Class 4 (4th Engineer) MEP 📅 Dec 2025

Exam Question

(a) How is fuel (HFO) for a marine diesel engine (main engine) being delivered from a fuel oil storage tank up to the combustion chamber? Explain with a line diagram. (10)

(b) What is the significance of the following:

(i) Heating arrangement with temperature control. (3)

(ii) Prevention of air lock in the system. (3)

Reference Answer

### (a) HFO Delivery from Storage Tank to Combustion Chamber
The delivery of Heavy Fuel Oil (HFO) from the storage tank to the main engine's combustion chamber is a multi-stage process designed to store, transfer, purify, treat, and pressurize the fuel to meet the specific requirements for efficient combustion. The system can be broken down into the following key stages:
1. **Storage & Transfer Stage:**
* **Bunker/Storage Tanks:** HFO is stored in large double-bottom or dedicated side tanks after bunkering. These tanks are fitted with heating coils (usually steam or thermal oil) to maintain a pumping temperature (approx. 40-50°C) to reduce viscosity sufficiently for the transfer pumps.

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