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Not too hot, not too cold

Few serious problems with using VLSFO have been reported following the 2020 fuel switch deadline but an early lesson is that correct temperature management is crucial

In the run-up to the 1 January implementation of the 0.50% sulphur limit there was widespread concern that switching between different compliant fuels could lead to problems. At least one large global tanker operator went to the extent of securing worldwide VLSFO storage to ensure its vessels would be able to take on compatible fuels. In the event VLSFO use has created relatively few headaches.

The assumption had been that VLSFO would be widely used by vessels without scrubbers as it would be significantly cheaper than using MGO. And that appears to be the way it turned out for the first quarter of the year at least. However, the effect of Covid-19 on the fuel market has, albeit perhaps temporarily, changed the economic case. By mid-May, in Singapore, MGO was reported as being US$4 a tonne cheaper than VLSFO. That would seem appealing to ships’ engineers who have had to deal with clogged purifiers.


But it is much too early to assume that all the hard work and resources refiners have put into developing VLSFO, and the all the effort the shipping industry has expended to be ready for the new blended products, have been wasted.


Last year, a number of shipping, refining, fuel supply and standards organisations, with IBIA prominently involved, worked together to produce Joint Industry Guidance on the supply and use of 0.50% – sulphur marine fuel (JIG) which was released on 20 August.


The publication has been developed by experts from across shipping, refining, supply and testing of marine fuels.


The publication still represents best practice for stakeholders across the marine fuels and shipping industries, from fuel blenders and suppliers to end users. It presents the specific safety and operational issues relating to the supply and use of 0.50% sulphur fuels, an overview of fuel quality principles, and the controls that should be put in place to ensure that safety issues are identified, prevented and/or mitigated. It addresses issues such as fuel compatibility, fuel stability, and fuel handling and storage, and contains a comprehensive review of existing operational factors that can affect safety.


Among its key messages is the need to ensure fuel quality by making sure that blend components are suitable for bunker fuel production, with particular attention being given to ensure that the final product is stable. Fuel suppliers and purchasers should provide adequate information to the ship concerning the fuel as supplied to enable ship crew to identify and manage potential safety and operational issues associated with certain fuel properties and characteristics.


Reflecting a widespread worry, the guidance notes that fuel characteristics are expected to vary considerably between bunker stems. The ship’s crew will need to adopt a more proactive approach to fuel management. They will need to know the fuel characteristics as loaded and be able to respond to the requirements, especially in terms of on-board temperature requirements and any commingling.


While compatibility between fuels from different supply sources can be a concern in today’s environment, assessing compatibility of 0.50%-sulphur fuels from different sources will be key. To the extent possible, fuel should be loaded into an empty tank. The available space for new bunkers to be loaded should be taken as the capacity of the empty tanks in order to avoid commingling on loading.

The JIG emphasises that ship operators and fuel suppliers should review operational practices to allow sufficient time to test for compatibility between existing and proposed bunker fuel delivery, especially if no “empty” dedicated storage tank is available on the ship.


So, what has the actual experience of using VLSFO been? IBIA’s Regional Manager for Asia, Alex Tang has been talking to two Singapore-testing companies to find out.


Gowri Shankar, Tribocare’s Regional Sales Manager- Asia, said: “During the last months of 2019 and during the first two months of 2020 we observed that fuels with widely different formulations were supplied across the world and even in the same port, including Singapore, with viscosities ranging from 2 cSt up to 380 cSt. Lately a stable trend has been observed in fuel quality across the globe.


In my opinion, I dare to say that the quality of VLSFO fuel is far better than HSFO fuels. The calorific value of VLSFO fuels is definitely higher than HSFO fuels which means there is certainly a reduction in fuel consumption and hence fuel savings for the buyers. The majority of the fuels we have tested have low asphaltene content and middle to low micro carbon residue (MCR) which was an initial worry, since there were concerns for the detergency properties of the newly formulated 40BN cylinder oil, with regards to high MCR content fuels.”


“As regards to the problems faced,” Shankar said, “we are repeatedly contacted regarding stability issues of the new VLSFOS with vessels facing filter and purifier chocking issues. Those stability issues were expected, since those fuels are produced by blending residues with distillate fuels to bring down the sulphur content to the compliant level. When you mix paraffines with aromatic residue you have to take special precautions to maintain the stability of the fuel, specifically the ‘capacity’ of the fuel matrix to keep the asphaltenes in suspension. Unfortunately, not all blends are successful. Once the stability of the fuel is disrupted and the asphaltenes start to precipitate, the process is not reversible. There is nothing you can actually do to bring the fuel back in a stable condition and the only choices are to either debunker or live with this. The majority chooses to live with the problem instead of getting into a legal dispute regarding the quality of bunkers, which results to a heavy burden for the crew, who need to manually clean the overloaded purifiers.


He continued: “We have also noted an interesting fact that the purifiers are getting clogged due to mishandling of fuels by ship’s staff. We have handled a few cases where the ship was supplied with fuel which has a viscosity of about 30 to 40 cSt and density was about 945 to 965 Kg/m3. Since the ship staff was used to set up 98⁰C as fuel heating temperature at the inlet of the purifier, they continued maintaining the same for those low viscosity fuel. The main function of the purifier is to remove the dirt/catfines/heavier particles from the fuel. The highly viscous HFO had to be heated to reduce its viscosity so that the separation would be more efficient. In this case, though, the VLSFO fuels already have low viscosity and density. When these fuels are heated at 98⁰C and passed through the purifier, the purifier clears all the heavier particles including asphaltene. Again, this leads to overloading the purifier and clogging it. We have observed that by reducing the purifier inlet temperature, this problem has gradually reduced.

Shankar concludes: “Further to the stability issues, there are also certain issues with high pour points, especially effecting bulk carrier vessels when they load temperature sensitive cargos. Therefore, we always advise buyers to procure fuel that is fit for purpose and not just compliant with ISO 8217 requirements.”


Martin Chew, Regional Sales Manager- Asia Pacific, Innospec Fuel Specialities, reported that bunker alerts from global bunkering ports are continually highlighting teething problems with VLSFO. Many expected to see this as suppliers used unfamiliar blend components to achieve lower sulphur levels while continuing to include residual streams. “Regarding the ISO 8217 specification, we have seen many VLSFO deliveries to be off spec with the main parameters being flash point, TSP and pour point which, together, made up about 45% of all off spec cases in April,” Chew said.


Chew said that VLSFO instability issues very similar to those seen with HSHFO but “due to the process and components used to produce the VLSFO, this issue has become more pronounced post 2020”.


He also made the point that testing the fuel to ISO 8217 was giving shipowners a false sense of security. He explained: “A very good example of this was a VLSFO that was found with on-spec total sediment potential (TSP) caused countless stability issues during operation. At the same time, surprisingly, many off-spec TSP cases don’t lead to similar issues. The conclusion is that ISO 8217 gives an indication of the fuel quality but doesn’t guarantee it is fit for purpose. We are of the opinion that Reserve Stability Number (RSN, ASTM D-7061) is a better indication of the fuel stability compared to TSP.” According to Chew the issue of unstable fuel can addressed by using the right fuel treatment, for example dispersant and stabilisers.


He also notes: “Due to the heavy components used to produce the VLSFO, high pour point VLSFO is becoming quite common. This is particularly an issue for low viscosity fuels where fuel handling and purification is done at a relatively lower temperature. On many occasions, the handling and purification temperature falls below that at which wax forms. This is similar to the cloud point of MGO. One needs to understand that once the wax is formed, much more energy is required to raise the temperature and melt.”


Chew said that wax formation had caused many cases of purifier clogging and failures. These cases had often been mistaken as instability of the fuel causing asphaltene sludges. He said: “This is not surprising as it is not easy to spot the difference between sludge and wax on-board a vessel. On many occasions this issue can be easily solved without breaking the purifier water seal by increasing the purification temperature gradually until wax disappears.”


Finally, Chew said that premature failure of engine components, for example excessive liner wear and piston ring breakage, has become common. He added that the question to ask was: “Is this an issue caused by VLSFO?”.


He said the answer was: “Yes and no. But from what we have seen, it is much more likely that components and lubrication cause 80-90% of these failures. Only a mere 10-20% can be attributed to poor VLSFO combustion, leaving causing excess deposits on the piston ring packs. This eventually causes rings and liners to fail. Where this is the case, one should consider a combustion catalyst to assist the VLSFO burn more efficiently.”

In a recent interview with Bunkerworld the global head of Bureau Veritas’ Marine Fuel Services, Charlotte Rojgaard, like Sankar and Chew, raised the issue of the temperature of the fuel.


“It is all about temperature management to ensure the correct viscosities are applied for separations and injection. This is not a new challenge but whereas the RMG 380 fuels pre-2020 did not vary much on viscosity, the VLSFOs currently vary quite a bit.”


In the article she also stressed that it remained important to keep different fuels separate. World Bunkering asked: “Was BV aware of any incidents that have led to main engine failure?”


Rojgaard said: “Main engine failure requires that the fuel makes it to the engine. If the fuel treatment system is filled with sludge, the problem is more likely fuel starvation. It has always been good housekeeping not to mix fuels onboard due to potential compatibility issues. This recommendation still stands.”


Following on from the Joint Industry Guidelines, Videotel produced and e-learning package. How important did she think chief engineers being aware of potential issues has been?


“I think it is very important that the chief engineers are aware of the challenges related to fuels,” Rojgaard replied. “In the end, they are the ones that have to manage the fuel they receive onboard.”


World Bunkering asked, from the limited experience so far, did she think any clear lessons had emerged?


Rojgaard replied: “It is still early days and we are still building up experience. One lesson learnt is the importance of preparation and education. Also, as predicted, onboard temperature management is key.”


The industry was, in general, well prepared and has been learning how to manage VLSFO. It would be ironic if, against all expectations, MGO pushed the new blended products out of the market.

Charlotte Rojgaard

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