Question

The effect of on stability when a tank is partially filled with liquid.

When a tank is partially filled with a liquid, the ship suffers a virtual loss in metacentric height which can be calculated by using the formula:

FSE = virtual loss of GM = i/W X ρ X 1/ n2 m

Where

i= the second moment of the free surface about the centre line, in m4

w=the ship’s displacement, in tones

ρ = the density of the liquid in the tank, in tones /cu.

N=the number of the longitudinal compartments into which the tank is equally subdivided

i X p = free surface moment, in tonnes m

Free surface effects therefore depend on:

(i) Density of slack liquid in the tank,

(ii) Ship’s displacement in tonnes,

(iii) Dimensions and shape of the slack tanks,

(iv) Bulkhead subdivision within the slack tanks.