New Manufacturing Cycle to Improve the Life of Packing Cups for Hyper-Compressors

Abstract

Hyper-compressors are subjected to very high operating pressure, maximum and fluctuating, strongly impacting design and life of all cylinder components. Components subjected to fatigue (both high cycle fatigue and low cycle fatigue) can experience a failure in a very short time that may cause large production losses. Packing cups proved to be one of the most critical cylinder components and the fatigue behavior of the packing cups subjected to alternating loads, due to the suction and discharge conditions, is their key design factor. A thorough study has been performed in order to increase the safety factors in all critical regions of the packing cups analyzing a new manufacturing cycle that allows optimizing the compressive pre-stresses on the lube oil parts due to the autofrettage procedure. The approach included a dedicated sensitivity FEM analysis of the autofrettage pressure to determine the correct residual stresses at the lube oil parts in order to keep them under compressive stress in operating conditions and Fracture Mechanics Calculations based on BSI7910 aimed at achieving a design able to survive with a threshold defect larger than the minimum detectable defect.

WITHDRAWN: A failure analysis study on the packing cups of a hyper compressor

“…In order to investigate the stress state of the lube oil ducts, the Lame's equations were used [5]. Using …”

“…The fatigue cracks usually initiate from the surface defects such as fretting and machine marks [2]. Maggi et al showed that the typical failure modes of packing cups are tangential or radial [5].…”