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How does a Diaphragm Valve work?

Diaphragm valves are used for the on/off and throttling of liquids that can carry a large number of suspended solids. The flexible membrane of the valve carries such operations. The flexible membrane generally manufactured with an elastomer like Ebonite, Neoprene, Butyl, Hypalon, PP-HDPE, and PTFE. These are generally reinforced with metals.

Diaphragm valves have linear motion characteristics. There is separation between the fluid and parts of the operating mechanism. This makes them ideal for corrosive or viscous service since it avoids contamination to or from the outside.

A flexible membrane made of elastomer provides the tightness. We can also reinforce the diaphragm with some metal. A linear movement axis punch tightens the shaft until it makes contact with the body.Thereby it acts as a seat.

The applications of diaphragm type of valve are mainly for low pressures and watered–down pates that would corrode and clog most other equipment. They are fast opening.

To comply with these operations, the valve stem rises or falls in a linear way up to the tension point of the membrane until it comes into contact with the seal of the valve body in the lower part of the same, producing the total closure of the valve.

As shown in the below figure, the diaphragm valve has a stem that from a distance also serves to know if it is open (stem up) or closed (stem down).

There are two types of diaphragm valves

  • Weir type diaphragm valve
  • Straightway diaphragm valve.

Weir Type Diaphragm Valve (Restricted Passage)

The weir-type diaphragm valves as shown in the below figure, have a raised seat that the diaphragm comes in contact with. This type of valve is best suitable for clean fluids, less suitable for slurry and viscous flow, may buildup either side instead of complete draining. We can use this type of diaphragm valve in opening, closing, and regulating services.

Straightway Type Diaphragm Valve (Direct Pass)

We use the straightway type diaphragm Valve for open and close service.We call this type of valve as a Straight-Thru. It is an extension of the pipeline and a practical solution to the problem of plugging, contamination, and abrasion it characteristics are minimal pressure drop, no cavities, bidirectional flow, self-draining.

General Operation and Maintenance instructions

  1. Valves and their components can get damaged if operated outside the pressure range for which they were designed.
  2. When determining the materials of the valve components, the chemical fluids that will pass through it must be taken into account, to be compatible and avoid damage.
  3. Check the valve hardware during maintenance, as over time they tend to loosen.
  4. Excessive force must not be used to open or close the valve while hand-wheel operation.

Specifications for the Order

  1. Diaphragm material
  2. Bonnet type.
  3. Type of operation.
  4. Working pressure.
  5. Operating temperature.
  6. Stem type.
  7. Body material.

General Ratings and Features of Diaphragm Valve

Typical Diaphragm Size

Generally Diameter size range: from 0.5 up to 14”.

Pipe Connection

Threaded, butt-weld, clamp, flange, socket, and spigot welded.

Diaphragm Material

Buna N (Nitrile Butadiene Rubber), Butyl Rubber (IIR), Ethylene Propylene (EPDM), Hypalon (CSM), Natural Rubber (NR), Neoprene (CR), PTFE, and Viton (FKM).

Body

Cast Iron, Cast steel, Bronze, SS 304/316, Aluminum, PVC, PP, Polypropylene.

Body Lining

Neoprene, EPDM, Viton, Ebonite, Silicon, PTFE (Poly Tetra Fluor Ethylene).

Temperature Range

Depending on the diaphragm material, the temperature range can be -10°C (-14° F) to + 170 ° C (+ 350 °F).

Pressure Range

Depending on the material.

Typical Applications

Chemical, fibrous pulps, pulps, sewage, pharmaceuticals, mines, boiler condensate treatment, water treatment.

The fluid remains never in contact with the valve components because valve membrane keep the fluid separate from valve components. Therefore, these valves are most suitable for viscous or corrosive fluids.

In addition to being a valve for use for zero leakage lines.

Advantages of Diaphragm Valves

  • The cost of the valve is usually low
  • The fluids are not in contact with the components. It has no packaging.
  • The probability of leaks is very low.
  • Minimal pressure loss, and extreme safety.
  • Fluid stagnation does not occur, so clogging is minimal.
  • There is a little pressure /head loss.

Disadvantages of Diaphragm valves

  • Excessive use of force could damage the diaphragm.
  • Require more maintenance because of diaphragm wear.
  • Not advisable for high-pressure applications.
  • Open and close operation is a bit slow.