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Quantity surveys

The name "quantity surveys" indicates the purpose for which these surveys are required, i. e. to determine the quantity of cargo or bunkers. There are several methods by which quantity can be determined, but not all are necessarily applicable to every case.


Draft survey

The purpose of a draft survey is to determine the weight of cargo on board the vessel. By measuring the draft, the marine surveyor can use the ship's plans and information to compute the immersed volume of the vessel. Using the density of the water in which the vessel is floating, the surveyor can then calculate the weight of the vessel. From this total he subtracts the weight of the vessel's structure and other weights on board which are not cargo. The difference is the cargo weight.


Weight and Measurement

If the cargo has been conveyed to the ship's side in railway wagons or road trucks it can be physically weighed as it passes over a weighbridge. Deduction of the vehicle's tare weight results in the weight of the contents being determined. In this case the surveyor will usually be required to obtain the weight dockets from an independent weighbridge, check them and issue a weight certificate.

General cargo can be weighed, but since freight is frequently charged on cubic capacity it may have to be measured to determine the space it occupies. This is done by means of a tape measure and surveyors may be required to check the measurements of a particular item, or possibly the space occupied by general cargo in a hold or container.


Ullage survey

Ullage survey or ullaging is the customary method with liquid cargoes and is occasionally used in special cases for dry bulk cargoes. The surveyor measures the depth of free space above the liquid in each tank. He then calculates, using the ship's tables, the volume of liquid in each tank. He measures the density and temperature of each liquid and then computes the volume of liquid at standard temperature and pressure.


Тally survey

An effective step to avoid the shortage claim is to arrange tally survey of the cargo. This means checking or keeping a record of the cargo loaded into or discharged from a vessel (lorry, railway car, warehouse, container etc.).

 

 


Bunker survey

Bunker survey requires the surveyor to sound the fuel and diesel tanks or to witness their ullaging / sounding by a ship's engineer and obtain temperatures where possible. The surveyor needs to sight the chief engineer's records of fuel obtained at previous ports and note the specific gravity recorded. This, after possible correction for temperature, is then used for the calculation of quantities on board. Checking bunkers is one of the task required of a surveyor when carrying out an "On hire / Off hire" survey. However a bunker survey may be called for as a stand alone survey.

 

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