Valves

Description

Valves are mechanical devices that control the flow of liquid, gas, slurries, and fluidized solids through a pipeline. Valves can be manually controlled by pedal, hand wheel or lever; they may also operate automatically, driven by changes in pressure, temperature or flow. Usually valves, perform functions like controlling the fluid flow, regulating the quantity/process pressure, changing the direction of flow, releasing the excess pressure. Usually the valves are made of metal or plastic. Based on the operation there are two types of functions that a valve can perform to maintain a continuous flow of liquid. In addition to continuous flow maintenance, it can also act as a switch to stop/start the flow of the liquid.

Valve Parts

A valve has the following components:

• Body and Bonnet
• Disc / Valve Member / Rotor
• Ports
• Spring
• Seat
• Valve balls
• Stem

Types

Industrial valves can be classified as follows:

• Ball valves - on/off control without pressure change
• Butterfly valves - regulating the flow in large pipes
• Check valves or non-return valve - permits unidirectional flow
• Diaphragm valves - used for carrying compliant materials
• Gate valves - on/off control with a small decrease in pressure
• Piston valves - used for fluids which carry suspended solids
• Safety valves - operates automatically to relieve excess pressure
• Globe Valves - good for regulating the flow
• Poppet Valves - used to regulate the fuel intake and exhaust gases
• Plug Valves - slim looking valve for on/off control but with a small drop in pressure
• Needle Valves - accurately controls the flow

Classification

Based on their operation, valves are classified as follows:

• Manual
• Solenoid
• Hydraulic/Pneumatic

Applications

Valves are mainly used in pipes and engines. Applications cover oil and gas, mining, water treatment, chemical, petrochemical, thermal power plant, and automotive industries.