CHECK VALVES
CHECK VALVES
Chemline offers several types of plastic check valves in different materials for all services from water to aggressive chemicals. Ball checks and spring (cone) checks are made in the smaller diameters. Swing checks are available to 8”
and wafer check valves up to 24” plus.
Check Valve Selection
True Union Check Valves
Materials | Sizes | Fluids - Corrosives, w/Solids, Potable Water, High Purity Water | Cost | Model |
---|---|---|---|---|
PVC | 1/2” to 3” | COR, POT | $$ | ES Spring (Cone) Check |
PVC | 1/2” to 2” | COR, SOL, POT | $ | EC Series Ball Check |
CPVC | 1/2” to 2” | COR, SOL, POT, HPW | $ | DC Series Ball Check |
PVC | 1/2” to 3” | COR, POT | $ | EF Series Foot Valve |
PVC, PP, CPVC, PVDF | 1/2” to 4” | COR, SOL, POT, HPW | $$$ | BT/BC Ball Check & Foot |
Swing Check Valves
Materials | Sizes | Fluids - Corrosives, w/Solids, Potable Water, High Purity Water | Cost | Model |
---|---|---|---|---|
PVC, CPVC | 3/4” to 4” | COR, POT | $$$ | SW Series Swing |
PP, PVDF | 3/4” to 8” | COR, POT, HPW | $$$ | SW Series Swing |
PVC, PP, PVDF | 3/4” to 8” | COR, POT, HPW | $$$$ | SC Series Swing |
Wafer Check Valves
Materials | Sizes | Fluids - Corrosives, w/Solids, Potable Water, High Purity Water | Cost | Model |
---|---|---|---|---|
PVC | 2-1/2” to 8” | COR, POT | $ | WE Series Wafer |
PVC, PP, PVDF | 2” to 12”* | COR, POT, HPW | $$ | WP Series Wafer |
PVC, PP, PPG, PVDF | 3” to 10” | COR, POT, HPW | $$$ | PW Series Wafer |
* Sizes up to 40” available special order.
Why a Check Valve?
Check valves prevent back flow, allowing flow in one direction only. They close automatically as soon as flow stops or starts to reverse. All Chemline check valves have 100% shutoff. Check valves serve to protect pumps, filters and other equipment where back flow can cause damage. They are often installed on the discharge side of a pump to keep pipes full. If installed too close, high turbulence can cause damage or excessive wear of valve parts. They do not work well with pulsating flows, where constant opening-closing can cause the same problems.
Check valves are intended for control of clean fluids and are not generally recommended for slurries or applications with crystals or debris. The exception is the
ball check valve, which will tolerate some solids.
How do Check Valves work?
Check valves close completely when flow reverses. Fast closing is required to minimize back flow and slamming force of a closing disc.
Ball checks have a free-floating machined ball that rests against an elastomer seat when closed. The preferred position is vertical where gravity assists the ball to close but they work equally well horizontally with some back flow. The ball rotates in the flow path to “self-clean” so they tolerate some impurities. Ball checks require about 2 meters (7 ft.) of water head above the valve to close 100%.
Spring (Cone) checks are similar to ball checks but have a cone shaped disc with spring to assist in closing. Spring checks require half the seating head (pressure) to close compared to ball checks. That allows the user more choice of installation locations. The standard spring is PTFE (“Teflon”R) - covered for maximum chemical resistance.
Swing checks have a disc completely inside the body and open with full flow. They have a one-piece moulded flanged body and are installed mainly in frp composite pipe systems in heavy industry. An access cover permits repairs without removing the valve from the line.
Wafer check valves are compact and cost effective in large diameters. Springs are recommended for fast closing. The diameter of valve orifice is less than full port because the disc must open inside the piping.
How are Check Valves connected to piping?
Socket welding is the usual pipe connection method for PVC and CPVC valves up to 4”.
Threaded ends are available but are often expensive to install due to labour to thread pipes. Some chemicals tend to leak through threads.
Polypropylene (PP) and PVDF True Union check valves have metric ends to connect to standard metric (DIN) pipe and fittings (offered by Chemline). Butt fusion is the technically best joining method, essential for PVDF, and required for high purity water. PP metric socket ends are popular in other applications. Chemline supplies butt fusion and socket fusion pipe welders and pipe tools.
Flanged ends are available on ball and spring checks for connection to dissimilar piping material of all types. Swing check are all only flanged and wafer check valves are installed between pipe flanges. They require bolts/nut/washer sets. Wafer checks have face O-ring seals but swing checks require flange gaskets. Chemline recommends GA series low torque flange gaskets with all plastic flanged valves.