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Excessive Heating of Refrigeration Compressors

Excessive heating of the compressor leads to a decrease in the viscosity of the oil and one reduction of its lubricating power. The bearings, if subjected to inadequate lubrication, tend to warm up more, and this accentuates even more the loss of viscosity of the oil and increases the lack of lubrication. This process quickly causes excessive wear, and also causes a rubbery thickening and a carbonization of the oil.

In the case of excessive heating of the compressor, there is often the presence of scratches or grooves on the plunger of the piston. The coefficient of expansion of aluminum is higher than that of steel or of the cast iron of the cylinder, and therefore the piston, when subjected to high temperatures, expands beyond the cylinder liner and rub against the wall of this until eventually even causing a block total. In most cases the segments did not break because the piston lock was produced before they would break.

A high exhaust temperature can cause the carbonization of the oil on the exhaust valve.

In particularly critical cases, the carbonization is such that the deposits can reduce the movement of the valve and cause leakage of exhaust gases; these then put a downward pressure on the piston, both during the suction stroke and during compression.

Lubrication of the connecting rod foot can only be done correctly with alternating loads on the plug.

During the compression stroke the lower surface of the of the connecting rod is under load; this allows the oil to penetrate into the free space left by the movement between the pin and the upper surface of the connecting rod. When the stroke is reversed, the load on the pin is reversed and the movement is in the lower part of the connecting rod. When a piston is continuously subjected to a downward pressure, the inversion of the clearance between the piston pin and the small end can not take place, so there is no longer one adequate lubrication of the lower surface of the end of the connecting rod.

The noticeable release of heat that accompanies this type of failure is evidenced by the coloring dark aluminum near the top of the connecting rod.

Excessive Heating of Refrigeration Compressors

Author, Andrea Geymet  Linkedin Page
Export Manager at Linea3C Srl

4th September 2019

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