Page 81 - Introduction to Naval Architecture

68 FLOTATION AND STABILITY

Figure 4.30 Cargo shift

Compared with the stability on initial loading there will have been a
slight improvement due to the settling of the cargo.

Preventing shift of bulk cargoes
Regulations have existed for some time to minimize the movement of
bulk cargoes and, in particular, grain. First, when a hold is filled with
grain in bulk it must be trimmed so as to fill all the spaces between
beams and at the ends and sides of holds.
Also centreline bulkheads and shifting boards are fitted in the holds
to restrict the movement of grain. They have a similar effect to divisions
in liquid carrying tanks in that they reduce the movement of cargo.
Centreline bulkheads and shifting boards were at one time required to
extend from the tank top to the lowest deck in the holds and from deck
to deck in 'tween deck spaces. The present regulations require that the
shifting boards or divisions extend downwards from the underside of
deck or hatch covers to a depth determined by calculations related to
an assumed heeling moment of a filled compartment.
The centreline bulkheads are fitted clear of the hatches, and are
usually of steel. Besides restricting cargo movement they can act as a
line of pillars supporting the beams if they extend from the tank top to
the deck. Shifting boards are of wood and are placed on the centreline
in way of hatches. They can be removed when bulk cargoes are not
carried.