3.1.5 On-board Quantity (OBQ) Measurement
3.1.6 Small Volume On-board Quantity (OBQ) Sampling When OBQ is accessible, samples should be obtained from all compartments containing liquid volume. An attempt should also be made to sample nonliquid volumes. Samples taken should be in sufficient quantity to permit any required analysis. Samples shall be taken in accordance with “API MPMS Chapter 8.1 - Standard Practice for Manual Sampling of Petroleum and Petroleum Products”.
3.1.9 Sea Valves
Confirm in the presence of the vessel’s personnel that sea valves and overboard discharge valves are in the closed position and sealed before and after cargo transfer. Seal valves to the extent possible, so as to be able to determine whether they were used during the cargo operation. Record the seal numbers.
Obtain and record reference heights from the calibration tables prior to taking opening cargo and water measurement. Record the observed gauge heights; investigate any discrepancies between the reference and observed heights. Determine the amount and nature of any material on board (OBQ) prior to transfer. Where On-board Quantity (OBQ) is found prior to transfer, it must be quantified. Determine the OBQ as specified in “API MPMS Chapter 17.4 - Method for Quantification of Small Volumes on Marine Vessels (OBQ/ROB)”: • For liquid material and water, use trim/list corrections if the liquid is in contact with all bulkheads in the compartment and the vessel is not on an even keel or has list. Use a wedge
3.1.10 Bunker Inspection
A bunker inspection should, when necessary, be performed before and after the cargo transfer operation. Measure the contents of all service, settling, and bunker storage tanks before and after transfer. If bunkering was conducted during cargo transfer operations, request from vessel personnel a copy of the BDR (Bunker Delivery Receipt).
3.1.7 On-board Quantity (OBQ) Temperatures
Temperatures shall be obtained, recorded, and used for cargo volume correction whenever depth of material and the nature of the material permits. If the temperature cannot be measured, the gross observed volume (GOV) shall be reported as Gross Standard Volume (GSV).
Vessel cargo gauging should not be performed during bunkering operations.
formula if the liquid does not touch all the bulkheads of the vessel’s compartments.
3.1.8 Slop Tanks
• For nonliquid material, multipoint gauging is recommended to determine if a wedge condition exists. If the material measured is not a wedge, the average of the multiple readings should be used for volume determination. However, if only one gauge point is available, the material shall be assumed to be evenly distributed over the tank bottom.
3.2 During Transfer
Obtain gauges and temperatures of the contents of slop tanks to determine the interface and the separate quantities of Free Water (FW) and slop oil. Take a separate sample of the water layer, if possible. Calculate the quantities; if any slops are to be commingled with the cargo, they are to be treated as OBQ and recorded appropriately. Keep slops samples separate from cargo samples.
3.2.1 Communications A reliable means of communication between the shore and vessel should be arranged. Vessel, shore, or measurement personnel who notice a problem during any stage of the transfer that could affect subsequent events should promptly notify all key personnel so that timely action can be taken.
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