Unigas K990A, Installation Manual

Page: 11 / 112

PART I: SPECIFICATIONS
11
Checking the proper gas train size
To check the proper gas train size, it is necessary to the available
gas pressure value upstream the burner’s gas valve. Then subtract
the backpressure. The result is called
pgas. Draw a vertical line
matching the furnace input value (600kW, in the example), quoted
on the x-axis, as far as intercepitng the network pressure curve,
according to the installed gas train (DN65, in the example). From the
interception point, draw an horizontal line as far as matching, on the
y-axis, the value of pressure necessary to get the requested furnace
input. This value must be lower or equal to the
pgas value, calcula-
ted before.
The values in the diagrams refer to natural gas with a calorific value of 8125 kcal/Stm
3
(15°C, 1013 mbar) and a density of
0.714 kg/Stm
3
.
The values in the diagrams refer to GPL with a calorific value of 22300 kcal/Stm
3
(15°C, 1013 mbar) and a density of 2.14 kg/
Stm
3
. When the calorific value and the density change, the pressure values should be adjusted accordingly.
GAS PRESSURE
mbar
K750A
Stm
3
/h
K890A
Stm
3
/h
GAS P
R
E
SSURE
mbar
K990A
Stm
3
/h
ATTENTION: the gas rate value is quoted on the x-axis, the related network pressure is quoted on the y-axis
(pressure value in the combustion chamber is not included). To know the minimum pressure at the gas train inlet,
necessary to get the requested gas rate, add the pressure value in the combustion chamber to the value read on
the y-axis.
0
5
10
15
20
25
100 200 300 400 500 600 700 800 900
Potenza / Output (kW)
Minima pressione gas in
rete / Minimum inlet gas
pressure (mbar)
Rp 2" (50)
DN65
Power kW
mini
mum g
a
s pr
ess
ure
in
the
ne
twor
k
mbar
DN65
Where:
Natural gas pressure shown in diagram
Real gas pressure
Natural gas flow rate shown in diagram
Real gas flow rate
Natural gas density shown in diagram
Real gas density