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ASM Failure Analysis Case Histories

Handbook of Case Histories in Failure Analysis

Edited by
Khlefa A. Esaklul
Khlefa A. Esaklul
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ASM International
Volume
2
ISBN electronic:
978-1-62708-215-0
Publication date:
1993
Book Chapter

Failure Analysis of a Space Shuttle Solid Rocket Booster Auxiliary Power Unit (APU) Fuel Isolation Valve

By
J.H. Sanders
J.H. Sanders
IIT Research Institute, Marshall Space Flight Center
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;
G.A. Jerman
G.A. Jerman
National Aeronautics and Space Administration, Marshall Space Flight Center
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Published:
1993
Page range:
19 - 23

Abstract

A precipitation-hardened stainless steel poppet valve assembly used to shut off the flow of hydrazine fuel to an auxiliary power unit was found to leak. SEM and optical micrographs revealed that the final heat treatment designed for the AM-350 bellows material rendered the AM-355 poppet susceptible to intergranular corrosive attack (IGA) from a decontaminant containing hydroxy-acetic acid. This attack provided pathways for which fluid could leak across the sealing surface in the closed condition. It was concluded that the current design is flight worthy if the poppet valve assembly passes a preflight helium pressure test. However a future design should use the same material for the poppet and bellows so that the final heat treatment will produce an assembly not susceptible to IGA.

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J.H. Sanders, G.A. Jerman, 1993. "Failure Analysis of a Space Shuttle Solid Rocket Booster Auxiliary Power Unit (APU) Fuel Isolation Valve", Handbook of Case Histories in Failure Analysis, Khlefa A. Esaklul

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