A FAILURE ANALYSIS APPROACH TO SOLVING REFRIGERANT CONNECTOR FAILURESIN RAIL COACH AIR-CONDITIONING UNITS

Investigation of failures in connectors of compressor suction and disc harge lines in roof mounted package air conditioners designed for use in passenger coaches of Indian Railways was the objective of the study . The connectors consisted of copper pipe and corrugated red brass fle xible tubing reinforced with bronze wire braiding. Resonance between t he discharge line and the first harmonic of the compressor excitation frequency was the cause of failure in this line. in the suction line r esonance was ruled out as a reason of failure. Tests conducted on the compressor connector subassembly to simulate shocks encountered during coach movement could replicate field failures. A change in the compre ssor mounting from soft to rigid resulted in elimination of the failur es in these simulated tests. So shock was concluded as a reason for su ction line failures and a change in mounting of the compressor has bee n recommended as a solution to prevent failures. The connectors have b een changed to plain copper tubes with a geometry tested for absence o f resonance with compressor excitation frequencies. (C) 1998 Elsevier Science Ltd. All rights reserved.