Cargo measurement. The EXXONVOY 84 tanker voyage charter form contains a comprehensive "Cargo measurement clause". Before loading, the master is required to measure the on-board quantities of oil, water and sediment residues, which are segregated in all holding tanks and slop tanks.
After loading, the master must determine the cargo quantities loaded. He must prepare and promptly submit to the charterers a written tank-by-tank tillage report ("tillage" is the space between the tank top and the top of the liquid oil) . This must contain all measurements of oil, water and sediment residues before loading and quantities of oil loaded.
If there is any deficiency between the master's loaded figures and the bill of lading figures, usually supplied by the shippers at the terminal, the master must carry out a recalculation and if there is still a discrepancy, he must issue a Letter of Protest to the oil supplier and advise the charterer immediately. In earlier days of tanker operations, a difference between ship and shore figures was acceptable, sometimes between 0.25 to 1 per cent of the bill of lading quantity. This clause now does not seem to make allowances for any margin of tolerance and the difficulties of ship and shore figures tallying precisely are obvious. What is a "deficiency"? The master may be uncertain and may also be uncertain about giving letters of protest to the suppliers, especially if the suppliers are in ports where problems have arisen.
Before discharging, the master must again measure the quantity of cargo on board. The vessel must discharge all free flowing and pumpable oil, and, if ordered by the charterer, all free flowing and pumpable residues of oil, water and sediment. The clause states also that:
"Vessel's . . . obligation shall not in any way be qualified or limited by any purported custom of the trade which is based on a stated in-transit loss or which otherwise excuse the vessel from discharging all free flowing and pumpable cargo and residues."
Before the oil price increases of 1973 and 1979 the custom of the trade allowed acceptable loss by evaporation of some oil. After the increase and because of the introduction o£ inert gas systems and sealed tanks, evaporation losses are less acceptable and the above clause, in favour of the charterer, maintains that the obligation of discharging the quantity of oil which was loaded lies on the owner. The measurement of crude oil cargoes can be quite imprecise and full of errors, some possibly quite expensive, mainly owing to the shape and structure of the ship's tanks and the sediment in them from previous cargoes. In 1982, in a case decided in the United States, Sun Oil Company v. The Mercedes Maria, a court first decided that 0.5 per cent tolerance or "allowance" was a "custom of the trade". When the case went to a higher court on appeal, this decision was rejected. It was said in the court that ". . . measurement is better characterised as an art than as an exact science". Therefore little precise tolerance values can be assumed.
One problem that can arise is the interpretation, of the words "free flowing and pumpable". Cargo heating may be necessary to make a cargo free flowing and pumpable, but the ship's structure and any sediment in the tanks may also reduce pumpability.
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