Air Compressor Troubleshooting and Solutions

Spencer Bates
6 min readJun 20, 2021

With the development of motor technology, the compressor is considered as “general machinery”, especially in the coal chemical industry, machinery industry and other industries.

For distance measurement applications, both incremental and absolute encoders can be chosen — from a technical point of view. The advantages of absolute encoders are reflected in accuracy and performance, while incremental encoders seem more economical and practical.

A correctly working compressor determines the safe operation of the whole air conditioner or refrigerator. For example, during the operation of a piston compressor, there would be burnout, oiler failure or low pressure and gas shortage. Once these problems occur, the appliance would not work right.

How to quickly and accurately detect and solve these problems in time affects the compressor operating rate and product output.

This article will analyze all common faults of AC compressors and provide solutions.

From the perspective of airflow, a possible fault is that the wind pressure or the temperature of compressed air is too high, which may cause spontaneous combustion of carbon deposits and explosion of the pressure vessel if the protective device fails.

Another possible problem is that the air volume is insufficient or the air volume is too low, which will affect production.

From the perspective of the compressor structure, there are four types of problems: problems of the lubrication system, cooling water circuit, compressed air circuit and mechanical failure.

  1. Compressor Shell Burnout

When a piston compressor is in operation, the Babbitt layer of the main bearing shell or connecting rod bearing shell may be burnt or fall off. This causes the temperature of the bearing shell to rise, producing high temperature and smoke, making the Babbitt alloy melt.

-1.1 Low Oil Temperature

In the past, we are worried about the high oil temperature of the crankcase that can cause burnout. It is stated in the manual that the oil temperature cannot exceed 60℃ or 70℃, but there is no lowest limit.

However, oil temperature lower than the standard may cause the same fault. In winter, after the compressor is shut down, the oil temperature in the crankcase of the compressor is lowered. So the oil is very viscous and the shell is burned after the machine is turned on again. Therefore, it is better to use low-consistency oil in winter.

-1.2 Low Oil Level in Crankcase

If the lower hole of the oil level is blocked, the dropping oil level cannot be found. And if the crankcase oil level is too low, the oil pump will suck in air intermittently.

Air drag is generated in the drainpipe, causing the oil film of the bearing shell damaged. Afterwards, the compressor shell will be poorly moisturized gradually, and it leads to burnout in the end.

-1.3 Clearance Between Bearing Shell and Shaft

We used to adopt the method of pressing lead wire to measure the clearance between the bearing shell and the shaft.

This method is suitable for measuring the main bearing shell because the main bearing is fixed and the upper shell cover is buckled on the main journal that will not move when the bolt is tightened.

However, the method is not appropriate for the measurement of connecting rod bearing shell. When tightening the connecting rod, the lead wire will be squeezed. If the connecting rod is tilted, it cannot truly reflect the clearance.

Therefore, we should use a dial indicator to measure the clearance according to the size of the shaft.

  1. Oil Injector Failure

-2.1 Fail to Fill Oil

If the oil injector is not filled with oil, it should be disassembled and inspected.

If the plunger and the pump body are excessively worn, causing the gap to increase and the pressure oil to leak back, you should clean, and repair, and replace them.

-2.2 Fail to Suck Oil

If the oil injector does not suck oil, and it does not drip oil when viewed from the oil cover, it means that the oil suction valve is stuck, or the oil cover is not installed tightly, and the air has entered.

It is necessary to clean the oil suction ball valve in the oil injection pump and replace the rubber ring of the oil cover.

-2.3 Insufficient Oil Supply

The insufficient oil supply of the oil injector is due to long-term operation with an uncleaned system, which has resulted in pipeline blockage finally. Or it may be that the nut joint is not tightened after overhaul, causing oil leakage. To solve it, you should clean the pipeline and tighten the joints.

  1. Low Pressure and Insufficient Air Volume

When the compressor pressure is low and the air volume is insufficient, if there is no air leakage in the compressed air pipeline, it is usually the problem of the compressor unit itself.

There are several problems that cause the insufficient exhaust volume of the compressor unit.

-3.1 Timely Maintenance

First of all, check whether the compressor discharge has decreased after maintenance. How long has the service last? If the environment is not ideal, check whether the air filter is blocked when the compressor runs for 2000 hours.

If the air filter is not blocked seriously, you can just carry out a dust removal procedure. If the blockage is serious, you should replace the old air filter with a new one.

Most of the time, there is no big problem when the discharge of the compressor drops. The problem is that the customer neglects the maintenance and the air filter of the compressor is blocked. After replacing a new air filter, the compressor can work normally.

In addition to an air filter, lubricant and other filter elements are also critical. Check whether the lubricant is within the standard range. If it is missing, please add it appropriately.

-3.2 Open Intake Valve

If the discharge of the compressor decreases, check the unit.

If your compressor has just been served with a maintenance service, and there’s no problem with three filters and oil products, a technician should check the intake valve of the compressor.

Remove the intake hose, open the compressor, and watch whether the opening of the intake valve is normal.

Generally, the theoretical design service life of the intake valve is 100000 times. Due to the different brands and batches of each manufacturer, the quality may be different. Therefore the failure of the intake valve may lead to the decrease of the unit’s exhaust volume.

If the intake valve cannot be fully opened when the compressor is loaded, it can be concluded that the decrease of exhaust volume is the fault of the intake valve, which should be removed for maintenance or replacement.

-3.3 Motor Failure

After the troubleshooting of the intake valve and the exhaust volume of the unit is still unchanged, you should consider whether the motor is functioning well.

Due to the local short circuit in the motor coil, or bearing wear and motor shaft wear, the motor speed is lower than the rated speed, which reduces the discharge capacity of the compressor. The motor coil and bearing should be overhauled, and the discharge capacity of the compressor should be tested after repair.

-3.4 Working Pressure is Set to Be Low

If the working pressure switch of the compressor is set to be lower than standard, it should be raised to an upper value.

During factory debugging of the compressor, the working pressure is set according to customer needs. During customers’ use period, it may be set at a differential pressure. For example, when the compressor starts to pump air into the air tank, and the pressure reaches 10kg, the compressor stops or unloads. When the pressure reaches 7kg, the compressor starts up again. There is a pressure difference between them. This process can leave the compressor with a rest to protect it.

Different compressor switches have different adjustment methods. One is that the pressure difference is fixed by the switch itself, which only regulates the automatic shutdown pressure and the maximum pressure. This kind of switch is equipped with two buttons adjusted by a slotted screwdriver. The two buttons must be adjusted in the same way. Otherwise, they will move together and stop, stop and start again, and burn out the electrical appliances.

The other is to regulate the starting pressure (low pressure) and the stopping pressure (high pressure).

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Spencer Bates

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