In water supply systems, check valves are often used to prevent backflow of contaminated liquid into clean, uncontaminated fluid. This can occur in industrial, marine and mining operations, pumps, pipelines, power generation and HVAC systems.
When selecting the correct check valve, many different factors should be considered. These include valve rating, line size, installation and connection type, maximum leakage rate, pressure drop, and any special requirements.
The choice of the right type, size and specification will ensure the best possible performance from the check valve. This will help to ensure that the valve operates correctly and that any issues associated with operation are addressed quickly and easily.
Rubber check valves can be a cost effective solution to the problem of backflow prevention in pumped systems. They are available in a wide range of sizes and can be manufactured from various materials.
They are easy to install and can be incorporated into the upstream side of the pump to prevent backflow. The check valve can be fitted with an upstream backflow device, an electrical position switch, or a visual indicator.
A rubber check valve offers a high level of safety and is therefore an important addition to any pumped system. They are designed to operate at a low differential pressure, preventing reverse flow and allowing fluid to circulate in the upstream direction.
Typically, the valve will open only slightly when it is required to do so. This is because the degree of opening will be dependent on the differential pressure. However, when the differential pressure is very low, the valve may be fully closed. This can lead to increased resistance, pressure drop and potentially the formation of flutter.
The speed at which the valve closes is also important. In pumped systems, if the valve closes very fast this can increase the likelihood of surges occurring.
For this reason, check valves should be selected with a slower closing time. This is particularly important where the upstream pump will be operating at a high frequency of start-up and closure.
These valves can also be fitted with hydraulic dampers to reduce the risk of slam, especially when they are installed in a pumping station where frequent starts and stops are required. Hydraulic dampers dissipate the kinetic energy that is generated by the closure of the valve, ensuring that the disc does not return to its closed position until it has met the damper again.
Rubber duckbill check valves are a highly reliable alternative to metal swing or flap check valves, as they can not rust or seize. Consequently, they can often remain in service for up to 35 years or more.
They can be fabricated from a variety of elastomers, including chloroprene rubber, chewing gum, and EPDM rubber. These elastomers are resistant to the toughest thermal conditions.
The specialized elastomers used in Proco’s check valves offer users peace of mind when handling fluids at temperatures from -65 F to 400 F. These elastomers are not only resistant to the harshest of fluids, but they are also low maintenance, making them a great option when designing or operating a system that can withstand these extremes.