Low Sulphur Fuels Cause Pump Deterioration

Due to new regulations, the shipping community is faced with new challenges on a large scale, especially those ships that operate both inside and outside environmental zones and switching over from one fuel to another.

For a long time the traditional approach to operation on heavy fuel oils (HFO) has been “pier-to-pier”. This is all going to change, said Allweiler, a world-leading provider of marine pumps to the shipping industry.

When global ship operator BW Gas overhauled a low-performing fuel service pump, it discovered high wear on pump elements. BW Gas concludes that a contributing factor to the increased wear rate on the pump can be the 0.1% Sulphur marine gas oil used in EU ports, however it is also clear that other factors play a significant role.

“As a global LNG owner & operator, we set high standards for environmentally-friendly operation.  And we continually monitor the pump performance of our 11 steamturbine-driven LNG tanker fleet when in LSMGO operation,” said Johan Christian Øwre, Superintendent BW Fleet Management.

The BW LNG fleet utilizes to a large extent the boil-off gas from the cargo as fuel for propulsion and consequently leaves a very small sulphur emission footprint.

“We have managed the current emission regulations very well and proactively overhaul any pump showing signs of deteriorating performance,” said Øwre.

“Today we have a lot more knowledge about the effects of low sulphur content diesel fuels,” said Christian Martin, Business Development & Marketing, Allweiler.

The majority of pump problems occur on vessels in global operation. When approaching an environmental zone - like the Sulphur Emission Control Area (the English Channel, North Sea and the Baltic Sea and other European harbours), they must switch from heavy fuel oil (HFO) to diesel oil to comply, e.g. with the EU Directives which limit the sulphur content of marine fuel oils down to 0.1%.

“Some vessels, depending on areas of operation, are more affected than others.  When two different fuels are mixed there is a risk of incompatibility, which may cause clogging of fuel filters and separator, sticking of fuel injection pumps and considerable pump deterioration,” he said.

Allweiler confirms that several major shipowners operating in the deep sea trade are facing major overhauls or full pump replacements. And the main concern is low viscosity levels when operating with low sulphur diesel fuels. 

Martin explained: “When switching from HFO to diesel, oil temperatures must drop from 150 degrees to 40 degrees. This process is extremely difficult to manage, due to the resulting low viscosity of diesel caused by too high temperatures. Or the very high viscosity HFO levels caused by too low temperatures.”

Extremely low sulphur content and consequent low viscosity levels have a strong impact on fuel injection and pump/valve lubrication. Pumps must be capable of handling low viscosity fuels while retaining the required pressures and capacities.

Servicing hundreds of shipping clients around the world, Allweiler is experiencing an increased demand by shipowners for technical evaluations and modification recommendations of existing pumps.

“Compared to the past, today’s fuel oil pumps encounter new operational conditions. Shipowners are in doubt about the effects of low sulphur content diesel fuels and the limits that pumps can handle, especially when exposed to mixed fuels,” said Martin.

All fluids. No limits
Pumps must carry out their intended functions under defined conditions and with a defined high level of reliable operation.

“Optimal pump performance depends on the type of materials used to construct the pump, which must be appropriate for the liquid’s chemical and physical properties, operational conditions, such as pressure, speed, temperature, and the areas of operation,” said Martin.

Allweiler 3-screw pumps are modified, comprising specially treated materials, to minimize the risk of sudden break downs, thus providing long-term reliable operation.

 Allweiler is one of the very few manufacturers giving accurate and clear answers to functional safety of marine pumps, undertaking pump assessments to evaluate premature wear, and recommending the right, cost-efficient solution.