A pressure relief valve is an important safety device designed to open in order to relieve excess pressure and then to close once pressure conditions return to normal. It seeks to limit the maximum system pressure and acts as the final line of defence in an overpressured situation. Without a pressure relief valve, pressure could build to an excessive level in which a machine or device could be damaged or personnel could be harmed.

The primary purpose of a pressure relief valve is the protection of life and property by venting fluid from an overpressurised vessel. By providing an alternate flow path to the tank when flow in the circuit is otherwise blocked, the valve diverts a portion of the fluid through its auxiliary route.

Many hydraulic systems use a pressure relief valve as a primary means to limit maximum system pressure. Without a pressure relief valve in place, pressures could potentially build to an excessive level and create a process upset, instrument or machine failure and endanger human lives.

By providing an alternate flow path, the pressure is relieved by allowing the pressurised fluid to flow from an auxiliary passage out of the system.

Griffco Pressure Relief Valves

From Griffco, offering a variety of pressure relief valves and options that work in many different applications.


Types Include:

  • M-Series: Small connections (1/4″ to 1/2″ or DN 8 to DN 15)
  • G-Series: Medium to large connections (1/2″ to 4″ or DN 15 to DN 100)
  • High-Flow: High-flow connections (1/2″ to 2″ or DN 15 to DN 50)
  • Medium-Pressure:  Medium Pressures to 800 psi (55 bar)  (1/2″ to 1″ or DN 15 to DN 25)
  • High-Pressure: High-pressure connections up to 4000 psi (275 bar) in sizes from 1/4″ to 1″(DN 8 to DN 25)

Variations and Options Include:

  • Unibody: valve with union connections, made from a solid PVC or CPVC body
  • PTFE Flanged: G-Series valve with flange connections, made from a solid PTFE body
  • Pressure Switch: Relief valve with Alarm Switch (1/4″ to 1″ or DN 8 to DN 25)

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