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Confusing the On/Off Valve with the Control Valve: When is a Globe Valve Necessary?
- astelmekanik
- Mar 14
- 5 min read
1) What is an On/Off Valve, What is a Control Valve? (It's Simple)
On/Off (Open-Close) Valve
On/Off Valve
Purpose: To open or shut off the line.
Operating Principle: It is either fully open or fully closed. If left partially open, some types may cause problems.
Typical Examples: Ball valve, butterfly valve (depending on the application), gate valve, etc.
When is it ideal? It is used for isolation, maintenance shut-off, line separation, and commissioning works.
See Related Products:
On/Off Valve Group → Click for productsBall Valves → Click for productsButterfly
Valves → Click for products
Control Valve
Purpose: To keep the flow rate, temperature, or pressure within the desired setting.
Operating Principle: Fine adjustment is made through continuous modulation according to the signal coming from the system.
When is it necessary? When a value must be maintained at a setpoint:
Hot water outlet temperature must remain constant at 60°C
Steam/hot water coil flow must stay stable
Differential pressure must remain within limits
Flow rate must be managed within a certain range
See Related Products:
Control Valves → Click for productsActuated Valves → Click for productsPneumatic Actuators → Click for products
2) Why is Glob Vana Strong in the "Control" Business?
Master, the body geometry of a globe valve is designed to restrict flow gradually and in a controlled way. What that means is:
With a small movement, the flow rate does not suddenly jump, so the change is more predictable.
With the correct trim/characteristic, the system operates more stably.
By nature, it is more suitable for throttling.
On/Off valves, on the other hand, are mostly focused on isolation:
When used for throttling, some types may suffer from increased seat wear, along with noise and vibration.
Control sensitivity remains limited.
The system becomes more prone to oscillation (hunting).
Related Products:
Class Norm Globe Valves → Click for productsBellows Sealed Globe Valves → Click for productsGlobe Valves → Click for products
3) When Is a Globe Valve Necessary? Clear Field Scenarios
If one of the following situations exists, saying “we can manage with an On/Off valve” usually ends up costing more.
Scenario A: Heating/Cooling Coil Control
If a temperature must be maintained at a setpoint in places such as fan-coils, AHU coils, or heat exchanger inlets, a globe valve or another valve designed for control duty should be preferred.
If control is done only by opening and closing an On/Off valve, the temperature will fluctuate and comfort will decrease.
Suggested Links:
Globe Valve → Click for productsControl Valve / 2-Way - 3-Way → Click for productsActuator → Click for products
Scenario B: Steam Lines and Precise Flow Requirement
Steam control is more sensitive. The wrong valve increases both the risk of water hammer and the difficulty of control.
When selected correctly, a globe valve delivers a much more controlled result in this duty.
Suggested Links:
Steam Equipment / Valves → Click for productsStrainer (for protection) → Click for products
Scenario C: Pressure Fluctuation, Noise, and Vibration Complaints
If throttling is being attempted with an On/Off valve, excessive differential pressure may occur across the valve and create noise.
A globe valve + the correct characteristic provides smoother operation.
Scenario D: If There Is “Hunting” in the System
If thermostatic control is constantly swinging back and forth, the problem is often the wrong valve characteristic or wrong valve authority.
A globe valve selected with proper control-valve logic can significantly reduce this problem.
4) Technical Selection: This Is Where We Look at the Data
4.1 DN / PN (Size and Pressure Rating)
DN: Must be compatible with the pipe diameter.
PN: Must match the line pressure rating. The wrong PN causes both safety and service life problems.
Link: Globe Valve Category → Click for products
4.2 Kv/Cv (The Value That Carries the Flow)
One of the most critical parameters in control applications is the Kv (metric) or Cv (imperial) value.
Kv expresses the flow passing through the valve at a certain pressure differential. In practice, think of it as the valve capacity.
If you choose a valve that is too large for control duty, precise control becomes difficult. The flow rises too quickly at small openings.
If you choose a valve that is too small, it cannot deliver the required flow and the system becomes restricted.
Field rule: In a control valve, the goal is to keep the valve operating in a reasonable working range. If the valve is constantly running around 5% to 10% open, control quality gets worse.
4.3 Valve Characteristic (Equal % , Linear, etc.)
Control valves come with different characteristics:
Equal Percentage: Frequently preferred in heating/cooling applications with variable loads.
Linear: May be more suitable in certain processes.
If the selected characteristic is not compatible with the system curve, control becomes either too aggressive or too unresponsive.
4.4 Valve Authority and Differential Pressure
This part matters: control quality does not depend only on the valve itself, but also on how the pressure losses are distributed across the line.
If there is not enough ΔP (pressure differential) across the valve, control performance drops.
With excessive ΔP, noise, cavitation, and trim wear increase, especially on the water side.
Note: At this point, a correctly selected control valve, balancing elements, and the right pump selection all need to work together.
5) The 6 Classic Problems You Get When You Try to Do Control with an On/Off Valve
Temperature or pressure fluctuates.
The system starts hunting and cannot remain stable.
The valve seat/seal wears out faster.
Complaints about noise and vibration increase.
Energy consumption rises (pump, boiler, cooling system).
The user keeps coming back saying, “the setting does not hold.”
6) Mini Decision Guide (The Most Practical Part)
Do you only need isolation? → On/Off valve
Do you need to keep a value at a setpoint?(temperature, flow, pressure) → Control valve approach; in most scenarios, a globe valve is the right solution.
Is it for HVAC coil / heat exchanger control? → Modulation + correct characteristic + suitable Kv
Is there corrosion or chemical risk? → Material selection matters(consider stainless steel options)
7) Final Word (Plain Summary for the Installer)
Master, an On/Off valve shuts the line, while a control valve manages the system. If control is required, trying to force the job with an On/Off valve just because it is already on hand usually costs more later. And in many applications, a globe valve helps that control work in a more stable and predictable way.
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