Water Quality; Water Quality For Steam Boiler Systems; Steam Boilers - Viessmann VITOMAX 200-HS Operating And Service Instructions

Water quality

Water quality for steam boiler systems

Steam boilers

In its natural state, most untreated water
will be unsuitable as boiler feedwater.
The type of boiler feedwater treatment
should be matched to the raw water
quality. As its quality may change, regu-
lar checks are required.
The water feed pipe downstream of the
boiler feedwater treatment should be
equipped with a suitable water meter to
record the volume of top-up water added
to the return condensate; this also pro-
vides an indirect check on the steam
draw-off volume.
It is always advisable to return as much
condensate as possible to the feedwater
tank. The condensate may also have to
be treated so it conforms to the require-
ments of the boiler feedwater (according
to table 1).
These requirements, plus those of the
boiler water (according to table 2), mean
that – according to the raw water condi-
tion and the top-up water volume – at the
very least a suitable chemical or thermal
water treatment system must be instal-
led, and there should be a facility for add-
ing oxygen binders (possibly alkalines
and phosphates) into the feedwater tank
supply line.
Table 1: Saline boiler feedwater requirements
Permiss. operating
pressure
General requirements
pH value at 25 °C
Conductivity at 25 °C
22
bar
Colourless, clear and free of undissolved sub-
µS/cm Only standard values applicable to boiler
The requirements are monitored by
measurements made by suitable, pref-
erably uncomplicated devices (either
every 24 h or 72 h or in line with national
requirements, subject to operating
mode). These test values, the volume of
top-up water, the chemical consumption
and the required maintenance should be
entered into a boiler log to enable the
operating conditions to be checked at
any time.
> 0.5 < 20
stances
> 9
water
> 20
> 9