All You Need to Know About Valves

From homes and cars to oil production and the human heart - few things would operate the way we're used to without valves.

While there are myriad types of valves, they all have one main function: to regulate the flow of a fluid. Whether it's gas, liquid, slurry or fluidized solids, valves regulate the flow by opening, closing or partially obstructing passageways.

Due to the wide variety of applications, valves range from simple, inexpensive, manually-operated parts to automatic valves costing thousands. They are also available in an infinite number of sizes.

In short, valves can be classified in the following main groups:

• One-port valves, which can only allow the fluid to move along the pipe or stop it from moving. These valves cannot direct the fluid in a specific pipe, but in some instances can change the speed at which the fluid is moving. An example would be the valve used in a kitchen tap.

• Two-port valves do a similar job, but the flow can go in either direction between two ports. Some valves are also designed to regulate varying amounts of flow, for example needle valves. Usually a mechanism or flow metre will be used to indicate by how much the valve is open.

• Three-port valves
  These valves are designed so that flow coming in at one port can be directed to either the second or the third port, or all flow can be stopped.

• Four-port valves, which have two passages to connect to other ports. These valves are used where fluids in a system need to be tested without affecting the pressure in the system.

Generic valve types include ball valves, which allow on/off control without the pressure in the pipe dropping; butterflyvalves, which regulate the flow in pipes with a large diameter; and check valves, which allow the fluid to pass in one direction only.