1、Lessons Learned Entry: 0745Lesson Info:a71 Lesson Number: 0745a71 Lesson Date: 2000-03-07a71 Submitting Organization: JSCa71 Submitted by: Larry GreggSubject: Potential for Low Oxygen Levels in Non-Enclosed Areas Description of Driving Event: On January 4, 1995, at approximately 8:50 a.m., two techn
2、icians 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 tanke
3、r vent 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 larg
4、er 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 t
5、he 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 r
6、ain. 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 sus
7、pend 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 wa
8、s overcome 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
9、that 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: Under certain environmental conditions, oxygen deprivation
10、hazards are possible during cryogenic operations in non-enclosed areas.Recommendation(s): Care should be taken whenever cryogenic materials are involved in an operation to prevent injuries due to the development of local areas containing non-breathable atmospheres even if the operation is in an “ope
11、n“ area. Personnel involved should be trained to recognize this hazard and active ventilation should be provided where required.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): a71 Exploration Systemsa71 Sciencea71 Space Operationsa71 Aeronauti
12、cs ResearchAdditional Key Phrase(s): a71 Cryogenic Systemsa71 Emergency Preparednessa71 Environmenta71 Facilitiesa71 Ground Operationsa71 Hazardous/Toxic Waste/Materialsa71 Human Factorsa71 Personal Protective Equipmenta71 Policy & Planninga71 Risk Management/Assessmenta71 Safety & Mission Assurance
13、a71 Test FacilityProvided by IHSNot 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-,-,-
