Boiler water test

Because of the inherent difficulties involved in any attempt at automatic control of feedwater treatment, it is necessary that the exact condition of the boiler water be known from day to day, in order that necessary treatment can be applied for the correction of any unsatisfactory conditions which may exist.
This knowledge is obtained by means of a few simple tests, which are conducted periodically on all vessels, samples being taken from each boiler, reserve feed tank, feed tank and from the discharge lines from condensate pumps in operation.

The following boiler water test shall be made:
1 Boiler water pH
2 Boiler water conductivity
3 Boiler water sulphite or hydrazine excess
4 Excess of phosphate
5 Condensate pH (every 24 hours)
6 Hot weil temperature test
7 Hardness of feedwater
8 Excess of oxygen in condensate

Depending on the make of treatment compound used, some of these tests can be easily made with the same equipment.

Table 1 - Recommended boiler water characteristics
Boiler pressure bar	pH	Alkalinity to Penolphtalein ppm CaCQ3	Chlorides max ppm CI	Phosphate ppm P04	Dissolved solids ppm	Sulphite or Hydrazine excess ppm Na2S04 N2H4
0-15	10.5-11.5	50-300	300	30-70	1500	50-100	0.1-0.3
15-30	10.5-11.5	150-300	150	30-70	1000	50-100	0.1-0.3

1 To convert from Chioride as ppm CaCO3 to ppmNaCl, multiply by 1.17.
2 To convert from Chloride as ppm CaCO3 to ppm Cl, muitiply by 0.7 1.
3 To convert from Alkalinity as ppm CaCO3 to ppm NaOH, muitiply by 0.8.
4 To convert from Phosphate as ppm P04 to ppm P2O5, muitiply by 0.75.

Table II - Recommended feed water characteristics
Boiler pressure bar	Chioride max ppm Cl	pH	Dissolved O2 max mi/litre
0-15	5	8.5-9.0	0,04
15-30	5	8.5-9.0	0,04

Residual hardness in F.W.T. max 0. 1°dH.

1 To convert from Chioride as ppm CaCO3 to ppm NaCI, multiply by 1.17.
2 To convert from Chioride as ppm CaCO3 to ppm Cl, multiply by 0.7 1.
3 To convert from Oxygen from ml/litre O2 to ppm (weight for weight) O2, multiply by 1.5.

HARDNESS
A water with higher content of Caicium or Magnesium salts feels "harder" when washing with soap than water with lower content of same. Hardness is normaily measured in °dH (German degree of hardness). 1 °dH correspond to 10 ppm of CaO or equivalent 7.8 ppm MgO.

Due to make of treatment used, there are several kinds of test kits available, each one corresponding to the test log sheets in order to get the treatment company's opinion.

DRAWING SAMPLES for a BOILER WATER TEST

Always remember that the chemical analysis can never be more accurate than the sample. The sample must be truly representative of the water in the boiler.
The sampling connection to the boiler shall be shortest possible and well cooled. Sampling lines should be flushed thoroughly by allowing the water to run trough for at last half a minute. All equipment to be kept scrupulously clean and rinsed four times with sample water before the sample is measured out.

© 2010 Lars Josefsson Steamesteem in a computerized world Marine steam boilers today and yesterday.
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