Class 4 (4th Engineer) MEP 📅 Oct 2023

Exam Question

With reference to the treatment of water for auxiliary boilers:

(a) State the major risks from: (6)

(i) Hard water

(ii) Soft water

(b) Describe FIVE types of boiler water tests that are carried out on board stating the reason for EACH (5)

Reference Answer

### (a) Major Risks from Untreated Water
#### (i) Risks from Hard Water
Hard water contains dissolved mineral salts, primarily calcium (Ca²⁺) and magnesium (Mg²⁺) bicarbonates, sulphates, and chlorides. Its use in a boiler without proper treatment presents the following major risks:
1. **Scale Formation:** When hard water is heated, the solubility of hardness salts decreases, causing them to precipitate out of the solution and form hard, insulating scale on heat transfer surfaces (boiler tubes, furnace walls).

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