Abstract: On July 26, 2006, Employee #1 performed a pneumatic leak test on a 6-in. diameter, Schedule 40, jacketed, steel pipe, after coworkers welded sections of it. Employee #1 then secured a test tree on the end of the pipe with an adjustable wrench, then pressurized the pipe, and checked it for leaks for ten minutes. After the pipe passed the leak test, Employee #1 tried to bleed pressure from the pipe. He disconnected the air compressor line from the test tree, so he could bleed compressed gas from that opening. However, he had difficulty separating the compressor line, so he tapped it with a wrench to free it. During this time, the test tree was blown apart from the coupling, and struck him in the face and upper torso. An investigation revealed that the coupling manufacturer's website gave specific installation instructions for the coupling that required the application of a minimum of 250 lbs to a maximum of 300 lbs of torque to assemble the bolts. It was concluded that the most likely reason the coupling did not hold the test tree was that the assembly bolts were not tightened to the appropriate torque because an adjustable wrench was used instead of a torque wrench. The employee was hospitalized with an unspecified fracture.