REG NASA-LLIS-0553-1997 Lessons Learned Communicating System Requirements.pdf

1、Lessons Learned Entry: 0553Lesson Info:a71 Lesson Number: 0553a71 Lesson Date: 1997-05-27a71 Submitting Organization: JSCa71 Submitted by: L. UnderwoodSubject: Communicating System Requirements Description of Driving Event: A particulate sampling filter was ruptured during use due to excessive diffe

2、rential pressure. The filter was in use in an oxygen system, and the Quality Assurance technician recording the sampling results noted that the failed filter element was not the type required for the procedure, as it was incompatible with the sampling being performed.The failed filter was not the ty

3、pe required by the users. The users had received the filter housing “cleaned and ready for service“ from another organization. The type of filter element installed was not considered an issue, because both organizations used only one type of filter and presumed that it was the same type.The users th

4、ought that the filter was Teflon, which was normal for their use. The actual filter element was cellulose ester. In addition to being incapable of handling the differential pressure, cellulose ester filters are not recommended for use in oxygen service by the manufacturer. Manufacturing, Materials,

5、and Process Technology Division (EM) has recommended a maximum service pressure of 20 psia for cellulose ester filter elements in oxygen service.Lesson(s) Learned: Positively Verify System and Component Specifications and Requirements Rather than Rely on Assumptions Derived from Professional Knowled

6、ge of Past Practices.Recommendation(s): 1. Always provide specific instructions to other organizations when you are requesting support or returning equipment. All materials installed in sensitive systems (such as oxygen systems) Provided by IHSNot for ResaleNo reproduction or networking permitted wi

7、thout license from IHS-,-,-must be approved by competent technical authorities. Some organizations have the necessary expertise in house; other organizations should consult with experts such as the JSC Manufacturing, Materials, and Process Technology Division (mail code EM) or the White Sands Test F

8、acility Laboratories Office either to review the materials or provide a referral to an alternate technical resource.2. Organizations that require gas sampling of potentially hazardous systems should ensure that approved procedures are available for the task and that employees are trained in the prop

9、er operation and hazards of the systems.3. The cleaning facility must be made aware of the required filter element type by each requester seeking an assembled filter housing for use in sampling procedures. The filter type/material should then be indicated on the paperwork and/or marked on the assemb

10、ly provided to the requester.4. When uncertain about system requirements, treat it as a critical system!Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): N/AAdditional Info: Approval Info: a71 Approval Date: 1997-05-29a71 Approval Name: Ronald A. Montaguea71 Approval Organization: NA3a71 Approval Phone Number: 281-483-8576Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-