About the Selection and Installation of Control Valves

The selection of control valves should be based on the characteristics of the control system, the source of disturbance and the S (valve resistance ratio) value.

General selection principles

1. the valve on the differential pressure change is small, the change of the given value is small, the change of the main variables of the process is small, as well as S>0.75 control objects, it is appropriate to choose linear flow characteristics.

2. Slow production process, when S > 0.4, it is appropriate to choose linear flow characteristics.

3. The requirement of a large adjustable range, the pipeline system pressure loss, opening changes and differential pressure changes on the valve is relatively large occasions, it is appropriate to choose equal percentage flow characteristics.

4. Fast production process, when the dynamic process of the system is not well understood, it is appropriate to choose equal percentage flow characteristics.

5. According to previous experience can also be selected according to the following table flow characteristics.

6. Quick-open characteristic: suitable for two-position operation or when the maximum flow capacity of the regulating valve needs to be obtained quickly. When the regulator must be set in a wide proportional band, the regulating valve can also be selected with the fast-opening characteristic.

Valve type selection

1. According to the process variables (temperature, pressure, pressure drop and flow rate, etc.), fluid characteristics (viscosity, corrosiveness, toxicity, containing suspended matter or fibres, etc.) and the requirements of the regulating system (adjustable ratio, leakage and noise, etc.), regulating valve pipeline connection form to choose a comprehensive regulating valve type.

2. In general, priority is given to small volume, through the capacity of large, technologically advanced straight through single, double-seat adjustment valve and common sleeve valve. You can also choose low S-value energy-saving valves and compact regulating valves.

3. According to different occasions, different types of control valves can be used. Specific when to use what type of regulating valve, we will come out with a detailed explanation.