BUTTERFLY VALVES
BUTTERFLY VALVES
Chemline’s plastic butterfly valves include concentric (full seat), double eccentric, and damper designs. A wide selection of materials are available for all services from water to aggressive chemicals. Chemline butterfly valves have had successful long-term experience in thermoplastic and composite piping systems, also tank trucks.
Butterfly Valve Selection
Elastomer Seated Butterfly Valves
Materials | Sizes | Disc | Seat | Cost | Model |
---|---|---|---|---|---|
PP, PVDF | 1-1/2” to 16” | PP, PVC, CPVC, PVDF* | EPDM, FKM** | $$$ | Type 58 |
PP | 16” to 24” | PP | EPDM | $$$ | Type 58 |
PVC, CPVC | 2" to 12" | PVC, CPVC | EPDM, FKM | $ | Type 60 |
PVC | 2-1/2” to 8” | PVC | EPDM, FKM | $ | Type 61 w/420B SS Shaft |
PVC | 2-1/2” to 8” | PVC | EPDM, FKM | $$ | Type 61 w/316 SS Shaft |
PP | 2-1/2” to 8” | PP, CPVC, PVDF, ABS | EPDM, FKM | $$$ | Type 61 w/316 SS Shaft |
PVC, PP, CPVC | 1-1/2” to 14” | PVC, PP, CPVC, PVDF | EPDM, FKM | $$$$ | Type 57P |
PP | 16” to 24” | PP, PVC, CPVC, PVDF | EPDM, FKM | $$$$ | Type 75 |
PP | 28” to 40” | PP, PVC | EPDM, FKM | $$$ | GY Series Giant |
PVC, PP | 2” to 12” | PVC, PP | EPDM, FKM | $$ | Type 71 Double Eccentric |
* PVC & CPVC discs up to 10”, PVDF disc to 12”
** FKM seats up to 16”
Fluoropolymer Lined Butterfly Valves
Materials | Sizes | Disc | Seat | Cost | Model |
---|---|---|---|---|---|
PPG, PPSG w/steel core*** | 3” to 12” | PFA covered SS | PFA | $$$ | HY Series Hybrid |
Vinyl Ester carbon-glass filled Composite | 2” to 12” | PFA Covered SS and others | TFM and others | $$$$ | CST-K Series ChemValve |
Ductile Iron-Epoxy Coated | 1-1/2” to 42” | PFA Covered 316SS and others | TFM and others | $$$$ | CST Series ChemValve |
*** Hybrid butterfly valves have a PFA liner
Low Leakage Damper Butterfly Valves
Materials | Sizes | Disc | Seat | Cost | Model |
---|---|---|---|---|---|
FRP | 24” to 96” | FRP | None | $$ | DBF Series |
Why a Butterfly Valve?
Their quick opening quarter-turn operation makes butterfly valves popular. They are generally the most economical plastic shut-off valve type in all sizes above 3”. Pressure drop is low, making them a good choice as an isolating valve. Maintenance is simple due to the small number of moving parts. Their short face-to-face-dimension makes them space efficient and relatively light.
Butterfly valves are used in on/off applications as well as for modulating flow control. Each valve has a range where it operates with relatively linear flow control.
Relatively low stem torques make them inexpensive to actuate. Most Chemline butterfly models may be actuated at minimal mounting cost. Electric and pneumatic actuators, plus all accessories are available.
Although not designed for abrasion resistance, Chemline butterfly valves with optional PVDF discs last the longest and are a better choice than ball valves.
Butterfly valves stand up better than ball valves in subzero temperatures because the bodies are sandwiched between flanges leaving only the operators
exposed to possible impact.
Installation requires pipe companion flanges, gaskets and bolts/nut/washer sets.
How do Butterfly Valves work?
Most Chemline butterfly valves are “concentric” design. A stainless steel shaft passes through a plastic disc with a similar diameter to that of the connecting pipe inside diameter. Fluoropolymer lined valves have a one-piece disc/shaft. The disc rotates 90 degrees, fully closing against a full elastomer or fluoropolymer seat for a tight shutoff. The shaft passes through the center of the body. Concentric design meets the pressure requirements of most plastic or composite pipe systems. Valves are bidirectional because pressure resistance is the same with valve installed in either flow direction. Although the disc is in the center of the flow stream, because it can be relatively thin, concentric design produces lower pressure drops. The full elastomer seats extend to cover the valve faces contacting the pipe flanges. The valve body is non-wetted.
Type 71 valves are “double offset”. The shaft axis is offset from the valve centerline between valve flange faces AND offset from pipe and valve’s centerline. The disc lifts up and away from the valve seat rather than squeezing into it. This means the seat can be a relatively thin ring shape. Because the disc is not squeezing into the seat, shaft torques is low, requiring smaller electric or pneumatic actuators. Type 71 is bidirectional but has a preferred flow direction for the tightest closure. The design requires a thicker disc than concentric, producing higher pressure drops.
Chemline offers FRP low leakage damper valves up to 96” /2400 mm. They have no elastomer seat but are designed for minimum gas leakage due to tight tolerances on the disc/body mating surfaces.
How are Butterfly Valves connected to piping?
Wafer body butterfly valves fit between mating flanges. Bolt holes in the valve body allow the bolts or studs to pass through and serve to center the valve properly for a good seal against mating flange faces.
Lug body valves are available in the ChemValve and Hybrid models. Flange bolts are threaded into the valve body from both sides. No nuts are used. Lug
bodies allow the valve to hold full pressure on one side of the piping while the other flange is removed. Equipment such as heaters, filters, pumps, etc. located
between lug body valves may be removed and maintained while system pressure is maintained.