.6 upstream protection device fails
 
The GB7588-2003 stipulates that the traction drive elevator should be equipped with the car upstream overspeed protection device, and all the elevators installed before this are installed. At present, there are several common types: rope clamp, speed limiter-car safety gear, speed limiter-pair safety gear and permanent magnet synchronous brake. Among them, rope clamp, two-way speed limiter-car safety gear and strong speed limiter-pair safety gear are monitored by speed limiter. The failure of upstream overspeed protection device is usually manifested as the failure of speed limiter-safety gear.
 
To sum up, when the elevator brake fails and the car goes down with overload, the elevator will overspeed. If the speed limiter safety gear system overtakes when overtaking, the car can still stop effectively after its return exceeds 115 of the rated speed. However, if the speed limiter safety gear system fails, the elevator squatting accident cannot be avoided. When the elevator traction capacity is insufficient or the control system fails, when the car exceeds the bottom end station, the main engine or brake will lose power through the end station protection switch, and the car can also be stopped. If the end station protection switch fails, squatting accident will easily occur when the elevator overruns. When the elevator goes up with light load, if the brake fails, it will cause the elevator to go up and overspeed. For the elevator that is not equipped with the up protection device or the up protection device fails, the top rush accident will occur. For the elevator that the up protection device is the strong speed limiter safety clamp system, if the speed limiter safety clamp system fails at this time, the top rush accident will also occur. When the elevator goes up and approaches the top end station due to the failure of the control system, if the protection switch of the end station fails or the space on the top floor of the elevator does not meet the requirements, there is a possibility that the car will rush to the top.


Through the above analysis, we can see that,Only the safety components of the elevator, such as the brake, are reliable and effective in order to avoid the occurrence of the elevator squatting and top accidents.Therefore, in addition to the daily maintenance and annual inspection of the elevator should be in accordance with the relevant provisions of the elevator safety components to do a good job of inspection and maintenance measures, but also should be easy to cause the elevator squat bottom and top of the parts to carry out targeted inspection and maintenance, in order to achieve the purpose of preventing accidents.

Article Source: Special Equipment Supervision and Inspection Station, Elevator Circle, Nanping City, Fujian Province

If there is infringement, contact Li delete

 


Keywords:

AVIC Elevator Equipment, AVIC Elevator, Elevator Sales, AVIC Elevator Sales, Elevator Maintenance