Diaphragm valves are very popular in process industries.

70 years ago diaphragm valves were developed from the American company Saunders and applied for the first time in industrial processes.  A major advantage of these valves compared to ball valves, angle seat valves or butterfly valves is, that the volume flows can be precisely regulated. Also the possibility to automate the diaphragm valve, makes it an indispensible instrument in industries, chemical and process engineering.

The company SED Flow Control GmbH in Bad Rappenau is one of the world’s leading manufacturer of diaphragm valves. We are describing below not only plastic diaphragm valves, but also metal diaphragm valves.

The simple design following the Saunders principle, the long service life, easy handling and finally also the low price compared to other control valves, brings along numerous advantages in plant engineering. In case of abrasive media, the sealing membrane is the only wear part. In the pharmaceutical industry, this membrane will be exchanged for safety reasons at short invervals. Medium shut-off is made by means of a membrane via the web in the valve bottom section. As only the valve body as part of the pipe system and the membrane have any medium contact, diaphragm valves are easy to maintain and to clean. For maintenance or cleaning purposes only 4 screws have to be unlocked, in order to exchange the membrane. The valve body does not need to be disassembled and can remain in the pipeline.

A typical application is precision dosing of media in plants of the dosing technology. For this application it is typical to install a pneumatic drive. Besides the classic handwheel, the basic body provides the option of operating the pneumatic drive as (NC) normally closed, (DA) double acting and (NO) normally open. By this, you cover 99,9 % of the procedural requirements in plant construction. All drives represent the current state of the art and are equipped with a NAMUR connection.

For the plastic diaphragm valves the user can select between valve bodies made of PVC U, PVC C, ABS, PP or PVDF, a distinction is also made in specific connection variants. The different versions, as screw fittings with gluing sleeves, gluing spigots and screw fittings with welding sockets, welded unions and nozzles keep all options open.

Our supply range: diaphragm valves made of plastic

ABS diaphragm valve with gluing sleeve

PVDF diaphragm valve with welded union

PVC C diaphragm valve with gluing sleeve

PP  diaphragm valve with PP/ST flange


Diaphragm valves made of the above mentioned materials or with PFA lining provide the best possible corrosion protection. The membrane is the wear part of the valve. Historically, such developments come from a German area in Baden-Wurttemberg and are based on decades of experience under operational conditions. The special know-how lies in the mixture of the raw material.

The company SED FLOW CONTROL GmbH, Bad Rappenau are the world leaders in develpments of valve technology for the pharmaceutical industry. Apart from valve bodies made of stainless steel, in the precision casting process and as forged body, also block valves according to the application (p + id flowchart) are manufactured in accordance to the latest technical standards on 5-axis CNC machines. Special solutions require intensive application support of the supplier. In pharmaceutics the diaphragm valves should be designed from the point of view of independent deflation in a certain angle and absence of dead spaces.

The valve bodies can be supplied with flange or threaded socket, as metal body made of GG25, GGG40.3, stainless steel or lined with  PP, PVDF or hard rubber. According to application, the membrane is available as elastomer in the materials EPDM, FPM (on request also silikone, NBR or butyl) or with a chemically high resistant PVDF coat at the medium side.
By using a diaphragm valve, water hammers can be avoided. Used as manual valve, diaphragm valves are suitable for controlling rarely operated places, and beyond that as control valve or as extraction valve.

Pneumatic drives are available in three switching functions:

- Normally closed / NC / normally closed / spring force closed - air open / safety position closed (most frequent application case)
- Normally open/ NO / normally open / spring force open - air closed  / safety position open (application among others as emergency valve or in cooling circuits)
- Double acting / DA / double acting / air open - air closed (mostly for filling processes, since no safety position, but fast switching times)

Advantages of diaphragm valves:

- low-maintenance valve
- the inner parts are very well cleanable
- CIP compatible
- high flow rate
- low pressure loss
- compact and sturdy design
- low weight
- adaptable to various accessories and measuring equipment
- low market price

Stainless steel diaphragm valve with internal thread


Stainless diaphragm valve wih flange


Grey cast iron diaphragm valve with PFA lining

Automated grey cast diaphragm valve

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