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Parent Category: Safety Info Posts

Category: Chemical Process Safety (PSM/RMP)

Published: 17 August 2014

The host facility, an anhydrous ammonia storage facility,  contracted with a company, who in turn, contracted with Respondent (sub-contractor) to perform services on pipelines within the facility. Respondent provides sixteen different services or “lines”, as it refers to them. Each of these lines is comprised of crew members that have been trained and tested in that particular discipline. Some of the crew members are trained in multiple lines, and, based on their respective amount of experience, may be designated as a crew lead. One of these lines involves the installation of isolation plugs (also referred to as mechanical plugs) into pipelines. These plugs serve as a barrier between flammable gasses in the pipelines and hot work, such as welding. The plug has a series of bolts that are tightened in order to expand a two-part rubber seal that presses outward against the pipe. Once the rings are expanded, the plug is filled with water and pressurized by bleeding off the air within the plug. A through-port is installed and connected to a hose, which is placed in a bucket of water approximately 35 to 50 feet away. The purpose of the hose and bucket is to detect the accumulation of pressure behind the plug, which results from hydrocarbons being released from the pipe due to the presence of heat. If there is pressure build-up, the hot work is supposed to be stopped by the individual monitoring the plug and will not recommence until the pressure is reduced. The plug also has a gauge that measures the pressure of the water in between the rubber seals. As was the case here, improper installation and/or handling of the plug can result in serious injuries.

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