Butterfly non-return valves

What is a butterfly non-return valve?

Of the non-return valves installed between the discs, the models equipped with a butterfly disc are the simplest in operation. The closing disc is pivoted on one side and the valve is installed with the pivot facing upward. Gravity keeps the disc in the closed position, but it opens when the flow coming from the correct direction reaches the valve. Reverse flow does not open the check valve.

Selection of a butterfly non-return valve

We assist in the selection and sizing of a check valve that meets the requirements of the application.

The butterfly non-return valve is a typical check valve for water systems. The seating retention of GESTRA CB butterfly non-return valves has been reinforced with a separate closing spring, making them extremely robust. In larger sizes than DN 100, the flow resistance is clearly lower than with the GESTRA RK model. However, if low flow resistance is a procurement criterion, the flow resistance in the butterfly non-return valve remains significantly higher than in the double-disc check valve.

Damped Water Hammers

Backflowing liquid can cause a high closing force/pressure that the valve components cannot withstand. It is quite typical that from sizes DN 500 upward, a closing damping is used. Damping can also be used in smaller sizes.

Damping can be done hydraulically, where damping pistons directly slow the disc movement. Another method is using a gear (mechanical/hydraulic). In this case, the disc’s lever is connected to the lever of a hydraulic cylinder. Both have a gear that dampens the closing force.

With gear-equipped damping, a higher duration of closing pressure can be achieved than with purely hydraulically damped valves. It is important to determine the closing pressure in a failure situation. For example, when the pump stops, the pressure of the back-flowing water should be determined before sending out a request for quotation. Damped check valves are typically of the tilting disc (tilting disc check valve) or double-disc type.