The Essential Handbook on Swing Check Valves

In industrial, water and wastewater applications both, swing check valves play a pivotal role in controlling the flow of liquids and gases. This article provides an all-encompassing guide to swing check valves, design , functionality, and maintainance to ensure longevity and performance.

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dn350 swing check valve

Design of Swing Check Valves

Swing check valves typically consist of a valve body, a disc, and a hinge. The disc swings on the hinge &#; in the forward flow, it moves away allowing fluid to pass, and in the backflow, it swings back onto the seat, effectively creating a seal.

api check valve

Materials and Composition

Swing check valves are generally made from durable materials like bronze, cast iron, carbon steel, stainless steel, or PVC. These materials are meticulously selected to ensure resistance to corrosion, high pressure, and temperature fluctuations.

Swing Check Valve Animation

swing check valve animation

Structure and Components

A typical swing check valve consists of a valve body, a disc, and a hinge. The disc is pivotal, as it opens when the fluid flows in a forward direction and closes to the reverse flow and prevent backflow. The hinge is what keeps the disc attached, allowing it to swing either to an open or closed position.

API swing check valvestainless steel swing check valve

Velocity distributions under di&#;erent mass &#;ow rates For Swing Check Valve

The velocity distributions on the symmetry plane of the swing check valve are displayed below when the valve opening is 4%. Upon water vapor passing through the valve seat, a high-speed jet is observed, as indicated, with the maximum velocity reaching approximately 12 times the inlet velocity. This results in a high Mach number. Additionally, a distinct vortex is observed at the bottom of the swing check valve, which is attributed to the presence of the high-speed jet. At the top of the swing check valve, where the cross-sectional area is smaller compared to the bottom, water vapor flows along the surface of the valve disc due to the valve&#;s structural configuration. Figure 4 illustrates the velocity distributions at various mass flow rates, specifically highlighting instances where significant variations are observed. It is evident that the influence of the high-speed jet becomes more prominent as the mass flow rate increases.

velocity distributions under di&#;erent mass &#;ow rates for swing check valve

API 594 swing check valve dimensions

API 594 is a standard set by the American Petroleum Institute (API) that specifies the requirements and dimensions for check valves, including swing check valves, which are used in the petroleum and natural gas industries.

The API 594 standard covers two types of check valves:

• Type A: This type includes swing check valves and tilting disc check valves.

• Type B: This type covers piston check valves and ball check valves.

So for swing check valves, It is API 594 Type A standard.

The dimensions specified in API 594 for swing check valves include face-to-face dimensions, which are critical for installation, as well as dimensions of other parts like the valve body, valve disc side, and hinge pins.

Face-to-face dimensions are important as they tell you how much space the valve will take up along the pipe, ensuring compatibility with the pipeline it&#;s being installed in. For example, a typical 6-inch swing check valve complying with API 594 may have a face-to-face dimension of around 292 mm (or around 11.5 inches), but this can vary.

It&#;s important to note that there are multiple dimensions and specifications within API 594, and these can also change. Since swing check valves come in various sizes and pressure ratings, the dimensions will vary accordingly.

For the most accurate and up-to-date information on API 594 swing check valve dimensions, I recommend consulting the latest version of the API 594 standard or contact THINKTANK who specializes in API-compliant valves. We are a professional swing check valve manufacturer based in China, specialize in the production of various industrial valves, including swing check valves. It&#;s important to conduct due diligence and research when choosing a manufacturer, to ensure the products meet the standards and specifications required for your particular application. Our engineers and valve specialists can provide valuable insights on the specific dimensions required for your application.

swing check valve relation between disc opening angle and time

distribution of pressure and temperature at different mass flow rates For swing check valve

The following image shows the distribution of pressure and temperature at different mass flow rates.

When the mass flow rate is below 10% of the rated flow, the pressure variation is minimal, resulting in a negligible temperature difference. However, as the mass flow rate increases, a significant pressure difference becomes evident, with the maximum pressure difference reaching 0.4 MPa at a flow rate of 40% of the rated flow.

Analyzing the temperature distributions, it is apparent that there is a notable temperature variation at higher mass flow rates, with the maximum temperature difference reaching 200 K.

distribution of pressure and temperature at different mass flow rates

hydraulic swing check valve

Hydraulic swing check valves are composed of several key components, including the valve body, valve seat, valve disc, valve cover, and heavy hammer.

In terms of the pipe lengths associated with hydraulic swing check valves, the upstream pipe length is typically designated as 4D, indicating that it should be four times the nominal diameter of the valve. Similarly, the downstream pipe length is typically specified as 10D, meaning it should be ten times the nominal diameter of the valve. These pipe length ratios help ensure proper flow dynamics and optimal performance of the swing check valve in the hydraulic system.

hydraulic swing check valves

Swing check valves are subject to various standards that dictate their design, dimensions, material specifications, testing, and marking. The selection of a standard depends on the industry and the specific application. Some of the widely recognized international and industry standards for swing check valves include:

1. API 6D: Issued by the American Petroleum Institute, this standard covers the design, manufacturing, and testing of valves primarily used in the oil and gas industry.
2. API 594: Also from the American Petroleum Institute, this standard covers design and dimensions specifically for check valves, including swing check types.
3. ASME B16.34: Issued by the American Society of Mechanical Engineers, this standard covers the pressure and temperature ratings, dimensions, tolerances, and materials for flanged, threaded, and welding end valves, including swing check valves.
4. MSS SP-71: Developed by the Manufacturers Standardization Society, this standard covers iron swing check valves.
5. BS : A British Standard which specifies requirements for swing check and tilting disc check valves made of steel, used for oil and gas applications.
6. ISO : This International Organization for Standardization standard specifies requirements for steel check valves, including swing check valves, for petroleum, petrochemical, and allied industries.
7. DIN : A German standard specifying face-to-face dimensions for swing check valves.

When selecting a swing check valve, it is important to choose one that adheres to the standards applicable to your industry and region. It is also critical to understand the specifications of the system in which the valve will be installed, such as pressure, temperature, and fluid compatibility, to ensure that the valve will perform effectively and safely.

Operation of Swing Check Valves

Flow Direction

Swing check valves are self-actuating. The pressure of the fluid passing through the valve forces the disc to swing away from the valve seat, allowing flow. When the flow ceases or reverses, the spring or disc returns to its seat, preventing backflow.

api check valve

Pressure Drop and Flow Rate

It&#;s important to understand that the full swing check valve operation can create pressure drop in the system due to the swinging motion of the disc. This pressure drop must be accounted for in system design to ensure that adequate pressure is maintained for proper functioning.

swing check valve relation between disc opening angle and pressure difference

Applications

Swing check valves are widely used across various industries including petrochemical, pharmaceutical, water treatment, and food processing. They are particularly useful in systems where it is necessary to prevent backflow, such as in pumping applications or in systems with varying pressures upstream flow through.

Swing Check Valve HS Code

As of my last knowledge update in September , the Harmonized System (HS) code for a swing check valve would likely fall under the category of taps, valves, and similar appliances. Please note that HS codes can change, so you should verify the most current code with a relevant authority or through an updated resource in your nation.

Typically, swing check valves could fall under the following HS code:

.30 &#; Check valves

This code is used for international trade and classifies the swing check valve under a broader category of taps, cocks, valves, and similar appliances for pipes, boiler shells, tanks, vats, or the like, including pressure-reducing valves and thermostatically controlled valves.

However, as HS codes can be detailed and specific, and there may be updates or changes, I would recommend consulting a customs specialist or using an updated tariff schedule to confirm the current HS code for swing check valves in your country or the country you are exporting to.

dn500 20&#; swing check valve

horizontal check valve

In fluid control systems, swing check valves are crucial components used to prevent backflow. Their installation can be either horizontal or in vertical position, depending on the system&#;s requirements. In this article, we will focus on the vertical installation of swing check valves and its significance.

The Need for Vertical Installation

Vertical installation of swing check valves is usually preferred when space is limited or the pipeline is vertically oriented. Additionally, in some applications, a vertical installation may facilitate better flowing fluid dynamics within the system.

In a vertical installation, gravity can assist in the closing of the valve. This is particularly useful in low flow systems where the weight of the fluid might not have sufficient force to fully close the valve.

Swing check valve installation guide

Installing a swing check valve properly is crucial for its optimal operation and for ensuring the safety and integrity of the piping system. Below is a general installation guide for swing check valves. Please note that you should always consult the manufacturer&#;s instructions and relevant regulations, and ensure that personnel are qualified for the installation.

1. Inspection and Preparation:

• Check the valve to ensure it is free of damage and that it meets specifications.

• Ensure that the pipeline where the valve will be installed is clean and free from debris.
• Confirm that the valve is compatible with the fluid it will control and that it meets the required pressure and temperature ratings.

2. Orientation:

• Swing check valves should be installed in the correct orientation for proper operation. Typically, swing check valves are installed in horizontal pipe runs, but some can be installed in vertical pipe runs with upward flow.
• Ensure that the valve&#;s hinge pin is oriented horizontally to allow the disc to swing freely.

3. Positioning:

Position the valve in the location where it will be installed. Ensure that the flow arrow on the valve body matches the direction of flow in the pipeline.

4. Installation:

• If the pipeline is existing, ensure it is depressurized and drained.
• Use appropriate gaskets between the valve flanges and the pipeline flanges.
• Insert the valve between the flanges, ensuring proper alignment.
• Install the flange bolts. Tighten the bolts in a crisscross pattern to ensure even pressure.
• If using a threaded swing check valve, apply thread sealant and screw the valve into place, making sure not to over-tighten.

5. Testing and Inspection:

• Once the valve is installed, gradually pressurize the system.
• Check for leaks around the flanges and repair if necessary.
• Confirm that the valve operates correctly by observing the flow through the system. The valve should allow flow in one direction and prevent backflow.

6. Maintenance:

• Keep records of the installation.
• Develop a maintenance schedule according to the manufacturer&#;s recommendations.

Safety Notes:

• Always use personal protective equipment (PPE) during installation.
• Follow all local codes and standards.
• If you are not experienced or trained in valve installation, consider hiring a qualified professional.

Maintenance of Swing Check Valves

Routine Inspection

To ensure the longevity and performance of swing check valves, it is essential to perform regular inspections. This includes checking for leaks, ensuring that the hinge pin is not damaged, and that the disc swings freely.

Cleaning and Lubrication

Over time, debris can accumulate in the valve, affecting its operation. It is crucial to periodically clean the valve and apply suitable lubrication to the hinge to ensure smooth operation.

Replacing Worn Out Parts

In the event that parts of the valve become worn out or damaged, they must be replaced promptly to avoid valve failure. This includes replacing the disc or the hinge pin if they become excessively worn.

Testing

Regular testing of the valve under operating conditions is essential to ensure that it is functioning correctly. This might include pressure testing to ensure that the valve is sealing properly under cracking pressure and that there is no leakage.

Conclusion

Swing check valves are an indispensable component in many industrial applications. Understanding the design aspects, operational principles, and maintenance procedures is vital for those who utilize these valves in their systems. Regular inspection, cleaning, and timely replacement of parts are crucial in ensuring their longevity and optimal performance.

8 swing check valve 300lb

We, at THINKTANK, take pride in being a reliable supplier of swing check valves. Our commitment to quality and precision sets us apart. We manufacture swing check valves that conform to international standards and meet the stringent requirements of various industries. Each valve undergoes rigorous testing to ensure optimal performance and long-lasting durability in diverse industrial applications. By employing advanced manufacturing techniques and utilizing high-quality materials, we deliver reliable swing check valves that offer efficient fluid control, effectively prevent backflow, and contribute to the overall reliability and safety of fluid systems. With our expertise and unwavering dedication to customer satisfaction, we have earned a reputation as a trusted supplier of dependable swing check valves. Contact us today and you will have no worries in your valve business.

DN80 swing check valve

Often overlooked and misunderstood, check valves play a vital role in water management systems and are a staple in practically every industrial application. 

What is a check valve?

A check valve is a component that can be fitted on to the end of a pipe or channel and acts as a one-way/non-return valve that opens under pressure. While water can travel out of the check valve, it cannot travel back through the check valve.

Image credit: Proco Products

Check valves can come in a range of sizes, designs and materials, all of which can have an effect on the efficiency of the component.

While we will mainly look at check valves from the perspective of their application in various water uses, check valves are also used to process a variety of different fluids, materials and gases.

Check valves perform an essential function in preventing reverse flow &#; where potentially polluted water is allowed to travel back into a system and contaminate clean water resources.

How does a check valve work?

Check valves are a common sight in industrial systems and are used to remove wastewater and other contaminated fluids. Check valves feature a single inlet and outlet where water can pass through it but not back up it, and it is operated by a pressure differential, according to Proco Products.  

A pressure differential, in the context of check valves, is when the pressure of the water inside the valve is greater than the pressure keeping the valve closed. When the pressure on the inlet side is greater, the valve opens automatically, allowing the water to pass through it - this is called cracking pressure.

Cracking pressure is a specified minimum operational pressure that determines when the valve will open and allow water to flow.

In a water system, for example, multiple check valves will be placed in a series to prevent any backflow of contaminated water that could compromise clean water supplies. This also helps to reduce the risk of any reverse flow that could result in water hammer.

What is water hammer?

The phenomenon known as water hammer, also known as valve slam, is when flow reverses before the valve is completely closed. Once the valve has closed, the sudden change in flow direction and the velocity results in water hammer.

Water hammer proceeds when water in motion is suddenly forced to stop. When the flow of water at the leading edge comes to a stop, but the water behind it continues to move - it starts to compress.

The build-up of the kinetic energy of the water converts to a high amount of pressure energy, creating a hydraulic shock wave that travels at almost the speed of sound, just less than 343 meters per second, through the pipeline.

When repeated extreme pressure surges in connected piping, valves and pumps, it can cause catastrophic damage and ruptures to a water system and its intricate pipework.

Should water hammer occur, it can completely destroy a system that could cost tens of thousands of dollars to repair.

In the event that water hammer occurs, but a water system continues to operate successfully, the repeated impact of water hammer can lead to systems and components becoming fatigued and could seriously compromise the integrity of a system. 

Types of check valves

Check valves have many purposes and roles in a lot of applications &#; from your home to large industrial wastewater management models.

This means there is a range of different check valves specially designed to suit the requirements of a specific project.

Swing/flap check valves

Swing/flap check valves or PVC check valves are the simplest design of check valves and are used in small homes to large scale industrial plants.

Image credit: DOE Handbook

A metal disc pivots on a hinge or trunnion to prevent reverse flow. Most larger-scale check valves use this design due to their simplicity. With a life span of five to seven years, these valves are often a component that needs to be replaced frequently.

Despite being a popular check valve, due to its cost and simplicity, steel flap and swing check valves can rust, stick and over time become prone to jamming with debris that requires manual cleaning.

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For more information, please visit Globe Valve.

When these valves fail, they allow backflow and water hammer to occur. Abrasive sludges and corrosive slurries can create wear and will damage the valves rendering them inoperable.

Ball and spring check valves

A ball and spring check valves are known for their durability and how easy they are to install. They operate when the inlet pressure is greater than the cracking pressure, pushing a ball or disc back and overcoming the strength of the spring.

Image credit: Speciality Manufacturing

When the inlet pressure drops below the cracking pressure or backflow occurs, the spring forces the valve to close &#; stopping the water escaping or travelling back up the pipe.

While ball and spring check valves are known for their reliability, the main drawback to this type of check valve occurs when it needs to be inspected for maintenance. In order to check the valve, it has to been removed completely from the system.

The ball and spring design are used for air check valves.  An air check valve has one main function &#; to allow air flow in one direction whilst preventing air flow from the other side. Air check valves are fitted to air compressors so that it can keep certain part pressurized and others allow other parts to become de-pressurized.

Duck bill check valves

The duck bill check valve came into use in the s and was brought in to replace swing/flap valves. Over the decades it has become increasingly popular in industrial applications.

Working similarly to its namesake, a duck bill check valve open like duck&#;s bill to allow the water or matter to pass through it.

Image credit: Proco Products

Duck bill check valves rely on a flexible rubber diaphragm which creates a valve that will remain closed unless positive pressure is applied.

Unlike swing/flap check valves, rubber duck bill check valves are increasingly less vulnerable to rusting, they cannot seize or bind and are considered to be one of the most reliable and long-lasting check valves in the market today &#; with Proco Products valves lasting up to 35 &#; 50 years.

Duck bill check valves also do not suffer from mechanical wear, and the rubber design allows for greater elastomer innovations and flexibility.

For projects that require a valve to be submerged on the seafloor or underwater, duck bill check valves offer the advantage of being barnacle and algae resistant &#; an important feature for saltwater projects such as the Marine Wastewater Outfall Diffusion project in .

Another benefit of a duck bill check valve is its ability to cope with water hammer. Cal Hayes, general manager at Proco Products, said the new series 750 duck bill check valve is an example &#;because it is made out of rubber, instead of creating a huge valve slam back [water hammer], our rubber is inherent to flex so that when pressure is applied to the outside, it is allowed to flex".

This is another form of a surge relief valve that can protect your piping system from the build-up of pressure surges &#; manufactures such as Emerson Process Management and Daniel Measurement and Control Inc offer valves of this design.

Other designs

These are the three common check valves types, but there are other designs such as the dual plate types (butterfly check valve) and the ball type and plug type check valve.

Each of these has a unique way in which they operate; the butterfly check valve has two folding disks that move towards a centreline with the forward flow and close with reverse flow.

Image credit: Hard Hat Engineer

A ball type and plug type check valve work on the principle of gravity &#; when there is enough pressure in the flow the ball is lifted, then it drops the ball roll back to close the opening.

Image credit: Hard Hat Engineer

In-line check valves

An in-line component can refer to any useful object in a circuit that is attached to an adjacent fluid conduit &#; a check valve placed in a line. They are used to either enhance or upgrade an existing system.

Whereas a check valve&#;s main focus is to prevent the backflow of water into a system, an in-line check valve is used to prevent the backwards transmission of pressure.

For example, a check valve is generally installed after a pump in a series that makes use of an accumulator, a cold-water tank that facilitates water flow. The in-line check valve prevents stored energy from making its way back into the pump.

Excess energy that is stored in an accumulator can be damaging to a system, and it must be controlled for hydraulic systems to be safe and reliable.

How do you choose the right check valve?

Check valves are typically installed at the discharge point of a piping system to make sure that the fluid or matter that is being pumped out does not flow back into the system. There are a number of different check valves on the market and choosing the right one can be a difficult task.

Here are five things you should consider before choosing the right check valve:

Application

It sounds simple, but properly understanding what application your check valve needs to serve is critical in selecting the correct check valve.

Is it for a water sewage treatment plant? Is it handling corrosive materials? Is the discharge point below water? These are obvious conditions that can easily be overlooked when choosing a check valve.

A usual mistake that is made when selecting a check valve is choosing a valve that fits the system but cannot efficiently handle the flow conditions or the matter passing through the valve.

Water is one of the frequent matters that check valves handle and requires little special treatment. Most, if not all check valves, can handle water efficiently enough - depending on the flow rate.

But what if your check valve is handling corrosive chemicals? While a duck bill check valve is more than suitable to deal with water, can the rubber handle the corrosive chemicals, or will they destroy the check valve?

What if you need a check valve for a water sewage plant, a simple swing/flap check valve could do the task, but what will happen when sludge and debris clog up the metal hinge and stop it from being able to close?

Flow rate

Just as important as knowing what matter your check valve will be handling &#; it is important to know the rate of flow. Typically, this is recorded in terms of gallons per minute (GPM), gallons per hour (GPH), or litres per second (L/S).

If your application is producing a rate of flow greater than 8 feet per second flowing through the valve, there is an increased chance your valve will deteriorate quicker &#; regardless of whether you are using a rubber-seated valve or metal-seated valve.

Inlet pressure

Understanding your inlet pressure will help you select which style of check valve best suited for your needs. It can help you decide whether you need an in-line check valve, a slip-on check valve or a flanged style check valve.

Deciding on which one you need to use will depend on where the check valve will be located in your pumping system.

Back pressure

Back pressure is the differential pressure between the inlet and outlet pressures of your system. You need to know if your check valve can withstand the back pressure that it could be exposed to.

For example, say you have a valve installed at the end of a pipe, and it is pumping water in the Thames river. When the Thames water level rises, how deep with the valve be submerged? When the water rises above the valve, that is the point at which back pressure is created. Can your valve cope with that amount of back pressure?

Location

Is your valve discharge point above or below ground? Is it submerged? Is it in a hot sandy country, or on a cold desolate one?

Again, these appear to be obvious conditions that we could never forget &#; but properly understanding the location of the valve will have a massive impact on the check valve you need to select.

Sand can corrode a metal valve; the sun can deform a rubber duck bill check valve (always ensure you use the proper elastomer to prevent this) and ice can freeze a swing/flap check valve open.

The check valve symbol

Check valves provide one-way flow, and it is vital to install them in the correct alignment.

Below are two check valve symbols: the top one, flow is allowed from the bottom of the pipe but not the other way, the bottom, the valve will only allow flow when the pressure at the bottom is greater than the pressure at the top (taking into account the rating on the spring).

Image credit: Valve Products

Materials Matter

It could be hard to see the relationship between Formula One and check valves, but there is a connection: elastomers, or rubber. If you want to win Formula one you need to understand tyres, specifically the rubber they use.

Cal Hayes believes he is more in the business of designing new compatible rubbers for different types of chemicals in check valves than designing new check valves.

&#;There are so many different types of elastomers that can do so many different things. If you look at NASCAR, of if you look at F1, there are people that get paid millions of dollar per year to come up with a better tyre that lasts longer - it&#;s the same with the check valve.&#; 

The material that is used in the construction of a check valve can determine how long it will last for and what matters it can deal with. In the case of duck bill check valves, the elastomer can have a major impact on the quality, efficiency and life span of the valve.

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