## Purpose

Ship’s stability calculations not only rely on the ship’s geometry but also on the knowledge of where the ship’s centre of gravity (G) is positioned. Although the distance of G from the keel can be ascertained for various conditions that the ship may be in, it is essential that it is accurately known for one specified ship condition.
To this end, the need to carry out an inclining experiment becomes necessary and from this, two facts should become known
1. the displacement; and
2. the position of G in a known ship’s condition.
The inclining test is carried out to find the lightship KG at the lightship displacement. It is sometimes known as a ‘controlled list experiment’. By conducting the experiment by means of a series of weight shifts, the GM of the vessel can be ascertained under the test condition. This GM value can then be compared with the ship’s KM to obtain the vessel’s KG value: KM – GM = KG

The environment of the dry dock is ideal for performing such a stability check. While the vessel is in the dock, it is usually in its light condition, the water is still and the facilities for moving known weights are readily on hand

## Conditions for Carrying Out the Inclining Experiment

1. The vessel should be upright.
2. The moorings should be slack, allowing the vessel to be inclined without restraint.
3. The vessel should be in still water conditions.
4. The density of the water should be known.
5. There should be no free surface action inside the ship’s tanks.
6. The contents and weights of all the ship’s compartments should be known.
7. Calm weather conditions should prevail.
8. The vessel should be clear of all unnecessary personnel.
9. The light condition displacement should be known from the builders.
10. The fore and aft draughts and the mean draught should be noted

## Experiment Preparations

The ship in an upright position, in its light condition, is fitted with a wire plumb line suspended from a high point on the transverse centre line. The ‘plumb bob’ on the end of the line is set into a horizontal trough of light oil or other viscous substance to dampen the movement of the plumb bob, once the vessel is inclined. Fastened to the edge of the trough is a graduated scale batten, measured in millimetres.

The inclining weights are then placed on board, preferably by the dockside cranes. These weights are usually fitted with a wheeled platform to assist movement on board the vessel, throughout the period of the experiment. Finally, all non-essential persons are sent ashore and the gangway is landed.

## Conduct of the Experiment

The vessel is then caused to be listed over, by moving the weights of the ship’s centre line, to a measured, accurate distance in a horizontal direction.
List Moments + Displacement = GG1 (namely the horizontal shift in the ship’s C of G)
Unless the displacement value is known, it would be usual practice to carry out a draught survey prior to conducting the experiment in order to obtain the exact displacement figure.

### Graphic Presentation (vessel floating freely)

1. Consider the two similar triangles ABC and GMG1
2. In triangle ABC: AB represents the length of the plumb line.
3. BC represents the deflection when the ship is heeled.
4. In triangle GMG1: GM represents the ship’s metacentric height in this condition.
5. GG1 is the shift of ‘G’ due to the moving weight.
As the triangles are similar:
Then Tan Ã˜ = GG1 + GM but Tan Ã˜ = BC ÷ AB
Therefore: GM = GG1 × AB + BC
But GG1 = (w × d ) ÷ Displacement
Therefore: GM = (w × d × AB) ÷ (Displ. × BC)
Where: w × d = list moments (in tonne metres)
AB = Length of the plumb line (in metres)
BC = Deflection of plumb line (in metres)
Displ. (W) = Ship’s weight in this condition

### Differences between MC/MC-C and ME/ME-C engines

The electrohydraulic control mechanisms of the ME engine replace the following components of the conventional MC engine: Chain drive for camshaft Camshaft with fuel cams, exhaust cams and indicator cams Fuel pump actuating gear, including roller guides and reversing mechanism Conventional fuel pressure booster and VIT system Exhaust valve actuating gear and roller guides Engine driven starting air distributor Electronic governor with actuator Regulating shaft Engine side control console Mechanical cylinder lubricators. The Engine Control System of the ME engine comprises: Control units Hydraulic power supply unit Hydraulic cylinder units, including: Electronically controlled fuel injection, and Electronically controlled exhaust valve activation Electronically controlled starting air valves Electronically controlled auxiliary blowers Integrated electronic governor functions Tacho system Electronically controlled Alpha lubricators

### Main engine interlocks

Interlocks are provided so that the engine can be started or reversed only when certain conditions have been fulfilled. When there is a remote control of engines, it is essential to have interlocks. This reduces the possibility of engine damage and any hazards to the operating personnel. Turning gear Interlock . This device prevents the engine from being started if the Turning gear is engaged. Running Direction Interlock . This prevents the fuel from being supplied if the running direction of the engine does not match the Telegraph. Starting Air Distributor in end position . This prevents starting from taking place if the shifting of the Distributor has not been completed. Main Lube. oil pressure, Piston cooling pressure, Jacket water pressure, and important parameters must be above the required minimum. Auxiliary Blower Interlock . The Auxiliary Blower is provided in case of Constant pressure turbo charging. Air Spring pressure Interlock . In case of the present generation

### Why is a man hole door elliptical in shape?

Any opening in a pressure vessel is kept to a minimum and for a man entry an elliptical hole  is lesser in size than the corresponding circular hole. More over it is prime concern to have a  smoothed generous radius at the corners to eliminate stress concentration. Hence other  geometrical shapes like rectangle and square are ruled out.  To compensate for the loss of material in the shell due to opening, a doubler ring has to be  provided around the opening. The thickness of the ring depends on the axis length along the  dirrection in which the stresses are maximum and the thickness of the shell. It is important to  align the minor axis along the length of the vessel, as the stress in this direction is  maximum. Longitudinal stress: Pd/2t where P= pressure inside the vessel, d= diameter of the arc, t=  thickness of the shell plating  Circumferential stress: Pd/4t  More over a considerable material and weight saving is achieved as minor is along the  direction of maximum stress.