Check valves are a common feature in many water and wastewater applications. They prevent backflow of contaminated water from entering clean system supply lines or the other way around. They are available in several different designs and can be made from a wide variety of materials including metals, polymers and rubber.
Choosing the right type of rubber check valve is crucial for system reliability. This is because the correct type of valve will ensure that the flow is always in the direction it should be, even when the system is subjected to extreme weather conditions.
The valve should be selected based on the pressure drop, line size and rated capacity of the system. It should also be inspected and maintained regularly to avoid issues that can arise with worn elastomers, seat seals and leaks or other problems caused by contaminants.
A check valve must also be designed to resist water hammer, the occurrence of which is common in systems that pump pulsating or reverse flow fluids such as treated effluent. For this reason, some check valves are fitted with hydraulic dampers which act as a cushion on the valve disc as it comes into its seated position. This dissipates the kinetic energy of the flow and allows the valve to close slowly.
Tilting Disc Check Valves
The tilting disc design of these check valves is well suited for pumping systems that have low flow rates and are exposed to pulsating or reverse flow flows. This is because the internal shafts of the valve are within the flow stream, thus reducing the likelihood of contamination or blockage from forming on the inside of the valve.
These valves also offer enhanced resistance to water hammer, thanks to the damping effect of their hydraulic dampers. The dampers allow the valve to close slowly and this helps to reduce the onset of water hammer by preventing the slam action which is often associated with these valves.
Slanted Seat Check Valves
The slanted seat check valve features a double eccentric shaft position and an increased seating angle to reduce the risk of water hammer. This ensures that the check valve closes quickly over the first 85% of its angular travel before meeting the damper, then slows down and cushions the valve door until it returns to its fully closed position, sealing the valve.
They are suitable for pumping systems with a low flow rate, and they are especially recommended in wastewater applications that can be subject to pulsating or reverse flow flows. They also have a reduced clogging potential due to their shorter valve stroke and they are also highly resistant to backflow.
Swing Check Valves
The swing check valve is a basic, inexpensive type of check valve that does not require any external power to operate. These are a great choice for most applications as they have a full bore opening that ensures efficient operation of the check valve.
They are also a great choice for systems that need to handle liquids at very high or low temperatures as these are made from specialized elastomers that can withstand fluids ranging from -65 deg F to 400 deg F. These elastomers are also resistant to corrosion, making them ideal for use in environments where the piping system will be subjected to abrasive materials such as raw sewage or sludge.