Page 268 - International safety guide for oil tankers and terminals

INTERNATIONAL SAFETY GUIDE FOR OIL TANKERS AND TERMINALS

In general, the following principles apply:
ื่อการศึกษาเท่านั้น---
The vertical centre of gravity must be lowered in the most
effective way.
Where slack double bottom tanks exist, these should be filled
14.1.5้องสมุด ศูนย์ฝกพาณิชย์นาวี
(‘pressed up’), starting with those on the low side, followed by
those on the high side.
No attempt should be made to correct a list by filling
compartments on the high side as this is likely to result in a
violent change of list to the opposite side.

If the pressing up of slack double bottom tanks is insufficient
to regain stability, it may be necessary to consider filling empty
double bottom ballast tanks. It must be recognised that this will
initially result in a further loss of stability caused by the
additional free surface effect. However, this will soon be
corrected by the effect of the added mass below the ship’s
original centre of gravity.

The restraint provided by moorings should be considered. To
attempt to control a list by adjusting mooring ropes’ tension
could be dangerous and is therefore not recommended.

On completion of loading, the number of slack holds should be at
a minimum and, in any event, not more than that specified in the
ึ
stability information book.

14.1.4 Sloshing

‘Sloshing’ is the movement of liquid within a hold when the ship is rolling
---ใช้เพ
or pitching.
It can give rise to:

Structural damage caused by the slamming effect of the liquid against
the ship’s side or bulkheads.

An electrostatically charged mist in the ullage space in holds partially
filled with a mixture of oil and water, such as dirty ballast or retained
tank washings. This can occur with only a slight rolling motion.
In order to eliminate these problems, slack holds should be avoided
wherever possible. This may be difficult when loaded with an oil cargo,
งานห Longitudinal Stress
but may be more readily achieved when the vessel is in ballast.

Consideration should be given to the distribution of the weights along the
ship, taking account of the ship’s longitudinal strength.

Venting of Cargo Holds
14.1.6
The vent lines from the cargo holds may lead to either individual vent
outlets, or to a main gas line venting system which expels the
hydrocarbon vapour through a riser at a safe height above the deck, or to
an inert gas pipeline system.
Owing to the greater movement of liquid within the cargo hold in rough
sea conditions, the possibility of liquid entering the vent line is greater
than on a conventional tanker. Various trap systems may be incorporated,

234 © ICS/OCIMF/IAPH 2006