The purpose of SIM Draft Surveys is to determine the weight of cargo on board the vessel using the density of the water in which the vessel is floating; from this total they subtract the weight of the vessel's structure and other weights on board which are not cargo. The difference obtained is the cargo weight. This survey includes reading the vessel’s drafts, measuring the ballast water, fuel and diesel oil and other liquids on board, and calculating the final quantity by using the vessel’s approved dead-weight scales and tank tables, and other documents.
SIM On-Hire Surveys / Off-Hire Surveys are conducted to determine the extent of damage which may have occurred to the ship and her equipment between the commencement and termination of charter. This inspection also includes the checking of documents and certificates and the establishment of quantities of fuel and stores on board.
SIM surveyors take measurements and calculation of bunker quantity on board in connection with Charter delivery/re-delivery. They sound the fuel and diesel tanks or witness the ullaging / sounding by a ship's engineer and obtain temperatures where possible. Checking bunkers is also required of a SIM surveyor when carrying out an "On hire / Off hire" survey; however a bunker survey may be called for as a stand alone survey.