17 Jun '17, 01:58

June 17, 2017, 1:58 a.m.

The quantity to be loaded is given in metric tons. There are three different ways to state the quantity, either:
- 4000 mt +- 5% MOLOO -- Load from 3800 mt to 4200 mt on owners option
- 4000 mt +- 5% MOLCO -- Load from 3800 mt to 4200 mt on charterer option
- 4000 mt ------------------- Load 4000 mt

MOLOO means that it is the owner, represented by the captain that states the quantity to be loaded. MOLCO means that it is the charter that states the quantity.
The cargo loading temperature is given either fully refrigerated, ambient or on a given temperature. Ambient means the temperature is equal to the air temperature if the shore tank is located on the surface. It also states what temperature the cargo is to be discharged at.
The maximum allowed filling limit when loading is 98% and it is the safety relief valve setting and the cargo temperature that give the filling limit. To find the filling limit either use the operation manual for the vessel or the cargo density table. When using the density table, calculate the temperature of the cargo from the absolute pressure. When obtained the basic information on the cargo, start planning the loading. Calculate the filling limit in each cargo tank and then plan the loading rate. The loading rate is determined by three factors: cargo temperature, the ambient temperature, and whether a vapor return used.
When during loading needed to run the cargo plant, there are various ways to run the plant. It depends on the temperatures and the flexibility of the plant.
If set up to load two different cargoes e.g. ethylene and propane, then the cargoes must be separated from each other. This called segregation of cargo tanks, cargo cooling plants and lines. Taking out small pipes on the cargo lines does segregation, those pipe parts are called "spool pieces". The spool pieces are taken out of the lines and the main line is blanked of flange covers. Additionally segregate the cargo cooling plant e.g. two plants are used for ethylene and one is used for the propane. It is stated in the Certificate of Fitness how the lines and compressors can be segregated. F.e. if there 4 cargo tanks there could be a possible segregation with cargo tank 1+2 and 3+4.
When loading a partial cargo try to use the manifold that is linked directly to the tank that is loaded. F.e. if going to load on tanks 2,3 and 4, then use the manifold for tanks 3+4. All spool pieces are marked according to the diagram. Many of the spool pieces have the same diameter but have a different length, so try to keep your spool pieces orderly. Normally the spool pieces are mounted on the cargo lines, so there should not be any problem keeping them organized.
Before commencing the loading to cool down the tank shell as mush as possible, the optimal is less than 10oC above cargo loading temperature. The resulting temperature of the tank shell depends on how much time is used, the amount of cargo remaining on board, and the arrangement of the lines to the cargo tanks. Thermometers on the outside of the tank shell used in order to achieve the proper temperature. When loading fully refrigerated propane, try to get the temperature on the outside on the cargo tank shell below -35 C before start loading. When the cargo tank shell is chilled down before arrival, the time used for loading will be reduced.
Before arrival to loading port the cargo tank shell must be chilled down, and cargo lines and spool pieces must be readied. Only then will we be able to reduce the time used in port.