Narrative:

Local mechanics were performing servicing of a crew oxygen bottle using an oxygen servicing booster. The bottle to be serviced was connected; shop air was supplied to the oxygen booster (after the incident the shop air supply source was found set to 150 psi); the oxygen source bottle was opened (the mechanic noted that the source bottle was at 2000 psi); the crew bottle was opened; and the oxygen booster was turned on to begin servicing. The mechanic reported the booster applied 3 pumps into the crew bottle to service it to the desired pressure. The crew bottle was turned off; the oxygen booster was turned off; then the source bottle was closed. Immediately after the source bottle was closed the mechanics in the vicinity reported a flash and loud explosion. After the explosion a large scorch mark was noted on the wall directly behind the oxygen booster and an adapter kit that was on the shelf behind it. A brass cap on the back of the booster appeared to be the discharge location of the blast. Upon close inspection the cap and the line behind it had signs of exposure to extreme heat. As that cap was facing the wall the explosive force was directed back and up away from the mechanics performing the servicing. No personnel were harmed by shrapnel or the direct force of the blast. The only injuries reported were minor hearing loss directly after the explosion. As I am not familiar with the internal working of the oxygen booster that was being used I cannot speculate to the cause of a mechanical failure. Based on the witness statements of the 3 mechanics present standard procedures were followed and no unsafe activities were reported. The report of a flash; signs of a high temperature discharge; and presence of oxygen suggests possible ignition fueled by the oxygen. No obvious sources of ignition were found anywhere near the oxygen storage area of the shop. The external safety valves mounted on the oxygen booster had no obvious visual defects. As I was the lead on duty the mechanics present reported the incident to me directly after it occurred. We have taken the oxygen booster out of service. I took statements from all personnel present and submitted an incident report to maintenance control.

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Original NASA ASRS Text

Title: A Maintenance Supervisor reported that an oxygen servicing booster blew a brass cap due to extreme heat.

Narrative: Local mechanics were performing servicing of a crew oxygen bottle using an oxygen servicing booster. The bottle to be serviced was connected; shop air was supplied to the oxygen booster (after the incident the shop air supply source was found set to 150 psi); the oxygen source bottle was opened (the mechanic noted that the source bottle was at 2000 psi); the crew bottle was opened; and the oxygen booster was turned on to begin servicing. The mechanic reported the booster applied 3 pumps into the crew bottle to service it to the desired pressure. The crew bottle was turned off; the oxygen booster was turned off; then the source bottle was closed. Immediately after the source bottle was closed the mechanics in the vicinity reported a flash and loud explosion. After the explosion a large scorch mark was noted on the wall directly behind the oxygen booster and an adapter kit that was on the shelf behind it. A brass cap on the back of the booster appeared to be the discharge location of the blast. Upon close inspection the cap and the line behind it had signs of exposure to extreme heat. As that cap was facing the wall the explosive force was directed back and up away from the mechanics performing the servicing. No personnel were harmed by shrapnel or the direct force of the blast. The only injuries reported were minor hearing loss directly after the explosion. As I am not familiar with the internal working of the oxygen booster that was being used I cannot speculate to the cause of a mechanical failure. Based on the witness statements of the 3 mechanics present standard procedures were followed and no unsafe activities were reported. The report of a flash; signs of a high temperature discharge; and presence of oxygen suggests possible ignition fueled by the oxygen. No obvious sources of ignition were found anywhere near the oxygen storage area of the shop. The external safety valves mounted on the oxygen booster had no obvious visual defects. As I was the Lead on duty the mechanics present reported the incident to me directly after it occurred. We have taken the oxygen booster out of service. I took statements from all personnel present and submitted an incident report to Maintenance Control.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.