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
