In process industries, it is essential to have accurate measurements for various physical parameters such as pressure, temperature, flow rate, and more. To ensure reliable and precise measurements, the industry uses different types of instruments, including valves, control valves, and other measurement devices.
Valves:
Valves are critical instruments used in process industries to control the flow of fluid or gases in a pipeline system. There are different types of valves, including gate valves, ball valves, butterfly valves, and globe valves. Gate valves are often used in applications where a full open or full close shut off is required. Ball valves provide a tight shutoff and are suitable for isolation applications, while butterfly valves are best used in applications where quick response is required. Globe valves are used where a high amount of control is needed to regulate the flow of fluid.
Control Valves:
Control valves are instruments used to regulate the flow rate of a fluid in a process system. They consist of a valve body, an actuator, and a positioner. Control valves come in different types, including globe control valves, butterfly control valves, and ball control valves. Globe control valves are commonly used where the flow control range is wide, and precise control is required. Butterfly control valves are best suited for applications where fast response is needed, while ball control valves are used for applications that require precise control.
Control Valve Types:
There are two types of control valves, linear and rotary. Linear control valves provide a linear flow characteristic, which means that the flow rate of the control valve increases linearly with stem travel. Rotary control valves provide a modified linear flow characteristic. This flow characteristic allows the valve to operate within a wider turndown range while maintaining good control.
Valve Actuators:
Actuators are devices used to operate valves. There are different types of actuators, including pneumatic, hydraulic, and electric. Pneumatic actuators are commonly used in process plants because of their reliability and speed. Hydraulic actuators are used where high forces are required to operate large valves. Electric actuators are commonly used in the oil and gas industry, where there is no compressed air available.
Valve Positioners:
Valve positioners are devices used in controlling valve operation. They are installed on the valve stem and provide feedback to the control system about the valve’s position. Valve positioners ensure accurate control of the valve, which is critical for maintaining the process’s desired setpoint. There are different types of valve positioners, including electro-pneumatic, electro-hydraulic, and digital positioners.
In conclusion, valves and control valves are essential instruments used in process industries to control the flow of fluid and gases through pipeline systems. The use of these instruments ensures precise and reliable measurements that are crucial for maintaining process efficiency and quality. The industry uses different types of valves and control valves, depending on the nature of the application. The use of valve actuators and positioners further enhances the accuracy and reliability of these instruments.