Introduction to the Types of Valves

 Introduction to the Types of Valves

Because of the diversity of the types of systems, fluids, and environments in which valves must operate, a vast array of valve types have been developed. Examples of the common types are the globe valve, gate valve, ball valve, plug valve, butterfly valve, diaphragm valve, check valve, pinch valve, and safety valve. Each type of valve has been designed to meet specific needs.

Some valves are capable of throttling flow, other valve types can only stop flow, others work well in corrosive systems, and others handle high pressure fluids. Each valve type has certain inherent advantages and disadvantages. Understanding these differences and how they effect the Valve’s application or operation is necessary for the successful operation of a facility.

Although all valves have the same basic components and function to control flow in some fashion, the method of controlling the flow can vary dramatically. In general, there are four methods of controlling flow through a valve.

  • Move a disc, or plug into or against an orifice (for example, globe or needle type valve).
  • Slide a flat, cylindrical, or spherical surface across an orifice (for example, gate and plug valves).
  • Rotate a disc or ellipse about a shaft extending across the diameter of an orifice (for example, a butterfly or ball valve).
  • Move a flexible material into the flow passage (for example, diaphragm and pinch valves).

Gate valves are generally used in systems where low flow resistance for a fully open valve is desired and there is no need to throttle the flow.

Globe valves are used in systems where good throttling characteristics and low seat leakage are desired and a relatively high head loss in an open valve is acceptable.

Ball valves allow quick, quarter turn on-off operation and have poor throttling characteristics.

Plug valves are often used to direct flow between several different ports through use of a single valve.

Diaphragm valves and pinch valves are used in systems where it is desirable for the entire operating mechanism to be completely isolated from the fluid.

Butterfly valves provide significant advantages over other valve designs in weight,space, and cost for large valve applications.

Check valves automatically open to allow flow in one direction and seat to prevent flow in the reverse direction.

A stop check valve is a combination of a lift check valve and a globe valve and incorporates the characteristics of both

Safety/relief valves are used to provide automatic over pressurization protection for a system.

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