Cause analysis of the action of safety gear in the

Elevator safety gear action cause analysis

elevator safety gear action cause analysis and inspection precautions

preface

elevator safety gear is a safety device that makes the elevator car stop on the guide rail in an emergency under the control of the speed governor. It is one of the important safety protection devices in the elevator safety protection system, which can protect the safety of passengers and equipment in the case of elevator overspeed and falling. Next, combined with the action principle of safety gear, the reasons for the action of safety gear, especially the causes and analysis of misoperation, as well as the author's usual inspection experience, talk about some points for attention in the inspection of safety gear

1 elevator safety gear

1.1 there are 5O through holes in the safety gear action coding disk, which constitutes the principle of binary cyclic code

the action of the elevator safety gear device is to make the rope gripper clamp the speed governor rope through the action of the speed governor. As the car moves downward, the speed governor rope lifts and pulls the safety gear linkage mechanism, and the safety gear linkage mechanism acts to drive the safety gear braking elements to contact the guide rail, so that the safety gear on both sides of the guide rail is clamped on the guide rail at the same time, At the same time, the electric switch configured on the speed governor and safety gear acts to cut off the safety circuit of the control system and stop the motor

1.2 types and application scope of safety gear

safety gear can be divided into instantaneous safety gear and progressive safety gear according to its working principle

according to GB7588-2003 "safety code for elevator manufacturing and installation", instantaneous safety gear can only be used for elevators with rated speed below 0.63M/s, and progressive safety gear can be used for all elevators

1.3 design requirements of safety gear

according to the requirements of GB7588-2003 safety code for the manufacture and installation of elevators and GB/tl0058-1997 technical conditions of elevators, elevator safety gear must meet the following design requirements:

1) when the car with rated load falls freely, when the safety gear acts, the average deceleration of the car should be between 0.2g and 1.0g

it is necessary to understand their respective advantages. 2) when the car distributes the load evenly, the inclination of the car floor should not exceed 5% of its normal position after the safety gear acts

3) the safety gear should have an electrical safety device, which cuts off the power supply of the motor before the safety gear acts

4) the stopping distance of instantaneous safety gear is less than 50mm, and the minimum stopping distance of progressive safety gear is smin=v2/19.62+0.122; The maximum value is smax=v2/3.924+0.256, where V is the action speed of the governor

2 causes of safety gear action

2.1 protective action

under the action of faults such as overspeed and falling, the safety gear action is caused by the principle of speed governor safety gear linkage, which plays the role of safety protection

2.2 malfunction and troubleshooting of safety gear

the function of safety gear is when the elevator car is overspeed. When the speed of sliding or falling reaches the action speed of the governor, the governor operates the safety gear to clamp the elevator car on the guide rail after it stops safely, so as to prevent accidents. However, in actual use, there are some situations in which the safety gear acts when the elevator car does not overspeed and the speed governor does not act

2.2.1 misoperation caused by improper adjustment of speed governor

the speed governor is not adjusted well or there is a layer of grease on the contact surface between the eccentric cam and the rubber wheel. During operation, the centrifugal force of the rubber wheel increases, causing the wedge at the other end to seize the cam slot, resulting in misoperation of the safety gear

Troubleshooting: adjust the governor spring to synchronize the speed of the governor with the speed of the traction machine; Wipe the greasy surface I of the rubber roller with alcohol, and regularly maintain the speed limiting wheel

2.2.2 maloperation caused by improper clearance between wedge block and guide rail of safety gear

1) some safety gear have different lateral clearance between wedge block and guide rail due to some installation errors during installation. This series of testing machines are mainly used for various steel strands. In order to ensure that the clearance between wedge block and guide rail is consistent, the method of adjusting the height of two wedges is adopted, resulting in inconsistent height of wedge block. In this way, during use, the wear of the guide shoe bushing under the wedge reduces the lateral positioning of the car guide shoe, and increases or decreases the lateral clearance between the safety gear wedge and the guide rail. In addition, the long-term operation makes some sundries, dust and guide rail lubricating oil mixed together, accumulated between the wedge and the guide rail, which is not removed in time, resulting in resistance between the wedge and the guide rail when the wedge runs synchronously with the car. When the resistance reaches a certain value, the wedge on the side with small clearance will act, causing the car to be stuck on the guide rail, so that the safety gear will misoperate

Troubleshooting: the installation must be in place to minimize the height difference of the wedge. If the wedge at the low end affects the guide shoe bushing below it, it must be adjusted in place

2) during the use of elevator, the clearance between wedge and guide rail will change due to vibration, wear and other reasons, resulting in inconsistent lateral clearance between wedge and guide rail. When the clearance is too small, it is also easy to cause misoperation of safety gear

Troubleshooting: according to the technical requirements, adjust the clearance between the wedge block of umbrella pliers and guide rail side III to ensure that the clearance is within the range of 2 ~ 3mm

2.2.3 misoperation caused by ineffective wedge action

too much oil stains between the wedge and the wedge seat, and the wedge action is not sensitive, which will lead to the failure of the wedge to reset the umbrella after the action of the safety gear, and the clearance between the safety gear and the guide rail is too small, which is also easy to promote the misoperation of the safety gear

Troubleshooting: the maintenance unit should regularly clean up the grease deposited in the wedge and lubricate it regularly with a small amount of Vaseline

2.2.4 misoperation caused by tensioner failure

the tensioner and shaft are short of oil, causing the tensioner to heat and bite, resulting in the misoperation of governor rope lifting safety gear

Troubleshooting: the maintenance unit injects oil into the tensioning wheel of the pit to ensure that the tensioning wheel rotates flexibly and is maintained regularly

2.2.5 maloperation caused by insufficient tension of speed governor steel wire rope

insufficient tension of speed governor steel wire rope, slack of speed governor steel wire rope, especially in high-rise elevators, speed governor steel wire rope is easy to entangle with lower deceleration switch, lower limit switch and lower limit switch (especially after the test of speed governor safety gear), resulting in maloperation of safety gear

Troubleshooting: readjust the tension of the speed governor wire rope and tighten it

2.2.6 maloperation caused by poor lifting action of the safety gear

the driving part of the connecting rod pull arm of the safety gear is lack of oil and rusted, resulting in inflexible action of the pull rod. After the safety gear acts, the lifting rod is not completely lifted, causing the safety gear to grind the guide rail and run. If there is a bulge in the guide rail interface, the safety gear will act again

Troubleshooting: the maintenance unit shall regularly clean the rotating part of the pull rod and lubricate it regularly

2.2.7 maloperation caused by other reasons

due to decoration, there will be more foreign objects established in factories in the future, such as stones, falling into the shaft and stuck into the wedge of safety gear, resulting in maloperation of safety gear

Troubleshooting: if the elevator suddenly makes an abnormal noise during operation, it must be carefully checked to eliminate the fault, so as to prevent foreign matters from clamping into the wedge of the safety gear, resulting in the misoperation of the safety gear