Non-return valves

The task of non-return valves or backflow valves is to prevent the flow of the media in a certain flowing direction.
In the case of gases, their relatively small density as compared to liquids must be considered, which means that if the non-return valve is to be absolutely tight, attention must be paid to valve leakproofness.

Some manufacturers of metal seated non-return valves, such as Gestra, lap the sealing surface of their Disco-type non-return valves, which results in a density class corresponding to standard DIN 3230, Part 3 test specification BO1 (leakproofness test by air).
Tightness can be improved through the use of a soft seal, for example, an O-ring, in which case Gestra’s non-return valves can be regarded as belonging to tightness class A according to test specification BO1.

In the case of certain gaseous media, such as oxygen, for example, valve cleanness is important. Under oxygen-rich conditions, the risk of self-ignition exists in valves containing dirt particles if the process temperature should rise due to an increase in the flow rate.

Our product range covers all non-return valve models used in the industry. They can be divided into four groups.

The most conventional models are flanged or welded non-return valves up to PN 40, which are manufactured by ARI in our case, whereas welded high-pressure non-return valves up to PN 500 are manufactured by STRACK.

Flanged valves in our product range are manufactured by GESTRA. According to the nominal size, pressure rating and, above all, pressure loss, a model suitable for a certain process can be selected from our product range of Disco, flap non-return valves or dual-butterfly non-return valves.

It is also important that non-return valves are dimensioned and not selected based on the pipe size only.

Our product range also covers ASME non-return valves up to the pressure rating of 2500#, as well as non-return valves that can be locked in the open position.

In addition, the seat valve range of ARI Armaturen also includes a closable non-return valve.

Additional information on non-return valves is available in the Gestra general brochure.

Also, listen to our concise webinar presentation Choice and dimensioning of non-return valves.