Fuel consumption

20th July 2009, 08:56
There is a discussion at present by BI engineers about fuel consumption. Are there figures available about the ships we sailed on compared with modern ships?
Do I remember correctly that Southern Cross used 200 tons a day ?

Satanic Mechanic
20th July 2009, 12:41
fuel consumption can be a very open to interpretation and variables.

If you are comparing engine efficiencies then you are far better getting the specific fuel consumption in g/kW hr or the imperial equivalent lb/ hp hr. rather than daily rates.

Modern slow speed diesels we are down to around 155 - 160 g/kw hr which if you compare to modern car engines of around 200- 230 g/kw hr you can see why we get a tad peeved about getting accused of being the The Great Satan of Worldwide Pollution.

On the other hand if it is hull form efficiencies you are wanting to compare then it gets a bit complicated but I would be inclined to simplify down to power divided by speed at that power to give you a figure in kw/knot. Its the easiest way that I know of.

Now lets get those old notebooks out and get some figures

20th July 2009, 21:44
On the old oil fired jobs a 15% margin was the norm with bunkers, as far as consumption figures with say a 8,000 ton single screw freighter @ 10knots 2,700 ihp, VTE, Scotch Boilers, 34 tns per day
On a 4 stroke diesel on a ship of a similiar size with 2,500 shp 11tns per day.
This comparison speaks volumes does it not?

21st July 2009, 00:03
I'm reminded of a conversation I once overheard between an old Lykes Lines Master and the Captain of a U.S. Navy warship. The Captain mentioned how fast his ship could go, and then asked the Master what the maximum speed was of his ship. The Master said he didn't know, he always ran his ship at her most economical speed and never worked her up to full speed. The Master then mentioned the daily fuel consumption of his ship, which he knew to the barrel, and asked the Navy Captain how much fuel his ship burned. The Navy Captain said he had no idea because his fuel was replenished at sea every third day.

21st July 2009, 08:41
300K DWT tankers max. bunkers, was in excess of 6000tons, when the bunker price went up to US$300+/ton/HFO one Chief I knew used to pull the Master's leg, by saying that he'd had an offer of 5% of the bill to go to another bunker man!

21st July 2009, 10:20
I was working for sulzer at the time when they broke the 50% thermal efficiency 'barrier' with a customer's engine on the test bed in winterthur. admittedly running on MDO and not a residual fuel.

Which leads on to the fact that ships use significant volumes of residual fuel that otherwise would be forming a waste mountain or covering the world with even more motorways! Checking out some basic refinery figures the residuals account for something between 20 to 35% by volume of crude stock so perhaps shipping should trumpet the fact that it uses up the residuals rather than use up even more MDO and so requiring even more crude to be refined.

I do wonder though at the economics of container ships sailing as fast as they do. speedy turn round in port is one thing but would a knot or two less make all that much difference to the shipment of goods especially today with less freight and low freght rates?

On a tanget, last week as i flew from guernsey to torbay ( Berry head VOR to be precise) passing over the eastbound traffic bellow were a car transporter, a tanker and a maersk continership. the exhaust from the first two probably rose to 500ft or so before dissipating but the exhaust from the containership went up at least another 500ft where it met the inversion layer and formed a small cumulus cloud as the water content met the colder air layer. an indication of wasted energy perhaps?