A recent survey conducted by independent Singapore bunkering publication Manifold Times has found the introduction of coriolis mass flowmeters (MFMs) to have minimally affected the bunkering flowrate of equipped bunker tankers, especially when taken into the context of shipowners’ delivery requirements.

Since 1 January 2017, the local bunkering sector has been conducting MFM bunkering operations for all marine fuel oil deliveries; the programme was extended to include distillate deliveries from 1 July 2019.

Shipowner’s perspective

Major shipowners and operators were keen to share their bunkering experiences at Singapore port with Manifold Times. From the overall survey with shipowners and bunker suppliers, it seems the ideal flowrate for receiving marine fuel was around 500 metric tonnes per hour (t/h) – a standard readily met by Singapore bunker tankers.

“We conduct between 10 to 16 bunkering operations per month at Singapore port and have not experienced any significant reduction of flow rate during bunkering,” a Singapore-based top 10 international ship management source told Manifold Times.

The Director of a dry bulk shipping firm which conducts more than 80 bunkering operations at the republic per month pointed out any delays in bunkering was likely “caused more by inflexible ex-wharf supply and short supplies and congestion [at Singapore port]”.

“The flow rate is fine because within the dry bulk sector we require max rate of up to 500 t/h due to the flange/connection etc,” he stated.

A source from amongst the world’s largest container shipping lines noticed MFMs produced “no negative impact” in delivery flowrates.

“The current MFM flowrate is acceptable for bunker delivery to be completed within the vessel port stay under normal circumstance,” he said. “While having a higher flowrate may sound attractive, the corresponding higher pressure may have safety concerns.”

Bunker supplier’s perspective

Local suppliers experienced with the technical operation of MFM-equipped bunker tankers had more to add when asked if MFMs severely reduced the delivery flowrate of their barges.

A terminal source shared MFMs, including those from manufacturer Endress+Hauser, could perform at up to 1,000 t/h. However, vessel safety would be more of a concern at such a high output.

“On average, delivery throughput of 400 – 500 t/h can be easily achieved with MFMs. In any case, it’s the receiving vessel that has restrictions and they ask us to reduce our flow rate due to the arrangement of their vessel piping system,” he explained.

“Most of the time the receiving vessel cannot take the maximum flow rate given by the bunker tanker. There is nothing to do with restrictions, if any, from MFMs.”

The Director of a bunkering firm noted the importance of getting a correctly sized MFM and pipeline configuration for the bunker tanker to ensure optimal flow.

“The installation of an MFM system onboard a bunker tanker typically introduces between half to one bar of pressure into the piping system which results in a 5-10% drop in flowrate on level ground,” he noted.

“During actual operations, variables affecting flow rates include viscosity, temperature, back pressure from head, whether receiving vessels are restricting the receiving rate, and more.

“At sea, we typically encounter freeboard of between 5 to 20 metres for receiving vessels. In general, we encounter a drop of 1 bar of pressure for every 10 metres but this doesn’t stop us from ensuring throughput of between 400 – 600 t/h for clients.

“This is especially so as a good number of bunker vessels in Singapore have dual cargo pumps rated at 1,000 m³/hr driven by main engines or electric motors which ensure the flowrate of 400 – 600 t/h is easily achievable.”

The owner of another bunker supplier, on the other hand, claimed a 5-10% decrease in flowrate after installation of an MFM onboard a bunker tanker as already a “safe estimation”.

“There is no logical reason for any big drops in flowrate after installing an MFM onboard. Even if there were any drops, this could be easy compensated by increasing pressure from the pump side.”

Other bunker suppliers approached by Manifold Times highlighted their marine fuel delivery vessels had to meet SS 648:2019 - Code of practice for bunker mass flow metering; a locally developed standard which bunker tankers pass before engaging in commercial operations.

SS 648:2019 covers the requirements of bunker quantity measurement using a coriolis MFM system including governs metering system qualification, installation, testing, procedures, and documentation for bunker custody transfer.

“Suggesting the installation of coriolis MFMs onboard to have affected the bunkering flowrate of equipped bunker tankers is not entirely accurate and without context,” noted the Director of a top Singapore bunkering firm.

“Each MFM has a QMax (i.e., the maximum flow rate) which will depend on meter selection, the bunker tanker’s piping system, amongst other variables. Meeting this requirement and more ensures proper delivery.”

Bunker deliveries conducted within the specified minimum (Qmin), maximum (Qmax), and minimum measured quantity (MMQ) flow rates under SS 648:2019 ensures best practice for marine fuel delivery operations, added management personnel of another bunker supplier.

Metcore International

Darrick Pang, Managing Director of Singapore-based MFM system measurement solutions provider Metcore International Pte Ltd (Metcore), shared further technical details with Manifold Times.

“Introduction of any extra instrument such as a MFM within the pipeline of a bunker tanker will definitely affect flowrate but this also depends on how the system has been setup and the way the MFM is installed,” he stated.

“Any pressure drop is normal, and this can be mitigated with correct sizing of the MFM and working with meter vendors to calculate the flowrate before installation.

“Though coriolis MFMs have no mechanical parts, it is typical to experience up to a 1.0 bar pressure drop in a normal cell.

“Flowrate is very very subjective and there are many possibilities affecting it.”

Other areas affecting flowrate after installation of a MFM onboard a bunker tanker include design of its pipe system, type of pumps used, height of the receiving vessel, and more, he added.

Endress+Hauser

In summary, the situation could be best explained by Mohamed Abdenbi, Business Process Consultant, of Endress+Hauser (S.E.A.) Pte. Ltd., the Singapore branch of Swiss-based MFM manufacturer Endress+Hauser.

“We have not heard of MFM systems affecting flowrate of bunker tankers. Reason is that MFMs are sized in a way to achieve optimum condition between pressure drop and accuracy. In addition to that, the availability of different MFM sizes allows us to select the best possible meter without reducing the flow rate during bunker operation.”

Photo credit: Manifold Times
Published: 18 July, 2023