Dual Plate Check Valve

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Dual Plate Check Valve

▪ An all-purpose non return valve that is much stronger, lighter in weight and smaller in size compared to a conventional swing or lift check valve
▪ Employs two-spring-loaded plates hinged on a central hinge pin.
▪ When the flow decreases, the plates close by the action of torsion spring before flow reversal takes place.
▪ Offers the twin advantages of No Water Hammer and Non Slam simultaneously.
▪ Also referred to as SILENT CHECK VALVE
▪ Most efficient in operation irrespective of fluid and service conditions and the easiest to handle and install in any piping system with no constraints
▪ Design as per API 594
▪ Pattern A?

Features

Elimination of water hammer


  • Closing of valve independent of back pressure and back flow. 
  • Due to spring assisted closing, valve closure starts as soon as flow velocity reduces below   the designed minimum velocity 
  • Thereafter closing rate follows the flow velocity reduction pattern. 
  • The valve closes as the flow velocity approaches zero and well before the flow reverses. This eliminates water hammer.

Non slamming

  • The two plates in Dual Plate Check Valve are hinged in the center vertically for horizontal installations, eliminating effect of gravity. 
  • Also the momentum developed as they move to the closed position is only a fraction of what is developed in a swing check valve
  • Weight of each plate is ¼th the weight of swing disc 
  • Tip velocity is less than half. 
  • Closes when flow velocity approaches zero and before the flow reversal. 
  • Flow cushions the plates and seat, minimizing slamming.

Lower pressure drop

▪ The design divides the total force in half
▪ One half the force on each plate requires one-half thickness, hence one-fourth the mass of a swing check disc.
▪ The weight of the plates does not increase the force required to move the plates.

Lower wear and tear of seat faces

▪ Plates are smaller in area and lighter in weight
▪ The unique feature of plate opening (i.e., it first lifts up at heel and then swings) ensures no rubbing actions against seat.
 ▪ This results in lower rate of wear and tear of seals.

Flexible installation

▪ More rigid that an equivalent length of heavy section pipe eliminating the need for any special support etc.
▪ Spring action enables valve to be installed in vertical or horizontal.

Design Standards

▪ Valve design conforming to API 594

▪ Type ‘A’ Dual-plate Wafer Check Valve
▪ Type ‘A’ Dual-plate Lug Check Valve
▪ Type ‘A’ Dual-plate Double-flanged Check Valve

▪ Valve design conforming to API 6D

▪ Dual – plate wafer-type check valve, short pattern
▪ Dual – plate wafer-type check valve, long pattern
▪ Seating
▪ Metal to Metal – either integral or over laid
▪ Soft Seating – integrally molded.

Advantages

▪ Light Weight resulting in easier handling and self-supporting.
▪ Compact & structurally sound design.
▪ Horizontal and vertical installation possible
▪ Can be installed for upside down flow due to spring assisted closure.
▪ Low Pressure Drop and reduced Energy loss
▪ Streamlined flow way.
▪ Efficient and Positive sealing under most flow and pressure conditions.
▪ Valve closes before flow reversal at zero velocity.
▪ Inherently Non-Slamming.  External devices/attachments not required.
▪ Water Hammer almost non-existent.
▪ Long life and trouble -free operation.

Disadvantages

▪ Dual-plate check valve is not piggable
▪ Disc check valves do not perform well for applications where there is heavily pulsating flow