• Very fast acting.
• Optional visual indication of operation.
• Optional electrical indication of operation.
• Wide range of adjustable opening pressures.
• Environmentally sealed microswitch.
• Optional EExd microswitch for hazardous area's.

Pyropress fast acting relief valves are used to protect oil cooled transformer installations against the risk of explosion which may occur under severe fault or short circuit conditions. Extremely rapid pressure rise can result from arcing with immediate vaporisation of cooling oil. This pressure must be relieved instantly to avoid the rupture of the transformer tank.

To ensure the prevention of such hazards a pressure relief valve is required to open quickly and relieve the increase in pressure. The valve must also have adequate relief area to release the volume of oil or gas necessary to restore the pressure to acceptable limits. The Pyropress valve meets all these criteria, and is designed to open fully, within 2 milliseconds when a safe maximum pressure limit is reached. The valve achieves its performance by a design of dual valve seals.

The valve is available with or without the deflective cover and microswitch. The cover is fitted with a visual indication of valve actuation, a mechanical valve lift indicator is provided on the top of the valve cover. In the event of the valve operating the bright red anodised aluminium indicator is pushed upwards, and is left protruding 50mm above the top of the valve casing. This can be manually reset. The microswitch provides remote indication of valve operation, by means of a manually resetable switch assembly. This can be used to provide a signal to an alarm or control panel. In installations where it is required to completely fill the transformer housing with oil, a bleed screw can be provided to remove all air trapped within the valve assembly. This is an option and should be requested.

The Pyropress TX50 series of transformer relief valves have an effective relief area of almost 15 cm2, and are suitable for transformers of up to 3,000 litre oil capacity and the TX135 series have an effective area of 140cm2 suitable up to 45,000 litres of oil. Both types provide opening pressure ranges between 4 and 12 PSI. These are factory set to customers requirements.

The Nitrile seals fitted to the TX50 series valves are suitable for use with Silicon and Midel transformer oils. For information on other oils please consult our sales office.

Technical Specification.

• Cover: Cast aluminium.
• Carrier: Anodised aluminium.
• Valve: Anodised aluminium.
• Outer seal: Nitrile Butyl rubber.
• Inner seal: Nitrile Butyl rubber.
• Valve spring: Carbon steel.
• Spacers: Stainless steel