Data from international fuel testing and inspection company Veritas Petroleum Services (VPS) mass flowmeter (MFM) Quick Screen Service detected several instances of operators not managing MFMs to the Technical Reference for Bunker Mass Flow Metering (TR 48:2015) during bunkering operations at Singapore port in 2018.
The MFM Quick Screen service for shipowners evaluates the performance of MFM during bunker deliveries in accordance to the Technical Reference for Bunker Mass Flow Metering (TR 48:2015) at Singapore.
“The Maritime and Port Authority of Singapore and Working Group on mass flow metering have done an excellent job to develop TR 48:2015,” Rahul Choudhuri, Managing Director, AMEA, told Manifold Times.
“However, these guidelines are not always followed by bunkering crew during operations on the waterfront.
“Based from collated data of the VPS MFM Quick Screen Service we were able to summarise and get a good idea of the key points stakeholders should look out for during a MFM bunker delivery process.
“These areas are the ones with a higher risk of non-conformance.”
The most reported cases of operators not complying to TR 48:2015 practices in 2018 were over line clearing practices, deliveries under the minimum mass flow rate (Qmin), MFM drive gain/damping, and the flow rate going beneath the low flow cut off value.
These problems, on the surface, may suggest violations during MFM bunkering but this is not always the case, clarifies Choudhuri who used the case of line clearing as an example.
Section 10.5.2.10 of TR 48:2015 states line clearing should not be repeated more than twice after completion of the pumping operation.
“We find it to be mistakes made by the bunker operator in most cases when line clearing is done more than twice, however, we are also aware that some vessels specifically request line clearing to be conducted for an extended period of time after the bunker operation thereby not conforming to TR 48:2015 practises,” he says.
“In light of this, we need to state that extended line clearing creates aeration and therefore affects the final MFM reading. A good line clearing & stripping should be around 10 minutes, and the maximum we have seen is up to 30 minutes.”
Choudhuri next points out the operation of MFM units beneath the Qmin to be the second most common TR 48:2015 issue detected by the VPS MFM Quick Screen Service.
“Mass flowmeters are designed to operate within certain tolerances and delivering bunker fuel beneath the Qmin over a period of time will certainly affect the device’s measurement uncertainty,” he explains.
“The delivery of bunker fuel below Qmin will affect the measurement uncertainty of the MFM.”
However, Qmin caused by e.g. the momentary changing of tanks or low pumping rate, and consistent Qmin over a period of time are two different operations.
“Specifically, shipowners will need to take notice of consistent Qmin over a period of time as this affects the total reading and measurement uncertainty of the MFM,” Choudhuri highlights.
The indication of excessive drive gain or damping where more deflection occurs in the flow tube, and aeration within the MFM system, are among the top TR 48:2015 non-conformances recorded; the scenario occurs when the MFM system detects entrained air, also known as aeration, introduced during the bunkering process.
The transfer of bunker material beneath the low flow cut off value was also within the list of top TR 48:2015 non-conformances registered by the VPS MFM Quick Screen Service.
"The low flow cut off value for fuel oil bunkering operations is usually set to around 10 metric tonnes (mt) per hour or less subject to pipe diameter and this is the lowest level that a MFM can measure to deliver fluid; anything below this value and the whole unit stops measuring which can be bad for the bunker supplier," says Choudhuri.
“But registering a transfer rate beneath the low flow cut off value does not necessary mean the equipment is not functioning well as it can happen when a supplier is conducting a tank to tank change operation while bunkering.”
He concludes: “As discussed in the above scenarios, the results themselves show how diverse the reasons are for TR 48:2015 non-conformances; a deeper understanding is important as not all cases mean we have a big problem.”
“This is also where trained personnel, such as the role of the bunker surveyor, comes in to tell the difference and will continue to exist.
“The surveyor’s role is still very important and these are just some of the issues which may or may not be the supplier's fault; which is why we want these operations to be well managed.
“Today, the bunker surveyor is more relevant than before as we have gone beyond the traditional surveying scope on just check on bunker quantity.
“Many practises in TR 48 are currently under review to upgrade it to a Singapore Standard (SS) and this includes the extended role of the bunker surveyor as well.”
Photo credit: Veritas Petroleum Services
Published: 10 January, 2019
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