Check valves and non-return valves are fittings for preventing backflow in pipelines. Due to their simple design, short overall lengths are possible. Check valves offer an optimum solution for large nominal widths, e.g. where intermediate flange connections are required or desired.
In general, a difference is made between DISCO check valves, DISCO flap check valves, double flap check valves, intermediate flange check valves and threaded ends check valves. Most check valves are mounted between two flanges. However, there are also check valves that can be mounted via female threads. Common sealing materials are NBR (90 °C), EPDM (120 °C), VITON (150 - 200 °C) and PTFE (200 °C). Higher temperatures are possible by using other seals such as graphite or FFKM.
The function of a Gestra DISCO check valve depends on the pressure and flow of the medium, also called opening pressure. In case of absence or drop of flow or pressure, the internal spring closes the cap or flap to prevent backflow of the medium. This function of a check valve prevents the downstream pipe from draining itself. For example, the Gestra DISCO check valves RK 86 for PN 40 and RK 41 for PN 6 to PN 16 belong to these valves. These check valves have a common nominal diameter range from DN 15 to DN 200. Gestra DISCO check valves RK 29 A, heavy-duty design, are made of high-quality stainless steel 1.4571 and can be used for high pressures up to 160 bar and temperatures up to 550 °C.
Gestra DISCO flap check valves have a similar function to Gestra DISCO check valves. The difference lies in the closing system. Unlike check valves, flap check valves have a round flap which is fixed on one side and opens in one direction at flow or pressure. Common sizes here are the nominal sizes DN 50 to DN 300. An economical and widely used flap check valve is, for example, the type 901-1 flap check valve.
Gestra double flap check valves are suitable for a more energy efficient pump application due to their significantly lower Zeta value. Due to the low resistance when opening the two flaps, pumps are able to operate with lower power consumption. These check valves are available in nominal sizes DN 50 to DN 500, depending on the design. Pressure stages are possible from 6 bar up to 160 bar. The housing materials used include grey cast iron, carbon steel or high-quality stainless steel.
An intermediate flange check valve has a disc inside the body, which is also actuated by a spring. The design / length of the intermediate flange check valve is in accordance with DIN EN 558-1 and may be mounted between flanges of a pipeline. DIN and ANSI flanges are used as flange types. These types of valves require considerably more installation space than, for example, check valves. The major advantage of these check valves, however, is their flow rate. The flow is not slowed down by a flap or constriction. Nominal sizes from DN 15 to DN 350 and pressure ratings from PN 16 to PN 40. The body materials available are cast steel 1.0619+N, forged steel 1.0460 and high-quality stainless steel 1.4408.
Threaded check valves can be fitted into pipelines from 1/2" to 2" with their female threads. The functional principle is the same as for the Gestra DISCO check valve. Brass (CW 614 N) is used as housing material and is therefore suitable for up to 16 bar.
We will be happy to help you select the right check valves or non-return valves for your process. Whether DISCO check valves, DISCO flap check valves, double flap check valves, intermediate flange check valves and threaded check valves, flanges, threaded connections and those in DIN or ANSI. We provide you with individual and tailor-made service to ensure that you get exactly the right fitting for your application. Contact us for a suitable offer or if you need further information about our check valves.