The check valve or one-way valve is designed to prevent backflow and ultimately protect the pump and compressor. They are available in a variety of styles and sizes, from 1/8 inch to the larger size that may be required. Check valves are widely used in many industries and various applications, from municipal water supply to mining and natural gas. The three most common types are swing check valves, double-door check valves, and silent spring-assisted axial flow check valves.

This is probably the most common check valve used today and is a full port design, which means that the valve flap is out of flow when it is fully opened. This type of check valve is ideal for applications with high solids percentages and fewer on/off cycles. Due to the travel distance of the disc, the swing check valve closes slowly. This will cause the valve flap to be closed by the last countercurrent, which will generate a huge pressure spike and cause water hammer. Water hammer is the pressure fluctuation that occurs when the fluid in motion is forced to stop or change direction suddenly, thereby generating pressure waves in the pipeline. This pressure wave can cause major problems ranging from noise and vibration to pipe collapse.

This valve is similar to a swing check valve and is slightly better in closing because the coil spring can help the two cantilever doors to close faster. Facts have proved that this is not the best choice when encountering water hammer, although their performance will be better than swing check valves. Generally, this type of valve is considered a ready-made commercial valve, with almost no customizable ones.

These full flow valves usually consist of a center-oriented stem disc assembly and a compression spring. This means that the disk stays in the flow stream. The media flows around it and does not require manual or automatic assistance to operate. When the pump is running, the valve is open. When the pump is turned off, due to the compression spring force acting on the valve flap, the valve closes slightly before the fluid flow is reversed, which almost eliminates water hammer.

Most of the requirements for check valves only consider the size of the pipeline and the pressure level, because in the case of a pipeline design that is too large or too small due to lack of or incorrect information, the medium pressure and flow rate may change dramatically. This is not always the best method when deciding which type of valve to use in the system. Other factors that need to be considered are working pressure, flow, specific gravity and temperature of the medium. It is strongly recommended to analyze the system design. It is necessary to understand the cause and root cause of valve failure. The most common failure is due to excessive wear of the internal parts of the valve. Springs, discs and stems wear prematurely because they are not stable during operation. When the disc is unstable due to insufficient flow to keep it in the fully open position, chattering may occur.

It is not difficult to determine the size of the center pilot valve. In addition to the required pipe size, pressure level and valve type (flange type, wafer type, etc.), the user also needs the actual working pressure, flow rate, medium type, temperature and specific gravity of the medium. This may be as simple as building a valve with a lighter spring, allowing the valve to fully open. In order for the valve to reach the fully open position, a lift limiter may be required to reduce the travel distance of the disc. When the valve is 100% open, it will remain stable in the flow and reduce premature wear and failure by eliminating the effects of chatter. It is very important to remember that these valves are designed based on actual flow values ​​rather than pipeline sizes. A valve of the right size will be in the fully open or fully closed position.

The benefits of using a silent check valve of appropriate size and position:

The initial "sticker impact" of large and small valves can be scary, so please consider the following questions:

Depending on the impact of income, wages and the cost of replacing the valve, the cost of replacing the valve can be very high. The price of off-the-shelf valves may be attractive, but what is the true cost of ownership? If the cost of a size valve is five times the original, but the service life is five times the original, considering the maintenance cost and production loss, consider how these factors affect the financial balance.

Although some applications require double-door and swing check valves to function properly and are required, these and other off-the-shelf valves are not the only solution. In any application that uses check valves, installing custom valves can improve performance and extend the life of the piping system. This translates into more value and overall, long-term cost savings.

Bruce Ellis is an internal sales consultant for Triangle Fluid Controls Ltd. His contact information is bruce@trianglefluid.com or 613-968-1100. For more information, please visit trianglefluid.com.