Basics of Swing Check Valve Operation

Check valves are used in fluid systems to ensure flow in one direction and prevent backflow. They protect crucial fluid system components, including other valves, pumps and piping. In addition to ensuring the unidirectional flow of fluids, these valves maintain the integrity and efficiency of pipelines. Swing check valves are available in various sizes, designs and materials to suit specific applications. 

The following guide discusses the swing check valve’s working principles, key features, advantages, disadvantages, applications and installation information to help you select the best options for your unique applications. 

What Is A Swing Check Valve?

The swing check valve is a mechanical valve that utilizes a swinging disc to allow forward flow and block reverse flow. The components of a swing check valve include:

• Valve body 
• Seat 
• Swinging disk
• Arm
• Pivot pin

The disk is hinged at the top of the valve body by the arm and the pivot pin is attached through the arm to allow the disk to hang in place. The disc swings freely on a pivot, opening when the fluid flows in the desired direction and closing when it flows in reverse. 

The disk has a 360-degree range and only opens at a specific minimum pressure known as the cracking pressure, which is applied under the seak and disk. When fluid flow stops and the cracking pressure reduces, gravity shuts the disk closed against the seat. Later, when the fluid attempts to reverse, the pressure forces the valve to close completely against the seat, preventing backflow. The arm may be weighted, or a spring can be installed over the arm to assist in closing the valve.

Types of Swing Check Valves

Swing check valves are categorized according to the operating procedure. Therefore, there are two main swing check valve categories:

• Top-hinged: This is the most common type of swing check valve with a hinge on the inner top of the valve body. The position of the disk allows this valve to swing freely and ensures it is in alignment.
• Tilting disk: The disk on this type of swing check valve is dome-shaped and rests at an angle in the closed position. This orientation allows it to open fully at lower flow pressures and close faster to minimize the effects of reverse flow water hammer. 

Advantages of Swing Check Valves

Installing swing check valves has several advantages for fluid systems, which include:

• Handling various fluids, including gas, chemicals and oil, making them suitable for numerous industrial applications.
• Having a tight shutoff due to the flexible disk and seat connection that accommodates minor misalignment. 
• Minimizing pressure as a result of the clear waterway and straight-through design.
• Being installed in either the horizontal or vertical positions.
• Featuring a simple design and construction make them simple and easy to maintain. 

Disadvantages of Swing Check Valves

Swing check valves may not be suitable for particular systems. They cannot eliminate water hammer occurrence because the discs have a significant distance to cover between the fully open and closed positions, and they’re not a good option where there’s pulsating or reversed fluid. Swing check valves are also slower than lift and spring check valves. 

Installation Information For Swing Check Valves

The most crucial factors to consider when installing swing check valves are the flow direction, pressure and nature of the fluid. If these factors are not considered, they may lead to catastrophic failure. Horizontal check valve installation is the most commonly followed because it meets pressure requirements and allows fluid to flow along the horizontal axis. 

However, some applications still require vertical installation, which means the effect of gravity on the system must be considered. Vertically installing a swing check valve increases the risk of water hammering because gravity may forcefully slam the valve against the seat, disrupting the flow and causing resistance inside the pipes. Additionally, vertical swing check valves are only effective with an upward-flowing fluid system. 

The installation procedure varies from project to project based on the factors mentioned above and the type of connection. However, the following steps act as guidelines for swing check valve installation regardless of the connection:

1. Pre-installation checks: This involves analyzing the system to ensure the valve size and specifications align with the system’s needs. 
2. Site preparation: It involves cleaning the pipes, ensuring all the flanges are aligned, and tightening the bolts. 
3. Prepare the valve: Start by removing foreign materials from the valve and verifying its functionality by pushing the disk away from the seat. 
4. Attach the valve: Install the swing check valve with the flow arrow pointing to the direction of fluid flow. Then screw it into place and secure all the pieces. 
5. Test the valve: Allow fluid flow to test whether the swing check valve functions as intended. 

After installation, the swing check valves require minimal maintenance through routine visual inspections to check for wear, rust, leaks and debris on the valve body and disc. In case of damage, these parts should be replaced promptly. Occasional cleaning of the valve disc and body also helps to minimize debris and buildup that may interfere with optimal performance. 

Applications of a Swing Check Valve 

Swing check valves are used in numerous industries. They can be made from various materials, including stainless steel, carbon steel, ductile iron, cast steel brass and bronze. PVC and ABS swing check valves are also cost-effective for applications with temperatures under 100 degrees Celsius (212 degrees Fahrenheit). 

They’re generally suitable for applications in systems that facilitate the flow of clean and non-solid state medium, ranging from petroleum, water, acid and chemicals. 

Primarily, swing check valves are used for water supply, wastewater pumping and slurry transport because they are less likely to clog or block. More specifically, swing check valves are employed in the following industries:

• Water supply systems:  Brass or stainless steel swing valves prevent municipal water supply systems contamination by stopping the backflow of dirty water into the system.
• Natural gas transmission: Gas pipelines and residential and commercial gas meters ensure safety by directing the gas flow to prevent hazardous leaks and fires. They’re essential for natural gas cleaning, compression and distribution. 
• Oil refinery: Fuel pipelines utilize swing check valves to minimize water hammers, ensuring efficient operation in these high-pressure and high-volume systems. 

Check Out MSEC’s Wide Selection of Check Valves

MSEC Inc. is a leading process equipment distributor and service provider partnered with some of the top manufacturers and valve distributors. Our inventory includes the Duo-Chek^® high-performance non-slam check valves in different sizes, configurations and pressure classes. These are smaller, lighter and more efficient for demanding applications than conventional swing check valves. 

With our Valve™ AID services, MEC can help customers gather valuable data on their critical valves with around-the-clock access to stay efficient during planned and unplanned downtime.

Contact us today for more information about Duo-Chek^® valves and other industrial swing check valves at MSEC Inc.

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