DIAPHRAGM VALVES
DIAPHRAGM VALVES
Chemline plastic diaphragm valves range from 3/8” to 10” manually operated and pneumatically actuated. A wide choice of materials is available for many applications. Chemline industrial diaphragm valves have been installed in Canadian chemical plants, picking plants and other heavy industry for decades.
Diaphragm Valve Selection
Industrial Diaphragm Valves
Materials | Sizes | Diaphragm | Operator | Applications | Cost | Model |
---|---|---|---|---|---|---|
PVC, PP, CPVC, PVDF | 1/2” to 10” | EPDM, PTFE | Manual | Heavy Industry | $$$ | Type 16 Flanged |
PVC, PP, CPVC, PVDF | 1/2” to 10” | EPDM, PTFE | Manual | Heavy Industry | $$$$ | Type 14 Flanged |
700 Series Diaphragm Valves
Materials | Sizes | Diaphragm | Operator | Applications | Cost | Model |
---|---|---|---|---|---|---|
PVC, PP, CPVC, PVDF | 3/8” and 1/2” | EPDM, PTFE | Manual | Water Treatment, General Industrial | $$$ | Type 720 Mini |
PVC, PP, CPVC, PVDF | 1/2” to 2-1/2” | EPDM, PTFE | Manual | Water Treatment, General Industrial | $$$ | Type 761 Compact |
PVC, PP, CPVC, PVDF | 3” and 4” | EPDM, PTFE | Manual | Water Treatment, General Industrial | $$$ | Type 760 Compact |
PVC, PP, CPVC, PVDF | 3/8” and 1/2” | EPDM, PTFE | Pneumatic-Piston | Water Treatment, General Industrial | $$$ | Type 710 Mini |
PVC, PP, CPVC, PVDF | 1/2” and 3/4” | EPDM, PTFE | Pneumatic-Piston | Water Treatment, General Industrial | $$$ | Type 731 Compact |
PVC, PP, CPVC, PVDF | 1” to 2” | EPDM, PTFE | Pneumatic-Piston | Water Treatment, General Industrial | $$$ | Type 750 Piston |
PVC, PP, CPVC, PVDF | 1” to 4” | EPDM, PTFE | Pneumatic-Diaphragm | Water Treatment, General Industrial | $$$ | Type 730 Standard |
Fluoropolymer Lined Diaphragm Valves
Materials | Sizes | Diaphragm | Operator | Applications | Cost | Model |
---|---|---|---|---|---|---|
PPG or PPSG w/PFA or PVDF lining* | 1/2” - 6” | TFM | Manual | Heavy Industries**, High Temperatures | $$$ | HD Series Hybrid |
* Hybrid ball valves have PPG or PPSG bodies lined with PFA or PVDF
** Heavy Industry = chemical plants, steel pickling, pulp & paper chem prep, metals refining
Why a Diaphragm Valve?
There are several reasons plastic Diaphragm valves are a better choice over other types like ball or butterfly.
They are abrasion resistant so will handle fluids with entrained solids, and slurries.
They offer relatively good control when throttling (adjusting) flow.
Unlike in a ball valve, there are no cavities, areas of fluid entrapment. Because they are self-draining sanitary design, diaphragm valves are suited for high purity applications.
The only wetted parts are the body and diaphragm. With a PTFE diaphragm, they are applicable in severe services beyond the chemical resistance limits of ball or butterfly valves with elastomer seals. These are process lines in chemical plants, steel pickling, etc. handling concentrated acids or chlorine based chemicals.
They are not straight through full port like a ball valve, so fully open, pressure drops there are higher. Multi turn operation means manual valves have better control, but are not quick to open-close.
The 700 series valves are of modular design with a wide choice of accessories. Usually they are installed on process skids for water treatment. They are compact and can be easily panel mounted. The pneumatically actuated models (especially those with piston actuators) are designed for long cycle life.
How do Diaphragm Valves work?
Chemline plastic diaphragm valves are “weir” type. There is a saddle across the flow path in the body. A flexible diaphragm seals over the weir when the valve is closed, even when solids are in the service. Manual operator is a multi-turn hand wheel. The compressor piece pushes the diaphragm down to seal both inlet and outlet ports.
Solid PVDF flanged diaphragm valves in steel pickling plants experience body bolt loosening over time and require constant maintenance. HYDRID diaphragm valves have specially designed diaphragms, which do not loosen, requiring little or no maintenance.
The 700 Series pneumatically actuated valves have long cycling life, especially with the piston actuator models. Electric actuators are not available on diaphragm valves.
How are Diaphragm Valves connected to piping?
Diaphragm valves with True Union ends are easy to connect to the same material piping. The valve body slips out for maintenance without moving piping. Installation labour for socket end True Union valves is low.
Socket welding is the usual pipe connection method for PVC and CPVC valves.
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 diaphragm 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 for connection to dissimilar piping material of all types. Chemline’s industrial diaphragm valves with solid one-piece moulded flanged bodies are often installed in composite (frp) flanged piping systems.
To reduce excessive stress on plastic flanges, Chemline recommends GA series low torque flange gaskets always be used.