ATEX Approved Breather Valves

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Pressure Vacuum Relief Valves | Breather Valves | Conservation Valve

Manufacturers of ATEX Compliant direct acting Pressure Vacuum Relief valves (also known as a Breather Valves or Conservation valves) which are special types of breather valves and are specifically designed for the Protection of bulk liquid storage tanks.

The Opti-flow CNC 380 series are a low pressure PVRV breather valve available in a variety of configurations to suit your needs. all the CNC 380 series of valves are also available in both weight loaded and springloaded on both the pressure and vacuum giving valve opional settings from 2 Mbarg to 500 Mbarg on both the pressure and the vacuum

Direct acting pressure / vacuum relief valves (also known as breather valves, conservation vents, or safety vents) are low pressure devices specifically designed to protect tanks, process systems and equipment from excessive pressure and vacuum.

As well as providing the primary layer of protection for tanks and process systems, pressure/vacuum valves also minimise emission losses of gases or vapours, thus protecting the environment and providing significant financial savings.

The range includes pressure only, vacuum only and combined pressure/vacuum valves, all available with flanged outlets or vented to atmosphere.

Pressure / vacuum relief valves are used extensively on bulk storage tanks, including fixed roof tanks with floating covers, to minimise evaporation loss. The valves prevent the build up of excessive pressure or vacuum which can unbalance the system or damage the storage vessel.

Pressure and vacuum protection levels are controlled with weighted pallets or springs and can be combined to provide the required pressure/vacuum settings. It is common to combine pallet and spring systems in one unit i.e. pressure settings require a spring section, whilst the vacuum settings use the pallet method.


Motherwell pressure vacuum relief valve can be configured with both weight-loaded or spring-loaded pallets. Flow through the valve is controlled by the weight of the pallet or the spring force acting on the pallet to keep the device closed.when the pressure is below the set limit

Once the pressure or vacuum in the tank reaches the pallet closing force, the pallet will start to lift off the seat and allow flow through the valve.

Due to its air-cushioned sealing technology, Motherwell valves prevent emission losses until very close to the set pressure, and prevents air intake until very close to the set vacuum. Leakage rates are consistantly better than allowed for in API2000 and ISO 28300 with certification provided on request

The geometry of the valves has been developed in order to optimise overall performance in terms of high flow capacity, set pressure, sealing and re-sealing.

The modular nature of Motherwell’s valves means they can be tailored to meet specific customer requirements: whether this is pressure or vacuum-protection only; or vapours and gases either piped-away or vented to atmosphere.

A weatherhood protects the pressure vent port and a mesh screen is fitted to prevent intrusion of foreign matter into the valve.


These are some of the options available for our Breather Valves.

  • Available in Aluminium, Carbon Steel, Stainless steel & other metals upon request
  • Valve sizes from 50mm (2") to 300mm (12")
  • We will line and coat valves if this is required with long life paint systems or PTFE
  • Valve sizing available, let our software do your valve sizing and recomend your solution
  • Flow capacity details available for all our Breather valves,
  • Full Range of Breather Valve Spares available, usually ex-stock for critical repairs and reduced downtime
  • Breather Valve Servicing and resetting available upon request
  • All our breather valves are certified and compliant with European ATEX and PED directives where applicable.

Our free valve sizing service ensures you have the right valve for you tank, let us advise you on the best breather valve for your tank

The Pressure / Vacuum Relief valves are available in a number of combinations illustrated below. click on any for more information

All of the above breather valve combinations are available in a range of sizes  and can have flanged outlets or vent to atmosphere on both the pressure and vacuum depending upon your requirements.


click Below for further product information

Pressure Vacuum Relief Valve PVRV (CNC380, CNC383, CNC385 & CNC386)Pressure Vacuum Relief Valve PVRV (CNC380, CNC383, CNC385 & CNC386)PV valves or Pressure and Vacuum Relief Valves are available in a variety of optionsPressure Only Relief Valves - PRV (CNC381 & CNC384)Pressure Only Relief Valves - PRV (CNC381 & CNC384)Pressure Only Relief Valves can relieve to atmosphere or to a closed line Vacuum Relief Valve (CNC382 & CNC387)Vacuum Relief Valve (CNC382 & CNC387)Manufacturer of ATEX approved Vacuum relief valves, our vacuum relief valves are used in on bulk liquid storage tanks around the world, the are available to atmosphere or closed lineSpring Loaded Pressure Vacuum Relief ValveSpring Loaded Pressure Vacuum Relief Valvespring loaded relief valve available in all configurations, either pressure and vacuum can be spring loaded or both