The use of mass flow meters (MFM) is mandatory for all fuel oil deliveries in Singapore as of 1 January 2017. However, issues related to bunker quantity remain prevalent.
Subsequent to previous alerts issued by Gard on Singapore’s adoption of mandatory bunker control and the new bunkering procedures, this article addresses some of the issues faced by our Members and clients when taking bunkers in Singapore following the implementation of the MFM requirements. The introduction of mandatory use of MFMs was intended to address frequent quantity disputes arising between the bunker barge and the receiving vessel, although these issues remain.
Causes of the discrepancies
There have been two main causes of the discrepancies when using the mass flow meter;
Gard has received reports indicating that some bunker barges were found to syphon fuel back to their tanks via pipe connections between the flow meter and the outlet flange going to the ship manifold. In such circumstances the MFM reading will be higher than the amount actually received by the ship’s bunker tanks.
The Maritime Port Authority of Singapore is currently investigating these issues and has suspended several barges from operations until completion of the investigation. It is worth noting that an MPA certified bunker barge should have all connections between the flow meter and the shipside blanked off and sealed as part of the certification.
Limitations of the MFMs
Some vessels have recently reported quantity difference exceeding their past experience. Some bunker surveyors have studies the discrepancy between the MFM readings and the vessel received figures for a duration of time. Out of 24 cases of discrepancies over the duration, the maximum discrepancy was 57.24 MT and minimum 6.79 MT. The average discrepancy, in the disputed cases, was approximately 19 MT.
These discrepancies can be due to:
Any errors in the tank calibration of the vessel would be consistent with or without the MFM. To identify this issue a vessel experience factor (VEF) from her previous bunkering operations should be taken into account.
Errors in the MFM reading can also account for such discrepancies. All MFMs have a maximum and minimum flow rate, commonly known as “Qmax” and “Qmin” respectively. These limits define the operational accuracy within which the system is qualified to operate. In other words, if the flow rate of the liquid is outside these limits, the calibration of the equipment may not be accurate. It is seldom that the flow rate exceeds the Qmax, as it is usually about 1,000 t/h (forward flow). However, during stripping of the bunker barge’s tanks, the flow rate can frequently fall below the Qmin. The longer the duration of the stripping, the more likelihood of a discrepancy between the MFM and the ship’s received figures.
Additionally, MFM parameters such as Damping, Drive Gain, Low Flow Cut Off Value & Air Index can affect the accuracy of measurement if they exceed the manufacturers’ recommended limits during the bunkering operation.
While stripping of the bunker tanks is allowed under the TR48 (Technical Reference For Bunker Mass Flow Metering), it has been noted that prolonged stripping operations causes frequent fluctuations in the flow rate with several instances of the flow rate falling below the Qmin. It has also been observed that some bunker barges conduct stripping operations in the middle of bunkering which is not permitted under TR48 and can lead to measurement uncertainty.
To ensure that bunker barge operators comply with all the necessary requirements, Gard recommend the following;
In addition to the physical checks, Members and clients could consider incorporating protective clauses in their bunker purchase contracts. The protective clauses could include the provision of the need to physically check the bunker quantities on the delivery barge before and after bunkering.
Gard will follow any developments of the bunker situation in Singapore and will revert with further updates when and if necessary. Members and clients are encouraged to contact Gard should they need further information or should they wish to share their own experiences with us, using the mail firstname.lastname@example.org