Pressure relief valves & pressure regulators - What's the difference?

[eleanorwest83]

What is the difference between a pressure reducing valve and a pressure relief valve? pressure-reducing/regulating/ relief/release - There are so many different options available!

I read this article on Fluid Controls that did a really good job of explaining pressure regulators, but I am a bit lost on the difference between regulators and relief valves.

 

[russ_watters]

A regulatory regulates the pressure in your system, changing one pressure into another, whereas a relief valve is a safety device that vents to atmosphere. They don't really have anything in common, so I'm confused as to what you would see in them that's similar.

 

[Dullard]

A pressure reducing valve is a device that varies cross-section (throttles a valve) to maintain a set-point pressure at it's outlet (or another point of interest). Ideally, this works over a range of flow conditions. A relief valve 'cracks' at a set-point-pressure, typically to prevent system pressures from exceeding some value. These devices might also be thought of as 'Series' and 'Shunt' pressure regulators, respectively. The simplest implementation of both devices involves a diaphragm which allows gas pressure to work against a spring to control a valve. in both cases, there are important non-idealities.