Failure Analysis of High Pressure Test Facility Control Valves.

摘要

In support of a series of upcoming Hydrocarbon Boost (HCB) Tests, facility operation demonstrations were run to validate the Air Force Research Laboratory (AFRL) Test Stand 2A (TS2A) Liquid Oxygen (LOX) and Gaseous Nitrogen (GN2) propellant systems were fully functional and able to meet HCB test requirements. While facility activation, blowdown, and system checkout tests were in progress, several anomalies were detected. First, it became apparent after a few tests, substantial audible leaks had developed in two control valves critical to tank pressurization. Second, anomalies in the data from the control system suggested that valve performance had changed in a manner suggesting leakage. These two issues caused TS2A to suspend operations until an investigation could be performed to determine the cause of the irregularities. The respective pressurization and vent systems were partially disassembled in order to borescope the valves. Subsequently, it was discovered there was significant damage to the valve plugs and seats. The valves were removed and replaced with valves from a different manufacturer that could meet the same performance characteristics. The replacement valves were previously operated in similar processes and had proved their capability to function under the required conditions. Test operations were restarted, and the replacement valves were closely monitored to verify there were no issues with their operations; there were none. This paper will describe the nature of the failure of the valves, and the impact on their capability to operate effectively. It will provide a failure analysis and lessons learned so that future procurements of high-pressure, high-performance control valves can avoid the mistakes made in the design and procurement of these kinds of valves.