There are several different components that make up a control valve. The stem, seat, and ball are the most important parts and determine the basic motions and flow control capabilities of the valve. These parts are often determined by the user’s specification, which is usually the same as the pipe itself. Other materials used include stainless steel, carbon steel, and chrome molybdenum steel. Carbon steel is the most commonly used material for control valves and is strong and able to handle most non-corrosive liquids and gases. Chrome moly steel, on the other hand, is used for high-temperature and pressure steam services. It is also stronger than carbon steel and has the same resistance to corrosion as stainless steel.
What Are the Parts of the Control Valve?
There are four basic parts of a control valve: the Ball, the Seat, the Bonnet, and the Positioner. The purpose of the bonnet is to support the Plug and Seat while they are assembled. This part also protects the valve against leaks during assembly. The other parts are described in this article. After reading them, you will be able to determine the functions of each part. Hopefully, this article has helped you understand the parts of control valves.
The stem of a ball valve can be turned to open or close the bore, depending on the type of operation. This valve has three basic options: manual, actuated, and electronic. Manual valves require that a human operator operate them, while electronic valves can be controlled from a distance or a controller. Manual valves have two major drawbacks. They are difficult to control, and the risk of water hammers can be high. Automatic valves, on the other hand, don’t require a human operator and are more suitable for remote and complex control systems.
The valve seat can perform multiple functions. There are different types of valve seats, including ball, globe, and angle, and each one is designed to serve a particular purpose. Seat materials also vary, from forged metal to bar stock and split construction. Single port valves are often used in services where shutoff requirements are strict. A single port valve is capable of handling the majority of applications. The seat is molded to withstand high-pressure fluids, which create an unbalanced force in the valve, which must be accounted for in the actuator.
A control valve’s bonnet is the removable cover that supports the moving parts of the valve. The bonnet also protects the plug and stem, which are connected by a stem. The plug and stem are made of hard material, such as heat-treated stainless steel, and are protected from fluid leakage by the packing that surrounds them. This packing is subject to regular inspection and replacement. The bonnet provides a seal for the valve and stem, and it also acts as a strength for the actuator.
A positioner is a device that directs the movement of a valve to control the pressure within a closed loop. The valves should be checked periodically to ensure that they are operating as they should. Positioners should be tested for a wide variety of factors, including their response time, hysteresis, dead band, minimum and maximum opening, and calibration. When performing valve maintenance, it is important to check the performance of the positioner without the valve in the circuit. It is essential to measure this parameter without the positioner in the circuit to isolate any potential problems with the valve or the positioner.
- Valve body
You should know what a valve body does before you buy one. The valve body determines the performance of a vehicle. It should be selected according to your driving style. For example, if you spend 70 percent of your time driving on the street and 30 percent off, you should buy an automatic valve body. You should also consider a manual/automatic valve body. For a full manual valve body, you must carefully choose the type of gearing you need for the vehicle.