Air compressor tripping refers to the air compressor overload, the protector disconnects, and the air compressor stops working. After the protector trips, it takes a long time to recover, resulting in the air compressor being unable to be used normally, and the user is delayed in production.

There are some uncommon reasons for air compressor tripping, but these uncommon possibilities are difficult to repair.

For maintenance personnel who are not familiar with the structure and principle of air compressors, encountering such problems will be a headache.

When encountering such a problem, it is recommended that you use the “elimination method” to eliminate the causes of the fault one by one.

1. Start under pressure

First, check the pressure gauge of the oil and gas tank of the air compressor. If there is pressure, it is preliminarily judged that there is pressure in the air compressor system, which causes the air compressor to start under pressure, causing the starting current to be too high, and the air switch trips to protect the unit. The reason for this situation is usually due to the failure of the minimum pressure valve or the blockage of the pressure relief system. Of course, it is also possible that the pressure gauge is faulty and misleads the maintenance personnel; the maintenance personnel can judge by checking the pressure of the oil and gas tank; the method is very simple, open the pressure relief valve in the air compressor system, when the pressure relief valve is opened, the pressure gauge of the oil and gas tank still shows that there is pressure, that is, the pressure gauge is faulty, otherwise, it is under pressure; the air compressor is overloaded, which will also cause the air switch to trip. Air compressor overload is usually caused by excessive resistance of the air compressor head, resulting in a large starting current of the air compressor, causing the air switch to trip.

Therefore, the role of lubricating oil in screw compressors is crucial. Its role is mainly manifested in four aspects: cooling, lubrication, sealing, and noise reduction. The quality of the oil and the amount of oil directly affect the normal operation and service life of the air compressor, especially the air compressor head. There are three main situations that lead to increased resistance in the air compressor head:

(1) High viscosity of lubricating oil.

(2) Coking of the air compressor head; coking of the air compressor head causes the friction resistance of the air compressor rotor to increase during operation, and the current of the air compressor increases accordingly.

(3) Excessive amount of lubricating oil in the air compressor head will also lead to increased resistance. After the air compressor is shut down, the oil shut-off valve is not closed in time, and a large amount of lubricating oil enters the air compressor head, resulting in a large starting resistance when the air compressor is restarted.

2. Electrical device failure

(1) Star-delta switch failure causes the air compressor to trip immediately after starting. During use, the air switch may be affected by the vibration of the air compressor, which may shorten the set start time or even trip the machine now of starting.

(2) Failure of the inverter can also cause the air compressor to travel. Instability of current and voltage, high temperature of the inverter, etc. can all cause the air compressor to trip.

3. Unloading valve failure

Function of the air compressor unloading valve: When the air consumption changes, the air intake valve adjusts the opening degree of the valve body to match the air consumption through the control system. It is a valve (solenoid valve) that controls the air intake and non-intake of the air compressor.

The most intuitive way to judge whether the unloading valve is closed or not is to remove the air filter, and you can clearly see whether the air intake baffle of the unloading valve is in a closed state or an open state. If the air intake baffle is stuck due to mechanical impurities, the unit can be opened smoothly after cleaning; if the air intake 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.

There is another fault that is difficult to find, which is the early opening of the unloading valve. Before the air compressor is started, the unloading valve is in a closed state, and when the air compressor is started, the unloading valve slowly opens. However, if the opening time is a few seconds earlier than the preset time, it will cause the starting current of the air compressor to increase and the air compressor to trip. To discover this fault, maintenance personnel must accurately grasp the startup time of the air compressor.

4. Lubricating oil causes high temperature tripping

The temperature-controlled bypass valve controls the on-off of the valve core through a temperature-sensing probe, and determines that the opening temperature of the temperature-controlled bypass valve is within 70±10℃; after long-term use, the accuracy of the probe decreases and it cannot operate at the normal temperature point, so that the hot lubricating oil coming out of the air compressor body returns directly to the air compressor body without passing through the cooler, and the temperature of the air compressor also rises, which is difficult to control, triggering a high temperature tripping; there is another situation where the lubricating oil with impurities passes through the temperature-controlled bypass valve, and the valve core is stuck, so that the valve core cannot be completely closed, and part of the lubricating oil returns directly to the air compressor body without passing through the cooler, resulting in poor cooling effect of the entire air compressor, triggering a high temperature tripping.

Therefore, when the lubricating oil of the air compressor fails or deteriorates, please replace the lubricating oil in time. Do not use inferior lubricating oil.