Operating instructions
26
Appendix
Water quality requirements according to TRD701
For steam operation it is advisable to feed back as much condensate as
possible to the feed water tank.
Treat the condensate with top−up water, so that the following conditions are
maintained:
Boiler feed water requirements
General requirements Colourless, clear and free
from undissolved
substances
pH value at 25ºC >9
El. conductivity at 25ºC mS/cm Only guide values
applicable to boiler water
Total alkaline earths
(Ca
2+
+Mg
2+
)
mmol/litre <0.015
Oxygen (O
2
) mg/litre <0.1
Bound carbon dioxide (CO
2
) mg/litre <25
Free carbon dioxide (CO
2
) mg/litre n. n.
Oxidisability (MnVII³MnII)
as KMnO
4
mg/litre <10
Oil, grease mg/litre <3
Boiler water requirements
General requirements Colourless, clear and free
from undissolved
substances
pH value at 25ºC 8.5 to 10
Acid capacity up to pH8.2 (K
S8.2
) mmol/litre 1 to 12
El. conductivity at 25ºC mS/cm <5000
Phosphate (PO
4
) mg/litre 10 to 20
The addition of phosphate is recommended, but is not always essential.
Conversion:
1mol/m
3
=5.6ºdH; 1ºdH=0.1792mol/m
3
; 1mval/kg=2.8ºdH
5692729 GB5692729 GB