Table 2.

FACTORS

for capacities at various pressure drops

 

Pressure   Pressure

 

drop, osi 

Factor 

drop, osi 

Factor

 1  0.707 

8  2.00

 2  1.00 

10  2.24

 2½   

1.12 

12 

2.45

 3 

1.22 

14  2.65

 4 

1.41 

16  2.83

 6 

1.73

(For capacities at other drops, use square root law or 
Table 2 below.)

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 

Regulator selection

To size a regulator, determine required cfh of gas and  pressure 
drop available at high fi re. 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

SPECIFICATIONS

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 fl ow remains proportional to air fl ow at all fi ring rates.

One regulator can be used for several burners controlled by the 
same air valve, but oft en it is better to have a separate regulator 
for each burner.

Dual-Fuel Burners. When a dual-fuel burners 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.

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 fi ring rates. (See Instructions 7218-2.)

A separate regulator for each mixer is preferred to avoid 
interference or interaction.

7219A

7219A Regulators

 are modifi ed 

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 fi eld.

7218 and 7219A Regulators

 accurately maintain a constant air/

gas ratio over a wide range of fi ring rates in both nozzle-mix 
and premix gas burner systems. Molded diaphragms ensure 
excellent tracking, repeatability, maximum fl ows, and superior 
 turndown.

Bulletin 7218/7219A

Page 2

Product Overview | Gas Ratio Regulators

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)