Duck bill check valve is a type of one way control valve which is used in water, gas, and liquid applications. The special duckbill shape of the check valve prevents backflow and allows forward flow. It can also be called rubber check valve, flexible back pressure valve, or slow closing valve.
Commonly seen in almost every fluid flow and pumping application, duck bill check valve are a key part of many industries including chemicals, pulp and paper, food processing, water and wastewater treatment, marine and mining, pumps, pipelines, power generation and HVAC. Designed to operate via a pressure differential, they automatically open when the upstream pressure exceeds a predetermined level and close when backflow is prevented.
In order to achieve optimal performance, check valves need to be based on the right material and engineering design. This is especially important in industries where there are likely to be a lot of high pressures and temperatures.
This is why a proper in-depth evaluation should be carried out on any project to ensure the correct check valve is specified. This should consider the line size, dimensions and connection type, maximum leakage rate, maximum pressure drop and any special requirements.
Generally speaking, a standard metal or plastic mechanical check valve may only need replacing after about 5-7 years whereas a high quality rubber product may be fully serviceable for up to 50 years. Using an appropriate selection of the best components and a proven design ensures that check valves remain in service for the lifetime of the installation, saving plant operators money.
Another critical consideration is the material that the valve is made from, the majority of duckbill check valves are based on food grade silicone or rubber. These materials have a high degree of resistance to abrasion, slurries and chemical substances.
The sealing area of a duckbill check valve is often 50% larger than that of a ball and spring valve. This provides a tighter seal, but does require a slightly higher cracking pressure to open the valve.
If a valve has debris on the seat or in the seal it can cause leaking or damage to the seal itself. This can also impact on the ability to seat a diaphragm.
This can have a severe impact on the sealing function of a check valve, allowing reverse flow in the event that the seat or the sealing element becomes damaged. As a result, it is vital that the check valve is properly installed and maintained to avoid the risk of water hammer or other damage.
It is also important to ensure that the check valve is positioned correctly and that the die cutting tool is of sufficient sharpness so that it can be cut symmetrically and without any flashing or burrs that could potentially affect its sealing performance. It should also be checked frequently and placed in an area that is not subjected to abrasions or scratches during use or storage.