Published: August 1,
Last updated: December 30,
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Knowing what makes a valve the right choice
Valves control gas and liquid flow in almost every process and system. As common as they are, choosing the right valve can sometimes be time consuming and confusing.
Begin valve selection by first gathering some basic information on system performance requirements. Knowing this will make it easier to find the right valve. The five tips in this article focus on how to match valve features with these requirements.
Tip 1 – Valve size and type
Choose the right valve type. Every valve needs to perform one or more basic functions:
Function determines the design of standard valve types. These are some of the most common valve types:
Properly sizing the valve is also important. The right valve choice means matching the valve’s size to expected flow through the system.
Common Valve Types at VMA, Valve Manufacturers Association of America
How to Select the Right Valve (with Pros and Cons) at Indelac Controls
Tip 2 – Materials of construction
Know the chemical compatibility requirements. The valve materials need to be compatible with the gases or liquids flowing through it. Plastic valves usually resist harsh or corrosive chemicals better than metal valves.
Miniature Ball Valves: Plastic, Brass or Stainless Steel? at ISM, Industrial Specialties Mfg.
Chemical Compatibility Chart at ISM, Industrial Specialties Mfg.
Tip 3 – Performance requirements
Determine the pressure and temperature requirements. Find out both the temperature and pressure ranges where the valve will be installed. Metal valves tend to withstand higher temperatures and pressures than plastic valves. Metal valves are also usually best for pressurized gases. This is because they tend to be stronger than plastic valves.
A Selection Criterion for Pump and Valve Reliability at Processing Magazine
Tip 4 – Check valves have special requirements
Be sure the new check valve will work as expected. Look at the response time needed as well as the cracking pressure required to open the valve.
Another consideration is normally closed vs normally open. There are basic check valve designs that require positive downstream pressure to open. These are usually referred to as normally closed check valves. There are other designs that require a positive backpressure to close. These are usually called normally open check valves. An appropriate choice between these two can improve check valve reliability. It is usually best to base this decision on whether the valve is usually open more or usually closed more during normal system operation.
Some check valve types may not work properly if mounted vertically instead of horizontally. Flow direction (upwards vs downwards) and fluid density both matter for check valve designs that can be mounted vertically.
Checking Out Check Valves – An Introduction at ISM, Industrial Specialties Mfg.
Tip 5 –Maintenance
Don't forget to consider ongoing maintenance. Any valve choice should include attention to maintenance requirements. This is important for both valve reliability and application stability.
A good example of this are ball valves. They resist clogging, jamming or malfunctioning. But they are not suitable for adjusting flow. Using them to control flow can lead to leaking or premature failure.
Valve connection type affects the ease and speed of repair or replacement. Each connection type (threaded, barbed, push-in, Luer, and so on) has its pros and cons.
Plant and Equipment Maintenance at HSE, Health and Safety Executive
Knowing where to start makes valve choice faster and easier
There it is. Knowing particular information beforehand, makes choosing the right valve easier and more certain. There will always be complications like application requirements, operating conditions and chemical compatibility. Starting with basic valve requirements will simplify and speed up valve selection:
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Some additional resources
How ISM can help you find the right miniature valve for your application
Personalized customer service and resources available at the ISM website can be a great help when selecting a valve. Available online resources include chemical compatibility reference guides, dimensional drawings and product data sheets. Our online and PDF flow control valve catalogs provide access to a wide variety of miniature valve types, connection types, materials and sizes:
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Valves are useful pieces of equipment that help control, limit, and shut off flow in a system. In a garden irrigation system, you could use valves to control when different plants get watered. While it is universally agreed that valves are helpful, choosing the right valve can be frustrating. We hear many customers make statements like these: "So many types exist! Some of them do similar things! I don't know what types of valves to use!"
No worries! Here at PVC Fittings Online, we carry all the major valve variations. In this blog post, we will outline what makes each unique. For basic users, the most important thing to remember is that a valve does one of two things: shut off or regulate. Some valves can do either/both, but this is a simple way to think of what you need a valve to do. It could help you in picking the right valve. We will now cover each of the major valve categories.
Ball valves are a good example of a shut off valve. They use a spherical seating to stop or allow flow. The ball has a hole through the center, so fluid can pass through when the handle is turned to the "on" position. When the handle is turned 90 degrees to the "off" position, fluid hits the solid side of the ball and is stopped.
The PVC ball valve pictured has been taken apart so you can see its inner workings. This one uses rubber O-rings to ensure a tight seal. Ball valves are shut off valves because they are not typically designed to be opened partially. They are meant to be completely open or completely closed. Depending on the type of ball valve you purchase, they may commit a bit of pressure drop. This is because the hole in the valve's ball typically has a smaller diameter than the pipeline itself.
Butterfly valves can function as a shut off valve or as a regulatory valve. They can fully shut off flow or be kept partially open, which limits flow. Controlling flow can be extremely helpful if you want to decrease pressure in a system. Fluid passing through a small opening will be restricted, making pressure further down the pipeline lower, depending on how far open the valve is. Butterfly valves can also be used as typical 90-degree turn valves, just switching between "on" and "off" positions.
Butterfly valves use a disc rotating around a central stem to control fluid passing through. The PVC butterfly valve pictured has a handle that can be stopped and locked at any position between fully open or closed. This allows for precise control. One major factor to be aware of when using butterfly valves is that they require flanges to install. You cannot simply attach them to piping. This makes installation a little more difficult, but not impossible! Another important trait of butterfly valves is that, due to the fact that the disc is always present amid flow, there is inherent pressure drop.
Gate valves, while usually used as shut off valves, can also function as regulatory valves. They use a "gate" that drops or lifts to control flow. When the valve is open, the gate is stored in the tall upper section of the valve, which is where gate valves get their unique shape. Unlike the previous two valves, gate valves are not a quarter-turn valve. They use a hand wheel to open/close whereas ball and butterfly valves use a lever handle. This makes it easy to keep them partially open and also makes operation of any kind easier.
One possible with using a gate valve for flow regulation is that fluid will be hitting the flat gate surface. Depending on how much pressure is in the system, this could cause wear-and-tear over time. The gate valve pictured here has a true union design, which means it can be easily taken apart. This is ideal for cleaning, maintenance, and repairs. Gate valved don't require flange; they can be placed directly into a pipeline.
Check valves come in many forms. The primary function of check valves is to prevent backflow. This makes them regulatory valves, as they control flow direction. Check valves are controlled by the fluid in the pipeline instead an operator, which makes them different from the valves we have previously examined. Check valves come in many different forms, but we will just cover the two most common types.
Swing check valves are a type of valve that uses a swinging function to prevent backflow in a system. The clear PVC swing check valve to the right has a disc that swings open if fluid is passing through the desired direction. If anything tries to flow backwards, the disc is pushed closed, stopping flow. Swing check valves create minimal pressure drop, as the disc is pushed completely out of the way when in operation.
The other major type of check valve is the ball check valve. Ball check valves use a ball or half-ball seating to eliminate backflow. The clear PVC ball check valve pictures uses a half-ball seating. When fluid passes the desired direction, it hits the rounded side and passes around and through. If fluid tries to flow backwards, it hits the concave side of the half-ball, pushing the valve shut. Due to the fact that fluid must flow around and behind the ball to get through, ball check valves produce moderate pressure drop.
Diaphragm valves, while not one of the most common types of valves, are very interesting and serve a specific purpose. They are perfect for limiting pressure in a system, making them regulatory valves. These valves have a flexible diaphragm that lowers toward or rises from a "weir" or "saddle" seating. The effect is that only a limited amount of fluid is allowed to pass through. The diaphragm valve pictured to the right has an easy-to-read indicator in the handle stem provides a clear reading of liquid flow within the valve.
We included this less-than-common valve to illustrate the fact that not all valves are simple or familiar. Many companies make their own unique valve variations, and not even the common varieties will look or operate the same way all the time. The best thing to do when you encounter something unfamiliar is to learn as much as you can about it. Who knows? Maybe it will be exactly what you need.
You're almost ready to choose a valve, but there's one more thing you need to determine: size. Proper valve size depends on a few important factors: pipe size, desired operating flow, material, and so on. "Pipe size" refers to the nominal size of the pipe the valve we be installed onto. Often, you will have a larger pipe leading into a valve and a smaller pipe after the valve. In this case, you will need to find a valve that has different-sized ends or use a reducing coupling as an adapter.
Operating flow is one of the most important factors, as some valves significantly reduce flow. If you need steady flow throughout the system, with zero pressure drop in the valve, you may need a valve with a larger body. If you want pressure to drop in the valve, you will want to carefully consider the type of valve you select. The material is another thing you need to consider, as sizing can vary from material to material. Copper piping has a completely different sizing system than PVC pipe, for example. So if you are hoping to use a PVC valve in a copper system, you may need to get a differently-sized valve or use an adapter.
Contact us to discuss your requirements of Pipe Line Valve. Our experienced sales team can help you identify the options that best suit your needs.