Class 4 (4th Engineer) MEKG 📅 Feb 2025

Exam Question

With regard to the carriage of crude oil and its associated products:

(a) Sketch an explosimeter suitable for testing pump rooms or tanks, and give a brief description of the operation of this explosimeter. (10)

(b) What periodic maintenance or checks are carried out on the P-V Breaker fitted on a tanker ship? (6)

Reference Answer

### (a) Explosimeter: Sketch and Operation (10 Marks)
An explosimeter, also known as a combustible gas indicator, is a critical piece of safety equipment used to measure the concentration of flammable gases or vapours in the air, expressed as a percentage of the Lower Explosive Limit (% LEL).
**Principle of Operation**
The device operates on the principle of a balanced Wheatstone bridge circuit. As stated in the provided reference, the bridge consists of four resistances. One of these resistances is a specially designed heated platinum filament, known as the detector or active filament, which is exposed to the sampled atmosphere. A second, identical filament, known as the compensator filament, is sealed in a chamber with fresh air and acts as a reference to compensate for ambient temperature and pressure changes.

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