Dipping Tanks

The content of the tanks must also be measured and recorded before discharge and again after discharge.  Ullaging the tanks after discharge, to find any quantities remaining in the tanks, is usually referred to as “dipping” the tanks. Apart from the question of deadfreight when a full cargo is not supplied, there may be considerations of seaworthiness if the vessel has slack tanks.  This applies to all tankers but is particularly important with gas carriers where the surface movement of cargo in the tanks could damage their structure.  With LNG carriers the spherical tanks because of their shape allow a greater range of quantities in the part filled tank than the box shaped integral tanks, where the surface movement can be greater. If a vessel cannot load to her full deadweight because, owing to the low specific gravity of the cargo, she is full to capacity but not down to her marks, the right or lack of right, to recover deadfreight will depend on the contract.  Whenever the vessel could load more cargo but the shore stops the loading, the ship should protest in writing to the shore, inform the charterer and await his authority before sailing.  Shortloading or overloading contrary to the charterer’s wishes could result in a claim for damages. Most ship managers will find that ships under their management tend to prefer certain trades and will become familiar with the virtues and vices of different loading and discharging terminals.  There is, however, one piece of advice which is always worth taking; that it is better to remember where to find the facts than to try to remember lots of facts. Having said that, any source of facts must be up to date.  There are many excellent (albeit costly) volumes available which list details of almost every berth in the world; many of them print a new edition each year or so.  This is not just a device to make you spend more money, the fact is there is constant change going on in the world of ports, docks, berths and terminals.  Usually, the change is for the better but shortage of money or even topographical changes can result in some facilities deteriorating.