Extending Replacement Intervals of Elastomeric Components by Evaluating Samples Removed From Service

Abstract

Elastomers play an essential role in pressure vessels as seals, hoses, gaskets, diaphragms, liners, and other critical components. Polymeric materials used for nonpressure applications such as electric power cable insulation have received more attention, with respect to the effects of aging and life management, than critical elastomeric pressure vessel components such as seals. Performance of these seals depends upon the effects of both time- and event-dependent aging. Understanding and addressing aging and degradation are fundamental to effective preventative maintenance and life cycle management programs. Proper management of elastomers is necessary for performance requirements and for cost containment. In one of the case studies presented, synthetic seals in engines were quite costly to change on the suggested OEM (original equipment manufacturer) maintenance schedule, where replacement intervals were based on assumed operating conditions applicable to other industries. When the actual service for these engines is as emergency diesel generators (EDGs, e.g., in nuclear power plants), the use is primarily in stand-by mode, and the usage is far different than that of the manufacturer's target application. In this investigation, the assessment of pressure seal performance was based on situation-specific operation and environmental parameters. This resulted in much longer replacement intervals. In another case study, alternate materials were identified that are expected to improve performance over the original material.