Class 4 (4th Engineer) MEKG 📅 Jan 2023

Exam Question

With respect to water used in a oil fired auxiliary tank type boiler for cargo oil heating at sea:

(a) Explain the problem associated with use of water from shore sources and state how these problems are dealt with; (10)

(b) What are the indication of leaking steam coil for heating cargo oil, and what action you will take. (6)

Reference Answer

### (a) Problems Associated with Shore Water and Their Treatment (10 Marks)
Shore-based water supplies are typically untreated for boiler use and contain various impurities that can cause significant operational problems, leading to reduced efficiency, damage, and potential failure of the boiler system. These problems and their corresponding treatments are detailed below.
#### 1. Acidity (Low pH)
* **Problem**: Shore water can be acidic (pH < 7) due to dissolved atmospheric gases like Carbon Dioxide (CO₂), which forms carbonic acid (H₂CO₃). A low pH (below 8.5) in boiler water causes direct acidic corrosion of the boiler's steel plates and tubes. The reaction is essentially the dissolution of the metal: $$ Fe + 2H^+ \rightarrow Fe^{2+} + H_2 $$.

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