21
For steam operation, return as much condensate as
possible to the feedwater tank.
Treat the condensate with top-up water, so that the fol-
lowing conditions are maintained:
Boiler feedwater requirements
General requirements
Colourless, clear and free of undissolved
substances
pH value at 25 °C
> 9
Conductivity at 25 °C
μ
S/cm
Only standard values applicable to boiler
water
Total alkaline earths (Ca
2+
+ Mg
2+
)
mmol/l
< 0.01
Oxygen (O
2
)
mg/l
< 0.1
Bound carbon dioxide (CO
2
)
mg/l
< 25
Free carbon dioxide (CO
2
)
mg/l
n.n.
Oxidability (Mn VII
⇒
Mn II) as KMnO
4
mg/l
< 10
Oil, grease
mg/l
< 3
Boiler water requirements
General requirements
Colourless, clear and free of undissolved
substances
pH value at 25 °C
8.5 to 10
Acid capacity up to pH 8.2 (K
S8.2
)
mmol/l
1 to 12
Conductivity at 25 °C
μ
S/cm
< 5000
Phosphate (PO
4
)
mg/l
10 to 20
The addition of phosphate is recommended, but is not always essential.
Conversion:
1 mol/m
3
= 5.6 °dH
1 °dH = 0.1792 mol/m
3
1 mval/kg = 2.8 °dH
Water quality
Water quality according to EN 12953-10
5692729
Appendix
