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Farris Safety-Relief Valves ATTACHMENT 1 2600 Series Farris "O" Ring Seat Pressure Seal for Conventional or BalanSeal Eliminates leakage and costly product loss as well as costly down and maintenance on troublesome applications such as: Operation too close to set pressure. Light, hard to hold fluids. Minute foreign particles. Vibratory applications. Corrosive fluids. Nozzle icing conditions. Discharge piping strains Sj DISC DISC HOLDER FLAT HD MACH SCREW W RING RETAINER WRING SEAT SEAL NOZZLE BLOW DOWN RING jack screw plug L THRU T ORIFICE FLAT HD MACH SCREW DISC DISC HOLDER 'Wring seat seal BLOW DOWN RING NOZZLE D THRU K ORIFICE Recognizing the need for a resilient seat in a safetyrelief valve for extreme tightness, Farris Engineering Corporation first made available an "O" Ring seat seal in early 1950. Although limited in pressure, the "0" Ring design received phenomenal acceptance since it made possible complete tightness at pressures much closer to the valve set pressure than was ever possible with the standard metal to metal seats. The present "0" Ring Seat Pressure Seal design is an improvement which allows the use of the "0" Ring Seat Seal to higher pressures and, equally important, the spring load is solely carried by the metal to metal por tion of the seat with the "0" Ring becoming a pressure seal within its recessed chamber and the outer edge of the nozzle, assuring the ultimate in tightness. The "0" Ring Seat Pressure Seal is available in our 2600 Series line of flanged safety-relief valves -- con ventional or BalanSeal construction - for pressures up to a maximum of 1500 PSIG, Referring to the selection tables on pages 22 thru 49, substitute a "C" for the fourth digit "A" in the type number for the conventional valve and a "D" for the fourth digit "B" in the type number for the BalanSeal construction when an "0" Ring Seat Seal is required-. 26FA10 becomes 26FC10 (Conventional) 26FB10 becomes 26FD10 (BalanSeal) The pressure limit of the Conventional or BalanSeal valves covered in the selection tables is the same for the 0 Ring design in all type numbers and orifices with the 150 lb., 300 lb. and 600 lb. inlet flanges. On the "0" Ring design in all type numbers and orifices 1500 lbs. is the limit for the "0" Ring design, not the conventional valve limit shown in the selection tables & charts. Refer to "0" Ring Material Selection Chart on page 21 for Temperature and Pressure ratings of the various "0" Ring materials available. 20 UCC 102959 Steel / Flanged Why an 'O" Ring Seal Pressure Seal? In the normal operation of a safety-relief valve the disc must lift off the nozzle very slightly to "simmer" allowing pressure buildup within the secondary orifice (huddling chamber), causing the valve to "pop" fully open. Simmering occurs many 11hies in the process industries where, as a result of process changes, minor upsets, etc., operating pressure fluctuates higher than normal, causing safety-relief valves to "simmer," but not fully open. This will cause serious misalignment in the valve and after the pressure drops the valve will very often continue to leak below the normal operating pressure, While this can be overcome by actually popping the valve, this is not always possible. The use of the Farris "0" Ring Seat Pressure Seal will always overcome this difficulty. As occurs very frequently operating pressures are too close to valve set pressures. As the operating pressure approaches the set pressure, seat loading is diminished reducing the force which affects tightness. With the use of the Farris "0" Ring Seat Pressure Seal, tightness can be obtained at relatively higher operating pressures than with metal to metal or other soft seat safety-relief valves. On light, hard to hold fluids such as hydrogen, helium, tight hydrocarbon, anhydrous ammonia, etc., metal to metal seats are often penetrated, causing leakage problems. The Farris "O" Ring Seat Pressure Seal will overcome leakage on these hard to hold fluids. On applications where heavy vibrations occur - i.e. barges, tankers, pumps, compressors, etc., leakage of metal to metal seats develop as a result for as the set pressure is approached the spring force is minimized and the vibration tends to reduce the effect of spring loading, causing leakage. The Farris "0" Ring Seat Pressure Seal will maintain tightness as the spring force is not a factor in the tightness of the "0" Ring design. Where occasional minute foreign particles are carried in the flowing medium, metal to metal seats are usually marred or scratched when the valve is blowing. This creates troublesome leakage problems after the valve closes. The Farris "0" ring seat pressure seal will absorb without damage the impact of these particles and will eliminate particle deformation of the mating metal seating surface on the nozzle as the valve closes, thus reducing the incidence of leakage m valves on most process units. When necessary, simply replace the "0" ring to maintain tightness. Due to corrosion, metal to metal seats may eventually leak. With the proper selection of the Farris "0" Ring Seat Pressure Seal tightness can more satisfactorily be maintained. Nozzle Icing conditions result from the refrigerant effect of the flowing media when a valve relieves. Ice actually forms on the seat, thus causing leakage. The Farris "0" Ring Seat Pressure Seal again overcomes this troublesome type of leakage. "O' Ring Material Selection Chart Ii,- '<V- rf.'-?. "-ISO SET; PRESSURE PSIG] Standard tightnaaa of "0" rlni valvan No bubbla* at 95% of aet pratiure. to both conventional and ballowi valvea. At aet pressures 60 psig and below, leakage teat ahall be made at 3 PSI6 below aet preiture Bmrvloe reoommendallona for "O' Ring material* BUNA N Sir Anhydraot Ammonia Butana Butana Butylana Cardan Dlsifda Dinitl Oil Etnyl Ether Ethylina Glycol Freon* #11 6 1! fad Oil Carolina Helium Hydrogen Hydrogen Sulphide Karatana Luba Oil Natural Gai Nltroten Oxygon Prepana Stoddard Solvent VITON Acetylene Tttrahramlde Alt Amyl Alcahnl Arachlar #IMA Bantlna Butadiene Butana Butana Butylana CarPan Disulphide Carbon Tetrachloride Chlorine (Dry Cat) Cyclohexane Dowthemt "A" VITON (con't.) Ethyl Chloride Ethyltnc Ethylene Glycol Ethyl Alcohol Gaieilne Hexane Hydrochloric Add Hydrogen Sulphide liebutyl Alcohol JP-4 Fuel TP-5 Fuel Kerottne Lube Oils Mercaptan Methylene Oichlorlde Natural Cat Naphtha Nitric Add Nitroian Oronltc SZOO 1 ISIS Propxne Prcpylcnt Propyl Alcohol Stoddard Solvent Sulphur Dioxide Sulphuric Add Toluene Trichloroethylene Turpentine Vinegar Water Syltnc SILICONE Air Helium Nitrogen Oxygen Them recommendations are a guide only and tcrvice life of the "0" Ring Is, ol course, dependent on tem perature, concentrations, catalysts that may be added and other conditions which ere beyond our control UCC 102960 21