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Sizing of the FGR pipe (FGR burners only)
ATTENTION! Performance curve is obtained in a plant designed according to the following guidelines, size the
FGR pipe as per the example below.
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Keys:
1 Stainless steel FGR pipe, insulated
2 Burner
3 Boiler
4 Bellow unit (a counter-flange supplied loose is to be
The temperature probe for flue gas temperature compensation must be installed on the chimney.
The internal diameter of the FGR conduit must be dimensioned considering a maximum speed of 10 m / s. Assume a volumetric flow
rate of recirculatig fluegases for the dimensioning equal to 20% of the comburent air flow.
ATTENTION! Pipe elbows increase pressure losses, so limit their use as much as possible.
Example:
Let's say 4.816 kW is the maximum burner output:
required combustion air flow will then be 5.800 Stm
Flue gas temperature:
Ambient temperature:
FGR flow for dimensioning:
FGR flow corrected for flue gas temperature:
FGR pipe section:
So in this example, pipe internal diameter must be larger than 245 mm to ensure proper FGR flow.
* FGR = Flue gas recirculation system
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/h = 1,61 Stm
/s in standard conditions (15 °C; 1.013 mbar).
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150 °C or 150 + 273,15 = 423,15 K
15 °C or 15 + 273,15 = 288,15 K
1,61 x 20% = 0,322 Stm3 / s
0,322 x 423,15 / 288,15 = 0,473 m3 / s @ (t = 150 °C)
0,473 m3/s / 10 m/s = 0,0473 m2
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welded to the FGR duct)
5 FGR butterfly valve
6 Siphon and condensate drainage
7 Stack
PART II: INSTALLATION
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