Article and photos by Gregory Havel
Pressure vessels–including boilers, water heaters, compressed air tanks, and water pressure tanks–operate under internal pressure greater than the atmospheric pressure, and are required by codes to be equipped with pressure relief valves, also known as safety valves.
Water heaters require a temperature-pressure relief valve (Photo 2). This is similar to the pressure relief valve on a boiler, except that it also has a temperature probe that extends several inches into the water heater through the inlet connection on the valve. In addition to opening to reduce high pressure in the water heater, these relief valves will open if the temperature in the water heater rises above 210º F (99º C) because of a failure of the operating controls.
Standard on Live Fire Training Evolutions, 2007 Edition, Chapter 4 “Acquired Structures.” Section 4.2.9 calls for closed containers (like boilers, tanks, and water heaters) to be drained and removed from the structure or vented with an inert atmosphere and left in place. An acceptable method of venting a closed container is to remove pressure from the boiler, tank, or water heater; drain it; remove the pressure relief valve; disconnect all piping including the fuel pipe; and leave it in place, empty, and with the many vent openings provided by disconnected piping.
National Fuel Gas Code, 2009 Edition (ANSI Z223.1—2009), especially section 10.3.6
Boiler and Pressure Vessel Code.
Standard on Live Fire Training Evolutions, 2007 Edition.
Gregory Havel is a member of the Burlington (WI) Fire Department; a retired deputy chief and training officer; and a 30-year veteran of the fire service. He is a Wisconsin-certified fire instructor II and fire officer II, an adjunct instructor in fire service programs at Gateway Technical College, and safety director for Scherrer Construction Co., Inc. Havel has a bachelor’s degree from St. Norbert College; has more than 30 years of experience in facilities management and building construction; and has presented classes at FDIC
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Subjects: Building construction for firefighters, safety valves on tanks, relief valves