{"id":112,"date":"2017-02-11T18:29:47","date_gmt":"2017-02-11T18:29:47","guid":{"rendered":"http:\/\/content.agfmfg.com\/blog\/?p=112"},"modified":"2022-03-31T15:55:43","modified_gmt":"2022-03-31T15:55:43","slug":"pressure-relief-valves-in-wet-sprinkler-systems","status":"publish","type":"post","link":"https:\/\/content.agfmfg.com\/blog\/pressure-relief-valves-in-wet-sprinkler-systems\/","title":{"rendered":"Pressure Relief Valves in Wet Sprinkler Systems"},"content":{"rendered":"

Save Time, Save Water…Save Money<\/em><\/h2>\n

In 2010, NFPA 13: Standard for the Installation of Automatic Sprinkler Systems<\/em><\/a> adopted the new standard requiring the installation of pressure relief valves<\/a> on all wet systems.\u00a0 Prior to 2010, pressure relief valves were only required downstream of pressure reducing valves and on gridded systems.<\/p>\n

<\/p>\n

The Requirement<\/h2>\n
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AGF’s Model 7000 Pressure Relief Valve<\/figcaption><\/figure>\n

In accordance with NFPA 13 (2010 edition – Sec. 7.1.2), and as maintained in every edition since*:<\/p>\n

“…a wet pipe system shall be provided with a listed relief valve<\/strong> not less than 1\/2 in (15 mm) in size and set to operate at 175 psi (12 bar) or 10 psi (0.7 bar) in excess of the maximum system pressure, whichever is greater.”<\/p>\n

However, “where auxiliary air reservoirs are installed to absorb pressure increases, a relief valve shall not be required.”<\/p>\n

Defining a System<\/h3>\n

It should be further noted that Chapter 3 of NFPA 13 (2013 & 2016 editions) goes to great lengths to define a system.<\/p>\n

Section 3.3.22 (2013) and Section 3.3.23 (2016) define a sprinkler system as:<\/p>\n

\u201ca system that consists of an integrated network of piping designed in accordance with fire protection engineering standards that include a water supply source, a water control valve, a waterflow alarm, and a drain.\u201d<\/p>\n

Also, NFPA 13 Section A.3.3.22 (2013) and Section A.3.3.23 (2016) expand on Chapter 3\u2019s definition further:<\/p>\n

\u201cas applied to the definition of a sprinkler system, each system riser serving a portion of a single floor of a facility or where individual floor control valves are used in a multistory building should be considered a separate sprinkler system. \u00a0Multiple sprinkler systems can be supplied by a common supply main.\u201d<\/p>\n

The Bottom Line<\/h3>\n

The bottom line is that one must install a relief valve downstream of any control valve. Typically, that’s one on every floor of a multistory building that a single riser supplies. Or, it’s two where the total square foot area of the floor requires two supply risers).<\/p>\n

This requirement intends to prevent pressure build-up from exceeding the working pressure of system components. Traditionally, the working pressure is 175 psi (12.1 bar).<\/p>\n

Relief Valve Rating<\/h3>\n

The pressure rating of the relief valve indicates an operating range of pressure for both the opening and closing of the valve. UL and FM standards for sprinkler system pressure relief valves require they to operate within that range.<\/p>\n

FM requires a relief valve to OPEN at a pressure no less than 85% of their rating and UL requires OPENING at a pressure no greater than 105% of their rating. Both standards require the relief valves to CLOSE within a percentage below OPEN.<\/p>\n

To choose a the right relief valve, compare static pressure against the rating. Compare static pressure to 90% of the relief valve’s rating to determine the estimated minimum OPENING. Compare to 80% of the relief valve’s rating for approximate maximum CLOSING.<\/p>\n

Install the relief valve where it is easily accessible for maintenance. Take care that the relief valve CANNOT be isolated from the system when the system is operational. A relief valve should NEVER have a shutoff valve or a plug downstream of its outlet.<\/p>\n

Relief Valve Location<\/h2>\n

One can locate the relief valve anywhere on the system. But, one of the most common and convenient locations is at the floor control assembly.<\/p>\n

By installing the relief valve in this location, contractors are able to take advantage of the close proximity of a drain riser. So, the safe draining of the relief valve is easy to accomplish.<\/p>\n

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Industry professionals designed products specifically for this purpose. They have a convenient place to install a pressure relief valve and its drain line, including:<\/p>\n