APPLICATIONS

The excess-flow shutdown valve is used for pipeline safety isolation, when excess flow occurs.

PRINCIPLE OF OPERATION

The excess-flow shutdown valve closes when a preset differential pressure ‘dP=Pu-Pd’ exists across the valve.

The valve is powered by the line-fluid pressure with no need for external actuators, pilots, instruments or an external power source.

SHUTDOWN SETTING ADJUSTMENT

The flow-rate at which the excess-flow shutdown valve closes, can be adjusted by varying the control orifice size ‘Do’, thus changing the valve’s differential pressure

dP = Pu – Pd

WATER-HAMMER PREVENTION

The excess-flow shutdown valve closes at a controlled speed, which is adjustable by a measuring orifice, while the valve’s flow rate reduces gradually as the valve closes bythe control orifice contour.

RESETTING – EXCESSIVE DEMAND

The excess-flow shutdown valve closes when the flowthrough the valve reaches a preset flow rate. The valve will
reopen when the: –

  • Over demand conditions are over.
  • Column’s downstream is charged through the valve’s bypass
  • The valve opens automatically when the downstream pressure is restored.

RESETTING – PIPE BURST

The excess-flow shutdown valve closes when the flow through the valve reaches a preset flow rate. The valve will reopen when the following procedure takes place: –

  • Pipe burst, causing the excess-flow conditions is rectified
  • Column’s downstream is charged by the valve’s bypass
  • The valve opens automatically when the downstream pressure is restored.

MANUAL ISOLATION

The excess-flow shutdown valve can be manually isolated by a handwheel or actuator.