Analysis of Causes of Insufficient Lubrication

Insufficient lubrication

The direct cause of wear is insufficient lubrication. Lack of oil will certainly cause insufficient lubrication, but lack of oil may not be caused by lack of oil. The following three reasons can also result in insufficient lubrication: Lubricants cannot reach the surface of the bearing; the lubricant has reached the surface of the bearing, but the viscosity is too small to form a sufficient thickness of the oil film; while the lubricant oil has reached the bearing surface, it is decomposed due to overheating. Lost, can not play a role in lubrication.

The blockage of the oil absorption network or the oil supply line, the failure of the oil pump, etc. all affect the transportation of the lubricating oil. The lubricating oil cannot reach the friction surface far away from the oil pump. The oil suction net and the oil pump are normal, but the bearing wear, excessive clearance, etc. cause oil leakage and oil pressure to be too low, so that the friction surface far away from the oil pump will not be lubricated, resulting in wear and scratches.

Liquid return is a common system problem, and one of the major hazards of liquid return is the dilution of the lubricant. After the diluted lubricating oil reaches the friction surface, the viscosity is low and a sufficient thickness of the protective oil film cannot be formed, resulting in wear over time. When the liquid volume is relatively large, the lubricating oil will be very dilute, and it will not only not play the role of lubrication, but also will dissolve the original oil film and cause the refrigerant to scour.

For various reasons (including compressor start-up phase), the temperature of the friction surface of the lubricating oil will rise rapidly and the lubricating oil will begin to decompose after exceeding 175°C. "Less lubrication - friction - surface temperature - oil decomposition" is a typical vicious cycle, and many vicious accidents, including connecting rod shafts and piston cartridges, are related to this vicious cycle.

Lack of lubrication and lack of oil can be seen in the disassembled compressor. The lack of oil is generally characterized by a large area, relatively uniform surface damage and high temperature, while the lack of lubrication is more in certain areas of wear, scratches and high temperatures, such as bearing surfaces away from the pump.

When the piston moves up and down, the load of the piston pin rotates between the upper part and the lower part of the bearing surface, which allows the lubricant to evenly brush over the piston pin and provide sufficient lubrication. If the exhaust valve plate bends or breaks, or the long-term high-pressure ratio of the compressor works, the piston pin will be unilaterally moistened.

The piston pin has a sloshing gap and the piston is thrown at the top dead center and knocks out of the valve plate and valve plate, creating a crash sound. Therefore, when replacing the valve, check the wear of the piston pin.

conclusion and suggestion

The lack of oil can cause serious lubrication problems. 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. Installing an oil separator can quickly return oil and extend the compressor's non-return operating time. Evaporator and return line must be designed with oil return in mind. Maintenance measures such as frequent start-up, regular defrosting, timely replenishment of refrigerants, and timely replacement of worn piston assemblies also help return oil.

Back-fluid and refrigerant migration will dilute lubricating oil, which is not conducive to the formation of oil film; oil pump failure and oil line blockage will affect oil supply and oil pressure, resulting in friction surface lack of oil; friction surface high temperature will promote the decomposition of lubricating oil, so that lubricant Loss of lubrication. The lack of lubrication caused by these three problems also often causes damage to the compressor.

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The source of oil shortage is the system. Therefore, replacing only the compressor or some accessories can fundamentally solve the problem of oil shortage.