Abstract: At approximately 9:25 a.m. on October 24, 1990, Employee #1 was pressure testing a 40 ft section of an 18 in. diameter steel cooling tower pipe. The line to be tested had been filled with water the night before. Nitrogen was to be used to raise the pressure to 150 lb for the test, and Employee #1 set up a nitrogen tank with extended copper tubing approximately 20 ft away from the weld test unit. He opened the tank and after approximately 3 minutes the pressure gauge on the test unit registered 45 lb. Employee #1 then tapped the gauge to check the reading. Apparently, the line was overpressurized and the welded cap blew off from the side of the test unit. The cap struck Employee #1, tearing off his right arm at the elbow.