The CVI dual plate check valve design is generally stronger, lighter, smaller, more efficient and less expensive than conventional swing check valves. The design meets API 594 which is approximately 25% the face to face dimension and 15% to 20% the weight, on most popular sizes, making them less expensive than a swing check valve. It is much easier to install between standard gaskets and line flanges. The savings compound during installation due to ease of handling and only one set of flange studs is required. Therefore, it is more cost effective to install, and also to maintain.
The CVI also offers special design features which make it a high performance non-slam check valve. These include a scrub-free opening, and in most sizes a unique independent spring design as well as an independent plate Stop hinge pin. Other configurations include lug type and double flange type.
The innovative dual-plate design of the CVI check valve employs one or two spring- loaded plates (disc halves) suspended on a central vertical hinge pin. As flow begins, the plates open in response to a resultant force (P) which acts as the center of the sealed surface area. The contact point of the reacting spring leg’s force (Ps) acts beyond the center of the plate area, causing the heel to open first. This prevents rubbing of the seal surface prior to normal plate opening, eliminating wear.
As the velocity of flow decreases, torsion spring action reacts automatically. This moves the plates closer to the body seats, reducing the distance and time of travel for closure. By having the plates closer to the body seats at the time of flow reversal, the valve dynamic response is greatly accelerated. This dramatically reduces the water hammer effect for non-slam performance.
At closing, the point of spring force causes the toe of the plates to close firstly. This prevents dragging of the heels of the plates and maintains seal integrity for much longer periods.
A spring design of CVI dual plate check valve( sizes6″ and larger) allows higher torque to be exerted against each plate with independent closing in response to the process stream. Testing has proved this action provides up to 25% improvement in valve life and 50% reduction in water hammer. Each of the dual plates has its own spring or springs, which provide independent closing action. These in-dependent springs undergo less angular deflection, only 140°as compared to 350°for
conventional springs with two legs.
Independent Plate Suspension Design
The CVI dual plate check valve unique hinge design reduces friction forces by 66% , which improves valve response significantly. Support sleeves are inserted through the outboard hinges so that the upper hinge is independently supported by the lower sleeve during valve operation. This allows both plates to close at the same time for quick response, and excellent dynamic performance.
Independent Spring Design