C.I.B. UNIGAS - M039175CD
20
ADJUSTING AIR AND GAS
Combustion head gas pressure curves depending on the flow rate
Curves are referred to pressure = 0mbar in the combustion head!
The curves referred to the gas pressure in the combustion head, depending on the gas flow rate, are referred to the burner properly
adjusted (percentage of residual O
2
in the flues as shown in the “Recommended combustion values” table and CO in the standard
limits). During this stage, the combustion head, the gas butterfly valve and the actuator are at the maximum opening. Refer to Fig. 28,
showing the correct way to measure the gas pressure, considering the values of pressure in combustion chamber, surveyed by means
of the pressure gauge or taken from the boiler’s Technical specifications.
Fig. 28
Key
1
Generator
2
Pressure outlet on the combustion chamber
3
Gas pressure outlet on the butterfly valve
4
Differential pressure gauge
Measuring the gas pressure in the combustion head
In order to measure the pressure in the combustion head, insert the pressure gauge probes: one into the combustion chamber’s pres-
sure outlet (Fig. 28-2) to get the pressure in the combustion chamber and the other one into the butterfly valve’s pressure outlet of the
burner (Fig. 28-3). On the basis of the measured differential pressure, it is possible to get the maximum flow rate: in the pressure - rate
curves (showed on the next paragraph), it is easy to find out the burner’s output in Stm
3
/h (quoted on the x axis) from the pressure
measured in the combustion head (quoted on the y axis). The data obtained must be considered when adjusting the gas flow rate.
NOTE: THE PRESSURE-RATE CURVES ARE GIVEN AS INFORMATION ONLY; FOR A PROPER SETTING OF THE GAS RATE,
PLEASE REFER TO THE GAS METER READING.
1
2
4
3
