Line displacement
Line displacement is carried out by inspector before bulk loading or discharge of a tanker in order to ensure the pipeline contents are the same before and after the operation.
This is all part of the loading/discharging procedure and is one of the most important during a custody transfer operation and for cargo reconciliation. It minimizes the disadvantage between cargo shipper and consignee when shore tank measurements are used for Bill of Lading and Outturn determination.
Is in both ship and shore interest to ensure that the quantities are as accurate as possible.
Time spent on the line displacement depends on the length of the shore line and how much cargo it holds. Cargo operations will be stopped while the inspector measures what has been loaded/discharged to/from the shore tank. Figures are compared with what has been discharged/loaded from/to the vessel. If both figures are approx. the same (2% tolerance of the line volume approx.) the line is considered as full and cargo transfer continues as normal.
In case there is a large discrepancy then delays can ensue. Line displacement is done again assuming differences and a claim of shortage has to be put on either the Terminal or ship system. Letters of protest are issued for future claims.
Many Terminals have a variety of differing methods of determining line fullness. There is a “Line press operation” (using a shore pump to press up the shore line), line circulation (tank to tank via the shore manifold or offshore manifold) and line displacement procedure.
