Class 4 (4th Engineer) SC&S 📅 May 2023

Exam Question

(a) State why cargo ships must have a collision bulkhead. (6)

(b) A double bottom tank is 1.2 m deep and has a sounding pipe extending 11 m above the tank top. The tank is filled with oil (rd 0.89) to the top of the sounding pipe. The double bottom floors are spaced 750 mm apart and are connected to the tank top by riveted angles, the rivets having a pitch of 7 diameters. If the maximum allowable stress in the rivets is 30 MN/m2, calculate the pressure in kN/m2 on the outer bottom and the diameter of the rivets. (10)

Reference Answer

### (a) Purpose of the Collision Bulkhead (6 Marks)
The collision bulkhead is a mandatory structural and safety feature on cargo ships, governed by international regulations such as SOLAS. Its primary purposes are:
1. **Limiting Floodable Length and Maintaining Watertight Integrity:** The collision bulkhead is the foremost transverse watertight bulkhead. In the event of a head-on collision, the bow structure is likely to be breached. The collision bulkhead is designed to contain the ensuing flooding to the forepeak tank, preventing progressive flooding into the forward cargo holds. This preserves the ship's buoyancy and stability, allowing time for damage control and preventing catastrophic loss.
2. **Structural Strength and Energy Absorption:** It is constructed with significantly higher scantlings (thicker plates and larger stiffeners) than other watertight bulkheads. As stated in the reference, it is heavily strengthened with vertical stiffeners and triangular panting stringers. This robust construction allows it to absorb a significant amount of collision energy and resist deformation, ensuring it remains watertight even after a severe impact.

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