Description of Driving Event:
A 125 pound per square inch pressure air line in a ground trench, used to supply test facilities, failed by splitting along the longitudinal weld. The 10 inch diameter steel pipe ruptured for a distance of about 15 feet. As a result of this failure, four manhole covers were blown into the air.
The air line that failed was in a covered ground trench and had been in place for about 15 years. During this time, moisture was present from surface water leakage and considerable corrosion had taken place on the pipe outside diameter. Inspection of the failed pipe revealed that the original thickness of 1/4 inch was reduced to almost zero in some places as a result of the corrosion. The failure was due to the corroded pipe no longer being able to withstand the internal working pressure.