Cargo Calculations on Oil Tankers using ASTM tables
Cargo (and caching) calculations are sometimes tricky.
Not because these are difficult but because there are so many variations to it. But we need to understand that at the very basic level, we calculate the volume from ullage tables and we need to be provided with density at the same temperature as the cargo.
We multiply both and we get the weight of the cargo. But for oil cargoes, we are either provided with density at 15 C or API at 60 F. In this case, we need to get the volume correction factor (VCF) to convert the volume at the observed temperature to the standard volume which is volume at 15 Deg C or Volume at 60 F respectively.
We then need to apply the weight correction factor (WCF) to convert the standard volume to weight. Different ASTM tables provide the value for VCF and for WCF. There are different ASTM tables for crude oil and for product oils. The one with letter A is for crude oils and the one with letter B is for product oil. ASTM tables without any letter are common for both crude oils and product oils.
Get your hands on ASTM tables and you will find that cargo (caching) calculations are not as difficult as it seems. Try the density tables: 0.9083, 0.9149, 0.9245, 0.9005, 0.9221, 0.09095, 0.9221, 0.9095
Source: https://www.myseatime.com/blog/detail/cargo-calculations-on-tankers-astm-tables