Reasons and troubleshooting methods for abnormal shutdown of air compressor

Abnormal shutdown of air compressor mainly refers to shutdown other than abnormal planned shutdown for maintenance. Usually, the main reasons for abnormal shutdown of air compressor are as follows.

1. Thermal relay tripping

When the current of the motor is seriously overloaded, the thermal relay will heat up and burn out the short circuit, causing the control circuit to disconnect and realize overload protection of the motor.

Maintenance method: 1. Choose a thermal relay of appropriate specifications; 2. Check the circuit fault and replace the appropriate thermal relay after eliminating the short circuit fault; 3. Change the way you operate the motor to reduce the number of times you start the motor; 4. Try to remove the terminals and the thermal relay. The oxide layer of the relay terminals and re-tighten the main wiring of the thermal relay.

2. Unloading valve failure

The air compressor unloading valve is a valve that when the air consumption changes, the air intake valve control system is used to adjust the opening degree of the valve body to match the air consumption, thereby controlling the air intake or non-intake of the air compressor. If a malfunction occurs, it will also cause the air compressor to shut down abnormally. If the air inlet baffle is stuck due to mechanical impurities, etc., the unit can be started smoothly after cleaning it; if the air inlet baffle is stuck on the guide rod, grind the guide rod with sandpaper and apply a small amount of grease on the guide rod; If the unloading valve is seriously damaged, the unloading valve needs to be replaced.

3. Power failure

Power failure is one of the most common reasons for air compressor shutdown, and it is also the best to check and repair. First of all, check whether the power wiring of the air compressor is correct, whether the power switch is closed to prevent someone from accidentally turning it off; whether the power fuse is blown, and whether the power supply voltage reaches 90% or more of the rated voltage. Then check whether all components of the pressure relay of the air compressor power supply are damaged and whether the given value of the pressure relay is appropriate.

4. High exhaust temperature

The excessively high exhaust temperature of the screw air compressor is generally caused by the excessive temperature of the oil cooler and water cooler, or it may also be due to sensor failure and other reasons. Some alarms can be eliminated immediately through the operation of the controller page, but sometimes an alarm of excessive exhaust temperature appears after elimination. At this time, in addition to checking the circulating water, the problem of lubricating oil must be considered. Note that there are two types of high temperatures: 1. The air compressor itself generates too much heat; 2. The normal heat generated cannot be taken away. For the first problem, the cause should be found on the air path, such as: damage and dirt of the suction and exhaust valves at all levels, air backflow and vortex caused by failure of the seal under the valve, which generates a large amount of heat. The air compressor has to go through four strokes: suction, compression, power, and exhaust to produce high-temperature, low-pressure gas. In order to ensure the normal suction of the next-stage cylinder or the user’s use of gas, the high-temperature gas must be forced to cool. In this case, part of the normal heat is dissipated into the environment and part is taken away by the cooling water. Poor heat dissipation and poor cooling system circulation are the main reasons for high exhaust temperatures. The radiator is blocked, the cooling water is insufficient, the water pump is damaged, there may be too much scale, the fan performance is poor, etc.

5. The machine head resistance is too large

Overloading the air compressor can also cause the air switch to trip. Air compressor overload is usually caused by excessive air compressor head resistance, which causes the air compressor starting current to be too large, causing the air switch to trip. The viscosity of the lubricating oil is too high, the amount of oil is too much or the machine head is coked, which may cause the air compressor to shut down abnormally.

Maintenance method: 1. Manually turn the air compressor to check whether the machine head and motor can rotate freely to determine whether the resistance has increased. When the ambient temperature decreases, the viscosity of the oil increases, the resistance also increases, the starting current of the motor becomes larger, and the starting time of the air compressor is extended. The ambient temperature at that time can be determined based on the exhaust temperature.

2. Slightly extend the starting time of the motor on the air switch while ensuring safety, so as to extend the starting time of the air compressor when the oil viscosity increases and ensure the normal starting of the air compressor. Do not extend it too much, as it will affect other electrical equipment.

Open the machine head, release some of the lubricating oil inside the machine head, and repair or replace the oil cut-off valve at the same time.

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