Double Flange Swing Check Valve
The Double Flange Swing Check Valve is an important valve in a large number of applications. We have dedicated our article today to explaining its importance, different types, and distinctive characteristics. In an effort to provide the information needed by those responsible for valves and their types at Water Care.
What is a Swing Check Valve?
A swing check valve with a disc that swings on a hinge or shaft. The disc swings out of the seat to allow forward flow and when the flow stops. The disc swings back on the seat to prevent reverse flow. The weight of the disc and return flow affect the closing characteristics of the valve.
Swing check valves with lever and weight or lever and spring
A lever and weight or lever and spring are often installed to achieve optimum performance. Swing check valves with lever and weight are suitable for installations with increased risk of water hammer at standard speeds. Swing check valves with lever and external spring are suitable for high pressure, insufficient back pressure and high flow speeds.
An important thing to note when installing a swing check valve is that it is not completely maintenance free as the disc needs to be cleaned from time to time. Moreover, a lever is often installed to enable visual check. Therefore, swing check valves are often installed where there are personnel.
Advantages of swing check valves
Easy maintenance
Swing check valves are easy to maintain. By loosening a few screws, the bonnet assembly including the hinge and disc can be removed from the body, and maintenance can be performed.
Unique disc design
The lightweight disc made of EPDM rubber with flange seal and steel gasket requires minimal force to open and close the valve.
Tightness of movement
The disc is mounted in a nylon sleeve, allowing it to move slightly horizontally and vertically to seal it completely tightly also in case of minor impurities in the seat. The seat is positioned at a 20 degree angle which provides tightness even at low back pressure.
Durability of materials
The hinge is made of acid-resistant steel and is firmly fixed around the shaft with screws to prevent play and thus ensure durability. In case of limited space, the hinge can be placed in the reverse position.
Prevention of water hammer
When installed with a lever and weight, the small-sized swing check valves provide the possibility of priming by manually moving the lever. The weight on the lever can be adjusted to achieve a soft closing against the seat as well as an optimal closing speed to prevent water hammer. A guard covering the lever and weight is available as an additional safety feature, as it eliminates the risk of injury. The guard is available with limit switches for remote monitoring.
You can find out more about the dangers of water hammer
Parts of a swing check valve
A swing check valve consists of a valve body, a seat, and a disc connected to the hinge. When a specified flow rate is encountered, the disc rotates to a horizontal position, allowing forward flow. It returns to the valve seat when the flow stops to prevent reverse flow.
Video showing the assembly of the parts of the sway check valve
Operating Principles
The disc of the swing check valve and the rocker are connected, allowing them to rotate at an angle around the pin shaft. When the input pressure to the disc exceeds the resistance pressure, fluid flows in the specified direction. As the valve opens, the disc disengages from its seat and rotates around the pin until it is fully open.
When the flow rate decreases, the valve disc rotates back to the closed position. This prevents fluid from flowing backward.
Types of Swing Check Valves
There are several main types of swing check valves. They can be broadly classified as top-hinged and tilt-disc valves. Each uses similar operating procedures with the main difference being the way the valve disc is deployed.
Top-hinged Swing Check Valve
The top-hinged swing check valve is the most common. In this form of swing check valve, the disc is mounted on the inside top of the valve, allowing the disc to open and close. When the disc opens, it is positioned on the edge of the fully formed turbulent flow profile.
Tilted Type Swing Check Valve
This swing check valve design allows the valve to open fully at lower flow rates and close faster than a standard swing valve. The dome-shaped disc with a central pivot point allows the valve to close faster than a top-hinged valve. This rapid closing helps reduce water hammer during backflow conditions. The valve disc remains in the flow path after opening.
Swing Check Valve Installation Challenges
Installing check valves requires careful attention to the direction of flow. Improper installation of a swing check valve can result in catastrophic failure.
Because of the pressure requirements for proper operation, the most common swing check valve installation is in a horizontal position. The horizontal position provides a simpler installation because it eliminates gravity as an additional factor.
Vertical Swing Check Valve Installation
Technicians may install a swing check valve in the vertical position, although the flow should be directed upward. Engineers should generally avoid installing in a vertical position if possible due to the effects of gravity.
Occasionally, process conditions may dictate that fluids flow downward. In such situations, a swing check valve should not be used. Gravity will keep the valve open continuously and unintended bypass will occur.
Swing check valves typically require little maintenance. Visual inspections should be routinely performed by a technician responsible for leaks, rust, and debris.
Applications in which a swing check valve is used
Swing check valves can regulate and transfer water, steam, oil, nitric acid, acetic acid, solid oxidizing media, and other corrosive media. They are typically installed in pipelines for petroleum, chemical, and water-based process flows. They are suitable for clean fluids, not media laden with solid particles or condensed with viscosity.
Swing check valves are a standard solution in a variety of industries. Power plants, gas transmission, and oil refineries frequently use swing check valves. Swing check valves help prevent improper gas flow that could lead to dangerous leaks or fires. These valves are widely used in gas pipelines – whether cleaning, distributing or compressing natural gas.
Because swing check valves work well with large, predictable flows, they are often used in wastewater treatment and water pumping.
In general, swing check valves provide good service for clean process media.
For the transfer of heavy crude oil, distillates, and viscous and heterogeneous materials, a spring check valve provides better service than swing check valves. In addition, intermittent flow can create a potential water hammer in a swing check valve. As a result, engineers typically prefer spring check valves for these applications.
