A duck bill check valve is a unique, one-piece elastomeric backflow prevention device which is shaped like a duck bill. They are a safe and environmentally friendly alternative to conventional flap gate check valves and provide reliable backflow prevention at low pressure differentials, preventing backflow of water or other fluids into a system.
The duck bill design is a very common valve type and is used in a wide range of applications. Chemicals, pulp and paper, food processing, power generation, water and wastewater treatment, industrial, marine and mining, pumps, pipelines and HVAC are some of the industries which use duck bill check valve to control flow and prevent backflow.
Unlike flap gate check valves, the critical sealing function is an integral part of the one-piece elastomer component – it is not separate from the valve as with a conventional diaphragm valve. This makes the Duckbill design a robust, low maintenance solution that can also operate in a variety of media including slurries, sludge or effluent.
It can be designed to operate in a few millimeters of water to several hundred kPa (psi) depending on valve size, geometry and compound characteristics. It is a simple, cost-effective solution to controlling backflow in sewage treatment plants and can be operated with no electrical power or manual operating assistance.
They can be manufactured in a number of different elastomer materials including medical and food grade silicone, liquid silicone rubber (LSR), Buna-N and Nitrile Rubber, EPDM, Neoprene/CR and fluorosilicone rubber to meet specific requirements and working conditions. They can also be supplied with an inner or outer undercut to ensure tight fixation and absolute sealing after coupling is made.
Installation and Operation: The duckbill check valve is operated by a pressure differential. When the pressure in upstream is higher than the pressure in the pipe, the rubber check valve will open to allow the flow and close when the back pressure reaches a certain level. This can be a very useful tool to prevent backflow in sewage pipes and other systems such as stormwater and effluent discharges, municipal flooding, wet wells, and breast pumps and manually operated respirators.
When it comes to installing the rubber duck bill check valve, it is important to lubricate the outside so that it can slide easily over the pipe end. This will protect it during installation and stop any damage during assembly.
Inline duckbill check valves are usually installed at the end of a pipe and can be secured on with flanges or slip on style connections. The flanged inline version should not be installed while mating the two pipe flanges together as this could rotate the valve before the fasteners are tightened.
Duckbill valves are generally specified for a service life of 30 years and if constructed from quality materials can be expected to remain fully serviceable for up to 50 years. This compares favourably with metal or plastic mechanical check valves which typically require replacement after a decade of service.