1、Lessons Learned Entry: 0872Lesson Info:a71 Lesson Number: 0872a71 Lesson Date: 2000-03-06a71 Submitting Organization: JSCa71 Submitted by: Larry GreggSubject: Use of Monitoring Processes for Cryogenic Transfer Description of Driving Event: On January 4, 1995, at approximately 8:50 a.m., two technici
2、ans at WSTF were overcome and collapsed from breathing in an oxygen deficient atmosphere that formed during shutdown operations following a transfer of liquid nitrogen (LN2) from a vendor supply tanker to a WSTF storage tanker. This transfer operation was normally controlled by monitoring a tanker v
3、ent line. Flow from this vent line indicated the tank was full, and the operation was suspended. There is also a liquid level indicator and a pressure gage on the WSTF tanker for monitoring purposes.On the morning of the mishap, conditions (high humidity and still air) existed which caused a larger
4、than normal water vapor cloud to form during continuous venting of cold gaseous nitrogen (GN2) during the filling operation. This venting is required to keep the WSTF tanker at a lower pressure than the vendor tanker during the fill operation. The cloud prevented the normal visual monitoring of the
5、vent line, the liquid level indicator, and the pressure gauge. The technicians, instead of positioning themselves to be able to monitor the vent line and gauges, located approximately 30 feet away from the tanker to both remove themselves from the heavy vapor cloud and also to remain out of the rain
6、. During the operation, the technicians would periodically approach the tankers to monitor the liquid level indicator and the pressure gauge. The vent line was never observed due to being obscured by the vapor cloud. After about 50 minutes, the weather got worse and the technicians decided to suspen
7、d the operation due to weather and because they thought the tanker was nearly full. Data collected later showed that the tanker was completely full, and that LN2 was being released through the vent line instead of GN2. As the first technician attempted to close the vent and transfer valves, he was o
8、vercome and collapsed due to the lack of oxygen. The second technician, who was monitoring the activity, also was overcome and collapsed due to the lack of oxygen. A few moments later, vendor personnel approached and eventually remove both technicians from the area. Later investigation indicated tha
9、t LN2 flow from the vent line coupled with adverse weather conditions created an oxygen deficient atmosphere in the area.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Lesson(s) Learned: A hazardous atmosphere can result in some environmental condit
10、ions when using overflow indications to monitor and control transfer operations of cryogenic fluids.Recommendation(s): Monitoring of cryogenic transfer operations should be accomplished by a method that indicates directly the degree of completion of the transfer operation rather than monitoring for
11、overflow indications indicating a full tank.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): a71 Exploration Systemsa71 Space Operationsa71 Aeronautics ResearchAdditional Key Phrase(s): a71 Cryogenic Systemsa71 Emergency Preparednessa71 Environ
12、menta71 Facilitiesa71 Ground Operationsa71 Ground Equipmenta71 Hazardous/Toxic Waste/Materialsa71 Packaging Handling Storagea71 Personal Protective Equipmenta71 Policy & Planninga71 Research & Developmenta71 Risk Management/Assessmenta71 Safety & Mission Assurancea71 Test FacilityProvided by IHSNot
13、for ResaleNo reproduction or networking permitted without license from IHS-,-,-Additional Info: Approval Info: a71 Approval Date: 2000-04-11a71 Approval Name: Eric Raynora71 Approval Organization: QSa71 Approval Phone Number: 202-358-4738Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
