The compressor lacks oil, so the harm is so great! Compressors are complex machines that operate at high speeds. Ensuring adequate lubrication of moving parts such as compressor crankshafts, bearings, connecting rods, and pistons is the basic requirement for maintaining normal operation of the machine. There are three common faults of compressors: motor burnout; oil shortage caused by freezing oil; liquid strike. Let's explain in detail the oil shortage caused by refrigeration oil.
Oil shortage Lack of oil is one of the compressor faults that can be easily identified. When the compressor is short of oil, there is little or no lubricating oil in the crankcase. The compressor is a special air pump, and a large amount of refrigerant gas is also discharged while entraining a small part of the lubricating oil (called running oil or running oil). Compressor running oil is inevitable, but the speed of running oil is different. There is about 2-3% lubricating oil in the exhaust of the semi-sealed piston compressor. Scroll compressor is 0.5-1%. For a 6-cylinder compressor with a displacement of 100m3/hr and a crankcase oil storage of 6 liters, 3% of the oil flow means about 0.3-0.8 liters/minute of oil flow, or the compressor runs without oil return The time is ten minutes. If the lubricating oil discharged from the compressor does not come back, the compressor will be short of oil.
There are two ways to return oil to the compressor: one is to return oil from the oil separator, and the other is to return oil from the air return pipe. The oil separator is installed on the compressor exhaust line, and can generally separate 50-95% of the oil. The oil return effect is good and the speed is fast. The amount of oil entering the system pipeline is greatly reduced, thereby effectively extending the operation without oil return. time. When the compressor is higher than the evaporator, the oil return bend on the vertical air return pipe is necessary. The oil return bend should be as compact as possible to reduce oil storage. The spacing between the oil return bends should be appropriate. When the number of oil return bends is relatively large, some lubricating oil should be added. Compressor noise, vibration or excessive current may be related to oil shortage, so it is very important to accurately judge the compressor and system operating conditions.
The wear caused by compressor oil shortage is generally more uniform. If there is little or no lubricating oil, severe friction will appear on the bearing surface, and the temperature will rise rapidly within a few seconds. If the power of the motor is large enough, the crankshaft will continue to rotate, and the crankshaft and bearing surfaces will be worn or scratched, otherwise the crankshaft will be locked by the bearing and stop rotating. The reciprocating movement of the piston in the cylinder is also the same. The lack of oil will cause wear or scratches. In severe cases, the piston will get stuck in the cylinder and cannot move.
Insufficient lubrication The following three reasons can also cause insufficient lubrication: 1. Lubricant cannot reach the bearing surface; 2. Although the lubricating oil has reached the bearing surface, the viscosity is too small to form an oil film of sufficient thickness; 3. Although the lubricating oil has reached the bearing surface, it is decomposed due to overheating and cannot play a lubricating role. Blockage of the oil suction network or the oil supply pipeline, failure of the oil pump, etc. will affect the delivery of the lubricant, and the lubricant cannot reach the friction surface away from the pump. The oil suction net and oil pump are normal, but bearing wear, excessive clearance, etc. cause oil leakage and oil pressure to be too low, so that the friction surface away from the oil pump can not get lubricating oil, causing wear and scratches.
Insufficient lubrication The following three reasons can also cause insufficient lubrication: 1. Lubricant cannot reach the bearing surface; 2. Although the lubricating oil has reached the bearing surface, the viscosity is too small to form an oil film of sufficient thickness; 3. Although the lubricating oil has reached the bearing surface, it is decomposed due to overheating and cannot play a lubricating role. Blockage of the oil suction network or the oil supply pipeline, failure of the oil pump, etc. will affect the delivery of the lubricant, and the lubricant cannot reach the friction surface away from the pump. The oil suction net and oil pump are normal, but bearing wear, excessive clearance, etc. cause oil leakage and oil pressure to be too low, so that the friction surface away from the oil pump can not get lubricating oil, causing wear and scratches.
Due to various reasons (including the start-up phase of the compressor), the temperature of the friction surface that does not get lubricating oil will rise rapidly, and the lubricating oil will decompose after exceeding 175°C. "Insufficient lubrication-friction-high temperature on the surface-oil decomposition" is a typical vicious cycle. Many vicious accidents including connecting rods and shafts and piston cylinders are related to this vicious cycle. Summary 1. The fundamental reason for the lack of oil is not how much and how fast the compressor runs, but the system does not return oil well. 2. The oil separator can be installed to return oil quickly, extending the operation time of the compressor without oil return. 3. The design of the evaporator and the return gas pipeline must take oil return into consideration. 4. The migration of liquid and refrigerant will dilute the lubricating oil, which is not conducive to the formation of oil film. Pay attention to the liquid return of the system. 5. The failure of the oil pump and the blockage of the oil circuit will affect the oil supply and the oil pressure, resulting in the lack of oil on the friction surface. Pay attention to the detection of the oil system. All in all, the root cause of oil shortage lies in the system. Only replacing the compressor or some accessories can not fundamentally solve the problem of oil shortage.
