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BIRKETT Pop Pilot Operated Safety Relief Valve
The nozzle is a patented push-in design, held in position with a locking ring. This reduces mechanical and thermal stresses at the seat, reduces inlet pressure losses, increases the discharge co-efficient and allows for lower specification body materials on corrosive duties.

Pilot valves will maintain full lift against high levels of back pressure, unlike spring loaded valves, which would need either differential setting or the addition of balanced bellows. The system operating pressure can be much closer to the set pressure on a pilot operated valve than with a standard spring loaded safety relief valve. System pressures in the region of 95% to 98% of set pressure are often accommodated.

Specifically for gas applications, Safeset pop acting pilot valves are quick acting with no delay between the pilot and the main valve opening pressures. With pop action pilot operation, the main valve is either in the fully open or shut position. The operation is characterised by a distinct rapid “pop” action, which is evident at the opening of the main valve, followed by a positive re-seat action when the main valve closes.

When set pressure is reached, the pilot valve opens rapidly; this action de-pressurises the dome volume very quickly and the main valve opens. The re-seating characteristic is equally positive: when the system pressure has fallen to the pre-set pilot re-seat pressure, the pilot drain seat closes rapidly. This action allows the dome to be re-pressurised very quickly, thereby closing the main valve completely.

The re-seat pressure of the Type 2 pilot valve is adjustable externally, independently of the set pressure adjustment.

The standard range of single outlet main valves consists of 8 body sizes, which by simple adjustment accommodates all 21 standard orifice sizes. This allows for easy adjustment should service conditions dictate a change in required orifice area.

Pilots can be adjusted to give zero overpressure and a blowdown typically equal to 3% of set pressure.

Type 2 Pilot must have the exhaust vent open to atmosphere or piped to a safe area.

A selection of accessories is available to suit system requirements. These include:     

• Back Flow Preventer
• External Supply Filter
• Remote Pressure Sensing
• Heating or Cooling Coils
• Field Test Connector
• Remote Uploader
• Dual Pilots