Auxiliary engine developments

Marine diesel engine specialists Wärtsilä and MAN B&W share a common goal in many respects. One such example is the intention to significantly increasing the time between overhauls (TBO) on their marine auxiliary engines

MAN B&W says that for any engine, the time between overhaul (TBO) is a constant focus for the designer and for the operator. The operator seeks the longest possible intervals, with respect to the initial investment and without having to spend too much on the daily service costs. Also, the engine designer seeks to obtain the longest possible overhaul intervals, with respect to market competition, design tools, procurement and manufacturing costs.

Wärtsilä offers the shipowner three types of auxiliary engine, the Wärtsilä 20, Wärtsilä 26 and Wärtsilä 32, for marine generating sets with electrical outputs of 495 to 8,640kW. The Wärtsilä 20 has cylinder configurations of four, five, six eight and nine cylinders in-line, while the Wärtsilä 26 and 32 are both offered with six, eight and nine cylinders in-line and 12, 16 and 18 cylinders Vee-form.

All are turbocharged four-stroke type built for reliable heavy-duty operation on the same heavy fuel oils as in the main engines.

MAN B&W has sold more than 100 L21/31s since the first L21/31 GenSet was installed onboard the Princess of Scandinavia. This set has now passed its 10,000 hours of service with a positive service record. The L21/31 is the third of the new generation of GenSets from Holeby. The first, the L16/24, was introduced in 1996, and the next, the L27/38, was introduced in 1999. The L27/38 has been particularly popular in the container ship market, and the sales record is approaching the 1,000 engine mark.

2,000th engine

Wärtsilä Corporation has also been strong in this market and has manufactured its 2,000th Wärtsilä 20 diesel engine in its ten year production run and service experience has confirmed its ability to achieve long times between overhauls. The engine manufacturer says that up to 24,000 hours operation between overhauls are achieved on light fuel oils.

The 2000th engine is one of three nine-cylinder engines being supplied as complete diesel generating sets for a 2500 TEU container ship being built at the German shipyard Aker MTW Werft GmbH in Wismar for the German shipowner Reederei Nord Klaus E. Oldendorff GmbH. This is one of 16 container ships of the same class from Aker MTW for various owners, for which Wärtsilä has also supplied Sulzer 7RTA72U-B main engines but with various configurations of Wärtsilä 20 generating sets according to the shipowners? requirements.

MAN B&W has also achieved an important milestone working with CP Ships (UK) Limited when its MAN B&W Holeby L28/32H GenSet reached its 24,000 hours operating interval and the owner is now heading for 30,000 hours before the main overhaul.

The company opened up the No. 3 auxiliary engine on Canmar Courage, which is seven years old and has run 24,441 hours since new without being opened up. The Canmar vessels are each powered by one six cylinder and two nine cylinder sets.

“We took a look at one unit to gauge if we could extend the running hours to 30,000, when I believe the main bearings should be inspected,” says Paul Siddons, technical director of CP Ships. He explains that the fuel used is 380 cSt and is quality controlled through full analysis before it is put to the engine. Also the lube oil is analysed every three months and frequently separated and always maintained within specification.

At 27,000 hours, if the pulled cylinder unit looks good, then Siddons says he will be confident in continuing the operation to 30,000 hrs, where a complete overhaul will be carried out, which is expected to take place at the end of the year.

This means that CP Ships plans to continue with these ships for 10 years and 30,000 hours. This is possible with the ships? load pattern ? where one of the three GenSets onboard is normally sufficient powerwise for the ships hotel load and the reefer containers.

Consequently, the GenSets are loaded at approximately 75-80% of MCR. Two of the GenSets are continuously running on 380 cSt HFO, whereas the third standby set is held on MDO. The third GenSet is only in operation for the additional bow thrusters power during harbour manoeuvring.

In order to even out the operating hours on all three sets, the power tasks for the GenSets are changed and turned around for each vessels? round-trip.

Common?rail

The leading development for Wärtsilä auxiliary engines in recent years is common-rail fuel injection and has been coming into service with a growing number of Wärtsilä engines during 2003. Although the majority of these are ships? main engines, with the largest installation being four Wärtsilä 16V46 engines with a combined output of 67.6 MW in the new passenger liner Queen Mary 2 being delivered in December 2003, there are also a significant number of Wärtsilä common-rail engines in marine auxiliary applications.

At present, only the Wärtsilä 32 engines are available for marine auxiliary applications with common-rail fuel injection. Their lack of visible smoke makes them particularly beneficial in port when engines might be lightly loaded supplying power for lighting, air conditioning and other hotel systems, as well as some engine-room ancillary services.

The first application of Wärtsilä 32 engines with common-rail injection is for powering generating sets in large container liners. The first such engine entered service in March 2003 in the containership Axel Maersk, built at Odense Steel Shipyard A/S in Lind?, Denmark, for AP M?ller. Similar plant has been on the Anna Maersk, Arnold Maersk and Arthur Maersk.

Each of these ships actually has four diesel generating sets, three with Wärtsilä 8L32 engines and one with a Wärtsilä 6L32 engine. One of the eight-cylinder auxiliary engines is equipped with common-rail fuel injection.

The Wärtsilä 8L32 sets each give an electrical output of 3460 kW at 720 rpm, and the Wärtsilä 6L32 set 2590 kW at the same speed.