Industrial valves are usually tagged as “zero-leakage” valves but this might not stand true at all times. Some common and simple problems can lead to valve leakage, thus leading to dangerous problems. Leakage is a very critical problem, especially in the case of check valves. Check valve leakage can lead to the sabotage of a system because the purpose of a check valve is quite crucial.
A check valve is employed to make sure that no fluid flows backward. In other words, check valves allow the flow of fluid only in one direction and ensure that there is no backflow. These valves are a cheap and effective solution in systems that require the prevention of backflow.
Check valves produced by industrial valve manufacturer are commonly used in domestic water systems, sewage systems, marine industry, oil and gas industry, and heating systems. When these valves turn faulty, they pose a risk of backflow, and this can be disastrous in situations like a sewage treatment system.
Leakage in check valves can be prevented by checking a few things beforehand. Here are some of the essentials that a buyer has to check before purchasing an industrial check valve to avoid check valve leakage.
Things to Check Beforehand
Classified as one-way or one-directional valves, check valves are primarily employed to avoid the reverse flow of fluids in a system. Not all systems require the same type of check valve – there is a wide range of valves that can be segregated on the basis of their type, function, leakage tolerance, and operating pressure limit. Take a look at these points before choosing the right type of check valve for a system.
- Proper Check Valve Type
Check valves are of many different types – swing check valves, lift check valves, non-slam check valves to name a few. Each of these valves, while functioning as a check valve in general, have unique features that make them the right choice in specific situations.
Here are some of the common types of check valves and their functions.
- Swing Check Valves – These valves allow full free flow of fluids but close automatically when the pressure in the pipeline reduces. Usually paired up with gate valves, these valves attain full closure when there is zero flow.
- Lift-check Valves – With a similar seating position to globe valves, lift-check valves arrive in three body patterns and are best when they are paired up with globe valves. For optimal functioning of this industrial check valve, the flow must enter from below the seat.
- Non-slam Check Valves – Featuring lesser flow resistance, non-slam check valves are designed specifically to withstand water hammering. These valves are employed in several industries including petrochemical industries as they initiate closure without creating excess pressure rise.
- Double-disc Check Valves – In these valves, two half-circle disks are hinged together and they hold open for positive flow and close during reverse flow.
- Tilting Disk Check Valves – Instead of two disks, a tilting disk valve employs a pivoted disk that opens and closes as per requirement. The function of this valve is similar to that of swinging check valves, but these provide a quicker response to pressure differences.
- Leakage Tolerance
As per ANSI standards, there are six different levels of check valve leakage rate. Each level indicated a particular range of leakage acceptable in a valve. Different check valves are produced with varying leakage rates as per their requirement.
These levels are labeled as Classes – Class I to Class VI each has its own standards and settings according to which valves are manufactured. Here is some basic data about these check valve leakage rate levels:
- Class II – Maximum leakage allowed is 0.5% of rated capacity; the capacity is tested by applying pressure to the valve inlet while the outlet is left open.
- Class III – Maximum leakage allowed is 0.1% of rated capacity; the capacity is tested by applying pressure to the valve inlet while the outlet is left open.
- Class IV – Maximum leakage allowed is 0.01% of rated capacity; the capacity is tested by applying pressure to the valve inlet while the outlet is left open.
- Class V – Maximum leakage allowed is 0.005 ml per minute of water per inch; the capacity is tested by applying pressure to the valve inlet after filling the entire body of the valve, connecting the pipe with water, and keeping the valve plug closed.
- Operating Pressure Limit
The specialty of industrial check valves is that they do not need an external control feature like a lever or automation. These valves operate based on the pressure difference across their length and the flow velocity of the fluids. There are many different standards that regulate the operating pressure limit of a valve.
Cracking pressure in valves is the pressure at which the static breaks and flow begin. For check valves, the cracking pressure can be anywhere between 1 and 5 psi. Based on specific requirements, check valves with different cracking pressure levels are manufactured.
Common Check Valve Leakage Troubles and Solution (700-900)
Leakage in check valves happens because of several reasons – it could be due to improper installation, poor maintenance, or even faulty valve manufacturing. Check valve repair is usually done by professionals as they require precision and careful handling. Here are some of the common check valve leakage trouble, their possible causes, and the solution to fix them.
When a check valve is unable to completely close during zero flow, then this situation might be considered a shut-off failure. Shut-off failure can render the valve useless and result in leakage. Be it in new or old valves, this is a common problem that occurs due to many reasons.
On the other hand, failure of shut-off valves or seizing up is also an issue that occurs often. If a shut-off failure occurs, then the function of the check valve is nulled as the valve will allow backflow. Backflow can be quite dangerous if the valves are employed in chemical and purification environments.
- Possible cause
The possible cause for shut-off failure might be the aging of internal components. Parts like gasket and washers losing their original grip can cause problems in shut-off. It is common for these parts to experience immense wear and tear after continuous usage.
Shut-off failure could also be caused by the obstruction of debris inside the valve. Dirt and debris from the fluids in the pipeline sometimes get stuck inside the parts of the valve and cause shut-off failure.
- How to fix
First, one needs to inspect the industrial check valve to understand what damage has been done. If it is found that the washers are causing the failure of the valve, then the best course of action is to replace the washer.
On the other hand, if the valve is caked with debris, then using a wire brush will be effective. One can also disassemble the valve and clean it thoroughly to avoid any future problems.
Leaks when Closing
When a check valve is not completely closed, then leakage occurs. Again, the issue could be caused by a variety of reasons. But leakage while closing might also mean that it is time for check valve replacement to take place.
When the proper closing of a check valve does not take place, it results in leakage and backflow. Leaks also open the way for hazardous situations and accidents when the fluid transported is a chemical.
- Possible cause
There are several possible causes for the leakage of a check valve:
- There might be debris blocking the closing of the valve, causing it to leak.
- The washer of the check valve could be worn out – this leads to improper functioning of the check valve thus resulting in leakage.
- Improper installation of the check valve also causes leakage. When the check valve is not the perfect fit for a given situation, there might be more problems than just leakage.
- How to fix
- If contaminations and debris are the cause of the obstruction and leakage, a thorough cleaning will keep the valve fully functioning.
- As for the problem with the washer or gasket, it is better to look out for a replacement – washers once worn out cannot be reused because they lose their grip and stop performing their function.
- Improper installation can be avoided if it is done with proper inspection. Also, if the valve size proves to be a problem, it is better to opt for a check valve replacement.
Leaking from Seat Seal
The valve seat is the component that maintains the air-tightness of the main body of the valve. It is in touch with the valve and ensures that there is no air leakage in the check valve. Air leakage can cause a change in pressure and this will hinder the performance of a check valve.
When the check valve seat is not sealed perfectly, there is leakage of air and fluid in the system. This is often inspected through a bubble test. This issue can cause many problems in the system including leaking, improper functioning, and backflow.
- Possible cause
Leakage from the valve seat can be due to the improper installation of the valve and the seat. If the valve seat is not placed perfectly, then it will lead to leakage of air and the fluid that the pipeline carries.
Also sometimes, due to wear and tear, the sealing of the valve crumbles. This will lead to a leaky check valve.
- How to fix
A leaky seat seal in a check valve can be fixed by either repairing it or replacing it. Proper care during installation will avoid any problem in the sealing of the valve.
Wear and tear of the seat of the valve can be avoided by proper lubrication. The valve stem experiences lots of damage because it is one of the most used parts of the valve
If the sealing is crumbling, then the valve seat should be replaced.
Leaking from Stem
Check valves usually do not have stems or bonnets, but a few special types of check valves feature a stem. While check valves prevent backflow automatically, some types of check valves are adjusted with external control. A few check valves are throttled manually, and for this, they have a stem.
A stop-check valve has a stem that will regulate the amount of fluid that passes through the valve. A disk is present in the valve that controls the fluid flow, and this disk is controlled by the stem.
Leaking from the stem means that the stem inside the check valve is malfunctioning and there is leakage due to it.
- Possible cause
The possible cause for leakage from the stem of a valve is that it has experienced too much wear and tear. As the stem controls the disc in a stop-check valve, a damaged stem cannot operate the disk properly. This will also lead to unregulated flow in the system.
Improper installation of the valve can also cause problems with the stem. If the stem is not placed correctly, then it cannot steer the disc.
- How to fix
In the case of a damaged stem, one has to find the proper replacement for it. Suck leakages and failures of check valves can be easily avoided by following a proper maintenance routine. Conducting a check valve test also helps in determining the quality and condition of the valve.
Repairing the packing of the valve can also help. Industrial valve manufacturers like DomBor ensure that check valves are manufactured with proper quality and from the right material so that they are perfect for a particular application.
Working Condition for Check Valve
Sometimes, industrial check valves are manufactured specifically to serve a particular industry. For this, they feature special characteristics and are capable of working under harsh conditions. Here are a few different types of check valves that are employed in special situations.
Cryogenic Check Valve
Cryogenic valves are special valves that are designed to be equipped in extremely low temperatures. These valves are used in the storage and transportation of cryogenic fluids, chemicals, and other fluids that need to be treated in low temperature and high-pressure conditions.
A cryogenic check valve has better temperature and pressure tolerance compared to a basic check valve – this is because a cryogenic check valve has to carry special materials. Usually, a cryogenic check valve can operate in a temperature range from -196°C to 120°C. As for the pressure range, it differs as per applications but generally, they can withstand pressure ratings as high as 750 psi.
Refinery Check Valve
Valves equipped in petrochemical industries and oil and gas industries need to be made of corrosion-resistant, strong material to withstand the chemicals they carry. Also, valves have a high chance of experiencing wear and tear in such industries as the fluids carried by the pipeline have high viscosity and a lot of debris.
Check valves used in refineries and similar situations are built to last long and withstand corrosion. These valves also have better precision in preventing backflow – this ensures that the refined material does not mix with the unrefined fluid. Also, some check valves used in such industries have filtering options that sort out debris.
These valves are manufactured adhering to European and American leakage standards like ISO 15848 and SHELL 77/132.
Marine Check Valve
In the marine industry, check valves are either used for transporting fluids like oil and chemicals, or they are employed inside the ship for maintenance purposes. In any situation, these valves are manufactured from corrosion-resistant materials like stainless steel to ensure that the valves withstand seawater.
Primarily functioning as non-return valves, marine check valves ensure that there is no backflow of seawater that is pumped back into the sea from a ship. Various types of check valves like lift check valves are used in the marine industry – lift check valves ensure that the disc is opened and closed as per the requirement of the fluid passage.
Check valves used for marine applications also withstand extreme temperatures. These valves sometimes transport steam, so it becomes necessary for them to withstand high temperature and pressure situations.
Domestic Check Valve
Check valves are very commonly found in domestic pipelines and irrigation systems. They are also used for regulating potable water. As these valves allow unidirectional flow, they find many applications in homes and residential spaces. Simple check valves can be often found in taps – they are used for regulating the flow of water, and to open and close the tap.
Check valves can be employed in pumping systems to prevent drainage. These valves can also be found in thermostatic mixers, spray systems, water meters and pumps, and booster pumps.
Storage Condition for Check Valve
Any valve, kept in storage, should be maintained with care to make sure that its quality is not reduced. In the case of check valves, there are a few standard storage conditions that need to be followed in order to keep the valves in their optimum functioning quality.
Here are a few standard storage conditions that need to be followed to keep check valves in their prime quality:
- Check valves are better functioning when they are stored in dry conditions. A dry and ventilated room is the best choice for the long-term storage of check valves. Outdoor storage of valves is not advised.
- To prevent the accumulation of debris and dirt inside the valve, the ends of the valve should be covered with end caps.
- If the valves are to be stored long-term, then periodical maintenance and inspection are advised. Ensure that the valves are kept at optimal temperature and pressure, and also that they do not experience any cracks or faults. Also, dirt from the body of the valve should be cleaned regularly.
- To ensure that the valve experiences less wear and tear while being used, one should lubricate the parts of the valves, even during storage.
As check valves serve several crucial purposes in a system, it becomes mandatory to maintain them. Proper care should be taken to prevent any failures or leakage issues. Also, these valves should be inspected for any problems from time to time.
Here is a small maintenance routine that can keep check valves running well for a long time.
- Cleaning – The outer area of a check valve can be easily cleaned with a cloth. This will remove any debris that has accumulated on top of the valve. As for the internal cleaning, it should be done when the valve is disassembled for service. By using a wire brush, the debris inside the valve can be removed
- Regular inspection – It is not uncommon for check valves to degrade over time. In fact, sometimes these valves get corroded and their performance goes down. Problems such as debris accumulation and corrosion can lead to leakages. This can be avoided by scheduling a regular inspection of check valves. During the inspection, the valve should be checked for any cracks, disintegrations, and corrosion spots.
Sometimes, the valves also malfunction because of the shift of some internal parts. This should be corrected during the regular inspection. Also, ensure that the valves do not face any issues in opening and closing quickly.
- Lubrication – Lubrication is important for the functioning of any valve. Check valves should be lubricated periodically to ensure that the internal parts of the valve face minimal wear and tear. Using the right lubricant is also crucial.
- Protective insulation – In the case of extreme temperature situations, an additional protective insulation will come in handy.
The Bottom Line
Check valves are one of the most commonly used valves in many industries. These one-way valves allow the flow of fluids only in one direction and prevent backflow. They do not require any external control to regulate the motion – they are self-actuated valves.
Check valves often experience leakage due to a variety of reasons. These can be avoided if the valves are maintained properly. A proper maintenance routine should be followed to ensure that industrial check valves do not face problems in functioning.
If you are looking for an A-grade Check Valve Manufacturer, then DomBor is the perfect choice for you. Find a wide range of check valves that are suitable for various industries and select the appropriate ones (Valve Selection Guide: Things You Must Know) for you. We also offer customization options, so you can design the perfect check valve that fits your requirement. Contact us today and get the best check valves for your needs!