Analysis of EDS Vessel Clamping System and Door Seal

Abstract

The V26 containment vessel was procured by the Project Manager, Non-Stockpile Chemical Materiel (PMNSCM) for use on the Phase-2 Explosive Destruction Systems. The vessel was fabricated under Code Case 2564 of the ASME Boiler and Pressure Vessel Code, which provides rules for the design of impulsively loaded vessels. The explosive rating for the vessel, based on the Code Case, is nine (9) pounds TNT-equivalent for up to 637 detonations, limited only by fatigue crack growth calculations initiated from a minimum detectable crack depth. The vessel consists of a cylindrical cup, a flat cover or door, and clamps to secure the door. The vessel is sealed with a metal gasket. The body is a deep cylindrical cup machined from a 316 stainless steel forging. The door is also machined from a 316 stainless steel forging. The closure clamps are secured with four 17-4 PH steel threaded rods with 4140 alloy steel threadednuts on one end and hydraulic nuts on the other. A flange with four high-voltage electrical feedthroughs is bolted to the door and sealed with a small metal gasket. These feedthroughs conduct the firing signals for the high-voltage Exploding Bridge-wire detonators. Small blast plates on the inside of the door protect fluidic components and electrical feedthroughs. A large blast plate provides additional protection. Both vessel door and feedthrough flange employ O-ring seals outside the metal seals in order to provide a mechanism for helium leak checks of the volume just outside the metal seal surface before and after detonation. In previous papers (References 2 and 3), the authors describe results from testing of the vessel body and ends under qualification loads, determining the effective TNT equivalency of Composition C4 (EDS Containment Vessel TNT Equivalence Testing) and analyzing the effects of distributed explosive charges versus unitary charges (EDS Containment Vessel Explosive Test and Analysis). In addition to measurements made on the vessel body and ends as reported previously, bulk motion and deformation of the door and clamping system was made. Strain gauges were positioned at various locations on the inner and outer surface of the clamping system and on the vessel door surface. Digital Image Correlation was employed during both hydrostatic testing and dynamic testing under full-load explosive detonation to determine bulk and bending motion of the door relative to the vessel body and clamping system. Some limited hydrocode and finite element code analysis was performed on the clamping system for comparison. The purpose of this analysis was to determine the likelihood of a change in the static sealing efficacy of the metal clamping system and to evaluate the possibility of dynamic burping of vessel contents during detonation. Those results will be reported in this paper.