Pneumatic Test of Pressurised Equipment: Its Hazards and Alternatives

Abstract

Pressure testing of pressurised equipment is crucial in establishing confidence that it is capable of performing the duty for which it has been designed and fabricated. A pressure test is usually mandated by pressurised equipment design codes for newly fabricated equipment. Also many regulations or industry codes for the design and fabrication of pressurised equipment require that a pressure test is performed on any modified in-service pressurized equipment to verify that the integrity of the equipment has not been compromised after such modifications. Although the usual and normally the preferred method of pressure testing is conducting a full hydrostatic test on the entire equipment (i.e. using a liquid medium, typically water), there may be occasions that a hydrostatic test is simply not practical. As an alternative to a full hydrostatic test, the designer may consider performing a localized pressure test or sometimes a full pneumatic test on modified equipment. It must be emphasized that a full pneumatic test can create extreme hazards to a facility and nearby personnel and therefore needs a careful and methodological assessment prior to being attempted on any equipment. This article is structured primarily as an attempt to assist the organizations in charge of design and inspection of newly fabricated or in-service equipment to identify general hazards associated with pneumatic test of pressurised equipment in a structured manner. An analysis of a simple cylindrical pressure vessel is presented to provide a better understanding of hazards associated with pneumatic test. Two tables in the paper provide the recommended exclusion zones from the equipment being pneumatically tested in order to reduce hazards associated with shock waves and/or projectile fragments. The paper also briefly explains alternative methods of testing in lieu of a full hydrostatic or pneumatic test. [1, 2]