Pump group meets low-sulphur challenge

31 Jul 2010
Imo fuel pump in the engine room

Imo fuel pump in the engine room

When a major oil-tanker operator discovered its existing fuel oil pump system could not meet new environmental regulations for ships entering European ports designated in emission-controlled areas (ECAs), pump group Colfax became involved.

Colfax responded with an Imo OptiLine pump solution that assured the operator’s tankers could use low-viscosity, low-sulphur fuel to meet current and upcoming regulations. The operator – which maintains 100 vessels and holds an ISO 14001 certificate for reducing its environmental footprint – wanted to comply with the low-sulphur fuel requirements as soon as possible.

The Colfax team from subsidiary Imo examined the tanker operator’s existing technology, evaluated its service environment and determined its current pumps could not handle the low-sulphur fuel. By contrast, the company’s previous pump supplier had been unable to fully explain why the current engine-room pumps were not capable of handling future fuel demands.

That lack of knowledge not only caused headaches and hassles for the tanker operator, but it also meant that if a suitable solution could not be found, its vessels might not be allowed to dock in certain ports in 2010. The Colfax team quickly confirmed that its solution would bring immediate benefits today and long-term advantages for years to come. Alfa Laval, the Imo AB distributor in the Middle East, played a key role in initiating the upgrade program.

The Imo OptiLine pump systems selected are of a screw design that relies on the rotors being lubricated by the pumped media. An oil film that builds up by the hydraulic balance in the pump causes the rotors to ‘fl oat’ and attract lubrication. The ship operator has installed 55 IMO OptiLine pumps on 12 of its tankers, enabling them to use low-sulphur fuel, and will outfit an additional 38 ships in the near future.

Unique challenge

Colfax believes that ship owners currently find themselves facing a unique challenge, resulting from an array of current and upcoming environmental regulations. Among them are the MARPOL Annex VI Regulations for the Prevention of Air Pollution from Ships, which stipulate that burning of high-sulphur fuel oils is not permitted within ECAs. Those regulations and the timetables for meeting them differ for ports around the world.

Since May 2005, specific MARPOL regulations requiring emissions from main and auxiliary machinery be kept within specific limits have been in force. They require, for instance, reduction of sulphur oxide (SOx) combinations, carbon dioxide (CO2) and nitrogen oxide (NOx) combinations.

Additionally, European Union directives for 2010 require ships at berths for more than two hours to use marine fuel oil with 0.1% sulphur content. This means that most ships have to switch fuel during port stay to low-sulphur, low-viscosity MGO. This fuel, due to its low viscosity and poorer lubricity, is expected to have a great impact on ships’ machinery, especially fuel oil pumps.

Prior to the regulations, ships could burn more viscous higher-sulphur fuel, often requiring heating so that it becomes less viscous and easier to pump. But the low-sulphur fuel is less viscous to begin with, and ambient temperature in a crude oil transport ship engine room easily reaches 40° C and higher – in some cases as much as 55° C. Adding excessive heat from pipes and engines will raise the temperature even further. As a consequence viscosity will fall, causing a significant change of operating conditions in the system. Ships therefore need cooling units to bring down the temperature of MGO to make it thick enough to pump.

Under some of the regulations, ships can continue to burn the higher-sulphur fuel until they near a port, at which point they must burn the lower-sulphur diesel. To do that, they need a fluid-handling system flexible enough to handle both.

Lowering total cost of ownership

The OptiLine pumps are designed without a mechanical seal, which makes them 100% leak free. Excess leakage can lead to actions from external parties – such as harbor authorities, class authorities and others – possibly resulting in denial of access to port, a delay in port or an extensive cleaning operation that cannot be handled by an engine-room crew. Such cleanings entail the expense of hiring an external specialist.

Leak-free operation and a long service interval (five years) are claimed to have a significant impact on the cost of spare parts, man-hours and cleaning. Colfax says that the tanker operator can therefore rest assured its choice of pumping solution will function in the most efficient manner with the lowest cost of ownership to keep it in compliance with low-sulphur regulations for years to come.

Through its global operating subsidiaries, Colfax manufactures positive displacement pumps and valves under the Allweiler, Fairmount Automation, Houttuin, Imo, LSC, Portland Valve, Tushaco, Warren and Zenith brands.

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