A control valve is a final control element that changes the available flow area in response to a control signal. By changing fluid flow, it can regulate process variables such as pressure, temperature, liquid level, or flow rate.
Control valves are usually divided into two motion groups: linear-motion valves, where the closure element moves along a straight path, and rotary-motion valves, where it turns around a shaft. Common body styles include globe, angle, three-way, segmented or V-port ball, butterfly, and eccentric plug valves.
What Is a Control Valve?
In an automated process loop, a control valve is normally a power-operated device. A sensor measures the process condition, a controller compares the measured value with the setpoint, and the actuator moves the valve in response to the controller output. A positioner may be added when the application requires more accurate valve-position control, diagnostic functions, or improved response.
The valve changes flow directly. Changes in pressure, temperature, or liquid level occur because the altered flow changes the process condition. This is why a control valve is commonly described as the final control element in a process loop.
A complete control-valve assembly commonly includes the valve body and bonnet, internal trim, actuator, and any required accessories. The detailed construction varies with the fluid, pressure drop, operating temperature, shutoff requirement, and control duty.
Two Main Control Valve Types by Motion
Classifying control valves by motion provides the first useful split because motion affects body construction, actuator output, packaging, flow path, and typical control behavior.
- Linear-motion control valves: The stem and closure element move in a straight line. Globe, angle, and many three-way valves belong to this group. They are widely used where controlled throttling, pressure-drop management, or specialized trim is important.
- Rotary-motion control valves: A ball, disc, or plug turns around a shaft. Segmented ball, butterfly, and eccentric plug valves belong to this group. They often provide compact installation, relatively high flow capacity, and lower assembly weight for a given line size.
Neither group is automatically better. A rotary valve may provide greater capacity and more compact dimensions, while a globe-style linear valve may offer more trim options for high pressure drop or noise control. The installed result depends on the selected valve, actuator, trim, piping system, and operating range. See the detailed linear vs. rotary control valve comparison for a closer review.
Common Control Valve Body Types
Motion class and body style are related, but they are not the same classification. Each body style creates a different flow path and introduces different capacity, pressure-drop, shutoff, maintenance, and actuator requirements.
Globe Control Valves
A globe control valve uses a plug that moves toward or away from a stationary seat. The internal flow path changes direction through the body, producing a controlled pressure drop across the trim.
Globe valves are common in steam, gas, water, and process-liquid service. Available constructions may include single-seat, balanced, cage-guided, low-noise, anti-cavitation, and multistage trims. This makes globe valves a practical starting point when throttling quality or pressure-drop control matters more than minimum valve weight.
The final configuration still depends on capacity, allowable leakage, fluid cleanliness, pressure differential, noise, cavitation risk, and actuator thrust. Compare the broader globe control valve configurations or view a representative single-seat globe control valve.
Angle and Three-Way Control Valves
An angle control valve has inlet and outlet connections arranged at approximately 90 degrees. The body can replace a separate pipe elbow and may provide a more direct discharge path in services involving flashing, high velocity, erosion, or drainage. Suitability depends on the trim orientation, flow direction, outlet conditions, and material selection.
A three-way control valve has three process connections and is used to mix two inlet streams or divert one inlet stream between two outlets. Mixing and diverting duties should not be treated as interchangeable without checking the body design, flow direction, pressure balance, actuator force, and fail position.
Examples include an angle control valve for a directional flow path and a three-way control valve for mixing or diverting duty.
V-Port and Segmented Ball Control Valves
A V-port or segmented ball valve uses a shaped opening to create a more predictable throttling characteristic than a conventional full-port on-off ball valve. As the ball rotates, the exposed flow area changes progressively.
These valves can provide high capacity, relatively wide operating range, compact construction, and a shearing action near the seat. They are often considered for liquids, gases, pulp, fibers, and fluids containing limited suspended solids. Seat construction, bearing loads, particle size, differential pressure, velocity, and required shutoff must still be checked.
A standard on-off ball valve should not automatically be used for modulating control. The port geometry, seat design, actuator, and positioner must support the intended throttling duty. See the segmented ball valve guide or a representative V-port control ball valve.
Butterfly Control Valves
A butterfly control valve uses a disc that rotates inside the valve body. Its short face-to-face dimension and relatively low weight make it attractive for large pipelines and applications where space and structural load are important.
Butterfly valves are frequently used for cooling water, air, gas, low-to-moderate pressure-drop service, and large-volume flow. Performance varies substantially among resilient-seated, high-performance, and offset designs. Disc interference, available pressure drop, minimum controllable opening, seat leakage, actuator torque, and cavitation risk should be checked before selection.
For corrosive liquids, a lined construction may be considered when the liner, disc, shaft, seals, pressure, temperature, and permeation limits are compatible with the complete service. One example is a fluorine-lined control butterfly valve.
Eccentric Plug Control Valves
An eccentric plug valve rotates the plug away from the seat as it opens. This reduces continuous rubbing between the seating surfaces and can provide a relatively open flow path.
Eccentric plug valves may be considered for viscous, dirty, fouling, wastewater, or light-slurry services. Their suitability depends on the port geometry, solids size and concentration, erosion pattern, seat construction, required shutoff, actuator torque, and access for cleaning or maintenance.
Control Valve Type Comparison
The following table is a first-screen comparison rather than a final selection rule. Specific designs within the same body-style family can behave differently.
| Body type | Motion | Common application fit | Verify before selection |
|---|---|---|---|
| Globe | Linear | Precise throttling, steam, gas, liquids, high or changing pressure drop | Cv, trim style, cavitation, noise, shutoff, actuator thrust and fluid cleanliness |
| Angle | Linear | Direction change, drainage, flashing or erosive service with suitable construction | Flow direction, outlet velocity, erosion location, trim orientation and downstream piping |
| Three-way | Usually linear | Mixing or diverting process streams | Port function, pressure balance, combined flow, thermal effects and fail position |
| V-port or segmented ball | Rotary | High capacity, wide operating range, fibers and some solids-bearing fluids | Port geometry, seat material, particle size, velocity, shutoff and actuator torque |
| Butterfly | Rotary | Large pipelines, cooling water, air and gas, low-to-moderate pressure drop | Minimum opening, disc clearance, seat leakage, cavitation and dynamic torque |
| Eccentric plug | Rotary | Dirty, viscous, fouling, wastewater or light-slurry service | Solids characteristics, erosion, seat design, cleaning access and breakaway torque |
Other Ways Control Valves Are Classified
Body style is only one part of a control-valve description. The following classifications affect how the complete assembly responds in service:
- By actuator power: Pneumatic, electric, hydraulic, and self-operated assemblies use different sources of force or torque. Available utility, response speed, duty cycle, control signal, environment, and fail action influence the choice. See the control valve actuator selection guide.
- By fail action: Fail-open, fail-closed, or fail-in-place behavior should follow the consequence of losing air, power, or signal. The required action is a process-safety decision and cannot be selected from the valve body style alone.
- By flow characteristic: Linear, equal-percentage, and quick-opening characteristics describe how inherent capacity changes with travel under defined test conditions. The installed characteristic also depends on the pressure distribution through the complete piping system. Learn more about control valve rangeability and operating range.
- By trim construction: Single-seat, double-seat, balanced, unbalanced, cage-guided, multistage, low-noise, and anti-cavitation trims change capacity, actuator load, leakage performance, noise, erosion exposure, and maintenance requirements.
How to Choose a Control Valve Type
Control-valve selection should begin with the operating duty rather than a preferred body style. The following sequence helps narrow the available options without treating any one type as universally suitable.
- Define the fluid and operating cases.
Consider fluid phase, composition, solids, viscosity, density, vapor pressure, corrosiveness, toxicity, and tendency to crystallize or polymerize. Evaluate minimum, normal, maximum, startup, shutdown, and upset conditions where they affect the valve. - Evaluate the required capacity across the operating range.
Size the valve for the actual pressure and flow cases rather than the pipe size alone. IEC 60534-2-1 provides established sizing equations for compressible and incompressible fluids within its stated scope. The control valve sizing guide explains the practical inputs. A control valve calculator can support preliminary liquid checks, but it does not replace full sizing or cover every fluid condition. - Check pressure drop, velocity, cavitation, flashing, and noise.
A valve that passes the basic capacity check may still experience trim damage, vibration, excessive sound pressure, or unstable control. Liquid vapor pressure, outlet pressure, recovery behavior, gas expansion, and downstream velocity can change the required body and trim. Review the difference between flashing and cavitation in control valves. - Match the motion, body, and trim to the duty.
Compare the available pressure-drop capability, flow path, solids tolerance, shutoff requirement, maintenance access, and installation space. High capacity alone does not prove that a valve will control well at the minimum flow condition. - Check materials and sealing components as a complete system.
Body, trim, seat, packing, gasket, shaft, stem, coating, lining, and fastener compatibility may differ. Chemical compatibility, temperature, pressure, erosion, permeation, fugitive-emission requirements, and expected cycling should be considered together. - Match the actuator and accessories to the valve load.
Actuator thrust or torque should cover the governing differential pressure, seating load, packing friction, breakaway load, and required safety margin. Confirm the available energy source, travel speed, environmental protection, fail action, positioner, feedback, and control signal for the complete assembly.
An oversized valve may spend most of its operating time near the closed position, where small movements create disproportionately large flow changes. An undersized valve may not reach the maximum required flow. Selection should therefore be checked across the expected operating envelope rather than at one design point.
Control Valve Types by Typical Application
Application tables are useful for generating a shortlist, but the final choice remains conditional on the actual service data and required control performance.
| Typical application | Possible starting types | Important checks |
|---|---|---|
| Steam and thermal service | Globe or angle valve with service-appropriate trim | Compressible-flow sizing, temperature, noise, condensate, erosion and fail action |
| Cooling water and water treatment | Globe, segmented ball, butterfly or service-specific water control valve | Valve authority, minimum flow, cavitation, water quality, seat leakage and corrosion; see the water-treatment control valve guide |
| Clean gas service | Globe, V-port ball or suitable butterfly valve | Gas expansion, outlet Mach number, aerodynamic noise, shutoff and emissions requirements |
| High pressure-drop service | Cage-guided, multistage globe or angle valve | Staged energy reduction, cavitation, flashing, noise, trim velocity, erosion and actuator force |
| Slurry, pulp or solids-bearing fluid | Segmented ball, eccentric plug or another service-specific open-path design | Particle size and hardness, concentration, settling, dead zones, erosion and cleaning; see the slurry control valve selection guide |
| Corrosive chemical service | Lined ball or butterfly valve, or corrosion-resistant globe construction | All wetted materials, liner limits, permeation, temperature, pressure and packing compatibility; see the corrosive-service control valve guide |
| Mixing or diverting duty | Three-way control valve | Mixing versus diverting construction, port orientation, pressure balance, thermal effects and fail position |
| Large line with limited available pressure drop | Butterfly or other high-capacity rotary valve | Disc clearance, minimum controllable opening, seat performance, dynamic torque and piping effects |
Control valve type selection begins with motion and body style, but it finishes with the actual operating cases. Capacity, pressure drop, fluid condition, controllable range, cavitation or noise risk, materials, shutoff, fail action, and actuator load must work together as one assembly.
After the duty has been screened, the MacoTango control valve range provides linear and rotary starting points for detailed sizing and configuration.