Check Valves: Types, selection, and uses

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Swing check valves are simple devices that allow liquids or gases to flow one way. With a disc that swings on a hinge, allowing fluid to flow in and closing to prevent backflow, swing check valves are available in a variety of sizes with a variety of features to fit specific application types. The swing design can also be modified to suit certain situations.

Check valves that swing are commonly used in water and wastewater applications. They are cost-effective, use a variety of materials, and have a variety of designs for specific functions. In order to determine whether swing check valves are suitable for an application, this article discusses their applications, advantages, and disadvantages. Check valves: A comprehensive guide to check valves!

 

How Does a Swing Check Valve Work?

The

swing check valve

employs an internal rocker swing structure. All the valve's moving components are situated within the valve body and do not breach the body except for the sealing gasket and the sealing ring in the central flange, eliminating any potential leakage points. This design ensures a complete absence of valve leaks. The connection between the swing arm and the valve disk in the swing check valve utilizes a spherical connection structure. This arrangement allows the valve disk a certain degree of freedom within a 360-degree range, offering appropriate positional compensation.

As the fluid travels downstream, it rushes through the valve disk, causing the valve to open. The pressure at which the valve opens is known as the cracking pressure. If the fluid pressure drops below the cracking pressure, the valve automatically closes. When the fluid reverses direction, the valve disk is pressed against the valve seat by the fluid's force, effectively sealing the valve.

 

Types of Swing Check Valves

 

The two major types of swing check valves are categorized as top-hinged and tilting disc. They all deploy similar operating procedures, with the main difference being the manner in which the valve disc is deployed.

 

Top-hinged

 

 

The top-hinged swing check valve represents the prevailing and widely used design. In this type of swing check valve, the disc is hinged at the upper interior, enabling it to swing freely, opening and closing the valve as needed. When the disc swings open, it aligns with the boundary of the well-established turbulent flow profile.

 

Tilting disc

 

 

 

In contrast to a standard swing check valve, this swing check valve fully opens at lower flow rates and closes quicker than a standard check valve. This valve's dome-shaped disc and central pivot point allow it to close faster than a top-hinged valve. As a result of the quicker closing, reverse flow water hammer is reduced. After opening, the disc remains in the flow path.

 

Materials of Swing Check Valves

 

A swing check valve's components are made of the same materials that are used in many types of valves. The following materials are commonly used to construct swing check valves. Swing check valves are suitable for a wide range of pressure, temperature, and environmental applications.

 

Valve Body and Disc Materials:

 

1. Stainless Steel: Stainless steel valves offer strength and excellent resistance to corrosion and rust. They are a suitable choice for systems operating under normal pressures and temperatures, except for saltwater applications.
2. Ductile Iron: Ductile iron valves are known for their strength and resistance to pressure, making them a cost-effective option. However, they are susceptible to rust.
3. Brass: Brass valves are well-suited for applications with high temperatures and pressures. They are more economical than stainless steel valves.
4. Bronze: Bronze valves provide a cost-effective solution, offering strength and resistance to rust.
5. Monel: Monel valves are ideal for underwater applications and exhibit resistance to acidic conditions.
6. Inconel: Inconel valves are designed for extreme environments, offering resistance to both corrosion and high temperatures.
7. PVC (Polyvinyl Chloride): PVC valves are the most budget-friendly choice for applications where media temperatures remain below 60°C.
8. ABS (Acrylonitrile Butadiene Styrene): ABS valves are stronger than PVC and suitable for use in applications with temperatures up to 100°C.

 

Valve Seat Materials:

 

FKM: FKM seats age gracefully and are suitable for use in petroleum systems. They exhibit high abrasion resistance and have a working temperature range from -20°C to 230°C.

 

1. Teflon (PTFE): Teflon seats possess a low friction coefficient and are resistant to various chemicals. Their working temperature range extends from -260°C to 260°C.
2. NBR (Nitrile Butadiene Rubber): NBR seats are known for their resistance to oil and high abrasion resistance. They operate within a temperature range from -35°C to 120°C.
3. EPDM (Ethylene Propylene Diene Monomer): EPDM seats are best suited for water systems but should not be used in oil and gas applications. They function within a temperature range from -40°C to 150°C.
4. Metal: Metal seats, while more prone to leakage than rubber seats, can endure higher working temperatures and harsh conditions.

 

Applications of Swing Check Valves

 

Swing check valves offer a straightforward and versatile solution in various industries, including:

 

• Power Plants: In power generation, particularly in cooling towers, silent check valves, also known as spring check valves, are employed. These valves incorporate a spring to facilitate controlled valve closure. They are a common choice for fluid control applications in power plants, ensuring efficient operation. Notably, spring check valves are best suited for high-pressure conditions due to the added spring resistance during valve opening.
• Natural Gas Transmission: Swing check valves play a pivotal role in preventing the improper flow of gas, which could lead to hazardous leaks or fires. These valves find widespread application in gas pipelines, residential and commercial gas meters, gas compressors, and other gas-related systems, enhancing safety and control.
• Oil and Gas Refineries: Refineries often utilize specialized non-slam check valves designed to counter water hammer, the pressure wave created by a slamming valve. These valves aid in mitigating the impact of water hammer in the complex processes of oil and gas refineries.
• Horizontal Water Lines: Swing check valves prove to be ideal for managing high-volume, consistent-pressure fluid systems, making them the valve of choice in wastewater treatment and water pumping facilities. They help ensure smooth and efficient flow in horizontal water lines.
• Custom Solutions: Recognizing that each system has its unique challenges, custom modifications or entirely bespoke valve designs are sometimes required to address specific flow issues. Customized solutions may involve adjustments like altering the valve angle or reducing the disc's weight. Valve manufacturers can assist in determining the best custom solution to meet specific application requirements.

 

Swing Check Valve Installation

 

Swing check valves can be installed either horizontally or vertically, with the valve facing upward. However, when a swing check valve is installed on a vertical pipe where the flow goes against gravity, there is a risk that the valve disc may forcefully close against the seat when the flow stops, potentially causing water hammer. Conversely, if the flow is in a downward direction, such as in applications like boiler supply lines and mining, where space is limited, the swing check valve remains in an open position, essentially negating its function. Consequently, swing check valves are not the preferred choice for vertical pipe installations and are predominantly positioned horizontally.

The specific installation procedure may vary based on the type of connection, be it threaded, flanged, or welded. However, regardless of the connection type, the following steps are recommended for the installation of any swing check valve.

 

• Check for the absence of any foreign materials within the valve, such as packing materials.
• Verify the valve's functionality by gently pushing the disc away from the seat.
• Ensure correct valve positioning by aligning it according to the arrow indicating the flow direction.

 

For threaded connections:

 

When installing a swing check valve with threaded connections, begin by hand-screwing the valve ends into the piping. Ensure you start the threading carefully to prevent cross-threading, which can damage the threading.

Hand-tighten the valve into both ends of the piping and then use a wrench to give it an additional half turn. Avoid over-tightening, as it can harm the valve.

 

For flanged connections:

 

Consider the use of a dismantling joint on one end of the valve for ease of installation and future maintenance.

Ensure that the pipe flanges are parallel before bolting the valve flanges to the pipes. When tightening the bolts, follow a crosswise pattern to prevent undue stress on the valve.

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For welded connections:

 

Before welding, prepare the piping by cutting it square, ensuring it's perpendicular to the valve surface, and deburr both the inside and outside of the pipe ends. Finish by polishing the pipe ends with sandpaper and cleaning them with a solvent.

Utilize solder flux to further clean the pipe ends and inside the valve end connections.

Properly support the pipes to prevent stress on the valve during and after welding.

During the soldering process, direct the torch away from the valve body to shield valve components. Maintain a continuous flame movement to avoid overheating and causing damage.

Testing:

After the valve installation, pass the media through it to verify that it flows in the intended direction. Additionally, inspect the system for any signs of leakage to ensure proper valve operation.

 

Maintenance of Swing Check Valve

 

Swing check valves are known for their low maintenance requirements and extended lifespan. However, to ensure their continued functionality and prevent potential issues like leaks due to foreign particles getting lodged between the disc and seat, it's essential to follow these maintenance guidelines:

 

1.Maintain Cleanliness:

 

Regularly wipe off dust and dirt from the swing check valve to prevent the accumulation of foreign particles.

 

2.Routine Inspections:

 

Periodically inspect the valve to identify any potential issues:

 

• Check for leakage, and if significant leakage is detected, consider replacing the valve.
• Examine the valve for signs of corrosion, rust, and wear.
• Monitor the pressure and temperature of the fluid passing through the valve, ensuring it falls within the valve's specified limits.

 

3.Replacement and Overhaul:

 

If replacement is necessary, conduct a thorough overhaul of the removed valve.

Clean all valve components meticulously with an appropriate cleaning agent, such as hydraulic fluid or the medium used.

Inspect the components for any debris, scratches, corrosion, wear, or rough surfaces. Smooth out any imperfections through lapping or other suitable methods.

Reassemble the valve components after the necessary maintenance.

 

4.Proper Storage:

 

Store the valve in a dry, well-ventilated room to prevent moisture, exposure to rain, and the onset of rust.

 

5.Secure Opening and Closing Parts:

 

During storage or transportation, ensure that the opening and closing parts are securely positioned in the closing device:

 

• Fix the valve disc in the open position.
• Use foam plates to block the inner ports at both ends of the valve's diameter.
• Seal the ports tightly with caps to prevent dust and rust, maintaining clean channels and flat end surfaces.

 

6.Regular Checks:

 

For long-term storage, conduct regular checks every three months to assess the condition of the valve:

 

• Evaluate the state of protection against dirt and rust on the two channels, the sealing surface, and welding joints.
• If dirt and rust are present, clean the affected areas and apply rust-resistant oil for protection.

 

Due to their lack of an external power source, swing check valves are widely used for a wide variety of horizontal piping applications. Athenavalve is professional

swing check valve manufacturer

.We offer swing check valves in carbon steel, stainless steel, alloy steel, special alloys like Monel, Inconel, Hastelloy, and others. If you need assistance identifying an optimal valve solution, please contact us today.

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