Boating NZ - - Boat World -

More than $250,000 in an­nual fuel sav­ings for two Royal New Zealand Navy ves­sels is on the cards thanks to a unique en­gi­neer­ing so­lu­tion de­vel­oped by the Navy and its fleet main­te­nance part­ner, Bab­cock (NZ)

Off­shore pa­trol ves­sels HMNZS Otago and HMNZS Welling­ton were de­signed to run (mostly) on just one of their two main en­gines. The speed gen­er­ated by one en­gine is gen­er­ally enough for op­er­a­tional re­quire­ments.

But the is­sue with this, says RNZN Lo­gis­tics Com­man­der Mar­itime, Cap­tain An­drew Nut­tall, is that the trail­ing shaft, even though not pow­ered by an en­gine, still turns be­cause of the wind­milling ef­fect of the pro­pel­ler through the wa­ter. This gen­er­ates heat in the gear­box.

“The pump sup­ply­ing coolant to re­move the heat is driven by the en­gine and, with it shut down var­i­ous com­po­nents be­gan over­heat­ing. To avoid that, both en­gines were run most of the time, even though only one was re­quired.”

This trans­lated into $200,000 of ‘wasted’ fuel used for every 1,000 hours of run­ning. Hav­ing both en­gines op­er­a­tional also re­quired more main­te­nance.

RNZN and Bab­cock de­vel­oped a sys­tem that cross-con­nected the cool­ing sys­tem, so that when an en­gine was shut down the pro­pel­ler could still ro­tate, while the heat gen­er­ated was cooled through the di­ver­sion of coolant.

“The sav­ing in fuel alone is im­pres­sive. Com­bine that with the re­duced main­te­nance costs and this so­lu­tion rep­re­sents an ex­cel­lent ex­am­ple of the value our en­gi­neer­ing team can add.”

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