1、Lessons Learned Entry: 1428Lesson Info:a71 Lesson Number: 1428a71 Lesson Date: 2002-04-11a71 Submitting Organization: LARCa71 Submitted by: Grant WatsonSubject: Potential Hazard from Vent, Drain, and Relief Lines (2002) Abstract: A mishap has brought to light the importance of properly designed vent
2、 drain, and relief lines. Even though these lines are directly open to the atmosphere, the potential for over pressurization and rupture exists.Description of Driving Event: The mishap occurred when a tank located in a section of pipe used to drain water from a 4,300 psi air compressor ruptured. Th
3、e tank is isolated from the high-pressure air by a manual drain valve. A pipe that exits the bottom of the tank is directly open to the atmosphere. For the past 40 years, operators have been opening the drain valve to drain oil and moisture collectors without incident. On the day of the mishap, an o
4、perator drained the system as usual, but when the valve was closed, a very small amount of debris in the valve seat allowed high-pressure air to leak into the low-pressure drain collector tank.Lesson(s) Learned: At first glance, rupture of the tank appears to be one-fault tolerance - the drain line
5、would have to clog, and the valve would have to leak. But, the high-pressure air, which contained significant amounts of water, enabled on event to cause both conditions. The valve leaked in a manner that resulted in the Joule-Thompson effect. This caused the high-pressure air to be “throttled“ to a
6、 lower pressure and much lower temperature (on the order of -50 F). The lower temperature caused ice to eventually clog the exit of the tank and degrade the mechanical properties of the carbon steel tank material. With the exit clogged, the pressure inside the tank increased until the weakened tank
7、ruptured.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Recommendation(s): Facility safety personnel are encouraged to survey their facilities and look for vent, drain, and relief lines that may be susceptible to the above scenario. Even though they
8、 are open to the atmosphere, vent, drain, and relief lines should be designed for the maximum system pressure. Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): a71 Exploration Systemsa71 Sciencea71 Space Operationsa71 Aeronautics ResearchAdditi
9、onal Key Phrase(s): a71 Accident Investigationa71 Facilitiesa71 Hardwarea71 Human Factorsa71 Mishap Reportinga71 Pressure Vesselsa71 Safety & Mission AssuranceAdditional Info: Approval Info: a71 Approval Date: 2004-06-04a71 Approval Name: Leslie Johnsona71 Approval Organization: LARCa71 Approval Phone Number: 757-864-9409Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
