Low sulphur, fuel switching and loss of propulsion

For vessels equipped or retrofitted with scrubbers, this will not be much of an issue. Similarly, for newbuilds designed to switch fuels, measures are taken at the design stage to segregate fuel lines and thereby avoid issues. But for vessels retrofitted with fuel-switching capacity, it is going to be extremely important to get the protocols right, because it not, vessels risk engine cutouts at crucial moments during a voyage. Becalmed vessels floating in the English Channel, one of the busiest shipping lanes in the world, could be disastrous.

A number of issues can arise if fuel switching best-practices are not observed; if the much-cooler MGO is introduced too quickly into fuel pumps and injectors, it causes them – especially if poorly maintained - to contract, causing a loss of fuel pressure at the pump, and leaks at the injector.

At other times, the extremely low viscosity of distillate fuels (anything below 2 cst, according to a California Air Resources Board report) versus thick, black bunkers can result in pressure losses which cut the engine.

The most dramatic problem is “gassing up”, which can happen where the 130-degree pipes required to carry the HFO are not given sufficient time to cool down to the ambient temperature of the distillate fuel, which often has to be refrigerated to less than 40°c in order to maintain workable levels of viscosity.

Up till now, fuel switching has really only taken place in the US, and particularly off the coast of California, where Marine Gas Oil (MGO) is in extensive use, and where Loss of Propulsion (LOP) incidents are commonplace. As of July 2014, 118 LOPs had been recorded since the July 2009 introduction of the state’s snappily titled “Fuel Sulfur and Other Operation Requirements for Ocean-Going Vessels within California Waters and 24 Nautical Miles of the California Baseline” regulation, allowing for a maximum of 1.5% sulphur content.

In a recent interview for Seatrade’s bunkering supplement, Eirik Andreassen, md of Veritas Petroleum Services (VPS) explained: “Some [shipowners and managers] are approaching us for help for instance with change over procedures, which will become a big thing. If you have seen the statistics from the US, particularly Californian waters where you have a lot of loss of propulsion due to fuel related issues, I think you will see a lot of them in European waters as well.

“We haven’t seen them in European waters [up til now] because mostly when you use distillate fuels you use them for your auxiliaries in port, but now you will have to use it for your main engine, you have switch from a very high density, high viscosity fuel to a very light product."

ExxonMobil recently brought out a new kind of fuel, HDME50, essentially a Low-Sulphur HFO, in order to allow existing vessels to traverse ECA zones without retrofitting. The fuel, like HFO, is extremely viscous and requires heating, with an injection temperature of 90°c versus standard HFO’s 130.

“The crew needs to be able to manage the transition,” said ExxonMobil marine marketing manager Iain White. At a decrease of 2°C per minute, it should take an hour to introduce distillate fuel, he explained. “What appears to be happening is that a number of ships are failing to do this.

“Shipowners need to have suitable procedures in place to ensure fuel switching is done safely.”

With far more vessels traversing an area much smaller and narrower than the California coast, vessel operators must ensure that crew are aware of the precautions when changing fuels – otherwise the English Channel threatens to become a minefield for shipping.

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