DieselShip's Online Content Library

Q1. With reference to Crude Oil Carriers

a) Explain Each of the following.

i) Segregated Ballast Tanks (3)

ii) Clean Ballast Tanks (2)

iii) Protective Locations (3)

b) i) Explain the Crude oil Washing System for cargo tank cleaning. (4)

ii) State the advantages of Crude Oil Washing. (4)

Q5. With respect to Induced Vibrations in a ships hull:

A. State FOUR sources of excitation that may induce vibration into the main hull girder;

B. Suggest methods for reducing the vibration levels induced by EACH of the exciting forces in A.

Q2. A. Explain how to distinguish between list and loll and describe how to return the ship to the upright in each case.

B. Explain the term angle of loll and state what, if any dangers it poses to a vessel.

Q4. List the hazards that arise with the carriage of liquefied gas in bulk. Describe, with the aid of a sketch, the details of construction of a prismatic cargo tank within a gas carrier designed to carry liquefied gas. (16)

Q1. With reference to Ship stability:
a. With the help of a neat sketch explain the relevant features of a G-Z curve.

b. What are the effects of the below mentioned conditions on the G-Z curve:

i. Increased freeboard,         ii. Increased beam, and        iii. Increased GM.

Q6. A. what is ‘form stability’ & ‘weight stability’. (6)

b) The end bulkhead of the wing tank of an oil tanker has the following widths at 3m intervals commencing at the deck: 6.0, 6.0, 5.3, 3.6 and 0.6 m. Calculate the load on the bulkhead and the position of the centre of pressure if the tank is full of oil relative density   0.8. (10)

Q7. A. Explain how trim occurs and explain the effect of trim on tank soundings. (6)

b) A vessel of 8000 tonne displacement has 75 tonnes of cargo on the deck. It is lifted by a derrick whose head is 10.5m above the centre of gravity of the cargo and placed in the lower hold 9m below the deck and 14m forward of its original position. Calculate the shift in the vessel's centre of gravity from its original position when the cargo is: (10)

(i) just clear of the deck

(ii) at the derrick head

(iii) in its final position.

Q8. Explain why the bilging of empty double-bottom tanks that are wholly below the waterline leads to an increase in GM. (6)

b. A ship of 22000 tonne displacement is 160 m long and MCTI cm 280tonne m, waterplane area 3060 m2 centre of buoyancy 1 m aft of midships and centre of flotation 4 m aft of midships. It floats in water of 1.007 t/ m3 at draughts of 8.15 m forward and 8.75 m aft.

Calculate the new draughts if the vessel moves into sea water of 1.026 t/ m2

Q9. A. Define hull efficiency and propeller efficiency. (6)

b. When a propeller of 4.8 m pitch turns at 110 rpm, the apparent slip is found to be —S % and the real slip is 1.5 S %. If the wake speed is 25 % of the ship speed, calculate the ship speed, apparent slip and the real slip. (10)

Q10. A. Why is it important in a tender ship to keep the double bottom tanks pressed up? (6)

b) A double bottom tank is 23m long. The half breadths of the top of the tank are 5.5, 4.6, 4.3, 3.7 and 3.0m respectively. When the ship displaces 5350 tonnes, the loss in metacentric height due to free surface is 0.2m. Calculate the density of the liquid in the tank. (10)