Proof Test Criteria for Thin Walled Pressure Vessels

Abstract

Service failures of pressure vessels are generally a consequence of inherent part-through surface of sub-surface defects. The catastrophic pressure vessel failures of the mid 50’s and 60’s necessitated the development of a technology for the understanding and thereby eventual elimination of these failures. Fracture mechanics evolved as the technology base for the analysis of failures and for the development of methodologies for the prevention of these failure occurrences. Paramount in the prevention of service failures has been the development of fracture resistant materials and proof testing procedures. Reference [1] (“Fracture Control of Metallic Pressure Vessels”) defines the necessary procedures for determining proof testing parameters for pressure vessels in which the critical flaw depth at proof pressure is less than the wall thickness. The increased usage of fracture resistant materials has resulted in an increase in the critical flaw size at proof pressure. Presently a significant percentage of aerospace pressure vessels have critical flaw sizes at proof that are in excess of the wall thickness. For most aerospace pressure vessels fabricated from 2219 aluminum the failure made at proof pressure is leakage.