Pressure Relief Valves

Pressure & vacuum relief valves (sometimes known as conservation vents) are essential to the safe storage of liquids and gases.

Employed across a wide range of industries, these valves provide a primary layer of protection by preventing excessive pressure or vacuum, which can potentially damage storage vessels. Pressure & vacuum relief valves open at a pre-set pressure and discharge vapour. Once vapour has been discharged, the pressure inside the tank will drop and the valve will close creating a seal.

But why are they so important? Simple. The greater the pressure, the greater the risk of catastrophic failure. Essentially, without pressure and relief valves gases or liquids contained in a vessel are simply not safe. Liquid or vapour cannot be vented when filling, emptying or releasing liquids or gases. This is especially important in environments where thermal climate changes are commonplace.

The B100 Series pressure and vacuum relief valves are robust enough to withstand all excessive pressure caused when vessels are filled with liquid or gaseous substances, when liquid or vapour is released and changes in environmental temperature or external hazards, such as fire.

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PV Features

Pressure and vacuum relief valves have several core features that demonstrate why they are essential to optimising vessel performance and safety, whilst significantly benefitting commercial operations. These are as follows:

Low-Cost Maintenance

Lightweight design provides easy handling whilst interchangeable components ensure standard parts are easily interchangeable.

Testing Quality

All products are factory tested and fully certified.


All products are designed so that they condensate drains away from seating areas.

Low Leakage

Standard seating design ensures minimum leakage of less than 1 scfh at 90% set pressure.

Internal Parts

Internal parts are stainless steel as standard. Non-standard materials available upon request.


All valves are supplied with full form flanges to meet individual requirements. Other connections are available upon request.

Non-Standard Applications

There are numerous options available for special applications. Exotic materials, such as Hastelloy and various plastics can be offered to suit the most hazardous of environments. Special coatings can be applied for extreme service. For low temperature duties, internal parts can be PTFE coated to prevent seizure.

*Specification Change*

All products are subject to continuous development and subsequently 3B Controls reserve the right to change specifications outlined in the catalogue without notification.

Product Highlights

  • Open vent weight loaded
  • Standard pressure settings +2mbarg to 100mbarg
  • Standard vacuum settings -2mbarg to -100mbarg
  • Size range 2” (50mm) to 12” (300mm)
  • Standard body materials – aluminium, carbon steel, stainless steel
  • Standard trim materials – stainless steel
  • Diaphragm material – PTFE
  • Removable seats
  • Standard form flanges – ANSI/DIN/JIS/Specials
  • Lightweight design
  • Steam jackets
  • Proximity switches to indicate pallet lift
  • Tri clamp/screwed connections available
  • Alternative materials for hazardous applications
  • Non-standard applications (consult factory)
B100 open vent pressure relief valve

B100 – Pressure & Vacuum Relief Valves

B200 Vacuum Relief Valve

B200 – Vacuum Relief Valves

b300 ov pressure relief valve diagram

B300 – Pressure Relief Valves