In this post, we will discuss the difference between two return valves of interest: a check valve and a non-return valve. These are two critical valves used commonly in some very importable applications.

A non-return valve lets the fluid flow in one direction. As the name implies, the primary function of a non-return valve is to keep the flow of fluid in just one direction. When fluid in the line reverses direction and begins to flow back the way it came, a check valve serves to stop or prevent the backflow by allowing flow in one direction. The check valves are primarily designed for pressure applications.

Check valves

Check valves are quite ubiquitous in their applications, in that they are found in almost every industrial application, where they act as one-way or non-return valves. Check valves are simple devices in their design. They help to execute an important function in fluid control. Check valves prevent reverse flows, therefore preventing damage and ensuring efficient operations.

When reverse water flow occurs, the phenomenon can result in a water hammer. High-pressure surges often follow this phenomenon in the existing pipework, valves, and pumps. It may result in severe damage or rupturing of the system, along with the pipework. Sometimes, the system may not break down immediately; the reverse flow of water could also lead to a gradual build-up of fatigue and the repeated impact of the water hammer, which might ultimately result in a loss of system integrity.

Properties and application

Check valves are two-port valves; hence, they have two openings; one for fluid to enter and the other for fluid to leave. Check valves have a single inlet and outlet. They are operated by a pressure differential. Above a certain upstream pressure, the check valve automatically opens without requiring any other intervention. The minimum operating pressure is a significant characteristic that describes all check valves. This pressure is known as the cracking pressure.

Check valves are used in many pumping applications and fluid flow. Examples include chemical processing, pulp and paper, food processing, water, and wastewater treatment, industrial, marine, and mining, pumps, pipelines, power generation, and HVAC. These are only a few of the many applications of check valves.

Non-return valve

Non-return valves are very important because they function in a unique style. They are an essential feature that helps in a typical retention system to prevent the return of water or reflux that may occur due to pressure loss or a reduction in the supply and flow of water. This helps to provide more excellent safety and precision for thermostatic tapware.

Non-return valves are unidirectional, allowing water to flow in just one direction. They are opened by the force of the liquid moving in one direction, and they close due to the effect of the gravity of the water trying to return in the opposite direction (counter-flow). The action of spring helps to close the valve.

Essentially, a non-return valve allows fluid flow in only one direction. The valve is designed and fitted to ensure that the fluid flowing through the pipe follows the right direction, especially in cases where pressure conditions can cause reversed flow. When the fluid flows through the non-return valve, it causes a reasonable pressure drop in the system. Typically, the design of the valve takes this into account when designing the device.

Properties and applications

They are two-port valves with two openings in the body; one for fluid to go in, while the other is for fluid to leave. Non-return valves are typical of different types. Common variants include the

• Spring-loaded
• Swing
• Clapper
• Swing check valves.
• Flap check valves
• Duckbill
• Dual Disc check valves
• Tilted Disc check valves
• Silent check
• Ball

Non-return valves are used in many different applications. For instance, non-return valves are applied extensively in mixing loops in heating and cooling systems to ensure proper operation, and with domestic water systems to prevent backflow.

What is the difference between a non-return valve and a check valve?

We’ve established that both valves are essential and that perform similar functions. In a nutshell, the design of a non-return valve allows it to prevent the backflow or reverse flow of a medium or fluid, and to protect the pump in question from getting damaged due to surge pressures of water hammer following pump shut-down.

The check valve, on the other hand, also known as a one-way valve, is a valve that allows fluid to flow through it in only one direction. To do more or order check and non-return valves for your industrial processes, feel free to contact us today at Adamant Valves.

The post What is the Difference Between a Check Valve and a Non-return Valve? appeared first on Adamant Valves.

4 types of sanitary check valves

* Lifting sanitary check valve

Lifting sanitary check valves are generally similar in structure to globe valves, with the disc moving up and down along the channel. It is reliable in action but has high fluid resistance and is suitable for small and light caliber applications. Lifting check valves are available in straight and vertical styles. Straight check valves can only be installed in the horizontal line, while vertical check valves are generally installed in the vertical line.

* Swing health check valve

The disc of the swing health check valve rotates around the shaft, and its fluid resistance is generally less than that of the lift check valve, so it is suitable for larger caliber applications. According to the number of the disc, swing check valves can be divided into three types: single disc swing, double-disc swing, and multiple disc swing.

Single disc swing check valves are generally used for medium-sized applications. When the single disc swing check valve is used in a large diameter pipeline, the slow closing check valve which can reduce water hammer pressure is preferred to reduce water hammer pressure. The double-disc swing check valve is suitable for medium and large-diameter pipelines, and the double-disc swing check valve with a small structure and lightweight is a fast development of the check valve. The multi-disc swing check valve is suitable for large diameter pipelines.

* Butterfly sanitary check valve

The structure of the butterfly sanitary check valve is similar to that of the sanitary butterfly valve. It is characterized by a simple structure, low flow resistance, and low water hammer pressure.

* Diaphragm check valve

The diaphragm check valve has a variety of structural forms, using the diaphragm as the opening and closing. Due to its good waterproof hammer performance, simple structure, and low cost, diaphragm valves have developed rapidly in recent years. However, the temperature and pressure of the diaphragm check are limited by the diaphragm material.

Application in a hot water heating system

Choosing the right type of check valve has a great influence on the protection of the water hammers. For example, a large number of water hammer accidents in the pump station are related to the check valve installed at the pump outlet. After the accident stops the pump, the water starts to flow back through the pump.

Under the action of the backflow, the check valve closes quickly. If the check valve is affected by the failure or bearing friction and its inertia, it may lag behind the time of starting the reverse flow, that is, when the backflow increases to a certain value, or even a quick shutdown at the moment of maximum backflow, high pressure can be generated at the check valve.

Shut-off of sanitary check discs is best when the flow rate is zero, but it is unlikely to be completed when the flow rate is zero. It is generally believed that as long as closed near zero flow is normal.

In the hot water heating system, the pressure pipe of the circulating pump can be set between the pressure pipe and the suction pipe in order to reduce the emergency stop pump water hammer. When the circulating pump is running, the check valve is closed because the water pressure on the outlet side of the pump is higher than that on the suction side.

When the pump stops suddenly, the pressure on the waterside of the pump decreases sharply, while the pressure on the waterside of the pump increases sharply. Under the action of this pressure difference, the water in the suction side pipeline of the circulating pump pushes the check valve to the water outlet side of the pipe network system, thus, the increase of pressure in the suction side pipe network is reduced, and the harm of water hammer is reduced and prevented.

The post How do Sanitary Check Valves Work in Hot Water Heating System appeared first on Adamant Valves.

1. Swing check valve

The flap of the swing check valve is disc-shaped. It rotates around the shaft of the valve seat. Since the channel inside the valve is streamlined, the flow resistance is smaller than that of the lift check valve. It is suitable for use in large-caliber occasions where the flow speed is low and the flow doesn’t constantly change. But it’s not suitable for pulsating flow. Its sealing performance is not as good as that of the lift check valve. The swing check valve can be divided into single-valve, double-valve, and multi-valve. These three types are defined mainly according to the valve caliber so as to weaken the hydraulic shock when the medium stops flowing or backflows.

2. Lift check valve

The flap slides alongside the vertical centerline of the valve body. It can only be installed on horizontal pipelines. Round balls can be used as valve flaps on high-pressure small-caliber sanitary check valves. The shape of the valve body of the lift check valve is the same as that of the sanitary shut-off valve, so the fluid resistance coefficient is large. Its structure is similar to that of the shut-off valve. Its valve body and valve flap are the same as those of the shut-off valve. There’s an orientation sleeve at the upper part of the valve flap and the lower part of the valve cover. The valve flap orientation sleeve can move freely up and down. When the medium flows downstream, the valve flap is opened by the medium thrust. When the medium stops flowing, the valve flap drops on the valve seat to prevent medium backflow. The inlet and outlet channel direction of the straight lift check valve is vertical to the direction of the valve seat channel. The media inlet and outlet channel direction of the vertical lift check valve are the same as that of the valve seat channel. And its flow resistance is smaller than that of the straight lift check valve.

3. Disc check valve

The valve flap rotates around a pin inside the valve seat. Its structure is simple and can only be installed on horizontal pipelines. It has a relatively poor sealing performance.

4. Pipeline check valve

The valve flap slides alongside the central line of the valve body. The pipeline check valve is a relatively new type of valve. Its size is small, weight is light, processing technology is good. But the fluid resistance coefficient is slightly larger than that of the swing check valve.

5. Pressed check valve

This type of valve is used to supply water to boilers and shut off steam. It has an integrated function of lift check valve, shut-off valve, and angle valve.

The post The Categories of Check Valves appeared first on Adamant Valves.

Sanitary class check valves can be classified according to service.

*  Swing sanitary check valve

The disc of the swing check valve is disc-shaped and rotates around the axis of the seat channel. The flow resistance of the valve is smaller than that of the lift-type check valve because of the streamline of the inner passage of the valve, so it is suitable for large diameter occasions with low flow rate and in constant flow. However, it is not suitable for pulsating flow, and its sealing performance is not as good as the lifting type.

*  Lifting sanitary check valves

The upper part of the disc and the lower part of the cover of the lifting sanitary check valve are processed with guide sleeve slips, and the guide slips of the disc can be lifted and lowered freely within the guide slips of the valve cup. When the medium forward flows, the disc by the medium thrust opens; when the media stop flow, the disc by the vertical landing on the seat, thus preventing the media countercurrent effect.

*  Butterfly sanitary check valve

Butterfly sanitary check valves are those in which the disc rotates around the pin in the seat. The butterfly sanitary check valve is simple in design and can only be installed in horizontal piping and is poorly sealed.

*  Piping sanitary check valve

Piping sanitary check valves are valves in which the disc slides along the center line of the valve body. The piping check valve is a new kind of valve, and it has many advantages such as its small size, lightweight, and good processing technology, which is one of the development directions of the check valve. However, it has a slightly larger fluid resistance coefficient than a swing check valve.

Then how to select the right sanitary check valve for you? Let’s see the advice below.

Check valves for incompressible liquids

Sanitary check valves for incompressible liquids are selected primarily for their performance in closing without the possibility of an unacceptably high impact pressure resulting from a sudden closure due to backflow.

Sanitary check valves for compressible liquids

Although check valves are used for incompressible fluid lines to minimize disc impact, they can be selected according to similar selection methods for incompressible fluids using check valves. However, the impact of compressible media can also become considerable for very large pipelines.

Check valves for compressible liquids may use a speed reducer if the range of media flow is large. The device works during the entire movement of the closing member to prevent rapid and continuous hammering on its end.

Determination of sanitary check valve dimensions

Check valves shall be sized so that normal fluid keeps the shutoff open steadily. For the maximum shut-down time, the check valve should close as soon as possible after the downstream medium begins to slow down. In order to size the valve in this case, the valve manufacturer must provide data for the selected size. In this way, it should be possible to find the valve size at a given flow rate when the valve is fully open.

Selection of sanitary check valve types

* For high-pressure check valves below DN50mm, vertical lift check valves and straight lift check valves should be used.

* For low-pressure check valves up to DN50mm, butterfly, vertical lift, and diaphragm check valves are recommended.

* For high-pressure check valves with DN greater than 50mm and less than 600mm, swing check valves are recommended.

* For DN greater than 200mm, less than 1200mm in the middle, and a low-pressure check valve, it is appropriate to choose a non-wear spherical check valve.

* Butterfly and diaphragm check valves should be used for low-pressure check valves with DN greater than 50mm and less than 2000mm.

* Slow closed swing check valve and slowly closed butterfly check valve should be used for piping with low or no water impact.

The post How to Select a Right Sanitary Check Valve? appeared first on Adamant Valves.

The check valve is also known as the counter valve, back pressure valve. This type of valve is automatically opened and closed by the force generated from the flow of the medium in the pipeline. It is a type of automatic valve. When a sanitary check valve is used in the pipeline system, its main role is to prevent media backflow and reversal of the pump and its driving motor and media discharge. The check valve can also be used in pipelines that supply the auxiliary system where the pressure may rise to the level above the pressure of the main system.

What is Ball Check Valve?

Ball check valves all use rubber balls as valve flaps. The mechanism is that under the influence of the medium, rubber balls can roll back and forth on the slide in the valve body to open or close the valve.

The Use and Features of Ball Check Valve

Single ball micro-resistance ball check valve HQ44X and double ball micro-resistance ball check valve HQ45X are characterized by large flow, small flow resistance loss, good sealing performance, muffled closing, the ability to reduce water shock.

They can be horizontally or vertically installed. Micro-resistance ball check valve can be used at the pump outlet of pipe networks such as cold water, hot water, industrial and domestic sewage to prevent media backflow. And in order to prevent media backflow, check valves should be installed on equipment, devices, and pipelines.

Conclusion

A ball check valve functions by means of a ball that moves up and down inside the valve. The seat is machined to fit the ball, and the chamber is conically shaped to guide the ball into the seat to seal and stop a reverse flow.

The post The Use and Features of Ball Check Valve appeared first on Adamant Valves.

Swing sanitary class check valve

The disc of the swing check valve is disc-shaped and rotates around the axis of the seat channel. The flow resistance of the valve is smaller than that of the lift check valve because of the streamline of the inner passage of the valve, so it is suitable for large caliber applications with low velocity and in constant flow. But it is not suitable for pulsating flow since its sealing performance is not as good as the lifting type.

Lift sanitary check valves

The upper part of the disc and the lower part of the cover of the lift sanitary check valve are processed with guide sleeves so that the guide slips of the disc can be lifted and lowered freely within the guide slips of the valve cup. When the medium forward flows, the disc will be opened by the medium thrust; when the medium stops flowing, the disc will sag down on the seat, thus preventing the medium from counterflow.

Disc sanitary check valve

A disc sanitary check valve is a check valve in which the disc rotates around a pin in the seat. The dish sanitary check valve is simple in construction and can only be installed in horizontal pipes, so its sealing is poor.

Pipe sanitary check valve

Pipe sanitary check valves are valves in which the disc slides along the centerline of the valve body. The pipeline check valve is a new kind of valve, with small volume, lightweight, and good processing technology is one of the development directions of the check valve. However, the hydraulic resistance coefficient of the pipeline sanitary check valve is slightly higher than that of the swing check valve.

How to select a suitable sanitary check valve?

Sanitary class check valves for compressible liquids

Although check valves are used incompressible fluid lines to minimize disc impact, they can be selected according to similar selection methods for incompressible fluids using check valves. However, the impact of compressible media may become considerable for very large pipelines.

Check valves for compressible liquids may use a speed reducer if the range of media flow is large. The device works during the entire slow movement of the closing member to prevent rapid and continuous hammering on its end.

Lift check valves are used if the media flow continues to stop and start rapidly, as in the outlet of the compressor. This check valve uses a lightweight disc that can withstand a spring load and has a low lift.

Dimensions of sanitary check valves

Check valves shall be sized so that normal fluid keeps the shutoff open steadily. For a maximum shut-down time, the check valve should close as soon as possible after the downstream medium begins to slow down. In order to size the valve in this case, the valve manufacturer must provide data for the selected size. In this way, it should be possible to find the valve size at a given flow rate when the valve is fully open.

Selection of sanitary class check valve types

* For high-pressure check valves below DN50mm, vertical lift check valves and straight lift check valves should be used;

* For low-pressure check valves up to DN50mm, butterfly, vertical lift, and diaphragm check valves are preferred;

* For high-pressure check valves with DN greater than 50mm and less than 600mm, swing check valves are recommended;

* For DN greater than 200mm, less than 1200mm in the middle and low-pressure check valve, it is appropriate to choose a non-wear spherical check valve;

* Slow closed swing check valve and slowly closed butterfly check valve should be used for piping with low or no water impact.

The post How to Select a Suitable Sanitary Check Valve? appeared first on Adamant Valves.

The sealing performance of the high-pressure check valve is not as good as that of the lift check valve. The butterfly check valve can be divided into single-flap, double-flap, and multi-flap types. These three types are defined according to valve caliber. The purpose is to prevent the media from stopping to flow or weaken the hydraulic shock when the media backflows.

2. The valve flap of the high-pressure check valve slides along the vertical centerline of the valve body. The internal thread check valve can only be installed in the horizontal pipe. Round balls can be used for the valve flap of the high-pressure-small-diameter check valve. The valve shape of the butterfly check valve is the same as that of the shut-off valve, so its fluid resistance coefficient is large.

The structure of the high-pressure check valve is similar to that of the shut-off valve, its valve body and valve flap is the same as those of the shut-off valve. There’re guide sleeves at the upper part of the valve flap and the lower part of the valve cover. The valve flap guide sleeve can be freely lifted within the valve lid guide sleeve.

When the medium flows downstream, the valve flap is opened by the medium thrust. When the medium stops flowing, the valve flap drops onto the valve seat with its own weight to prevent the medium from backflowing.

The channel direction of the medium inlet and outlet of the straight butterfly check valve is vertical to the channel direction of the valve seat. The channel direction of the medium inlet and outlet of the vertical lift check valve is the same as that of the channel direction of the valve seat. Its flow resistance is smaller than that of the straight type.

3. The valve flap of the high-pressure check valve rotates around the axis inside the valve seat. The butterfly check valve has a simple structure. It can only be installed on the horizontal pipe. Its sealing performance is good.

4. Pipeline check valve is a new type of valve. It has small in size and lightweight. Its processing technology is good. But its fluid resistance coefficient is slightly larger than that of the swivel check valve.

5. High-pressure check valve is used for feeding water to boilers and cutting off the steam. It has an overall function of lift check valve, sanitary shut-off valve, and angle valve.

The post The Structure of High-pressure Check Valve appeared first on Adamant Valves.

2. Lift check valve
It is a kind of check valve whose valve flap slides along the vertical centerline of the valve body. Lift check valve can only be installed on horizontal pipelines. On high pressure small caliber check valve, the valve flap can use round balls. The shape of the valve body of lift check valve is the same with that of the shut-off valve, so it has a relatively large fluid resistance coefficient. Its structure is similar to that of the shut-off valve. Valve body and valve flap are the same with those of the shut-off valve. The upper part of the valve flap and the lower part of the valve cover are machined with a guide sleeve. The valve flap guide sleeve can be freely lifted inside the valve guide sleeve. When the medium flows downstream, he valve flap is opened by the medium thrust. When the medium stops flowing, the valve flap drops onto the valve seat by its own weight, preventing medium backflow. The channel direction of medium inlet and outlet of straight-through lift check valve is vertical to the channel direction of the valve seat. The channel direction of medium inlet and outlet of vertical lift check valve is the same with the channel direction of the valve seat. Its fluid resistance is smaller than that of the straight-through lift check valve.

3. Disc check valve
Its valve flap rotates around the axis inside the valve seat. Disc check valve has a simple structure, can only be installed on horizontal pipelines. Its sealing performance is poor.

4. Pipeline check valve
Its valve flap slides along the centerline of the valve body. It is a new type of valve. Its size is small, weight is light, processing technique is good. It is one of the development directions of sanitary check valve. But its fluid resistance coefficient is slightly larger than that of the swing check valve.

5. Pressed check valve
This kind of valve is used to feed water for boilers and cut off the steam. It has combined functions of lift check valve, shut-off valve and angle valve.

Besides, there are other types of check valves that are not suitable for pump outlet installation, such as bottom valves, spring-type and Y-type check valves.

The post The Classifications of Check Valves appeared first on Adamant Valves.

Sanitary check valves are a kind of valve that relies on the flow of the medium to automatically open and close the valve flap to prevent the backflow of the medium. It is also known as a single direction valve, counterflow valve, and back pressure valve.

What are check valves used for

This type of check valve works automatically. Under the fluid pressure flowing in one direction, the valve flap opens. When the fluid flows in the opposite direction, the valve seat is affected by the fluid pressure and self-overlaying valve flap, so that the flow is cut off.

What are check valves used for?

A Sanitary check valve is a kind of automatic valve mainly used to prevent the backflow of the fluid medium, prevent the pump and actuating motor from reverse-rotating, and prevent the discharge of the container medium.

Check valves can also be used in pipelines supplying an auxiliary system where the pressure may exceed the system’s rated pressure. Check valves can be divided into swing-type check valves (which rotate around the center of gravity) and lift-type check valves (which move along the axis).

Another key feature of sanitary check valves is in the name. Their sanitary properties allow use in highly hygienic applications demanded by various industries like food, bio-fermentation, and pharmaceuticals.

How to pressure test a check valve

The valve flap axis of the lift-type check valve is in a position vertical to the horizontal surface. The channel axis and valve flap axis of the swing-type check valve are in a position nearly parallel to the horizontal line.

To conduct a strength test, introduce the test medium from the inlet to the specified value, with the opposite end closed. If there is no leakage from the valve body and cover, then it’s considered qualified.

To conduct a sealing test, introduce the test medium from the outlet. At the inlet, check the sealing surface, stuffing, and gasket. If there is no leakage from those places, then it’s considered qualified.

Conclusion

Adamant Check Valves are subject to MSS SP-61, an ANSI standard that institutes the requirements and acceptance criteria for shell and seat closure pressure testing. Proper pressure testing is conducted through various methods, which we will explore down below. One of our main goals is to prevent check valve failures before they occur—that’s why each sanitary check valve produced by Adamant Valves is thoroughly pressured and leak tested before being delivered.

Seat Test with Air

Check Valves are tested at an air pressure of no less than 80 psi.

Shell Test

Valves are tested at a gauge pressure no less than 1 ½ times the 100º F rating, rounded to the next highest 25 psi increment.

Seat Test with Water

Valves are tested at a pressure no less than 1.1 times the 100º F rating. The test medium is water.

Results:

The goal of each check valve pressure test is no observable leakage.

The post The Pressure Testing Methods for Check Valves appeared first on Adamant Valves.

A check valve is a non-return valve or a one-way valve designed to prevent backflow. Sanitary check valves are designed for use in applications requiring clean or sterile processing. They are often used in clean water systems as a safeguard against backflow contamination.

Double check valves usually consist of two check valves that are interlinked in case one fails. A double check valve or double check assembly (DCA) is a backflow preventer designed to protect water sources from contamination. It is also a valve used in compressed air braking systems on heavy trucks.

How Does a Check Valve Work?

The structure of a check valve is usually very simple, including parts such as a valve body, a valve seat, a valve disc, and a cover. The working principle of the check valve is to allow one-way flow and automatically prevent reverse flow. This type of valve is sensitive to flow and relies on the medium to open and close the valve seat. The inner disc allows the medium to flow forward, thereby forcing the valve to open. Once the flow reverses, the valve reverses automatically. The check valve is one of the few fully automated valves that can be circulated without manual intervention. So, now that you understand how check valves work, we can learn more about how double check valves work!

What is the Difference Between A Single and Double Check Valve?

The main difference between a single check valve and a double check valve is that double check valves provide extra security — if one of the check valves fails, the other valve will still be able to save the system from backflow contamination. Single check valves provide category 2 fluid protection, guarding against fluctuations in temperature, taste, or smell. A double check valve is for category 3 fluid protection protecting against contamination from low-toxicity chemicals like household cleaners.

Sanitary Double Check Valve Operation

spring loaded double check valve operation

sanitary double check valve application

What is the function of the double check valve?

Double check valves consist of two non-return valves connected in a series, operating under these two principles: 

1) Firstly, one check valve will still act, even if the other is jammed wide open.

2) Secondly, the closure of one valve reduces the pressure differential across the other, allowing a more reliable seal and avoiding even minor leakage.

Sanitary Double Check Valve Application

The small valves can be hard to notice, especially when integrated into existing valve bodies. Larger check valves may be installed with end ball valves for insulation and testing. Often, test valves are in place to attach the test equipment to assess whether the double check assembly is still functional. 

Where are Double Check Valves Used?

The double check valve is suitable for the prevention of back pressure and siphoning, but is not suitable for high risk applications. It is commonly used on lawn irrigation systems, fire sprinklers and mixed boilers. If the hazard is higher, even a relatively low risk such as the use of antifreeze in the fire sprinkler system, a more reliable sanitary check valve such as a reduced pressure zone device may be mandatory.

Conclusion

Thank you for reading our article and we hope it can help you better understand the operation and applications of double check valves. If you want to learn more about sanitary valves, we would like to advise you to visit the Adamant Valves homepage for more information.

The post Sanitary Double Check Valve: Function, Operation, & Application appeared first on Adamant Valves.