Pietro Fiorentini REFLUX 819/FO + DB/819 DN150 Spare Parts Kit – Technical Overview

The REFLUX 819/FO is a pilot-operated, dynamically balanced gas pressure regulator classified as Fail Open according to EN 334. Where the standard 819 is Fail Close, the /FO version opens upon main diaphragm rupture or loss of pilot feeding pressure — a characteristic demanded in gas turbine fuel supply, power plants and high-pressure transmission lines where an unintended shut-off is more critical than a pressure rise. It handles previously filtered, non-corrosive natural gas and is Hydrogen Ready for NG-H2 blending.

Design pressure reaches 102 bar, with an inlet range of 3 to 102 bar, a downstream setting range of 1 to 74 bar, and a minimum operating differential of 2 bar when used alone. Accuracy class is up to 2.5 and lock-up class up to 5. Nominal sizes span DN 25 to DN 300; the DN150 (6 in.) version connects to ASME Class 150, 300 or 600 RF/RTJ flanges or PN 16. The body is ASTM A 352 LCC cast steel for Class 300/600 and A 216 WCB for Class 150 and PN 16, with A 350 LF2 heads and plug, AISI 416 stem, vulcanised nitrile seat, rubberised canvas diaphragm and nitrile O-rings; leakage is bubble-tight, better than ANSI/FCI 70-3 Class VIII.

The +DB suffix denotes the integrated DB/819 silencer, which attenuates lamination noise by up to 30 dBA and reduces Cg and KG coefficients by about 5%; it can be retrofitted without altering the piping. Regulation is driven by 200-series pilots (204/A/FO, 205/A/FO, 207/A/FO) with an R14/A/FO pre-regulator and integral filter, and the modular top-entry body accepts PM/819 monitor and SB/82 or HB/97 slam-shut retrofits. The kit supplies the main diaphragm, seat and pad assembly, O-ring and gasket sets, and pilot and pre-regulator soft parts. Kits are configuration-specific and must be ordered against the exact model and body serial number.