- Easily used by ships maintenance staff right out of the box
- Instant indication of condition for motor bearings, gears, compressors, slewing rings, hoists, winches...
- Plan maintenance and have the spares available on time. Minimise off-hire and demurrage.
Fuel Oil Quantity Determination
Whatever the method of fuel oil delivery, it is possible to determine the volume received on the vessel by taking a sounding or ullage of the receiving tanks.
By making allowance for the vessels trim and or list the volumes can be calculated. At first sight this would appear to be an accurate method of determining the fuel oil volume received, but in reality it is frequently not the case. This is because of the size of the tanks involved, possible inaccuracies in the calibration tables and the difficulty of accurately correcting for trim or list.
Fuel Oil Delivery from Shore Side Tanks
When delivery is received from shore side tanks, the above method may be the only way of estimating the volume received. A better method would be the witnessing of the soundings/ullages of the bunker fuel storage tanks at the beginning and end of delivery. In all probability, it is not possible for the Chief Engineer or a member of ship’s staff to gauge the shore tanks and establish if pipelines were empty or full before and after the bunkering. The only practical way is to appoint a surveyor who has access to the tank and who will be able to carry out the pipeline calculations. Sometimes volume meters are available, but there is no practical way of verifying that meter readings are correct.
Fuel Oil Delivery from Road or Rail Wagon
Road or rail wagon deliveries occasionally take place. In general, these are usually related to distillates, with the fuel measured by a meter.
Delivery by Barge
When making an accurate bunker fuel quantity determination, it is necessary to take the temperature of the bunkers both at the beginning and end of delivery so that volumes can be corrected back to the standard temperature of 15°C. This applies to shore tanks, road or rail wagons and also a barge delivery.
The following example relates to a barge delivery, but the principle can equally be applied to other forms of delivery:For each tank, the opening soundings or ullages are taken along with the temperature of oil in the tank
- From the barge calibration tables, the observed volume can be determined
- The volume at 15°C is then determined by applying the volume correction factor (VCF) given in Table 54 of ISO 91-1. Table A shows an extract of Table 54B from this standard
- In order to determine the VCF, the density of the product being delivered has to be known
At this stage, the only figure available is that stated by the supplier on the Bunker Delivery Note.
|Tank m||Sounding||Temp °||Observed Vol m3||VCF||Vol at 15° m3|
Table B shows the opening readings, before discharge, of the barge, the stated density of the product being 990kg/m3. From this it may be seen that the total observed volume is 1236.758m3. This relates to the standard volume at 15°C, which is 1208.682m3. The VCF is taken from Table 54B for the measured temperature.
|Tank||Sounding m||Temp °c||Observed||VCF Vol m3||Vol at 15°c m3|
The total volumes delivered by the barge, both for observed and standard temperatures, can be found by subtracting the closing volumes from those at the start: The observed volume transfer = 1236.758 - 144.949 = 1091.809 m3.
The standard volume transfer = 1208.682 - 141.861 = 1066.821 m3.
|Density at 15°c Kg/m3||Factor for converting weight in vacuo to weight in air|
|841.2 to 903.4||0.99875|
|903.5 to 975.6||0.99885|
|975.7 to 1060.4||0.99895|
As already defined, density is the absolute relationship between mass and volume and not its weight to volume, by definition density is in vacuo. To convert weight in vacuo to weight in air, reference must be made to Table 56 of ISO 91-1. An extract of this table is shown in Table D.
The theoretical weight transferred in air: = Density (kg/m3) * Standard volume at 15°C (m3) x Factor = kg * kg/1000
= (MT) = 990.0 x 1066.821 x 0.99895
= 1055043.7 kg = 1055.044 MT
The value of 1055.044 MT represents the weight of fuel transferred in air, based upon the density given on the BDN. In order to determine the actual weight transferred, the density of the fluid delivered must be determined. This determination can either be by on-board testing or after laboratory analysis.
Assuming that the density determined from a representative sample of the bunkering is 985.1 kg/m3, the actual weight transferred in air:
= 98.51 * 1066.821/1000 * 0.99895 = 1049.82 MT
If the density is not determined from a representative sample, the BDN should be signed only for volume. If the supplier insists on a signature for weight, add “for volume only - weight to be determined after density testing of a representative sample”.
The example calculation given for a fuel delivery changed the actual delivery from:
Opening Closing 1224.39 - 144.949 = 1079.44 Changes to 1049.82 MT a saving of 29.62 MT or $14810 at $500/MT