SEDL / STP / STP1395-EB / STP12497S

Potential Ignition Mechanism of Buna-N O-Rings in Liquid-Oxygen

Newton, BE
Engineer, Wendell Hull - Associates, Inc., Las Cruces, NM

Wilson, DB
Consultant, Mesilla Park, NM

Stradling, JS
Consultant, Sunlit Enterprises, Las Cruces, NM

Pages: 17    Published: Jan 2000

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Abstract

Buna-N O-rings used in liquid-oxygen dewars have been implicated in fires when subjected to a shearing load. Such a loading occurs when the dewar flange receives a mechanical impact due to the dewar falling over. The ignition event has been replicated under controlled conditions but only when the O-ring has been previously distorted such as could occur during improper seating of the seal in the upper flange, or when forced extrusion of the seal occurs while exposed to liquid-oxygen. This paper applies an ignition model to the experimental system to extend the parameterization of oxygen pressure/temperature to the extent of O-ring damage, shear energy and oxygen flow. The model allows for heat loss and variable generation rates.