Types of Valves:
Due to various environments, system fluids and system conditions in which the valve operates, many types of valves have been developed. Each type of valve is design to meet some special requirements. Here are the various types of valves.
1. Types of valves according to function:
According to the nature of their design and function, valves categorized into three areas. On off Valves throttling valves and non-return valves.
a. On-off valves: On-off valve refers as block valves. These valves use to start or stop the flow of working fluid. Gate valve, plug valve, ball valve, pressure relief valve, safety valve, and tank bottom valves are the examples of on-off valves. Majority of these valves are hand operated, while they can be automated with the addition of an actuator. On-off valves use to change the direction. These valves provide isolation for maintenance purpose. Also, use where workers must be protected from potential safety hazards.
b. Non-return valves: Non-return valves allow the fluid to flow only in one direction. All check valves are non-return valves. These valves are used to prevent backflow of fluid, which cloud damage equipment or upset the process. These valves use for Protecting a pump or compressor from backflow when the pump/ compressor is shut down.
c. Throttling valves: Throttling valves use to regulate the flow, temperature or pressure of the working fluid. Pressure regulators, globe valve and automatic control valves are throttle valves. These valves move to any position according to the valve stroke and hold that position including the full open or full closed positions. Therefore, they also act as on-off valves. Many throttling valves design provides a hand-operated manual hand wheel/ lever. Some of the throttling valves equipped with actuator or actuation system.
2. Types of valves according to motion:
Valves are also classified according to the mechanical motion of the valve. Linear and rotary motions are the mechanical motions of valves.
a. Linear motion valves/ Linear valves: Linear motion valves have the sliding stem. This sliding stem pushes closure element into an open or closed position. Any internal valve device uses to open, close or regulate the flow, call the closure element. Gate valve, globe valve, pinch valve, split body, three-way valve, diaphragm valve, and angle valves are the linear valves. Linear valves are simple in design and easy maintenance.
b. Rotary motion valves/ Rotary valves: Rotary valves use closure element that rotates through a quarter turn or 450 range to open or block the flow. The butterfly valve is an example of a rotary motion valve. Rotary motion valves are smaller in size and weight as compare to linear valves.
3. Types of valves according to the application:
According to the application, valves classified as General Service valves, Special service valves, and Severe service valve.
a. General Service valves: General Service valves are versatile valves design to use in various applications without modification. These valves use for low-pressure rating, moderate temperature, and non-corrosive fluid. General service valves are interchangeable. Carbon or stainless steel used for this types of valves. Manually operated valves are general service valves.
b. Special service valves: These valves design for a specific purpose or single application. Special service valves usually handle demanding temperature, high pressure or a corrosive medium.
c. Severe service valves: Severe service valves are designed to handle volatile applications such as high-pressure drops that result in severe cavitation, choking, flashing, or high noise level. Severe service valves have highly engineered trims in globe style valves or special disc in rotary valves to minimize or prevent the effect of the application.
4. Types of valves according to port size:
According to port size, valves classified as full port valves and reduced port valves.
a. Full port valves: Valves in which internal flow is equal to full area flow are Full port valves. Full port valves use for on off and blocking, where stoppage or diversion of flow requires.
b. Reduced port valves: In this types of valves, the flow area of the port is less than to the area of the diameter inside a pipeline. This restriction in flow allows pressure drop. After passing of flow through closure element, partial pressure recovers after restriction (Reduced port). The primary purpose of reducing port valve is to control or throttle the flow.