1、Lessons Learned Entry: 0605Lesson Info:a71 Lesson Number: 0605a71 Lesson Date: 1998-11-16a71 Submitting Organization: SSCa71 Submitted by: Mark McCalmanSubject: LOX Barge Pumping Operations; Retaining Screw and Wear Ring Description of Driving Event: During LOX transfer operations in preparation for
2、 a Space Shuttle Main Engine (SSME) test (904-362) on the B-1 test stand, a LOX pump (barge #1, pump B) over pressurized, initiating a fire on barge #1. The fire was extinguished and mishap investigation procedures were initiated. The primary cause (determined by the board) was the backing out of a
3、retaining screw during LOX pump B operations. Further investigation highlighted the following:1. SSCs procurement (post 1988) of pump casings with configurations that were not per design (beveled area around retaining screw area), and2. Wear rings for the pump are re-used after pump rebuild if no ev
4、idence impeller to wear ring wear exists.The incident caused no injuries; however, damage to equipment including the barge, motors, lines, and decking is estimated at approximately $250,000. In addition, the pending SSME test was cancelled and rescheduled.Lesson(s) Learned: Adequate LOX pump hardwar
5、e and operations procedures, safeguards and baseline data must be in place to assure that all risks to people, facilities, equipment, or missions are identified and mitigated. Manufacturers recommended procedures should be integrated into SSC procedures when possible.Recommendation(s): 1. Ensure tha
6、t procedures associated with the LOX barge operations include the following: a. Use wear rings for one time use only. (Present method of staking screws prevents Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-proper installation of the retaining scre
7、ws if a previous stake mark(s) exists.)b. Develop a “standard recommended time“ during which the pump is allowed to cavitate without turning off the motor,c. Prohibit personnel access on the barge while any LOX pump is running,d. A briefing to include the potential hazards and site-wide experience w
8、ith this operation for all involved personnel.2. Inspect all LOX barge pumps to verify that the retaining screws on the wear rings are properly installed and staked. Replace multiple use wear rings and ensure that the cases have proper bolt hole configurations.3. Develop a vibration baseline and ana
9、lysis for the LOX barge pump motors and LOX barge pumps while coupled to the motor.4. Investigate and implement improvements on retaining screw design that positively holds the screws to the wear ring. Consider the following: a. Improve surface finish of inside surface of the aluminum housing to at
10、least a 125 rms for smooth flow of LOX.b. Repair existing deficient discrepancy holes on the pump housings that do not meet specifications.c. Improved pump-to-motor coupling.5. Issue a GIDEP Parts Advisory on the potential of additional counterbore mounting holes on pump casings.Evidence of Recurren
11、ce Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Energetic Materials - Explosive/Propellant/Pyrotechnica71 Facilitiesa71 Ground Operationsa71 Hardwarea71 Parts Materials & ProcessesAdditional Info: Provided by IHSNot for ResaleNo r
12、eproduction or networking permitted without license from IHS-,-,-Approval Info: a71 Approval Date: 1998-12-10a71 Approval Name: Elise Bowena71 Approval Organization: QA00a71 Approval Phone Number: 228-688-2545Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
