When you’re setting up a fluid control system, there are dozens of different types of valves you have to choose from. Each serves a specific purpose, but keeping them straight can get confusing. Many people have troublewith the difference between control valves and on-off valves.
Control valves and on-off valves serve different purposes depending on the degree of control you need for your system. Control valves are more precise, whereas on-off valves are more all-or-nothing. Read on to learn more about these two different valves and how they’re used.
Control Valves
As you might guess from the name, a control valve is used to control the flow of fluid in a system. They can maintain different variables at specific set-points, including density, concentration, flow rate, pressure, temperature, and liquid levels. A control valve includes a valve body, actuator, and positioner, as well as body assembly and trim parts.
The actuators on these valves can be pneumatic, hydraulic, or electrically powered, and they control how the valve opens and closes. The positioners monitor and control the actuator movements to maintain the desired set-point.
On-Off Valves
An on-off valve is a much less precise instrument than the control valve. It either allows for unimpeded flow or it shuts off flow completely. There are a couple of different styles of on-off valves, including ball, plug, butterfly, gate, and globe valves.
A ball valve consists of a ball with a channel cut through it that can be turned so the channel aligns with the rest of the line, allowing flow, or so that it doesn’t, shutting off flow. Butterfly valves have a flat piece of metal that rotates to open or close the channel. Gate valves and plug valves use conical pieces that slide down through the channel, sealing it securely shut.
Uses for Each
Control valves are used in situations where you need specific control over a piece of a system. These are excellent for jobs where precision is crucial and there are a number of factors that have to be tightly controlled.
Ball valves are good for more black-and-white situations. Because they’re all or nothing, they’re often used as emergency shutoff measures. You could even have a control valve and an on-off valve on the same system, with the on-off valve acting as a backup in case the control valve fails.
Discover How to Use Different Valves
On-off valves and control valves are similar in some senses, but the difference lies in their degrees of control. Where control valves can be very precise, on-off valves can do exactly what their name suggests: turn on or turn off. Each of the different valves has an important place in your system.
If you’d like to find the best valves for your system, check out the rest of our site at CPV Manufacturing. We have valves and fittings to suit every application, from shipbuilding and industrial gas uses to petrochemical and pharmaceutical systems. Check out our product selection guide and find the right valve for your needs.
FAQs
On-Off valves are designed to stop the flow and to open the flow fully with no control in pressure whereas Control valves can regulate and allow the required pressure to pass through it.
Which valve is better for on and off control? ›
Types of Valves for On-Off or Modulation Control. Choosing the right type of valve for your application depends on many factors. Some valves are well-suited for on-off service, while others are better for modulating control. Ball valves and plug valves are two types of valves that work best in on-off applications.
Is a shut-off valve a control valve? ›
On-off valves and control valves are similar in some senses, but the difference lies in their degrees of control. Where control valves can be very precise, on-off valves can do exactly what their name suggests: turn on or turn off. Each of the different valves has an important place in your system.
What is the use of on-off control valve? ›
An on/off valve is the fluid equivalent of an electrical switch: a device that either allows unimpeded flow or acts to prevent flow altogether. These valves are often used for routing process fluid to different locations, starting and stopping batch processes, and engaging automated safety (shutdown) functions.
What is the control valve for? ›
A control valve regulates the rate of fluid flow as the position of the valve plug or disk is changed by an actuator. Control valves are used to maintain a process variable as close as possible to the desired set point. Controller set points are typically flow rate, pressure, and temperature.
What is the advantage of control valve? ›
Control valves can help reduce water losses and contribute to efficient water supply management by regulating pressure, flow or level, regardless of changes in the supply network.
What is the difference between a control valve and an on-off valve? ›
On-Off valves are designed to stop the flow and to open the flow fully with no control in pressure whereas Control valves can regulate and allow the required pressure to pass through it.
How do you tell if a shut-off valve is on or off? ›
In order to tell if the valve is open or closed, the general rule is, if the handle is switched 90deg to the flow, it is off. As you can see from the diagram above, if the handle is in line with the flow path, it is on.
What is an example of an on off valve? ›
A tap to fill overhead tank is a good example of on-off valve. The tap is either fully open or fully closed. In case of on-off valve, there is no provision to control the flow at some intermediate level. In other words, they are not used for throttling purposes.
What does control of valve do? ›
A control valve is a valve used to control fluid flow by varying the size of the flow passage as directed by a signal from a controller. This enables the direct control of flow rate and the consequential control of process quantities such as pressure, temperature, and liquid level.
A control valve that is sized to operate around 60 percent to 80 percent open at the maximum required flow and not much less than 20 percent open at the minimum required flow will give the best control.
Where are control valves used? ›
Control valves are used in a range of applications. They're vital to the oil and gas industry, manufacturing sectors, chemical storage, and even for residential applications.
What are the three types of control valves? ›
3 Types Of Control Valves You Need To Know
- Double Block And Bleed Valves. Double Block & Bleed Valves provide primary isolation when directly mounted onto process pipework. ...
- Manifold Valves. Manifold valves are a type of control valve that is able to isolate and control the flow of media within a system. ...
- Ball Valves.
These problems can include friction sticking, flashing, cavitation, choked flow, acoustic noise, erosion, and chemical corrosion. Control valves are subject to a number of common problems. This section is dedicated to exploring the more common control valve problems, and potential remedies.
What is a control valve switch? ›
The Model PCVS is a weather proof and tamper resistant switch for monitoring the open position of fire sprinkler control valves of the wall and yard post indicator and butterfly types.
Which of the following valves is better for on off control? ›
Ball valve is used for on/ off control of pipes without pressure drop.
What is the best valve for control? ›
Generally speaking, needle valves are best for high or low-pressure systems and applications where accurate flow rate adjustments are needed. Pinch valves are ideal for applications with frequent operation and abrasive fluids, while diaphragm valves offer precise regulation in corrosive liquid or gas environments.
Which valve is preferred control valve? ›
Ball-segment valves are ideal for very precise control applications as they give linear control characteristics with high-flow capacity.
Which type of valve is preferred mainly for on off control with low pressure drop? ›
Butterfly valves are usually preferred for applications with low pressure drop. From a control stand-point, globe valves are better. In cases where the pressure drop is very low, the Cv required becomes very high and typically a globe valve would not have enough capacity to cover the required Cv.
