- With reference to the classification survey of a vessel in dry dock:
(a) list EIGHT separate items of the hull and associated equipment that would be examined by the surveyor;(4)
(b) describe TWO ways in which the thickness of a steel hull may be determined.(6)
(a) Eight items of hull and associated equipment examined in dry dock (4 marks)
When a vessel is dry docked for classification surveys, the surveyor will typically examine the following:
- Shell plating – for corrosion, deformation, cracks, and wastage.
- Keel and bottom structure – condition of the centre girder and strakes.
- Sea chests and gratings – condition of strainers and welds.
- Overboard discharge valves and fittings – including opening and internal condition.
- Rudder and rudder stock – for cracks, wear, clearances, and pintle condition.
- Propeller and shaft – including securing devices, blades, and shaft alignment.
- Stern tube and bearings – checking wear down and lubrication system.
- Anchors and cables – including securing arrangements, wear and wastage.
(Any eight correct items score full marks; ½ mark each = 4 total.)
(b) Two methods of determining thickness of a steel hull (6 marks)
- Ultrasonic Thickness Measurement (UTM):
- A non-destructive testing method.
- An ultrasonic probe is placed on the steel surface; sound waves reflect from the back wall, and the time delay gives the thickness.
- Used extensively by classification societies as it can measure without removing large areas of coating.
- Accurate and safe for in-service checks.
- Mechanical Gauging (Drilling / Micrometer method):
- Involves drilling small test holes or using callipers/micrometers on exposed edges.
- Less common today because it is invasive and weakens the structure.
- Still used in areas where ultrasonic testing may not be practical.
(3 marks each for describing two correct methods.)