Product Overview | Gas Ratio Regulators
Regulator selection To size a regulator, determine required cfh of gas and pressure drop available at high fire. Divide required cfh by Table 2 Factor for available pressure drop. Select smallest regulator with Table 1 (2 osi) capacity above this adjusted capacity. Never choose a regulator capacity based on more than 16 osi drop (even if more is available). 7218/7219A AIR/GAS RATIO REGULATORS 7219A Regulators are modified 7218 Regulators (7218 regulators have internal pressure sensing), with provision for remote downstream pressure sensing. The 7219A is used to sense downstream pressure at a point closer to burner or mixer. The downstream pressure sensing connection is made in the field. If burner nozzles are sealed-in and furnace pressure is other than atmospheric, regulator vent must be connected to the combustion chamber. Controlled gas pressure then will match furnace pressure; this is necessary to maintain the same air/gas ratio at all firing rates. (See Instructions 7218-2.) A separate regulator for each mixer is preferred to avoid interference or interaction. 7219A Nozzle-mix burners When used with nozzle-mix burners, the vent of a 7218 Regulator is cross-connected to the main air line downstream of the control valve. Regulator outlet pressure then equals air impulse pressure, and gas flow remains proportional to air flow at all firing rates. One regulator can be used for several burners controlled by the same air valve, but often it is better to have a separate regulator for each burner. Dual-Fuel Burners. When a dual-fuel burner's atomizing air is left on during gas operation, the 7218 Regulator can be set to com- pensate for the extra air over the controlled main air by adjust- ing the spring for up to 1 osi "leak" with no impulse pressure. Premix burners With its vent open to atmosphere, a 7218 Regulator can be used as an atmospheric regulator (zero governor) to supply gas to an aspirator mixer feeding premix burners. 7218 and 7219A Regulators accurately maintain a constant air/ gas ratio over a wide range of firing rates in both nozzle-mix and premix gas burner systems. Molded diaphragms ensure excellent tracking, repeatability, maximum flows, and superior turndown.
Table 1.
CAPACITIES scfh MAXIMUM WIDE OPEN with 2 osi drop through regulator and 2 psig inlet pressure Regulator gas gravity designation 0.6 1.5 7218-01 285 180 7218-0 540 341 7218-1 700 442 7218-2 1730 1090 7218-3 2800 1770 7218-4 4800 3030 7218-5 6900 4360 7218-6 9100 5750 7218-7 17600 11120
(For capacities at other drops, use square root law or Table 2 below.)
Table 2.
FACTORS for capacities at various pressure drops
Pressure drop, osi
Pressure drop, osi
Factor
Factor
1
0.707
8
2.00 2.24 2.45 2.65 2.83
2
1.00 1.12 1.22 1.41 1.73
10 12 14 16
2 ½
3 4 6
SPECIFICATIONS
Diaphragm Cover and Case: Unpainted Aluminum Body: Cast Iron
Seat: SST Shaft : SST Balancing Diaphragm: BUNA/Nylon (Standard) FKM/Polyester (7218-V) Gas Diaphragm: BUNA/Nylon (Standard) FKM/Nomex (7218-V) Maximum Inlet/Outlet Pressure: 2 psi Emergency Pressure: 5 psi (resulting in internal parts damage)
Maximum Ambient Temperature: 180°F (Standard) 350°F (7218-V)
Bulletin 7218/7219A Page 2
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