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Space Shuttle Orbital Maneuvering Subsystem (OMS) Engine Propellant Leakage Ball-Valve Shaft SealsEvidence of propellant leakage across ball-valve shaft seals has been noted during the disassembly of five flight engines and one test engine at the NASA Lyndon B. Johnson Space Center, White Sands Test Facility. Based on data collected during the disassembly of these five engines, the consequences of propellant leakage across the ball-valve shaft seals can be divided into four primary areas of concern: Damage to the ball-valve pinion shafts, damage to sleeved bearings inside the ball-valve and actuator assemblies, degradation of the synthetic rubber o-rings used in the actuator assemblies, and corrosion and degradation to the interior of the actuator assemblies. The exact time at which leakage across the ball-valve shaft seals occurs has not been determined, however, the leakage most likely occurs during engine firings when, depending on the specification used, ball-valve cavity pressures range as high as 453 to 550 psia. This potential pressure range for the ball-valve cavities greatly exceeds the acceptance leakage test pressure of 332 psia. Since redesign and replacement of the ball-valve shaft seals is unlikely, the near term solution to prevent damage that occurs from shaft-seal leakage is to implement a routine overhaul and maintenance program for engines in the fleet. Recommended repair, verification, and possible preventative maintenance measures are discussed in the paper.
Document ID
20000085163
Acquisition Source
Johnson Space Center
Document Type
Conference Paper
Authors
Lueders, Kathy
(NASA White Sands Test Facility NM United States)
Buntain, Nick
(Allied-Signal Technical Services Corp. Las Cruces, NM United States)
Fries, Joseph
Date Acquired
August 19, 2013
Publication Date
January 1, 1999
Subject Category
Mechanical Engineering
Meeting Information
Meeting: 35th Joint Propulsion Conference and Exhibit
Location: Los Angeles, CA
Country: United States
Start Date: June 20, 1999
End Date: June 23, 1999
Sponsors: American Society of Mechanical Engineers, American Inst. of Aeronautics and Astronautics, Society of Automotive Engineers, Inc., American Society for Electrical Engineers
Funding Number(s)
CONTRACT_GRANT: NAS9-95682
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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