Pilot operated pressure reducing valve

The need for pressure reduction:

 1. A well designed steam system will produce clean dry steam in the boiler house ready for delivery at high

pressure through the distribution network. This maximises the potential to generate and supply saturated steam

of the best quality at the lowest overall cost.

 2.However, the needs are different at the point of use. Here, low pressure steam can offer distinct advantages,

as the equipment designed and constructed to use it can:-

     A. Cost less to buy because of the lower pressure rating.

     B. Cost less to operate as flash steam loss is reduced.

     C. Benefit from better control due to a higherDP across the control valve

     D. Suffer fewer scaling problems due to a lower steam temperature.

  3.On certain applications (typically autoclaves, retorts, corrugators etc.) it can be easier to control temperature by

simply adjusting the steam pressure, as with saturated steam, the two are related. For these applications, proper

process operation can be achieved without the need for conventional temperature controls.

  4.Whatever the reason for reducing pressure, proper control at any time demands an automatic valve that can

reduce steam pressure accurately, reliably and at a cost to suit the application.

How the DP pilot operated pressure reducing valve works:

  1. The DP type pilot operated reducing valve, works by balancing the downstream pressure against a control

spring. This modulates a small valve plug over a seat (the pilot). The flow through this seat is directed in turn to

the main valve diaphragm, where it modulates the main valve.

  2. Under stable load conditions, the pressure under the pilot diaphragm balances the force set on the adjustment

spring. This settles the pilot valve, allowing a constant flow across the main diaphragm. This ensures that the

main valve is also settled to give a stable downstream pressure.

  3. When downstream pressure rises, the pilot valve closes, and pressure is released from the main valve

diaphragm through the control orifice, to close the main valve.

  4. Any variations in load or pressure will immediately be sensed on the pilot diaphragm, which will act to

adjust the position of the main valve, ensuring a constant downstream pressure.

DP pilot operated pressure reducing valve