Edmonton Valve & Fitting Blog

Weekly posts for northern and central Alberta engineers, plant operators, and buyers.

Proportional Relief Valves: One Way to Deal with Pressure

by Taryn Hardes, on Tue, Jun 17, 2014 @ 09:06 AM

Safety valves and proportional relief valves handle pressure in different ways

  relief valves small

Swagelok Proportional Relief Valves come in both high-pressure and low-pressure varieties. For more information, download the Swagelok Proportional Relief Valves catalogue. 

When your fluid system has too much pressure, what's the best way to bring it back to where you want it? Often times, a proportional relief valve is the way to go.

Proportional relief valves are designed to open gradually as pressure increases. They open when the system reaches a set pressure, and close when the system falls below that same set pressure. They are available for liquid or gas service. Please note that proportional relief valves should never be used as safety relief devices as specified by the ASME Boiler and Pressure Vessel Code.

Swagelok Proportional Relief Valves (PRV) come in 1/4" and 1/2" size options with a variety of set pressures ranging from 10 psig to 6000 psig. Edmonton Valve & Fitting stocks a vast inventory of bodies and springs to fit almost any customer application. The relief valves are easy to set yourself, but we can also have them set prior to being shipped out. They even have lock wire capability to discourage anyone from changing the setting. Many times when we are called out to the field to fix a proportional relief valve that isn't seating at the right pressure, we typically find that the lock wire has been cut and that someone has changed the setting.

Where does the fluid go when the pressure is released? Sometimes you'll see it vented out, but more likely it will be routed into a containment unit or back into the system itself, especially when you don't want the fluid to contaminate anything.

However, your specification may require a Proportional Safety Valve (PSV). Unfortunately, PRVs are not a replacement or an appropriate alternative to a PSV. PSVs are sometimes called pop valves because of the sound they make when they open. They are designed to blow wide open in an instant and evacuate as much steam as possible. The "safety" part refers to why they are used. They are intended to prevent equipment damage and or loss of life or limb. They have a certifiable and repeatable relieving capacity. Unfortunately, Swagelok does not manufacture PSVs and therefore you will need to go to another vendor to get a ASME certified PSV.

For many applications, a PRV will work just fine. For ordering information, download the Swagelok Proportional Relief Valve catalogue. If you aren't sure about which valve you need, or if you want to confirm, call us.


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