New ratings for Wärtsilä low-speed models

04 Oct 2011

More powerful versions of two designs in Wärtsilä’s RT-flex series of electronically-controlled, low-speed engines have been released, writes David Tinsley.

The RT-flex58T in its new E variant has a maximum rating of 2,350kW/cylinder compared to the 2,260kW/cyl of the D type, which will remain available to customers who prefer the existing rating.

The E version accordingly puts the maximum (R1) power spread into the 11,750-18,800kW range at 105rpm, compared with 11,300-18,080kW at the same running speed for the D engine. Mean effective pressure has been raised from 20.2 to 21.0 bar. While the rating spread for both versions begins at 7,900kW, the latter is obtained at 90rpm in the latest model, rather than at 84rpm as in the D-type.

The current generation of 580mm-bore engines, produced in five- to eight-cylinder format, has been conceived mainly for bulk carriers and tankers in the 20,000-circa 150,000dwt category.

The more recently introduced RT-flex82T engine series has been augmented with a B variant offering increased power and also a slightly modified running speed for the benefit of container vessel applications. The original output was 4,520kW/cyl on the R1/R1+ rating at 76/80rpm. The new B model gives 4,750kW/cyl at R1/R1+ rating points at 76/84rpm.

As a consequence of the development, the RT-flex82T-B offers a maximum power concentration of 42,750kW, in nine-cylinder configuration, compared to 40,680kW in its predecessor. The series otherwise comprises six-, seven- and eight-cylinder models.

The refinement of the two-stroke portfolio has also encompassed a design update of the RT-Flex68-D with the aim of achieving improved manufacturing-friendliness for the benefit of licensees and a slimmer outline to better meet installation requirements for containerships.

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