Description of Driving Event:
On 8/28/97, the last working day before Labor Day weekend, a Contractor's was installing a 3" copper underground compressed air line into a trench approximately 18" wide and 3 feet deep. After having completed about 100 feet of pipe, the Contractor's crew began a pressure test of the 3" pipeline for acceptance. The test was performed prior to installation of a secondary fiberglass pipe to cover the 3" copper pipe and backfill the trench. The specified working pressure of the 3" copper compressed air line was 125 PSI. The specified test pressure was 188 PSI. While the 3" copper line was still under pressure test, the crew began to install the secondary fiberglass pipe to encase the 3" copper primary pipe. As the crew was lowering the pipe into the trench, approximately 2:45 PM, the crew heard the sound of a "pop" and then the sound of leaking air coming from a pipe joint coupling. While the 3" copper line was still under pressure, one worker went into the trench attempting to check the location and the extent of the leak. While the worker was checking the position and direction of the leak from the pipe coupling, the soldered joint failed and the pipeline de-pressurized explosively. An 84-foot section of the pipeline that lead from the bottom of the trench to ground level was propelled approximately 8 to 9 feet longitudinally along the edge of the trench. Air from the explosive depressurization blew sand and soil on the worker in the trench. The sand abraded the worker's arms, chest, and abdominal. The pipe also struck the worker in the left knee and groin area. The worker was taken to the Edwards AFB Hospital for treatment. The worker was released from the hospital after treatment that evening. The worker was wearing personal protective equipment (PPE) including a hardhat, boots, safety glasses, and gloves at the time of the accident.
Lesson(s) Learned:
- Do not work on a pressurized pipeline.
- Reduce pipeline pressure before attempting to locate leak in the pipeline.
- Personal protective equipment (PPE) does save lives. The accident could have caused more serious injury had the worker not been wearing PPE.
- Pay extra attention to construction safety procedures during the last working day before a weekend or holiday. Construction workers tend to rush the last working before a weekend or holiday.
- Preparatory inspection is very important. Make sure specified materials are being used. Silver solder was specified for the 3" copper underground compressed air line. The Contractor used 95-5 solder instead. Silver solder grarantees a much higher strength of the joint.
Recommendation(s):
- Do not allow contractors or other workers to work on a pipeline while conducting high pressure test.
- Reduce pipeline pressure to 40 PSI to 60 PSI to locate a leak.
- Use silver solder on 2" and larger copper pipes.
- Strictly enforce the three phases of control in construction: preparatory inspection, initial inspection, and follow-on inspection.
- Have a safety meeting with the construction crew a day or two before a long weekend or holiday.
Evidence of Recurrence Control Effectiveness:
N/A
Documents Related to Lesson:
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Mission Directorate(s):
N/A
Additional Key Phrase(s):
- Facilities
- Safety & Mission Assurance.
Additional Info:
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