Hydrogen Disposal Flare System Hazard Identification and Mitigation Analysis

A hazard assessment on a hydrogen disposal flare system was conducted in preparation for a hydrogen turbopump test at the Air Force Research Laboratory (AFRL), Aerospace Systems Directorate at Edwards AFB, CA.  The test operations required the disposal of large quantities of liquid and gaseous hydrogen through a commercial flare system to prevent the formation of an explosive environment.  As part of the assessment, the primary steps in the test operation process were evaluated for the formation of a potential hazard by looking at each associated failure mode and the resulting affect on personnel and facilities.  Evaluation of each operational step was conducted in a Process Failure Modes and Effects Analysis (PFMEA) that identified the probability and severity of the identified effects and associated hazards.  If the probability and severity were unacceptable, mitigating steps were applied until the overall hazard risks were reduced to acceptable levels.  The recommendations of this assessment were incorporated into both the flare system design and the operational procedures.  This paper outlines the results of the PFMEA which include identification of the effects/hazards, available risk-mitigating techniques, and implementation of these techniques used for the mitigation of the identified hazards.  Based upon the findings significant design modification to the vender's commercial equipment was needed to comply with recent changes in the code.  Most of the identified hydrogen flare system hazards/effects were categorized into four groups:  internal explosions, obstructions, external explosions, and maintenance degradation.  Many corrective actions were implemented to mitigate both the probability and severity of the identified hazards.  In addition, this paper discusses the installation of oxygen monitoring systems on the flare system, determination of appropriate system purge requirements, installation of purge system status alarms, incorporation of a triple redundant flare ignition system with status indicators, and a number of other hazard risk mitigation techniques.  This comprehensive description of the hazards and mitigation of a hydrogen disposal system is a plant is vital part to safe operation of both hydrogen commercial and aerospace facilities.  <align="center">