What is a Control Valve?

Control valves are devices that regulate the flow of fluid. In a PLC (or) DCS system, control valves receive command signals from PID controllers.

The valve positioners change the instrument airflow to the valve actuator based on the signal received from the PLC (or) DCS systems.

This enables for the control of fluid flow through the valve, as well as the control of process factors such as pressure, temperature, & levels.

Valves are the primary final control elements.

Calibration Procedure

How is a Control Valve Calibrated?

The calibration procedure can be carried out in 2 ways:

1. Static Calibration
2. Dynamic Calibration.

Static Calibration

A static calibration is performed by placing the valve in a fixed location and measuring the flow rate at various pressure decreases.

Dynamic Calibration

A dynamic calibration involves changing the valve position and monitoring the flow rate at a constant pressure decrease.

Control Valve Calibration Procedure

Initially, a properly serviced control valve must be calibrated in three phases.

1. The first phase is valve calibration with no accessories. That’s stroke checking.
2. The next phase involves the positioner (I/P converter – Externally Mounted)
3. The final phase is a positioner with an integrated I/P converter (Smart Valve Positioner).

All of the above methods vary slightly between process plants based on their specific needs.

Nowadays, calibrating a control valve with the smart positioner is a common method used in industries.

Before starting the works, obtain the necessary work permissions, notify the process engineers, and isolate the valve as needed.

Set the PID controller to manual mode in PLC (or) DCS systems.

Calibrate control valves, including motorized and diaphragm types, along with safety valves and positioners, following precise procedures for accurate and reliable performance.

1. Control Valve Calibration Procedure
2. Calibration Procedure for Motorized Control Valve
3. Safety Valve Testing and Calibration Procedure
4. Calibration Procedure of Control Valve Positioner
5. Diaphragm Type Control Valve Calibration Procedure
6. Pneumatic Positioner Calibration Procedure
7. Loop Checking Procedure for Motor Operated Valve(MOV)
8. Calibration Procedure for Pneumatic valve positioner Fisher 3582