Diaphragm valve

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Diaphragm valves (or membrane valves) consists of a valve body with two or more ports, a diaphragm, and a "saddle" or seat upon which the diaphragm closes the valve. The valve is constructed from either plastic or steel.

Originally, the diaphragm valve was developed for use in non-hygienic applications. Later on the design was adapted for use in the bio-pharmaceutical industry by using compliant materials that can withstand sanitizing and sterilizing methods.

There are two main categories of diaphragm valves: one type seals over a "weir" (saddle) and the other (sometimes called a "straight-way" valve) seals over a seat. The main difference is that a saddle-type valve has its two ports in line with each other on the opposite sides of the valve, whereas the seat-type has the in/out ports located at a 90 degree angle from one another. The saddle type is the most common in process applications and the seat-type is more commonly used as a tank bottom valve but exists also as a process valve. While diaphragm valves usually come in two-port forms, they can also come with three ports and even more. When more than three ports are included, they generally require more than one diaphragm; however, special dual actuators can handle more ports with one membrane.

Diaphragm valves can be manual or automated. Their application is generally as shut-off valves in process systems within the food and beverage, pharmaceutical and biotech industries. The older generation of these valves is not suited for regulating and controlling process flows, however newer developments in this area have successfully tackled this problem.

In addition to the well known, two way shut off diaphragm valve, there are many other forms of the diaphragm valve including: three way zero deadleg valve, sterile access port, block and bleed, valbow and tank bottom valve just to name a few.

Contents

[edit] Actuators

Diaphragm valves can be controlled by various types of actuators. The most common diaphragm valves use pneumatic actuators; in this type of valve, air pressure is applied through a Schrader valve which raises the diaphragm and opens the valve. This type of valve is extremely quick and as such is one of the more common valves used in operations where valve speed is a necessity.

Hydraulic diaphragm valves also exist for higher pressure and lower speed operations. Some diaphragm valves are also controlled manually.

[edit] Body Materials

  • Steel type:

Cast Iron, Ductile Iron, Carbon Steel, Stainless Steel

  • Plastic type:

ABS (Acrylonitrile butadiene styrene), PVC-U (Polyvinyl chloride, unplasticized) also known as PVCu or uPVC, PVC-C (Polyvinyl chloride, post chlorinated) also known as PVCc or cPVC, PP (Polypropylene), PE (Polyethylene) also known as LDPE, MDPE and HDPE (see note), PVDF (Polyvinylidene fluoride)

[edit] Body Lining Materials

depending on temperature, pressure and chemical resistance, one of the following is used

  • Unlined type
  • Rubber lined type
NR/Hard Rubber/Ebonite,
BR/Soft rubber
EPDM
  • Fluorine plastic lined type
FEP/F46
PFA
PO

[edit] Diaphragm Materials

  • Unlined or Rubber Lined Type:
NR/Natural Rubber
NBR/Nitrile/Buna-N
FKM/Viton
SI/Silicone rubber
  • Fluorine Plastic Type:
FEP/F46,with EPDM back
PTFE/F4,with EPDM back
PFA,with EPDM back

[edit] Diaphragm valve manufacturers

  • Asepco
  • Hills McCanna
  • Bürkert
  • Gemü
  • George Fischer
  • ITT
  • Novaseptic
  • Praher
  • Robolux
  • Roplan
  • Saunders
  • Goyen / Tyco
  • Shangyu Valve

[edit] See also

[edit] External links

  • Praher Valves A manufacturers website offering free pdf downloads of product data sheets
  • Pipestock - A commercial site offering tables, specifications and showing pictures of product
  • Aquasyn A manufacturers site that shows customized diaphragm valves