Design Features & Benefits
- Rugged hinge pin and disc withstand shock of quick closing, providing years of service;
- Body seat ring orientation allows valve to close completely even in horizontal pipe run with no flow;
- Anti-rotation disc extends valve life under severe service conditions (by eliminating disc spin)
All CNI cast steel bolted bonnet swing check valves are available in a complete range of body/bonnet materials and trims (see page 42 for typical materials of construction). The valves are designed to provide fast check valve action and maximum service life. All swing check valves are full ported, and meet or exceed the design requirements of ASME B16.34.
Range of Materials
Standard body/bonnet materials include ten grades of carbon, low alloy and stainless steels. For special applications, they can be supplied in other grades of alloy and stainless steel. There’s a full range of trim materials to match any service. Standard and optional gaskets are available for a wide variety of service conditions.
Valves are designed to close quickly with positive shutoff in either horizontal or vertical (flow up) pipe runs. The body seat ring is installed on a 3° angle. This allows our swing check valve to close completely even when installed in a horizontal pipe run with no flow.
Our bolted bonnet design is simple to disassemble, easy to maintain. For example, our threaded seat rings are easily accessible for repair or replacement.
Our rugged hinge pin/hinge and disc construction is designed to withstand the shock of quick closing and provides years of service. Anti-rotation lugs on discs extend service life in turbulent, high velocity services which can otherwise cause spinning and wear.
Sizing Swing Check Valves
Three factors should be considered when sizing swing check valves; the pressure drop across the valve, the flow velocity of the fluid through the valve, and the location of the valve in relation to other piping components.
For best performance swing check valves should operate with fluid velocity sufficient to hold the disc in a stable position off the seat or fully open against the disc stop. Extremely high velocities should be avoided due to possible cavitation. In addition, there is a mid-range of velocity where the disc may become unstable as it approaches the disc stop. Operation in these velocity ranges should be avoided to achieve best performance and valve life.
Calculating Pressure Drop
Please refer to “Flow Calculations” in the Technical Data Section for swing check valve flow coefficient (Cv) and equations to calculate pressure drop through the valve.
Velocity equations are included in the Technical Data Section. When sizing swing check valves, the seat port velocity should be controlled within the general ranges specified below.
0√v – 55√v – Avoid this range.
55√v – 240√v – Generally optimum operating velocity range (See note).
Over 240√v – Avoid this range.
Where: v = The specific volume in ft3/lb of the fluid flowing.
NOTE: There is an intermediate operating velocity within this range at which the disc may become unstable. This non-optimum operating velocity range is generally from 115 √v to 135√v, however, upstream piping components placed in close proximity to the valve will tend to increase this range.
Influence of Valve Position
Swing check valves can be adversely affected by turbulence if placed too closely to other piping components such as pumps, control valves, meters, reducers, tees, elbows, etc. In general a minimum of 10 pipe diameters of straight pipe should be provided upstream of a swing check valve to minimize adverse conditions.
Two lugs on the disc prevent the disc from spinning in service.
This exclusive feature helps extend valve life in difficult services by eliminating disc spinning.
Outside Lever and Weight
All external hinge pin swing check valves 12" and smaller are available with an optional outside lever and weight. This feature can be used to either dampen or assist closing of the check valve disc depending on orientation. By using the lever and weight to counter-balance the disc, the valve opens at lower flow rates. By orienting the weight to add to the disc weight, the weight closes the valve faster. Please specify which orientation is desired when requesting this feature.
Optional Seat Types
Heavy duty, full ported seat rings have controlled seat width to provide maximum sealing force. Our optional threaded design allows simple, low cost replacement. For high temperature service, seat rings should be lock welded or seal welded. Please specify. Seat ring facings are available in many materials, including Co-Cr-A alloy or selection of non-cobalt alloy hardfacing, commonly specified for its excellent resistance to wear and damage. See page 42 for typical trims.
Standard Bonnet Joints
Body/bonnet joints on CNI valves are designed for rugged services with a more than adequate number of bonnet bolts. The standard joint varies, depending on valve class. These standard joints are shown.
Standard joint is a circular male and female configuration with a corrugated metal gasket.
The male and female joint confines the gasket O.D and I.D.
When specified, gaskets of other materials are available as an option.
Class 300 and up
The circular male and female bonnet joint is self-aligning and encapsulates the gasket.
Typical gaskets are spiral wound or double jacketed.