Pressure/Vacuum Relief Valves
(Breather Valves)

Weight or Spring-Loaded Pressure/Vacuum Relief Valves

Application

Direct acting pressure/vacuum relief valves (also known as breather valves, conservation vents, or safety vents) are special types of relief valves which are specifically designed for tank protection. 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.

Principle of Operation

The valves have a cast body which is flanged for connection to the storage tank. A weather hood protects the pressure exhaust port and a mesh cover is fitted to prevent the ingress of foreign matter for valves vented to atmosphere. Piped-away versions are also available throughout the range.

Both the pressure and vacuum sides of the valve incorporate a pallet and diaphragm assembly which rest on an 'O' ring seal to prevent leakage. This 'O' ring can be removed and the seat machined optically flat, producing a metal to metal seating arrangement if required. The weight of the pallet pushes the diaphragm against the seat to keep it closed. When the pressure or the vacuum increases, the pallet and diaphragm lifts and air/gas is allowed to flow.

Benefits

• Pressure/vacuum relief valves provide high gas flow from a compact valve size
• Range of sizes and materials to suit a wide range of applications
• Wide range of pressure and vacuum settings to provide maximum tank protection
  whilst ensuring minimum gas loss
• Valve sizing service assists optimum valve performance/cost specification
• Multiple configuration options for venting to/from pipes and/or atmosphere
• The Elmac technical team can advise on specific location queries

General Layout

	Body Cover Hood Pressure Guide Post Pressure Guide Post Vacuum Guide Post 'O' Ring 'O' Ring Mesh Mesh Pallet Pallet Stem Diaphragm Retaining Disc Weights

Material Specifications

* Special options and requests can be discussed with the Customer Services team.

Dimensions

* Does not include pallet weights for pressure/vacuum control.

Operating Limits

Variations

The pressure/vacuum relief valves are available in the following configurations:

• Pressure relief to atmosphere
• Pressure relief to closed line
• Pressure relief to atmosphere, vacuum relief from atmosphere
• Pressure relief to atmosphere, vacuum relief from closed line
• Pressure Relief to closed line, vacuum relief from atmosphere
• Pressure Relief to closed line, vacuum relief from closed line
• Vacuum relief from atmosphere
• Vacuum relief from closed line

Quick Links:

External Web Links

• Wikipedia - Pressure Relief Valve