Check valves may be the most misunderstood valves ever invented. If you mention check valves to most plant personnel, the typical response is 'they don't work.' In fact, those personnel may well have taken out the internals or repiped the system to avoid utilizing check valves. In other words, these valves may be the least popular valve in use today.
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This article will explore the basics of check valves, how they work, what types there are, how to select and install them, how to solve their problems, and why they are not always the cause of the problem.
Simply put, a check valve allows flow in one direction and automatically prevents back flow (reverse flow) when fluid in the line reverses direction. They are one of the few self-automated valves that do not require assistance to open and close. While some can be fitted with externally weighted and dampened devices for special circumstances, the majority do not have any outside assistance as found with on/off control or other valves. Unlike other valves, they continue to work even if the plant facility loses air, electricity or hydraulic pressure, or the human being that might manually cycle them.
As with other types of valves, check valves are found in a full range of sizes, materials, and end connections. The line sizes range from 1/8 inch or smaller to 50 inches and larger. They are made of bronze, cast iron, plastics, carbon steel, various grades of stainless steel and alloys such as Hastelloy, Inconel, Monel and titanium. End connections include threaded, socket weld, butt weld, flanged, grooved, wafer and insert type.
Check valves are found everywhere including in the home. If you have a sump pump in the basement, a check valve is probably in the discharge line of the pump. Outside the home, they are found in industries such as desalination, water and waste, chemical, food and beverage, geothermal, mining, oil and gas, power, pulp and paper, refining and more.
Like other valves, check valves are used with a variety of media: liquids, air, other gases, steam, condensate, and in some cases liquids with particulate or slurries. Applications include pump and compressor discharge, header lines, vacuum breakers, non-code pressure relief, steam lines, condensate lines, chemical feed pumps, cooling towers, loading racks, nitrogen purge lines, boilers, HVAC systems, utilities, pressure pumps, sump pumps, wash-down stations and injection lines.
Check valves are flow sensitive and rely on the line pressure and flow to open and close. The internal disc allows flow to pass forward, which opens the valve. The disc begins closing the valve as forward flow decreases or is reversed, depending on the design. The function or purpose of a check valve is to prevent reverse flow. Construction is normally simple with only a few components such as the body, seat, disc and cover. Depending on the design, there may be other items such as a stem, hinge pin, disc arm, spring, ball, elastomers and bearings.
Internal sealing of the check valve disc and seat relies on 'reverse' line pressure as opposed to the mechanical force used for on/off control valves. Because of this, allowable seat leakage rates are greater for check valves than with on/off control valves. MSS SP-61 'Pressure Testing of Steel Valves,' published by the Manufacturers Standardization Society, is one standard used by manufacturers to perform seat and shell closure tests for check valves (as well as other valves). Factors affecting check valve seat leakage include reverse pressure, media, and what the seat material is made of (such as metal or an elastomer). Metal and PTFE seating surfaces generally will allow some leakage while elastomers such as Buna-N and Viton provide bubble-tight shutoff (zero leakage).
Because of this, elastomers should be considered for air/gas media and low-pressure sealing. Important considerations when using elastomers for such valves are service temperature and compatibility of the elastomer with the media.
Regardless of type or style of valve, the longest trouble-free service will come from valves sized for the application, not necessarily the line size. Ideally, the disc is stable against the internal stop in the open position when flowing or fully closed when no flow or checking. When these conditions are met, no chattering of the disc will occur, thereby preventing premature valve failure. Unfortunately, most check valves are selected in the same way on/off control valves are selected, by line size and the desire for the largest Cv available. This ignores the fact that unlike on/off control valves that have actuation (manual, pneumatic, hydraulic or electronic), only the flow conditions determine the internal performance of the check valve.
Check valve internals are flow sensitive, unlike on/off control valves. If there is not enough flow and pressure to fully open the check valve, trim chatter occurs inside the valve. This results in premature wear, potential for failure and a higher pressure drop than calculated.
Whenever a metal part rubs against another metal part, wear is a result. That leads to eventual failure of the component itself. A component failure can result in the valve not performing its function, which in the case of a check valve is to prevent reverse flow. In extreme cases failure could result in the component(s) escaping into the line, causing failure or nonperformance of other valves or equipment in the line.
Typically, pressure drop is calculated based on the check valve being 100% open as with on/off control valves. However, if the flow is not sufficient to achieve full open and the check valve is only partially open, the pressure drop will be higher than what's calculated. This is due to the effective Cv of the valve being less than maximum when the check valve is partially open. In this situation, a large rated Cv actually becomes detrimental to the check valve (unlike with on/off control valves). This results in chattering of the disc and eventual failure. Such is not the case with some other valves. For example, with a gate valve that is fully open, the wedge is out of the flow path. Therefore, the flow through the valve does not affect the performance of the wedge whether that flow is low, medium or high.
Various types of check valves are available. Some of the more popular types are included below. All these can be used for clean media. As with other types of valves, specialty check valves can be found for unique applications. While no one type of valve is good for all applications, each has its advantages.
Taking time to contact the manufacturer to assist in selection can help you find the best fit. This is especially true if you are having problems with whatever type of check valve is presently installed.
Swing checks are a simple design using a disc attached to an arm that is hinged at the top of the valve (at the 12 o'clock position). Reverse flow and gravity assist the valve in closing. Swing checks can be used for most media and generally provide good flow capacity. They should only be installed in a horizontal flow position. This is because they will not operate properly in the vertical flow positions. They also don't tend to seal well in low backpressure applications. These check valves range in size from ½ inch and smaller to 50 inches and larger, and are available with threaded, socket weld, flanged or butt weld end connections. Swing checks are typically easy to inspect and maintain. In most cases, repairs can be performed with the valve in the line. Because of their design, swing checks are not fast-closing valves due to the travel distance from full open to close. This means they are highly susceptible to water hammer issues. Most swing check valves meet ANSI B16.10 face-to-face dimensions and will permit pigging of the line. There is a variation of the swing check called the tilting disc check. However, that version does not permit line pigging.
Piston or poppet style check valves are available as inline, inclined (Y-pattern), or conventional (90 degree T-pattern) body designs. All types are considered a silent check valve style that prevent water hammer and reverse flow. It does this by using a spring-assisted disc in line with the flow that has a short travel distance, resulting in a fast-closing valve. As forward velocity begins to slow, the spring assist starts to close the disc. By the time the forward velocity reaches zero, the valve disc is closed against the seat before reverse flow can occur, preventing pressure surges in the line and thus preventing water hammer. Most designs can be installed in any position, including flow down if the proper spring is installed. Piston/poppet check valves are available from 1/4 inch to 24 inches and larger. The body design selected will determine the pressure drop; inline designs will provide the best flow performance. Piston/poppet check valves are available with multiple different end connections including threaded, flanged, weldable, etc. Special end connections are available, but you would need to consult with the check valve manufacturer. Some of these check valves can be inspected and repaired in line. Ideally, this style of check valve should only be used for clean media service with no particulate.
Flange insert check valves are an extremely compact, wafer-style check valve for flanged piping. They are commonly used in-line and vary from ½ inch to 20 inches in size. This style is also considered a type of silent check that help prevent water hammer. Accordingly, they will have an internal spring that assists with closing of the valve. The flange insert check and its compact design allow it to be added to an existing system with minimum piping alteration required.
Center guided check valves are another type of silent check valve. They are also designed to prevent water hammer as well as reverse flow. This style is similar to the piston/poppet. It also falls under MSS SP125 & 126 for specifications. They are available in flanged styles with sizes from 2 to 24 inches and sometimes larger. Similarly, this style is best suited for clean media with no particulate.
Ball check valves use a ball inside the body to control the movement of flow. This style is also considered a type of silent check. The ball is free to rotate, resulting in even wear and a wiping action between the ball and seat.
This feature makes ball checks useful for viscous media. Ball checks are typically found in smaller sizes of 2 inches and less. Some designs include a spring to assist in closing and for use in 90-degree styles installed in vertical lines. Depending on the body design, pressure drops with ball types can be higher than with other types of check valves. Ball checks are available in various end connections including threaded and socket weld. Some body designs permit in-line repair/inspection.
Among the many factors to consider when selecting a check valve are material compatibility with the medium, valve pressure rating (ANSI), line size, application data (flow, design/operating conditions), installation (horizontal, flow up, or flow down), end connection, envelope dimensions (especially if replacing an existing valve to avoid pipe modifications), leakage requirements, and special requirements such as oxygen cleaning, NACE, CE Mark, etc.
There are many different check valve designs, with the oldest and most common being the swing check.
When replacing a check valve, it helps to ask the following simple questions:
Sometimes we get so busy or absorbed in other things, we forget the cause can help with the solution.
Common check valve problems include noise (water hammer), vibration/chattering, reverse flow, sticking, leakage, missing internals, component wear or damage. However, it is worth mentioning that normally the real cause is the wrong size, spring, and/or style for the check valve application. In such cases, the problem is the application, not the check valve.
Two of the most common problems with check valves are incorrect sizing or incorrect installation. Incorrect sizing comes in one of two forms. If the valve Cv is too small for the application, you would see a very high pressure drop which could lead to premature valve wear because of the high velocities involved. More commonly, if the valve Cv is too large for the application, there will not be enough pressure drop created across the check valve to fully open it. Any check valve that is not fully open has a high probability of chatter which will lead to premature valve failure. Incorrect installation involves not having the proper amount of straight pipe upstream of the check valve. Ideally a minimum of 10 pipe diameters of straight pipe upstream of the check valve is desired. This is to ensure a nice laminar flow going through the check valve. Shorter distances can cause flow turbulence and spin that can prematurely wear any style of check valve.
Examples of some other problems for check valves include reverse flow and water hammer. In both situations, a fast-closing valve is desired. Reverse flow can be costly, especially if it occurs at the discharge of a pump and the pump spins backwards. The cost to repair or replace the pump, plus the plant downtime, far exceeds the cost of installing the right check valve in the first place. With water hammer, you need a faster-closing check valve to prevent pressure surges and resulting shock waves that occur when the disc slams into the seat, sending noise, vibration and hammering sounds that can rupture pipes and damage equipment and pipe supports.
If the internals are missing or exhibiting excessive wear, two factors may be occurring. First, if the check valve selected does not have enough flow passing through to keep it against its stop, a valve with a lower Cv is needed to prevent the chatter of the internals. Second, if the check valve is used at the discharge of a reciprocating air or gas compressor, a specialty valve with a damped design or dashpot to handle high-frequency cycling is needed. Sticking can occur when scale or dirt is trapped between the disc and body bore. Leakage can happen from damage to the seat or disc or simple trash in the line. An elastomer is needed to provide zero leakage.
When installing check valves, point the flow arrow in the direction of the flow to allow the valve to perform its intended function. The flow arrow can be found on the body or tag. Make sure the valve type will work in the installed position. For example, not all check valves will work in a vertical line with flow down, nor will conventional or 90-degree T-pattern piston check valves perform in a vertical line without a spring to push the disc back into the flow path. The disc in some check valves extends into the pipeline when the valves are fully open. This could interfere with the performance of another valve bolted directly to the check valve. As we discussed earlier if possible, install the check valve a minimum of 10 pipe diameters downstream of any fitting or other piping system component that could cause turbulence. Notice, I said 'if it's possible.' After all, how many check valves have you seen bolted to the discharge of a pump? Many! A good source of reference for installing check and other styles of valves is MSS SP-92 'Valve Users Guide,' published by the Manufacturers Standardization Society.
Lastly, I like to compare check valves to doors ' whether that door is to your office or home. Typically, you open your office door at the start of the day and close it at the end, which is similar to what happens when a pump is cycled on and off. However, if someone stands at your door and constantly cycles it open and closed, what could happen? In most cases, the hinge pins would fail, since they are the weak link in the operation of your door.
Check valves face a similar situation. Pins, stems, springs or other components that are constantly cycled can fail. That is why it is important to properly select check valves for their specific applications. Line size does not necessarily equal check valve size. A check valve with a high Cv in a low flow application is doomed from the start. It is not the check valve's fault, it is the fault of the wrong selection for the application. The selected check valve would have worked fine in proper flow conditions. Unfortunately, the installed check valve is blamed for the failure, when in reality the culprit was the application. It is always best to review the application and service conditions with the manufacturer before purchasing a check valve to make sure the correct style and options are selected.
NOAH MILLER is the worldwide applications/engineered sales manager for Check-All Valve Manufacturing Company. With the company since , he's been assisting customers with proper check valve installation, check valve sizing, troubleshooting, and custom check valve designs. He regularly works with customers in the industries of oil and gas, steam, pharmaceutical, food and beverage, etc. He's considered the expert on check valve capabilities and is relied upon by engineers, field personnel, and purchasers to assist them with their check valve needs.Do you think you'll take a look at the valve's long-gone rogue? Uncover the mysteries and answers in this complete guide.
Check valves are important for fluid systems, allowing liquid to flow in one direction and stopping backflow. Among the numerous check valves available, people note the durability and reliability of brass ball valves. Understanding typical check valve problems and how to resolve them is critical for smooth system performance.
Check valve failure, which can happen due to bad maintenance, neglect, or misuse, among other reasons, when the valves malfunction or pipes, pumps, and well equipment are in danger.
Here, we will investigate check valve issues and prominent check valve manufacturers and provide troubleshooting tips.
Check valves come in various types. For example, Swing check valve, lift check valve, ball check valve, brass ball valve, brake booster check valve, PVC check valve, and vacuum check valve.
Effective troubleshooting requires an understanding of the function and design of all types of valves.
Check valves, or non-return valves, are essential equipment for preventing backflow. Mainly, they prevent 'backflow,' or fluids, from flowing in the other direction. The well might fill up again if the check valve malfunctions. They ensure it moves in only one direction, maintaining system efficiency and preventing potential damage.
To reduce check valve failures, install carefully, monitor regularly for issues, and perform preventive maintenance.
When dealing with check valve issues, choosing valves made by reputed valve manufacturers is serious. Below, we mention some of the most prestigious valve manufacturers and wholesalers.
It makes good valves, like brass ball valves, that reduce problems.
How to check the pressure balancing valve. Their makers provide special valves to control flow and pressure, which can impact check valve performance.
Water valve manufacturers make various water valves, including check valves. Choosing the proper valve for your unique application is critical to lowering the likelihood of complications.
How can you decrease the likelihood of check valves sticking?
Make sure all check valves are open and not stuck. A stuck performance may result in performance problems.
Picking the correct check valve and performing regular upkeep can lower the chance of this occurring.
It is important to find a broken check valve. This will help avoid issues and keep things running smoothly in suitable pumps, water heaters, and pool systems. Common symptoms of a malfunctioning check valve for a well pump are as follows:
Issues such as fluctuating water temperatures and excessive pressure in a water heater can indicate a broken check valve. Routine maintenance checks can help avoid a faulty check valve. To avoid system failure, check valves for leaks and seal them properly to catch problems early.
Recognizing the symptoms of a bad check valve is critical. These Symptoms include:
There are ways to release a jammed check valve, such as Tapping the valve body or Applying penetrating oil.
Well-pump systems frequently use check valves. The troubleshooting process includes looking for leaks, obstructions, and electrical problems.
Check valves to ensure a system's operation. Faulty check valves can cause backflow and water hammer.
Learn how to successfully troubleshoot and solve unusual problems with your sump pump check valve and compressor check valves in our Complete Guide to Check Valve Problems and Troubleshooting.
Therefore, it's important to inspect them often. Check valve makers must meet the ANSI MSS SP-61 standard. This standard sets the rules for checking the quality of check valves' shells and seat closures.
Here are the Procedures for Test and Replace a Check Valve:
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During the Shell test, we submerged valves in water at a pressure of 125 psi. They heat them to temperatures 1.5 times higher than their rating at 100 °F.
Measurements and times for each valve test should be two and a half inches per minute. In a minute, it may grow from 2.5 inches to 6 inches'a speed of 7 inches per 150 seconds. There should be no air gaps in the valve, of course. Putting a Closed Seat to the Water Test
Valve tests should take less than 30 seconds and measure 2.5 inches. The speed should be faster than 2-8 inches per 30 seconds or 10-18 inches per minute. Over 20 inches means you have 120 seconds.
Metal-seated valves can achieve leak rates of up to 40 ml/h/in2 of nominal valve size. Soft seating on the valves should prevent leaks.
A soft-seated valve does not expect any leakage, but a metal-seated valve can have up to 0.4 SCFH/inch leakage.
Lift-type and Swing check valves can also undergo pressure testing. The orientation of the finished product is the defining characteristic of these varieties. The pressure test consists of two phases:
The closed intake valve ensures a tight sealing test and forces fluid from the outlet. All is good with the valve if the packing, gasket, and sealing surface appear fine.
When testing a check valve, look for obstructions or debris in the foot valve, as a clogged foot valve might impair flow.
While typically well-constructed and appropriately designed, check valves require regular maintenance and attention like any other equipment. Neglecting the necessary tests and maintenance can lead to issues resulting in check valve failure.
Regular maintenance is essential to avoid clogged valve bodies. If issues arise, replacing the check valve on the well pump becomes necessary. Proper installation of a new check valve, whether a 2-inch one-way or an internal check valve, ensures smooth system functioning.
Here are the common check valve failures and ways to resolve them:
It happens when water flows back from the outlet to the inlet, indicating a check valve failure. It is especially problematic during discharge pump operations, as backflow can cause the impeller to spin in the wrong direction, leading to pump damage.
Fluid movement in check valves can cause debris to build up, making the valve stuck open or closed. Irregular maintenance contributes to debris buildup, and high-speed debris in the fluid can damage internal valve parts.
A water hammer occurs when a sudden blockage or fluid flow changes. It leads to pressure surges that can cause damage to pipes, fittings, and the check valve.
It is a common issue with swing check valves, and fluid backflow can cause sudden valve closure, leading to pressure fluctuations.
Seals such as elastomer ring seals check valve discs, balls, or plugs to their seats for proper shutoff. Over time, constant friction and frequent use can degrade these sealing materials, causing fluids to seep through the shutoff valves and leading to check valve failure.
Check valves to ensure a constant, unidirectional fluid flow until shutoff. Any flow disruptions or fluctuations indicate a check valve failure. Inconsistent flow can disrupt the intended operation of the check valve.
Troubleshooting well pump check valve failures and other types of check valve failures reveals the following causes:
Improper installation, assembly, and maintenance can result in severe valve damage, leading to early failure. Incorrect practices can cause premature wear and tear, compromising the valve's functionality.
Elevated temperatures cause valve parts to expand and deteriorate rapidly, affecting sealing integrity and causing leaks. High temperatures are detrimental to check valve performance.
Check valves require adequate fluid pressure for proper operation. Insufficient pressure can lead to frequent valve openings and closings, causing wear and tear on valve components. Low pressure, often caused by clogged or comprehensive pipelines, negatively impacts valve performance and can lead to failure.
Do you have a problem with your check valve? I'm here to break it down for you in plain English. We've got symptoms, preventive measures, and solutions for you, just like a trusty toolbox.
If your valve's making a racket, it's not jamming out; it's probably a water hammer. It's like a drumroll but in your pipes. This noise happens when the valve slams shut and the water smacks it.
If your wallet's taking a hit, it's a sign that your valves might be slacking. It's like a leaky faucet for your cash when they don't control the pressure.
When your valve's parts start looking rough around the edges, it's waving a red flag. It's like the valve's saying, 'I'm getting old, folks!' Sticky parts mean it's aging or getting rusty.
If you spot valve parts bobbing around in the water with sluggish flow, you have a problem. It's like finding breadcrumbs in your soup ' not a good sign.
Leaky pipes, anyone? They're like a neon sign screaming, 'Check your valves. There may be no hope for them! Finding the leak source will require detective work.
Equipment Going Bust:
When your gear starts acting up, it's like a domino effect. First, the valve's off, and then everything else follows. Fixing it might mean replacing the damaged parts.
Don't let your valves turn into a dumping ground for debris and junk. Get rid of those bits and bobs regularly. Think of it like sweeping the front porch.
Putting in a check valve isn't like assembling IKEA furniture without the instructions. Follow the manufacturer's guide ' it's like reading the map on a treasure hunt. Use the right valve for the right job.
Your valves need a little TLC, just like your car. Lubricate them to keep things smooth. Less friction means less wear and tear, and that's a win.
Picking the right valve size is like finding the right pair of shoes. You wouldn't wear clown shoes to a formal event. Make sure it's a match for your system.
It's like choosing the right tool for the job. Check if your valve's material plays well with others. You don't want it throwing a tantrum.
Reaction speeds matter. It's like picking the right vehicle for your commute. You wouldn't take a snail to a race, would you?
If your valve's leaking, it's like a detective story. First, figure out where it's leaking, like finding a leak in a boat. It could be loose bolts, busted gaskets, or a grumpy flapper. Tighten those bolts and swap out the damaged parts.
When a valve part's had enough, don't try to patch it up ' it's like putting a band-aid on a broken bone. Swap it out before it messes with the whole shebang. Sometimes, you might need a full valve replacement if things are way out of whack.
If you've got a water hammer, it's like trying to tame a wild horse. First, locate where it's happening ' like finding the wild stallion. Then, you can use water hammer arresters, release trapped air, change intake connections, or even throw in pressure-limiting valves. It's like calming the beast.
If your valve's stuck, it's like a traffic jam in your pipes. Take it apart, clear out the gunk, and double-check that the size matches your pipe. It's like unclogging your kitchen sink.
So, there you have it'the lowdown on check valves. Watch for those symptoms, follow some preventive steps, and you'll be the valve master in no time. Remember, it's all about keeping the flow smooth and the pipes happy!
A failing well pump often exhibits signs like inconsistent water pressure or unusual noises. One common culprit could be a faulty check valve. Understanding where to install check valves on water pumps is essential. Proper placement, such as the well pump check valve location, ensures seamless operation and helps diagnose issues promptly.
Understanding check valve direction is essential for air pumps or In-Line Spring Vertical Check Valve water systems. Homeowners often wonder, 'Do I need a check valve on my well pump?' The answer is yes. A well-maintained check valve guarantees an uninterrupted water supply and prolongs pump life.
In the historical context of the old valve factory, skilled artisans manufactured check valves to precise standards, showcasing quality craftsmanship. They engineered these valves, including 1-way water and stop check valves, to serve diverse purposes, emphasizing their versatility.
Enhancing the Best Way to Install and Assemble Check Valves:
Check valves are vital components in various applications, ensuring the unidirectional flow of fluids while preventing backflow. However, the effectiveness of these valves hinges on proper assembly and installation. This guide will explore the key considerations to ensure your check valves perform optimally.
For plumbing or hydraulic systems, here's a quick guide to help you identify issues:
To install, it's important to understand 'perplexity' and 'burstiness,' which impact writing quality. These factors play a significant role in determining the effectiveness of the written content.
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Here's a way to get the test valves flowing smoothly'proper from the start! These 3 pipe layout regulations are your non-negotiable roadmap to a continuing test valve installation, making the highest quality overall performance and operation of check valves:
Improper installation can lead to check valve failure and potential damage to the entire system. Installation methods may vary depending on the type of check valve. However, here are some best practices for flapper-type swing check valves:
For installing industrial check valves, we strongly recommend enlisting the expertise of qualified and licensed professionals. These people have put in valves before, so they know to ensure they are installed correctly. It's less possible that something will go wrong now.
Valve seats are critical components of check valves, responsible for sealing against the closure element to maintain proper shutoff. These seats may require replacement due to the following:
Neglecting the replacement of damaged valve seats can result in leakages, backflow, and non-return valve failure. Follow these steps for a successful replacement:
While most check valves operate automatically and do not require handles, stems, or actuators, stop-check valves are the exception. It is possible to control and isolate fluid flow with these valves externally. Handles on stop check valves may need replacement from time to time. Follow these steps:
In summary, knowing the different types of check valves is important. It is also essential to choose reliable valve makers. Additionally, having problem-solving abilities is necessary for ensuring efficient fluid systems. It is important to be proactive in maintenance and problem-solving when ensuring the system functions properly. It applies to all valves, including brass balls and check valves.
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