Weight and fuel consumption

[jraef]

I need some help from Marine Engineers.

My company is proposing a solid state electrical control system for large compressors used on tankers. Our main competition is using an old technology that consists of large heavy transformers. I know that space is always at a premium on marine vessels and our system is 1/2 the size, but doesn't increased weight also translate into increased fuel consumption when at sea? We are speaking of 3000-4000lbs extra per system, and 4 systems on each vessel between our two proposals. I would love to be able to show them an estimate of additional fuel cost, maybe as a ratio since I don't know any actual figures.

Any ideas?

"Venditori de oleum-vipera non vigere excordis populi"

 

[GregLocock]

Well, I wouldn't get your hopes up! I think a better line of argument might be the extra cargo that could be carried, but I don't think 8 tons in 100000 is really going to be conclusive!

Anway for the sake of argument, assuming that skin drag dominates (not unreasonable), and we take a smallish tanker

9. 17,500 DWT Product Oil Tanker [2001-08-29]
Jing Jiang Shipyard (Jiangsu New Century Shipyard Group) [Province: Jiangsu]
Length Overall: 158.00m Breadth Moulded: 27.00m Depth Moulded: 11.70m Design Draft Moulded: 7.00m CLASS: LR Main Engine: MAN B&W 7S35MC Speed: 13.0kn Owner: PT HUMPUSS INTERMODA

8 tons will increase the draft by 2 mm, and will increase the fuel consumption by 0.009%







Cheers

Greg Locock

 

[mshimko]

How much weight is "significant" depends on the vessel, it's design, usage, etc.

It's possible that the vessel when fully loaded is already "weight critical", in which case you may need to propose how the shipowner can compensate fot the additional 12,000lbs. I'm not a naval arch; but I've had engineering changes proposed for large ships and I was required to obtain a detailed weight analysis, even for changes of a few hundred lbs.

 

[jmw]

Fuel typically represents about 70% of the operating cost of a vessel. Not to be sneezed at and with low sulphur caps adding perhaps $65 a ton premium this will increase.
But, maintenance is an issue. Modern ship design is increasingly about "Unmanned Machinery Space" i.e. target is no people, no skills.
Capital cost is a key issue for the buyer and operating costs for the charterer.

JMW

http://www.ViscoAnalyser.com