ABSTRACT
This troubleshooting case study is on a particular model home refrigerator single-piston reciprocating refrigerant compressor. The manufacturer had made some modifications to the reciprocating component masses, to lessen the peak transient loads on all the compressor bearings, that is, main bearings, con-rod bearing, and wrist-pin bearing. Subsequent to these intended design improvements, the manufacturer started losing several million dollars a year on this refrigerator model from a 20% compressor failure rate within the 5-year warranty period. The compressor component at the heart of the failures was the wrist-pin bearing that connects the connecting rod to the piston. The author did simulations of the nonlinear dynamic orbital trajectory of the steady state once-per-revolution nonlinear wrist-pin dynamic orbit relative to its bearing. Those simulations uncovered the quite subtle root cause for the compressor failures that was not caused by bearing cyclic peak load. The root cause was discovered to be the lack of a small amount of bearing cyclic load reversal to allow cyclic lifting of the wrist pin off the oil supply hole that vents oil from the con-rod bearing film hydrodynamic pressure through a small hole in the connecting rod to the wrist-pin bearing, see Figure 7.1b. Simply put, the wrist-pin bearing failure was due to lubricant starvation. Root cause identification by the author immediately led to compressor design changes that eliminated the compressor failure problem.
