PART I: SPECIFICATIONS
12
Gas pressure burner head vs natural gas flow rate
Curves are referred to pressure = 0 mbar in the combustion chamber!
Gas pressure
in
combu
stio
n head
(mba
r)
H455A MG..
Stm
3
/h
H630A MG..
Stm
3
/h
Gas pressure
in
co
mbustion he
ad (mbar)
H685A MG..
Stm
3
/h
Combustion head gas pressure curves
Combustion head gas pressure depends on gas flow and combustion chamber backpressure. When backpressure is subtracted, i
depends only on gas flow, provided combustion is properly adjusted, flue gases residual O2 percentage complies with “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 , showing the correct way to measure the gas pressure, considering the values o
pressure in combustion chamber, surveyed by means of the pressure gauge or taken from the boiler’s Technical specifications.
.
Measuring 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
pressure outlet to get the pressure in the combustion chamber and the other one into the butterfly valve’s pressure outlet of the burner.
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.
1
2
4
3
Note: the figure is indicative only.
Key
1 Generator
2 Pressure outlet on the combustion chamber
3 Gas pressure outlet on the butterfly valve
4 Differential pressure gauge
Fig. 5
ATTENTION: THE BURNED GAS RATE MUST BE
READ AT THE GAS FLOW METER. WHEN IT IS NOT
POSSIBLE, THE USER CAN REFERS TO THE
PRESSURE-RATE CURVES AS GENERAL
INFORMATION ONLY.
