Diaphragm valves: Advantages and disadvantages of diaphragm valves
Diaphragm valve It is a type of valve that has a flexible diaphragm that partially opens, closes or obstructs one or more holes or conduits.

Diaphragm valves are used for cutting and throttling liquids that can carry a large amount of suspended solids. In the diaphragm valves the fluid is isolated from the parts of the operating mechanism. This makes them ideal in corrosive or viscous services, since it avoids any contamination to or from the outside.

The tightness is achieved by a flexible membrane, usually made of elastomer, and can be reinforced with some metal, which is tensioned by the effect of a linear axis-punch, until it makes contact with the body, which acts as a seat.

Diaphragm valves are the third most common type of linear motion valves. The valve stem is used to push down a flexible membrane, which in turn blocks the fluid path.

The main advantage of a diaphragm valve is the fact that the diaphragm isolates the moving parts of the valve from the fluid process. Industrial diaphragm valves are therefore suitable for handling aggressive fluids containing solid elements.

In addition, since the diaphragm assembly is not exposed to liquid, it can be made from cheaper materials such as cast iron, thus reducing the total cost of valve production. The development of new materials for diaphragm manufacturing allows These parts are used in most fluids. Its application is limited by the temperature that the diaphragm can withstand, typically below 175 °C.

Originally, the diaphragm valve was developed for use in unhygienic applications. Subsequently, the project was adapted for use in the bio-pharmaceutical industry, using compatible materials that can support cleaning and sterilization methods. Diaphragm valves can be either manual or automated. Their applications are often as shut-off valves in food, beverage, pharmaceutical and biotechnological process systems.

Diaphragm Valve Features

The flexible diaphragm attached to a compressor functions as a plug, when the valve stem lowers the compressor, the diaphragm produces a seal and cuts off circulation.

It is used for total opening or total closing, throttling and at low operating pressures, in corrosive fluids, sticky or viscous materials, fibrous semi-liquid pastes, sludge, food, pharmaceutical products.

There are two types of diaphragm valves:

  • Weir (restricted passage) : Weir type diaphragm valves can be used in opening and closing and regulating services
  • Straightway (direct pass) also called Straight-Thru. These direct-pass diaphragm valves are only used in opening and closing services.

Advantages and disadvantages of diaphragm valves


Advantage
  • Low cost.
  • They have no gaskets.
  • There is no possibility of leaking from the stem.
  • Immune to the problems of obstruction, corrosion or gum formation in the products that circulate.

Disadvantages
  • Diaphragm susceptible to wear.
  • High torque when closing with full pipe.

Characteristics and general ranges of diaphragm valves

  • Diameter range: 0.5 "to 14"
  • Pipe connection: Butt-weld welded, Clamp, Flange, Threaded, Socket and welded with breakwater
  • Diaphragm material: Buna N (NBR), Butyl (CIIR), Ethylene Propylene (EPDM), Hypalon® (CSM), Natural Rubber (NR), Neoprene (CR), PTFE and Viton® (FKM)
  • Temperature range: From -10ºc (-14ºF) to + 170ºC (+ 350ºF) - (Depending on the material)
  • Pressure range: From 13.8 bar (200psi) - (Depending on the material)
  • Fluid speed limitation: 15-20 ft / sec clean fluids and 8-10 ft / sec for sludge
  • Typical applications: Chemical, Fossil power plants, Pharmaceutical, Mines, Nuclear plants, Water treatments, ...