Reflux 819/FO H


Reflux 819/FO H is a pilot-operated gas pressure regulator designed and manufactured by Pietro Fiorentini. This device is suitable for 100% hydrogen applications.

It is mainly used for high-pressure transmission systems, power plants and for medium pressure gas distribution networks.

According to the European Standard EN 334, it is classified as Fail Open.

Click here to see the product page in the NG version / NG-H2 blending (up to 20%) version.


  • Accuracy class AC: up to 2.5
  • Nominal sizes DN: 1″, 2″, 3″, 4″, 6″, 8″, 10″, 12″
  • Lock-up pressure class SG: up to 5
  • Design pressure: up to 102 bar
  • Design temperature: from -20 °C to +60 °C
  • Connections: class 150, 300, 600 RF or RTJ according to ASME B16.5 and PN 16
  • Minimum differential pressure: 2 bar
  • Range of downstream pressure Wd: from 1 to 74 bar
  • Inlet pressure range bpu: from 3 to 102 bar


The configuration options can be compounded and aggregated differently. Please refer to the technical manual for all available combinations.
Slam shut



Click to download the file
Scroll to top
Please turn to portrait for a better experience

Please turn to portrait
for a better experience