Oil fuel

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Kathy A. Miles

I've searched the board for this and didn't turn up anything so I'm hoping someone can answer this. What type of oil was used when Olympic was converted? Do any ships in service now use it, and are there advantages/disadvantages of oil as opposed to diesel?
I also did read a thread which stated that the boilers would have still been used with conversion to oil, but not with diesel. Is this so? Please pardon my ignorance, but I'm assuming that when they used oil, they would still be producing steam pressure via the boilers. How did it work when they ran diesel?

Scott R. Andrews


The Olympic probably burned what is known as Bunker 'C', a thick nearly tar-like substance that is left over from crude oil after most of the more volatile and valuable components hve been distilled from it. This was the most common fuel type in use in large merchant ships that burned oil fuel, primarily due to it's low cost.

Boilers are fitted to produce steam to drive steam engines, be they of the piston reciprocating type or turbines. On ships with diesel propulsion, boilers aren't required as diesel engines are piston-type internal combustion engines - that is to say the fuel is injected directly into the cylinders of the engine and ignited there. In operation, the diesels on board a ship are not very different in concept to those which drive large commercial trucks; also, they're not all that far removed from the sort of engine that propels the automobile you drive.

Most modern cruise ships are diesel driven in one form or another. The smaller ones generally use large low speed engines which are directly coupled to the propeller shaft. In very large cruise ships, diesel-electric plants are the norm, with several smaller medium speed engines turning alternators which produce electricity use to drive the propellers via large electric motors. Lately, gas turbines (basically large jet engines) have also begun to make their appearance in electric drive, replacing the diesels driving the alternators.


Scott Andrews
I was at sea in the late 80`s and the ships I was on were quite modern, built in about `86.
The main engine was fuelled by "Heavy" (bunker "c"), but before it could be used it had to be pre-heated to some ridiculous temperature prior to injection into the cylinders of the engine. This was done to thin the tar like oil and turn it into a nearly gaseous state, so that injection was possible.
The unusual thing about these ships was that the electrical generators were fuelled by heavy as well. Normally generators are fuelled by "Light" Diesel, but the designers (Wartsilla of Finland) thought that heavy could be used with more heating and filtering. They did work, but on the six trips with the shipping company I became very good friends with the Wartsilla engineers who had to keep returning to the ships to repair the generators. These were the first ones installed in a ship (I think) they worked, it was 13 years ago so they might have got round the teething problems of the first ships.

Best Regards

WEll, Bunker Oil 'C' is still used as Steam Engine fuel. Some museal ships and railroad locomotives still use this fuel to fire their boilers.
The problem is to get the sticky thing into a liquid form, so mix it with air and enlight a flame to fire...
For this in railroad engines as in ships fuel bunkers a couple of steam heating tubes is mounted, the first couple is the pre-heating, and about the bunker reaches 50-70°C at this step. The last step is the pre-transport heating, which couses the oil short before entring the transportation lines and tubes to be preheated up to 110-130°C. Transportation is seldom done with a mechanicaly pump, more with steam driven injector like pumps in the transportation system, often short before the fuel burner. The steam 'draggs' the oil with it, and another steam jet will blow the steam through the burner nozzle to form a spray fog, which will readily mix with the air in the firebox, and is enlighted by a flame or the hot insulation stones of the firebox...
If sometimes the preheating was failure, the locomotive was nearly immobile, because the transportation lines were quickly clogged and so no fuel was transportated to burn into the firebox...
in RailRoad cases, the fuel comes in large barrel trucks, often having a electrical preheating, and in railroad trucks they also often have a steam fitting for steam preheating. The electric preheating also heats up the transportation pump, and without proper preheating the pump won't move, so the locomotive could not gets its fuel.... not realy a trick.
Modern steam engins are driven with diesel, so they have a burner like you can find in some modern steam heating boiler systems used for central heating of buildings, and they have the same electronical boiler and burner control, so the enlight the boiler, and adjust the flame in ability to the needed steam and power, and evenly switch the burner off if no steam is required, as in stations or traveling downhill.
so the engeneer can trigger the burner to flame manually befor part the station, but commnly the electronic will do, so these engines generate horrible power and are often less fuel consuming than diesel engines (even if most want not to believe!)
Attached is a picture-link of the ships engine with the boiler in the background, fuel is diesel, and the whole engine is controled by a single engine control stick, as some might now from their boat at home...

Click to:
Liners in the 1920s used what would now be called bunker C - it is very viscous and has to be heated before use in steam heaters. It also has to be settled as it contains residue from its source i.e. prehistoric vegetation. On tank cleaning it was possible to see some of the fern like matter deposited in the bottom of the settling tanks.

The Paddle Steamer Waverley still uses heavy oil but with a modern boiler installation the burners are automatic. With her old double ended Scotch boiler (like one of Olympics 24) the oil fuel supply was controlled manually.

Erik Wood

Speaking from experience...I say the following...I HATE BUNKER C!!!!

Bunker C actually has to be warmed before it can easily flow thru the pipes and when it is loaded the ship (especially engineering) has a stench that takes days to get rid of. It usually makes me nausas. If you want to get me sea sick take a small jar of bunker C and leave it uncovered, then add heavy weather and turn up the heat and yours truely will then, and ONLY then be sicker then sick.

Bunker C is still used today as mentioned above for steam plants.
Just to compound the felony somewhat; when I was in the bunkering department of a large fleet operator many and many moons ago:-

I seem to recall the two principal commodities were 'fuel oil' and 'gas oil', the former for boiler firing of steamships, the latter for diesel main engines.

However, it was often the case that boiler oil (fuel oil) would be supplied to motor vessels as the main propellant, it being more economical than diesel!


David Haisman

Ship's bunkers come in various grades, the more popular types for the great liners in my day were the H.F.O. M.F.O. and L.F.O. grades, the smaller vessels more likely to use M.D.O. (marine diesel oil) and Gas Oils.
As skipper on two bunkering tankers namely, the Beechcroft and Baccarat, our main services were to ships at anchor in the Cowes Roads and also the delivery of petrols, kerosenes ( two grades) and central heating oils to Poole the Isle of Wight and Shoreham.
H.F.O. (heavy fuel oil) was loaded by steam traced lines at the refinery and kept hot onboard with steam lines on the bottoms of the tanks until bunkering.
M.F.O. (medium fuel oil) was usually handled the same way and line clearing was done from the ship's manifold by the use of water.
Hence water is usually found in ship's bunkers quite often but drained off, the same as in refineries at certain times from the bottoms of the tanks.
In one of my previous posts I did mention how ships found water in their bunkers from time to time, well that is one of the reasons.
With ''light ends'' such as Gas oils, kerosenes and diesel fuel, these were regarded by us as ''static accumulators'' and an inert gas such as nitrogen was used for line clearing.
As always, one corner of the fire triangle was always kept out throughout the whole process although air blowing was not uncommon with some operators with H.F.O. due to it's flash point and s.g.
Kerosene , some may find hard to believe, is one of the most dangerous of products for static and is always gravitated for the first several hundred tons until pumps are put in. The old Queen liners were on H.F.o_Or perhaps M.F.O and were bunkered by a vessel around 75 years old called the ''Inveritchen''continually steam traced and was owned by Esso in those days.

When delivering bitumens, our ship was as warm as toast throughout and in heavy weather, the man on the wheel steered completely through a cloud of steam rising from the hot tank deck that was continuously awash from seas crashing on the fore deck!

I hope some may find that of interest.

David H
>>I hope some may find that of interest.<<

I did. It showcases how miserable it can be to handle this stuff, to say nothing of dangerous for the lighter grades.

Paul Rogers

Hello David.

You said: "Hence water is usually found in ship's bunkers quite often but drained off, the same as in refineries at certain times from the bottoms of the tanks. In one of my previous posts I did mention how ships found water in their bunkers from time to time, well that is one of the reasons."

If it's not a silly question, what are the other reasons that would lead to ships ending up with water in their bunkers?

You also said: "As always, one corner of the fire triangle was always kept out throughout the whole process although air blowing was not uncommon with some operators with H.F.O. due to it's flash point and s.g."

I'm really going to show my ignorance now. I assume "s.g." is specific gravity? Also, what are the components of the "fire triangle"? I'm guessing: (1) oxygen (2) the fuel itself and (3) some sort of ignition source; static electricity or heat?

David Haisman

To answer your questions Paul, the continuous use of heat in petroleum products will cause the eventual accumulation of condensation in bunkering tanks and shore storage tank farms.
Testing for the amounts of water which is always heavier than the product (with an s.g. of 1.0) is usually done by sounding as it always lies on the bottom of the tank.
This is carried out with a sounding line and brass measuring rod (brass being spark proof) covered in a green paste which will turn purple on contact with water.
The fire triangle is fuel air and ignition and as long as one of those is missing, safety in the handling of petroleum products is generally assured.
I mention the use of air blowing for line clearance for H.FO. but this is frowned upon by refinery operatives for good reason.
Air under great pressure can cause friction and the fire triangle again becomes apparent. However, with the low flash point and s.g. of that product it is considered safe by some operators on ships.
Small bunkering firms sometimes use that method as nitrogen can be expensive if used a great deal, again money comes into it.
When completion of bunkering is reached, sea water is introduced into the bunkering ship's tanks and the final line content of anything up to 5 to 10 tons or more, is blasted through the hose to clear it.
This may sound a lot but it's a small amount when bunkering up to a 1000 tons or more and quite harmless to the end product.
It's also extremely essential to get these lines clear for fear of developing ''cold plugs'' which can be a nuisance and a work up.
Nitrogen is always used with white oils or ''light ends'' as it's known in the trade and a small pressurised hose on the outboard side of the manifold was all that was required.
Once bunkering was completed, the main manifold valve was shut, the nitrogen valve opened up and the line content blasted onboard that way with the receiving ship's valves left open.
Yes, you are right. s.g. is specific gravity and it's extremely important to know the values when dealing with these petroleum products.

Regarding the use of the word ''heat'' in the fire triangle it's not accepted by refinery operatives in the UK. Consider petrol spilled on a hot road for instance and the chances are it will evaporate and not ignite.
Put a spark to it and it will almost certainly flash off.

David H

Paul Rogers

Thanks very much David - interesting stuff.

You said: "Consider petrol spilled on a hot road for instance and the chances are it will evaporate and not ignite. Put a spark to it and it will almost certainly flash off."

On a bit of a tangent, I remember my Dad telling me how, when he was an engineer in the RAF during WWII, he and his mates used to flick their fag butts into petrol drums - I have no idea why! (The butts just went out, allegedly). Apparently, as long as the drum was relatively full of petrol, everything was fine. Seemed to me at the time a strange way of playing Russian Roulette but, if there was very little oxygen in the drum, I guess the fire triangle wasn't present. I expect that people soon found out if there was only petrol vapour left in the drum!

David Haisman

Regarding your dad flicking fags into petrol drums and nothing happening, they probably knew the reason why.
Flashes have been witnessed by process operators when taking samples from ships tanks.
The reasons have always been the lack of air and the '' too rich to ignite theory ''.
Perhaps......who knows?....... When it happens it's usually too bloody late to find out anyway !

David H
Im not an engineer, but I understand that today diesel engines on big ships run on heavy fuel oil. Yes, the type you have to heat to make it liquid at all. I know engineers hate it in some way, but the motormen like it cause it gives them a lot of overtime with all the extra maintenance when the engines are run on HFO instead of DO.

Here the politicians are discussing banning the use of HFO on ships cause it gives more pollution i guess. I dont agree with this as I understand the HFO is pretty much refinery waste and cant be used for anything else than ship fuel. So, we will have a waste problem.

Ive heard of fuel oil grades like IFO 180 and IFO 380, anyone knows what this means? And if this is the same as the Bunker C mentioned above?
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