Causes and solutions of failure of electric hoist

Causes and solutions of failure of electric hoist

1. Press the starting switch and the electric hoist does not work

It is mainly because the hoist is not connected to the rated working voltage, and it can not work. Generally, there are three situations:

(1) whether the power supply system is to power the electric hoist power supply, generally use a test pen to test, such as no power supply, and then work after power supply;(2) the gourd master and control loop of electrical appliances, circuit disconnection or poor contact, also can make the hoist motor can’t electricity, appear this kind of circumstance, need to repair the main, control circuit, maintenance and repair, in order to prevent the main and control circuits to three-phase motor power phase and burned, or hoist motor electric operation, suddenly, must will hoist motor from the power cord to disconnect on the road, only to master and control circuit of electric transmission, then click start and stop switch, check the analysis and control electric circuit working condition, to have a problem electrical equipment or lines for repair or replacement, when confirm the master and control circuit of trouble-free, to reset test;(3) than the rated voltage of the hoist motor power down more than 10%, motor starting torque is too small, make the hoist lifting goods, and unable to work, check the input voltage of motor is measured with a multimeter or a voltmeter, etc, because of the voltage is too low, truly make motor can’t start, shall system voltage return to normal before the use of electric hoist.Sometimes, the voltage of the gourd motor is normal, and the gourd is not working, which needs to be considered for other reasons, such as: the motor is burned down, the motor needs to be replaced when repairing;Calabash is not used for a long time, poor maintenance and other reasons so that the brake wheel and the end cover rust dead, starting the brake wheel off not open, the motor only issued a “hum” sound, can not turn up, the calabash can not work.At this time, should remove the brake wheel, clean the corroded surface, and then re-test;If the motor is badly swept, it will not rotate. If this situation is found, it should be stopped, and the motor must be overhauled or replaced to ensure the normal operation of the hoist.In addition, the use of electric hoist overload is strictly prohibited in production. When the goods are overloaded, the hoist does not move the goods, the motor only makes a “hum” sound, and does not operate. When it is serious, the motor will be burned, and even cause an accident.

2. Abnormal sound occurs when electric hoist is running

Electric hoist a lot of trouble, for example, the control of electrical appliances, motor and reducer, etc appeared fault, is often accompanied by abnormal noise, the noise of the position and height and don’t have the difference, with the cause of the problem in different maintenance, want to listen to see more, can make use of, or according to the fault characteristics of noise, determine a sound position, looking for and repairs.

(1) Abnormal noise occurs in the control circuit and makes “hum” noise. It is generally caused by contactor failure (such as bad contact of AC contactor, voltage level mismatch, magnetic core stuck, etc.). The fault contactor should be overseen and replaced if it cannot be overseen.

Abnormal noise, (2) motor, should immediately stop, check whether the motor is single-phase operation, or bearing damage, coupling axis is not straight, and the chamber “sweep”, these will make the machine has abnormal noise, the noise of the different fault location and high and low and don’t sound different, single phase operation, the motor from regular strong and weak “buzzing” sound.When the bearing is damaged, it will be near the bearing, accompanied by a “buzzing” sound of “stomp – stomp”;When the shaft of the coupling is not correct, or the motor is slightly swept, the whole motor issues a very high “buzzing” sound, which is not always accompanied by a sharp and harsh sound.In short, according to the different noise, find out the fault, carry out item by item maintenance, restore the normal performance of the motor, when the motor fault is not dealt with, prohibit the use of hoist.

(3) the abnormal noise from the gear reducer, gear reducer failure (such as reducer or lack of lubricating oil bearing, gear, wear or damage to the bearing damage, etc.), then should stop check, first determine reducer reducer or bearing before use if the lubricating oil, oil change regularly in use, such as no lubrication, according to the requirement reducer will not only produce high “buzzing” sound, gear and bearing excessive wear or damage.Some people think that the reducer temporarily do not add or casually add lubricating oil, still can run, will not happen serious failure, this kind of thought is wrong.Our company installed a electric hoist, because the workers forgot to reduce the lubricating oil box, only a day of trial, the reducer is issued a very high sound, open the reduction box, found that the gear due to excessive wear and scrap.Reducer bearing damage, similar to motor bearing failure, will also emit abnormal sound near the bearing.In order to prevent the expansion of the fault, whether the reducer gear is excessively worn or damaged, or the reducer bearing is damaged, it is necessary to immediately disassemble, overhaul or replace, eliminate the fault and reduce noise.

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3. When braking, the downtime sliding distance exceeds the specified requirements

Electric hoist out of service for a long time, someone mistakenly adjust the brake adjustment nut, or brake ring wear is too large, so that the brake spring pressure is reduced, the braking force is reduced, when the shutdown, braking is not reliable, sliding distance exceeds the specified requirements, this situation as long as according to the hoist specification requirements, adjust the brake nut can be.But we should pay attention to the work, lifting heavy objects, prohibit the adjustment, inspection and maintenance of the brake.Sometimes, adjust the braking nut, stop falling distance in excess of the prescribed requirements, still encounter such a situation, consider other causes, first open brake ring first, check whether the brake surface with oil pollution, such as with oil, reduce the friction coefficient, can make the brake when sliding, falling distance in excess of the prescribed requirements, just adjust the braking nut is not much use, and only thoroughly clean brake surface (cleaning is easy to use benzine), restore the brake surface friction coefficient;Secondly, such as the brake ring loosening or damage, the brake ring can not ensure effective braking, only replace the brake ring;Sometimes find brake ring did not damaged, only poor contact damping ring and rear end cover cone, brake, the brake surface contact, less braking force is too small, the decline in excess of the prescribed requirements, maintenance and repair, in order to increasing the braking force, should find out the position of the poor contact, grinding, increase the contact area when braking, failing to grinding, need to replace accessories;The coupling of the hoist motor is not moving smoothly or stuck. After stopping, the contact between the brake ring and the cone of the rear end cover is bad or unable to contact, so that the brake effect of the hoist is good or bad. In such cases, the coupling should be repaired or replaced.In addition, the brake pressure spring for a long time to produce fatigue, so that the spring force becomes small, stop, the brake is not firm, you should replace the spring, readjust the braking force.

4, the motor temperature rise is too high

First of all, we should check whether the hoist is overloaded. Overloading will lead to motor heating. Long-term overloading will burn the motor.If the motor is not overloaded and still gets hot, check whether the motor bearing is damaged;It is also necessary to check whether the motor works in accordance with the prescribed working system, which is one of the reasons for the heating of the motor. When using, it should be strictly in accordance with the working system of the motor.When the motor is running, the brake clearance is too small, not completely off, resulting in a lot of friction, friction heating at the same time is equivalent to increasing the additional load, so that the motor speed is reduced, the current becomes larger and the heat, at this time should stop working, readjust the brake clearance.

5. If the weight rises to mid-air, it cannot be started again after stopping

To analyze the reasons, first check whether the system voltage is too low or whether the fluctuation is too large, in this case, only wait for the voltage to return to normal before starting;On the other hand, we should pay attention to the lack of phase in the operation of the three-phase motor, which can not be started after shutdown. At this time, we need to check the number of power phase.

6, can not stop or to the limit position still do not stop

This kind of situation is generally the contact welding of the contactor. When the stop switch is pressed, the contact of the contactor can not be disconnected, the motor can run as usual, and the hoist does not stop.To the limit position, if the limiter is out of order, the hoist will not stop.In this case, cut off the power immediately, so that the gourd forced to stop.After stopping, overhaul the contactor or limiter. If it is badly damaged and cannot be repaired, it must be replaced.

7. Reducer leaks oil

There are two reasons for oil leakage of reducer:

(1) between the reducer box body and the box cover, the sealing ring assembly is poor or failure damage, should be removed to repair or replace the sealing ring;

(2) The connecting screw of the reducer is not tightened. After stopping the machine, the screw should be tightened.

8. The reasons for sweeping of the motor are as follows:

The motor shaft bearing ring wear is serious, the rotor core displacement, or due to other reasons to make the stator core displacement, resulting in the motor cone rotor and stator clearance is too small, and the sweep occurs.Motor “sweeping” is strictly prohibited. When sweeping occurs, the supporting ring should be removed for replacement, and the gap between the stator rotor cone should be adjusted to make it uniform, or sent to the repair shop for repair.Through the analysis of common faults and treatment of electric hoist, so that hoist maintenance personnel to deal with faults, know where to start to check, improve the maintenance efficiency, in addition, but also for the operator to provide a method to deal with problems on the site.

Post time: Mar-24-2021