Aug 30, 2021 
Figure 1: The ammonia refrigeration compressor in the industrial scene.
Refrigeration Compressor not Starting
Figure 2: Mitsubishi Compressor ANB52FKFMT
* Maintenance Methods
First, you should test whether the supply voltage is too low, or the connection of the motor line is poor.
If the grid voltage is low, you can start the compressor again after the grid voltage is restored to normal. If the line connection is bad, you should examine and repair the connection between the line and the motor.
You should inspect if the exhaust valve plate leaks. If the exhaust valve plate or the seal is damaged, the leakage will cause the pressure in the crankcase to be high, resulting in the failure of starting normally. You should replace the exhaust valve plate and sealing.
You then check if the energy regulating mechanism is out of order. It mainly includes the check of the oil supply pipeline, the pressure, and the oil piston.
You then check if the energy regulation mechanism is out of order, which mainly includes the oil supply pipeline, the pressure, and the oil piston. And you can repair it according to the causes.
You should examine the condition of the temperature controller. If it is maladjusted, you should adjust it. If it is damaged, repair or replace it.
At last, you can inspect the pressure relay. After repairing the pressure relay, you should reset the pressure parameters.
Lack of Oil Pressure
* Maintenance Ways
You should check if there is oil leakage at the connection of the oil pump pipeline system or at the blockage. You can tighten joints. If it is blocked, dredge the oil pipeline.
You should figure out that the large opening degree of the oil pressure regulating valve or the fallen core leads to oil pressure failure.
If the oil pressure regulating valve is not properly adjusted, you should adjust the oil pressure to the required value. If the core falls off, it is necessary to re-install it and tighten it firmly.
Insufficient oil or ammonia liquid in the crankcase will cause the oil pump to fail to feed oil. To troubleshoot it, you can add oil, or stop the compressor and eliminate ammonia liquid.
The oil pump is seriously worn and the clearance is extremely large, resulting in low oil pressure. In this case, you should repair the oil pump, or replace it when the fault is serious.
Check the connecting rod bearing bush, spindle bush, small head bushing, and a piston pin. If they are worn seriously, you should replace the relevant parts in time.
Figure 3: The connecting rod bearing.
The gasket of the rear end cover of the crankcase is misplaced, blocking the oil inlet channel of the oil pump. The gasket should be disassembled and checked, and its position should be fixed again.
High Oil Temperature
* Maintenance
The shaft and bush are not appropriately assembled, leading to extremely small clearance. You should adjust the clearance to make it meet the requirements.
There are impurities in the lubricating oil making the bush rough. In this case, you should scrap the bearing bush first, and then replace it with the new oil. But if the bush is seriously rough, you should replace it.
The shaft sealing ring is installed tightly. You should adjust it to a proper position. And you can replace a new friction ring according to its condition.
If the high oil temperature is caused by the high suction and exhaust temperature of the compressor, you should properly adjust the liquid supply valve of the system to make the suction and exhaust temperature return to normal.
Abnormal Sound in the Crankcase
Figure 4: A crankcase.
* Maintenance Methods
You should check if the clearance between the connecting rod bush and the crankshaft journal is too large. If so, you can take measures to make the gap small or directly replace it with a new bush.
If the clearance between the main bearing and the main shaft journal is too large, causing collision and friction and making a sound. They should be repaired or replaced.
Inspect whether the split pin is broken and the connecting rod nut is loose. If so, replace the split pin and tighten the connecting rod nut.
If the coupling or the key of the coupling has faults, you should adjust the coupling or maintain the key or replace a new key.
The main bearing steel ball is worn, and the bearing frame is fractured. In this case, replace the new bearing.
Cylinder Wall Overheating
Figure 5: The compressor cylinder internal structure.
* Maintenance Ways
You should check the oil pump that may cause the oil pressure to be too low or the oil circuit to be blocked. To solve it, shut down the compressor for a comprehensive overhaul.
Inspect whether the clearance between the piston and the cylinder wall is too small or the piston deviates. The solution is to adjust the piston.
The seal of the safety block or the false cover is not tight, resulting in a mixture of high- and low-pressure. You should take measures to improve the sealing performance.
Check whether the suction temperature is too high. Adjust it to lower the temperature.
If it’s the bad lubricating oil of small viscosity that leads to the high temperature, you should stop the machine to replace the new lubricating oil.
Examine the cooling water jacket to know if the scale is too thick or the water is insufficient. You can remove the scale in time, or add the cooling water.
Inspect the conditions of the suction and exhaust valve plates. If damaged, they should be replaced in time.
Check whether the piston ring has been seriously worn. If so, replace a new one.
Serious Oil Leakage of the Shaft Seal
Figure 6: Six steps to replace the oil seal of the compressor.
* Maintenance Ways
Check whether the shaft seal assembly fails to meet the requirements.
Check whether the friction surface between the moving ring and the fixed ring has been rough. If it’s extraordinarily rough, you should carefully ground and reassemble the sealing surface.
The rubber-sealed loop is aging or the tightness is not set appropriately, which will lead to oil leakage. In this case, you should replace it with a new rubber sealed loop and adjust it to the appropriate tightness.
Check whether the spring of the shaft seal is weakened in spring force, resulting in the oil leakage of the shaft seal. You should remove the original spring and replace it with a new spring of the same size.
The sealing performance of the back of the fixing ring and the shaft seal gland is worse. To troubleshoot it, you should remove the fixing ring and clean and reassemble the back ring.
Adjust the crankcase pressure to the normal value. But before stopping the machine, you should lower the pressure of the crankcase first and check the exhaust valve for leakage.
