1、Lessons Learned Entry: 0871Lesson Info:a71 Lesson Number: 0871a71 Lesson Date: 2000-03-06a71 Submitting Organization: JSCa71 Submitted by: Larry GreggSubject: Safety Precautions in Operational Procedures Description of Driving Event: On January 4, 1995, at approximately 8:50 a.m., two technicians at
2、 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 vent li
3、ne. 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 than n
4、ormal 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 vent l
5、ine, 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. Duri
6、ng 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 suspend the
7、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 overcom
8、e 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 that LN2
9、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: All credible unsafe conditions that may be encountered during the ac
10、complishment of normal operating procedures must be anticipated, and alternate methods of action identified and included as appropriate.Recommendation(s): Analyze operating procedures for credible hazards and/or environments that may create unsafe conditions. Provide alternate methods of procedure a
11、ccomplishment to address these conditions and maintain operator safety during them.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 Syste
12、msa71 Emergency Preparednessa71 Environmenta71 Facilitiesa71 Ground Operationsa71 Hazardous/Toxic Waste/Materialsa71 Human Factorsa71 Logisticsa71 Packaging Handling Storagea71 Personal Protective Equipmenta71 Policy & Planninga71 Risk Management/Assessmenta71 Safety & Mission AssuranceProvided by I
13、HSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-a71 Test Facilitya71 TransportationAdditional 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-,-,-
