11 API6A GATE VALVES PAGE 65 MODEL M/HM GATE VALVE FEATURES FULL BORE THROUGH-CONDUIT The through-conduit design of the model “M” and “HM” gives a full round bore. Destructive turbulence is eliminated. SEALS WITHOUT LUBRICATION Model “M” and “HM” gate valves do not require lubrication for positive sealing in normal operation. Lubrication can be employed as an emergency measure to help effect a temporary seal in the event the gate or seals have become damaged by foreign matter in the valve. Two safety-capped grease fittings are provided so that the entire valve body can be filled with grease. REPACKABLE UNDER PRESSURE APV plastic stem packing can be added to the packing box while the valve is under pressure. SEAT INSERTS GIVE DOUBLE SEAL Seat inserts of PTFE (tetrafluoroethylene resin) give an initial PTFE-to- metal seal in addition to the metal-to-metal seal which is obtained when the gate assembly is fully expanded. All metal to metal stellite faced seating also available. TRIM CHART Application *H2S **CO2 Fluid Class General Service (A) Non Corrosive 30 FF Sour Service mod. to highly corrosive and chlorides (High H2S high CO2) >0.05 >30 HH * Hydrogen sulphide partial pressure (in psi a) as defined by NACE MR - 01 - 75 ** Partial pressure of carbon dioxide (in psi a). Formula: Partial pressure (PP) = well pressure (psi) X percent of constituent in total well fluid X 1/100 Example: CO2 PP= 3000 psi X 4% x 1/100 = 120 psi* Material must be chosen to resist CO2 weight loss corrosion. API Spec 6A Gate Valves