7.1.1 Apparent Loss / Gain
7.1 Introduction It is not uncommon to experience significant cargo quantity differences when moving petroleum or petroleum products by marine vessels. These differences can be broken down into Shore to Ship (after loading), Ship to Ship (in-transit variance), and Ship to Shore (after discharge). The most important difference is of course the difference between the load port (usually the Bill of Lading) and the discharge port outturn (usually the shore receipt amount) quantities. Nonetheless, to perform quantity reconciliations on a marine cargo movement it is important to review all of the various movements to establish which ones were problematic. These differences can be classed as either an “Apparent” loss or gain, or in some instances the difference could be a “Physical” loss or gain. If possible, try to investigate differences prior to issuing final figures. In scenarios where this is not possible, ensure that the client(s) is made aware of any significant difference as soon as operationally possible.
Apparent Loss / Gain is a difference in quantity which is not related to a physical loss or gain, and although the figures highlight a difference, there has been an error which can possibly be corrected or differences due to uncertainties in precision of the measurement systems which typically cannot be removed. The majority of individual losses and gains are apparent rather than real and fall into the following categories:
• Measurement Error
• Procedural Error
• Calibration Error
Measurement Error includes all the errors associated with measurement procedures, equipment and operator performance. These errors can be in liquid level or meter measurements, determining temperature, sampling, tank calibration, and laboratory testing methods. Procedural Error occurs when operations deviate from the industry measurement standards and good practice. An example would be the failure to ensure pipeline fullness at the start of the cargo transfer.
It should be noted that there are NO defined quantities or percentages of acceptable loss.
What is acceptable for one client may well be unacceptable for another client or even the same client in a different trading situation.
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