ICI - Innovative Creations, Inc. AX - Manual (Page 16)

WATER CHARACTERISTICS
14
6 WATER CHARACTERISTICS
For steam generators with heating surface over 15 sqm, there are some regulations that require limit
values for water characteristics. These values are listed in the tables below.
However, limits should be adopted for all generators as stated by qualified companies that recommend the
type of treatment to be carried out basing on careful analysis of the available water. Many faults and
sometimes serious accidents are caused by the use of water with non-conforming features.
6.1 FEEDWATER - LIMIT VALUES (entering the boiler)
Tab.1
Characteristics
Unit of measurement Pressure ≤ 15 bar Pressure ≤ 25 bar
pH 7 $ 9,5 7 $ 9,5
Total hardness mg/l CaCo
3
10 5
Oxygen (1) mg/l O
2
0,1 0,05
Free Carbon Dioxide (1) mg/I CO
2
0,2 0.2
Iron mg/l Fe 0,1 0,1
Copper mg/l Cu 0,1 0.1
Oily substances mg/I 1 1
Aspect Clear, limpid, no persistent foam.
(1) These values are valid to have a thermo degassing device. Without degassing device, the temperature of the tank
water must be increased to at least 80 Celsius (see chapter 2.3. - Feeding) to reduce the content of dissolved
gasses (O
2
and CO
2
). Chemical deoxygenators must be used to remove completely the oxygen from the feed water
and reduce as much as possible CO
2
corrosive effects.
6.2 OPERATING WATER - LIMITING VALUES
Tab.2
Characteristics
Unit of measurement Pressure ≤ 15 bar Pressure ≤ 25 bar
pH 9 $ 11 9 $ 11
Total alkalinity mg/l CaCo
3
1000 750
Total hardness mg/l CaCo
3
10 5
Maximum conductivity (4) µS/cm 8000 7000
Silica mg/l SiO
2
150 100
STD (4) mg/l 3500 3000
Conditioner (2)
Aspect Clear, limpid, no persistent foam
(1) To maintain in the boiler the parameters of alkalinity and silica within the prescribed or recommended limits, the boiler
must be purged, if possible continuously. The values of the concentrations in the feedwater and in the boiler water are
linked to the continuous purge by the following relationship:
Cc
Ca
S 100 % =
Where
S% = Percentage of purge with respect to the feed water supplied to the boiler;
Ca
= Real concentration of a certain salt or ion in the feed water
Cc = Maximum allowed concentration in the boiler for the same salt.
(2) Correct management presupposes normally the use of conditioners, whose dosages and limits are in relation to the
nature and characteristics of the additives themselves.
(3) Determined on a filtered sample
(4) The two parameters have the same physical meaning but the values can be correlated only if the chemical
composition of the water is known.
6.3 FREQUENCY OF THE ANALYSES
The frequency of analysis is determined evidently as a function of the use of the boiler and of the quality of
the water used; it is advisable in any case to check the pH, the total hardness and the alkalinity of the feed
and boiler waters at least every two days. Once a month, especially under conditions of variable operation, it
is advisable to subject meaningful samples of the boiler and feed waters to complete analysis.
It is also advisable to inspect the return condensate for traces of any highly contaminating oily substances
(reduction of evaporation from the water surface in the boiler caused by a layer of oil).