A bunker survey is carried out to determine quantity of bunkers onboard a vessel, and is conducted jointly with the Chief Engineer.

Often the bunker figure is required for a different date and time to that when the survey is carried out, and it is necessary to adjust the figures obtained for  ship’s consumption, bearing in mind that different time zones may be involved. The surveyor would check figures supplied by the Chief Engineer, as far as is possible.

Due to difficulties in obtaining a representative sample of the bunkers, and hence the exact density, it is usual to use density related to delivery docket for the calculations. The surveyor would exercise care, however for the figure given in these dockets is not always density at 15 C and a conversion may be necessary. Where a bunker survey is done on a supply vessel or rig, the quantity of different oils (including those drums), cement, mud, sediments and other drilling materials must be determined as well.

The survey can be done as part of an On-Hire survey, in conjunction with a survey on loading or discharge of cargo, or it can stand alone.

If it is done in conjunction with oil loading / discharge, the survey is usually done twice, prior to and after loading / discharge. If the vessel bunkers during cargo operations, surveyor would reconcile the final observed volume with the initial observed volume, the ship’s average consumption and the bunker delivery documents.

In addition, the surveyor may be requested to test the lower explosive limit (LEL) of the oil, and occasionally to take samples and arrange for laboratory tests.

The gas testing should be done through a vent pipe or tank hatch, but if this is not possible the sounding pipe may be used. If the result is lower than 15% LEL, samples must be taken and tested. Should the analysis of any sample show a flash point lower than 15°C / 60°F, a letter of protest should be given to the master and the terminal informed.

If a bunker survey is done for a draft survey, the weight in air of the bunkers should be calculated from the volume at ambient temperature, not at 15°C.