Pneumatic Control Valve Manufacturer in India

Pneumatic control valves use compressed-air actuators to regulate flow, pressure and other process variables through controlled movement of the valve trim. They are used where modulating control and remote process regulation are required through a pneumatic actuator and control system. Selection should consider required flow capacity (Cv/Kv), inlet and outlet pressure, differential pressure, temperature, fluid properties, required control range, trim characteristics and actuator requirements.

Pneumatic Actuator and Control Arrangement:

Pneumatic actuators provide the force required to position the control valve according to the process signal.

• Single Acting Actuator: Uses compressed air for movement with spring return to the designated fail position.

• Double Acting Actuator: Uses air pressure for both opening and closing movement.

• Air Supply: Commonly 4–8 bar according to actuator design.

• Fail Action: Fail-open, fail-close or specified position according to the actuator and pneumatic control arrangement.

• Positioner: Regulates actuator position according to the control signal.

• Solenoid Valve: Provides pneumatic switching for specified control arrangements.

• Position Feedback: Allows remote monitoring of valve position.

• Manual Override: Available on suitable actuator configurations.

Pneumatic Control Valve Configurations:

Different body and trim arrangements are available for specific flow-control and process duties.

• Pneumatic Actuated Globe Control Valve – Used for continuous throttling and precise flow regulation.

• Pneumatic Sleeve Type Control Valve – Uses a sleeve-style closure arrangement for suitable pressure and flow-control applications.

• Pneumatic Angle Control Valve – Changes the flow direction through an angle-pattern body while providing control.

• 3 Way Converging and Diverging Control Valve – Used for mixing or diverting process streams.

• Pneumatic Cage Control Valve – Provides guided trim movement and defined flow characteristics.

• Pneumatic Single Seat Globe Control Valve – Suitable for controlled throttling and shut-off duties.

• Fluorine Lined Single Seat Control Valve – Used for compatible corrosive services where lined construction is required.

• Pneumatic Double Seat Control Valve – Uses a double-seat arrangement to reduce unbalanced fluid forces in suitable flow-control applications.

• 3 Way Pneumatic Diaphragm Control Valve – Used for three-way process control where diaphragm actuation is suitable.

Flow Characteristics and Trim Selection:

Trim selection affects the relationship between valve travel and flow rate and should match the process control requirement.

• Linear Characteristic: Provides a proportional relationship between valve travel and flow capacity.

• Equal Percentage Characteristic: Provides progressively greater flow change with valve travel and is commonly used for variable pressure-drop applications.

• Quick Opening: Provides a rapid increase in flow at low valve travel and is used where this response is required rather than normal continuous throttling.

• Cage Guided Trim: Supports stable plug movement and defined flow characteristics.

• Single Seat Trim: Used for throttling applications where the selected seat and trim arrangement provides the required shut-off performance.

• Double Seat Trim: Can reduce unbalanced forces acting on the plug in suitable applications.

Pneumatic Control Valve Technical Specifications:

Materials for Process Service:

Material selection depends on the fluid, temperature, pressure, corrosion potential and required service life.

• Carbon Steel: Used for general industrial and process applications.

• Low Temperature Carbon Steel: Selected for reduced-temperature service.

• Stainless Steel: Used where corrosion resistance is required.

• Duplex Stainless Steel: Suitable for selected chloride-containing services.

• Super Duplex Stainless Steel: Used for more demanding corrosive environments.

• Alloy 20: Selected for compatible corrosive chemical service according to process chemistry and operating conditions.

• Nickel Alloys: Selected by specific alloy grade according to process chemistry, temperature and corrosion conditions.

• Fluoropolymer-Lined Construction: Selected lining material according to chemical compatibility, temperature and pressure conditions.

Pneumatic Control Valve Sizing Factors:

Correct sizing requires evaluation of the actual process conditions rather than valve line size alone.

Important factors include:

• Required Flow Rate

• Required Cv/Kv

• Inlet and Outlet Pressure

• Differential Pressure

• Operating Temperature

• Fluid Density and Viscosity

• Vapour Pressure for Liquids

• Gas or Liquid Service

• Minimum and Maximum Controllable Flow / Required Control Range

• Valve Travel at Expected Operating Points

• Required Flow Characteristic

• Noise and Vibration Considerations

Cavitation should be evaluated separately from flashing:

• Cavitation: Evaluate in liquid service where local pressure through the valve may fall below vapour pressure and subsequently recover.

• Flashing: Evaluate where part of the liquid remains vaporised downstream of the pressure reduction.

The valve, trim and actuator should be selected to provide suitable controllability across the required operating range and control-loop conditions.

Standards and Performance Testing:

Applicable requirements may include:

• IEC 60534 – Control Valve requirements where applicable

• IEC 60534-2-1 – Flow-capacity sizing

• IEC 60534-4 – Inspection/routine testing where applicable

• ASME B16.34 – Applicable valve pressure-temperature/design requirements

• ASME B16.5 – Applicable flanged connections

Testing may include:

• Shell pressure testing

• Seat leakage testing according to specified leakage requirement

• Valve operational testing

• Actuator functional testing

• Stroke and position verification

• Full-stroke verification

• Positioner calibration

• Control-signal response check

• Modulating-position verification

• Position feedback verification

• Fail-action test

• Pneumatic supply/function test

• Material verification

• Dimensional inspection

Pneumatic Control Valve Applications:

• Steam Flow Regulation – Controls steam flow to suitable process or utility equipment.

• Process Flow Control – Regulates compatible liquid or gas flow according to the control-loop requirement.

• Feedwater Control – Regulates water flow in suitable power and steam-generation systems.

• Pressure Control – Controls upstream or downstream pressure according to the process arrangement.

• Process Mixing and Diversion – Three-way configurations mix or divert compatible process streams.

• Chemical Process Control – Regulates compatible process fluids using suitable body, trim and lining materials.

Share the required flow rate or Cv/Kv, inlet and outlet pressure, process temperature, fluid properties, required control range, available air-supply pressure, control signal and fail-action requirement with Speciality Valve for Pneumatic Control Valve sizing and selection.