Causes and solutions for cracks in the air compressor casing

The air compressor casing is a place that many people easily overlook when maintaining the air compressor. After the air compressor has been used for a long time, cracks will appear in the parts. This situation is not uncommon. So, what are the causes of cracks in the air compressor casing? How should we check the cracks in the air compressor?

1. Causes of cracks in the air compressor casing

(1) Shell quality reasons: The probability of this situation occurring is very low, so most air compressors have been tested for water pressure and air tightness and tested before leaving the factory.

(2) Propane liquid enters the air compressor when it is started: When the air compressor is started, a large amount of propane liquid enters, and a strong collision occurs between the yin and yang rotors. The collision energy is transmitted to the air compressor casing through the shaft and bearings, causing cracks.

(3) Improper operation: If the operator does not strictly follow the operating procedures to check the air compressor before the air compressor is operated, the exhaust valve is not opened when the machine is started, causing the air compressor to be pressurized, or a large amount of propane liquid enters the air compressor before it is started and is not drained, resulting in a strong collision between the male and female rotors, and the load exceeds the shell’s bearing capacity.

(4) Poor maintenance quality: When the air compressor is repaired, an incorrect method is used to apply external force to the air compressor shell. When the air compressor is repaired, the bearings and the female and male rotors are disassembled and the assembly quality is poor, causing the female and male rotors to be pressed against each other, resulting in a load that exceeds the shell’s bearing capacity.

(5) Mechanical accidents: caused by mechanical accidents, such as piston rupture, connecting rod screw breakage, causing the connecting rod to break and fall off, or the balance iron on the crankshaft flying out and damaging the body, or the parts in the valve falling off and damaging the cylinder head, etc.

2. How to check cracks in air compressors

(1) Kerosene penetration method: When checking, first wipe the machine body and cylinder head with cotton wool soaked in kerosene. If there are suspected cracks, then wipe off the kerosene with dry cotton wool and immediately apply white powder. At this time, the kerosene will penetrate into the white powder where there are cracks, and the location and length of the cracks will be clearly displayed.

(2) Water pressure method: The water pressure method is to check the crack location by increasing the cooling water pressure. In repair shops with better equipment conditions, water pressure inspection is carried out on a special equipment-a water pressure tester. In units with poorer equipment conditions, some use ordinary hand pressure water pumps to modify simple equipment. When checking, first try to block the water pipe joints of the machine body or cylinder head, and only connect one of the water pipe joints to the water pump outlet with a rubber hose. A special cover of equivalent size should be used on the plane of the machine body to prevent cooling water from overflowing. Then turn on the switch to press the water pump to allow water to enter the cooling water jacket. After the switch starts to discharge water, turn off the switch and continue to press the water pump until the pressure gauge reaches 3-4 atmospheres, then stop supplying water. At this time, you can carefully check the machine body and the top and bottom of the cylinder head to see if there is any leakage or seepage. This can be used to determine whether the machine body has cracks.