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Occupational Safety and Health Administration OSHA

Accident Report Detail

Accident: 70704.015 - Employee Is Killed By Mechanical Explosion During Compressed

Accident: 70704.015 -- Report ID: 0521400 -- Event Date: 02/02/2015
InspectionOpen DateSICEstablishment Name
1025967.01502/03/2015Maac Machinery Co., Inc.
At approximately 9:30 p.m., on February 2, 2015, an employee, a welder, who had been employed by the company for approximately 10 work days, was welding and sim ultaneously pressurizing approximately a 500 gallon mild-steel vacuum tank for a ir leak testing. Arc welding process was utilized, Gas Metal Arc Welding GMAW i .e. Metal Inert Gas MIG with the Miller #24 MIG welder (Millermatic Model No. 25 2 and Argon inert gas tank). The vacuum tank was placed horizontally on the mov able platform that allowed for its transport and also rolling it around its axis for worker's convenience during welding and other tasks such as air leak testin g. The facility's air compressor regulated to approximately 134 psi was used for pressurizing the tank through its connections from one of the shop's main air l ines and a quick disconnect hose attached to the air regulating fixture on the t ank. A spray bottle with soapy water solution was prepared for air leak testing of the welds' sealing and penetration. Prior to performing the tank's air leak t esting, Employee #1 was welding caps on the tank's ends and its middle seam wher e two rolled cylinders were connected to form this tank. Once the current weldin g task was completed, Employee #1 capped and/or plugged all other openings in th e tank and connected the air regulating fixture equipped with a psi gauge and tw o handle-type ball valves to the tank caps 0.25-inch relief valve opening. Then, Employee #1 connected a quick disconnect air hose from the piped shop compresse d air supply to one of the handle-type ball valves on the air regulating fixture that allowed for pressurizing of the tank. Next, Employee #1 began to weld the tank's middle seam while air pressure was developing. The heat from the welding process imposed onto the tank further increased the internal pressure being buil t-up with supplied compressed air. This condition was observed by the Employee # 1's direct supervisor during a walkthrough of the welding area. According to the direct supervisor's recollection, at that time he advised Employee #1 to stop t he operation. Employee #1 acknowledged the command, stopped welding, and began t o walk in the direction away from his supervisor, along the long side of the tan k, towards Employee #1's tools and Welder Unit Number 24. When the employee walk ed around the end of the tank, and next to the tank's welded cap's edge, the cap ruptured (mechanical explosion due to rapid expansion of gas), striking Employe e #1. The ruptured cap was forcefully projected across the aisle from where the work was being performed. The cap's welds broke at the rolled stock's edge conne ction in the over-pressurized environment. Employee #1 was killed at the scene a s a result of multiple bodily trauma to head, upper, and lower body parts result ing in death.
Keywords: flying object, pressure release, rupture, struck by, tank, valve, welder, welding
Employee # Inspection Age Sex Degree Nature Occupation
1 1025967.015 35 M Fatality Welders and cutters

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