Relief Valves

Relief valves are utilised commonly as a protective device. This valve type is an angle type arrangement that has a disc held in place by a relieving mechanism. The mechanism can be pre-set so that the disc lifts from the seat at a given pressure and allows the fluid to vent.

Relief valves primary function is to prevent over pressurisation within a piping/instrument line. The lift point of the valve is generally set below the maximum pressure for the pipeline to ensure that the pipeline is protected suitably. The outlet of a relief valve can allow venting of the process fluid to either atmosphere or another location depending upon the medium itself.

There are three main types of relief valves:

  • Conventional spring loaded
  • Balanced spring loaded
  • Pilot operated

The conventional and balanced types are very similar with the primary difference being, in conventional relief valves the spring, guide and bonnet are all subjected to the relieved medium, however in the balanced type there is a means to protect the spring, guide and bonnet from the released fluid. Where these two versions rely on a spring to provide the resisting pressure the pilot version requires and externally plumber pilot line to ensure the valve remains sealed until the set point pressure is reached.

PAC’s history and experience across a variety of industries have seen our sales and engineering team supply relief valves to various customers and varying applications. Relief valves which are also commonly referred to as “Safety Valves” are vital to the function of many systems as such it is important that a supplier with the technical know-how and experience is utilised. Here at PAC, using our extensive experience and technical knowledge, we regular meet and exceed our customer’s expectations and requirements in a quality sphere.


Conventional spring loaded, balanced spring loaded, pilot operated


Forged and cast materials including cast/ductile iron, carbon steel (including low temperature service), stainless steel, duplex stainless steels, alloys (ie. bronze, brass), exotic alloys (ie. Monel, Hastelloy, titanium), engineering plastics


PN16 – PN160, 10psi-6000psi, 0-413 bar

Have a project you would like to discuss?
Get in touch directly with our Engineers and Project Managers.