The purpose of boiler water treatment on ship

The most common problem with the boiler water system is corrosion. If the boiler feed water were not treated properly it will lead to corrosion.
The deterioration of a metal or alloy or its properties due to reaction with its environment is known as corrosion.
There will be a dangerous effect on the boiler If boiler water is not treated properly.

Based on the boiler water test results boiler water chemicals are added from time to time basis.

Here below table summarises the purpose of boiler water treatment:

Boiler water-Summary of chemical treatment

Purpose of treatment Treating chemical Type of boiler
To prevent scale Sodium phosphates All up to 84 bar w.p
To give alkalinity Sodium hdroxide,Sodium carbonate All up to 84 bar w.p, All up to 60 bar w.p
To condition sludge poly electrolytes or starch or sodium aluminates All up to 84 bar w.p, All up to 84 bar w.p,All up to 84 bar w.p
To remove traces of oxygen Sodium sulphate or hydrozine All up to 42 bar w.p, from 31.5 bar to 84 bar
To reduce risk of caustic embrittlement Sodium sulphite or sodium nitrate All up to 31.5 bar w.p, All up to 31.5 bar w.p
To reduce risk of carry over of foam Anti foams All up to 84 bar w.p
To neutralize CO2 Neutralising Amines ----------
To protect steam condensate lines filming amines ---------

Summarizes the boiler water tests, the purpose of the tests, results and actions, to be taken

Dissolved oxygen sulphate reserve

Purpose of test:

To test oxygen and chemical content

Test Result Action to be taken
Low and persisting Check the source of air leakage and rectify
Low but steady Increase of dosage of sodium sulphate
High No action

Phosphate Reserve

Purpose of test:

To test the presence of phosphate compounds

Test Result Action to be taken
Low Add Phosphates
High No action,
Important to maintain the phosphate levels to a minimum of 10ppm

Feed water hardness

Purpose of test:

To test the presence of carbonate compounds

Test Result Action to be taken
High Add Phosphates
Low Good,
No action required

Alkalinity

Purpose of test:

To measure acidity or alkalinity of the boiler water

Test Result Action to be taken
High Partial blow down or add sodium sulphite
Low Add NAOH to get desired result

Dissolved solids

Purpose of test:

To test the presence of ferrous ions and metal contents

Test Result Action to be taken
High Partial blow down and take fresh feed
Low Good, No action required

Chlorides

Purpose of test:

To test the presence of chloride compounds

Test Result Action to be taken
High and increase Trace sources of leak and rectify. blow down completely and take fresh feed
Steady but high Can be reduced by phosphate treatment and partial blow down
Low Good, No action required

Hydrazin

Purpose of test:

To test the hydrazine reserve

Action to be taken
Trace sources of leak and rectify. blow down completely and take fresh feed

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