REG NASA-LLIS-0016-1991 Lessons Learned - Reversed Installation of a Check Valve Spring (Main Propulsion) Subsequent Spring Failure and Uncontrollable Reverse Flow.pdf

1、Lessons Learned Entry: 0016Lesson Info:a71 Lesson Number: 0016a71 Lesson Date: 1991-07-28a71 Submitting Organization: JSCa71 Submitted by: Donna CarrolSubject: Reversed Installation of a Check Valve Spring (Main Propulsion), Subsequent Spring Failure and Uncontrollable Reverse Flow Description of Dr

2、iving Event: When the shuttle orbiter main propulsion system oxygen manifold was pressurized to obtain gas samples, oxygen line to engine No. 3 also pressurized. The prevalves to all engines were closed and pressurization should not have occurred downstream of the prevalves. A small check valve is p

3、rovided parallel to each prevalve and allows expanding fluid trapped in the manifold legs of each engine, between the prevalves and the engine valves, to relieve back into the main manifold. Upon removal of the No. 3 check valve, it was discovered that the spring holding it closed was broken and had

4、 been installed backwards. The error in installation contributed to additional stresses on the spring during earlier flow tests that lead to this failure. If the faulty installation of the spring had remained undetected and the spring had failed during cryogenic operations, uncontrolled flows into t

5、he engine leg could have caused launch delays. An X-Ray technique was developed to inspect existing valves for proper installation of the springs. A mandatory inspection point was added to the fabrication assembly procedures to preclude installation errors for this spring.Lesson(s) Learned: An incor

6、rect installation of a critical component (orbiter main propulsion system check valve spring) can cause additional stresses, lead to a material failure, and result in costly launch delays.Recommendation(s): X-Ray techniques were developed and implemented to assure correct installation of existing ch

7、eck valve springs and a mandatory inspection point was added for the assembly of new valves.Evidence of Recurrence Control Effectiveness: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-N/ADocuments Related to Lesson: N/AMission Directorate(s): a71 E

8、xploration Systemsa71 Space Operationsa71 Aeronautics ResearchAdditional Key Phrase(s): a71 Aircrafta71 Cryogenic Systemsa71 Energetic Materials - Explosive/Propellant/Pyrotechnica71 Flight Operationsa71 Flight Equipmenta71 Ground Operationsa71 Ground Equipmenta71 Hardwarea71 Launch Vehiclea71 Parts

9、 Materials & Processesa71 Pressure Vesselsa71 SpacecraftAdditional Info: Approval Info: a71 Approval Date: 1993-09-10a71 Approval Name: Ron Montaguea71 Approval Organization: JSC/NS3a71 Approval Phone Number: 281-483-8576Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-