The cost of steam versus diesel

Ian6
2nd June 2009, 15:03
A few questions from on deck for the engineers amongst us. When I was at sea in the 50s and 60s by chance every ship in which I served was steam powered. They ranged in type from WW2 T2 tankers to passenger ships and in size from an 8,000 ton cargo ship to a 45,000 ton passenger ship. The two things they all had in common were boiler rooms and steam turbines. Sometimes the turbines were the direct means of propulsion, sometimes they generated electricity for the electric motors that drove the ship. They seemed reliable and there was less noise and vibration than the diesels of that era. From the bridge there were horror stories of the engine room phoning up to say they only had enough compressed air to start the diesel so many more times, some thing that never occurred with steam.

Now you would be hard pressed to find a steam ship. From the smallest to the largest new build the diesel is king. In the 50s the engineers with whom I sailed viewed diesels as hard work and unreliable although by definition those engineers mostly had steam-only certificates and saw a motor endorsement as another hurdle to promotion to senior levels.

I realise that it is straight economics that has caused this change. With steam propulsion oil was burnt for sometime before the ship could move in order to raise enough steam pressure to drive the turbines. When manoeuvring say through canal locks or entering an enclosed dock there were periods when the screws were still but the boiler continued to burn oil.

Finally my questions: on a full day running at sea, no stops or starts, does a diesel burn less oil than an equivalent steam ship used? The QE2 was famously converted in 1986 from steam to diesel. Were savings made every day or merely at the beginning and end of an Atlantic crossing? How did the cost of marine fuel oil burnt in boilers compare with marine diesel oil?

Ian

fred henderson
2nd June 2009, 15:21
Ian

The QE2 conversion in 1986 was not merely from steam to diesel-electric propulsion. She was the first major passenger ship to use the power station concept that is now universally employed in all new-built large passenger vessels. Nine MAN diesel engines were available to generate electrical power. They were brought on-line as needed to meet both propulsion and hotel requirements.

It was stated at the time that the conversion reduced fuel consumption by 250 tons per day. The fuel cost saving was sufficient to pay back the 100 million conversion in five years.

Fred (Thumb)

Ian6
2nd June 2009, 15:54
Thanks Fred

That sounds fairly convincing, not just waiting for the 'kettle to boil' but real savings.

Like so many changes we have seen harsh economics always win over sentiment.

Ian

Supergoods
2nd June 2009, 18:22
Initially the diesel vessels burned, as their name implied, diesel oil.
This is more or less double the price of Bunker C which was burned in steam ships.
Fuel consumption of the steam ship was roughly double the quantity burned by a diesel ship so the economics were pretty much a wash.
Steam turbines were reputably more reliable so had some advantages.
At some time it was discovered that large marine diesel engines could burn an intermediate fuel of heavier viscosity. This fuel was much cheaper and in some areas of the world it was, in fact, Bunker C (Persian Gulf for instance).
The diesels still usually burned diesel when manoevering in port.
Until comparitivly recently diesel engines were limited in output, so high perormance or large deadweight still required steam turbines. (For example early container ships and large tankers.

Fuel types commonly found:
Bunker C: A residual fuel after the refining process was completed and varying considerably in viscosity.
Intermediate Fuel Oil: A Blended product comprided of Bunker C and Gas Oil to achieve a specific viscosity (Common values were 1500 Redwood or 380 centistokes)
Ordinary Marine Diesel: Gas Oil delivered in a dirty (Bunker C) Barge
Gas Oil: Gas Oil delivered in a clean barge
No 2 diesel Diesel fuel as used in the road haulage industry, sometimes found on offshore supply vessels.
Medium speed diesels had further restrictions including the origin of the crude oil from which the blend was made.

A lot of the post above was learned buying fuel for a time charter operator between 1973 and 1983

Ian

surfaceblow
2nd June 2009, 19:31
The cost of the machinery for steam vessels is also higher then diesels. In the mid seventies the rule of thumb for Slow Speed Diesels was 1 million dollars per cylinder for a diesel plant which included all of the auxiliaries, tools, and spares to 8 - 16 million for a similar sized steam plant.

A set of low noise reductions gears can take up to a year to cut besides the cost to buy or lease them if you can find a company that still makes them. You could go turbo electric to avoid the reduction gears. Then you still have the cost of the boilers and the increased bunker capacity needed due to the increase fuel consumption.

Ian6
2nd June 2009, 22:24
Thanks for those replies. The argument is clearly settled. My Father-in-law was at sea for a lifetime until he retired in 1969 and sailed in motor-ships for the last 15 years. I was clearly one of the last dinosaurs.

Ian

Klaatu83
2nd June 2009, 23:10
Diesel engines not only burn less fuel but require no watchstanders. All the steam ships I sailed on required a round-the-clock engine room watch of one licensed engineer, one oiler and (on the older ships at least) one fireman/water-tender. The modern diesel ships I've sailed on required no engine room watch at all. The engines were monitored from the bridge, and one of the engineers (called the "Duty Engineer") was designated to answer an alarm in case anything went wrong.

Apart from the cost of fuel, however, once must also consider the less-easy-to-compute costs of maintenance and reliability. All of the diesel ships I sailed on required far more maintenance then any of the steam turbine ships I sailed on. Scarcely a night passed on some of them without the engine room alarm going off at least once. I also experienced far more instances of diesel engines breaking down at sea, leaving the ship dead in the water. On one memorable occasion a diesel ship I was on actually lost the plant in the middle of the Dover Straits!

Satanic Mechanic
3rd June 2009, 20:26
Probably the last of the steam turbine ships was built last year as even the LNG vessels are now Reliquifaction or Dual/Tri fuel diesel electric with the possibility of a slow speed gas engine always on the horizon.

With modern metalurgy, lubricants and technology the maintenance intervals for diesel engines have increased by huge margins so even the arguement of greater maintenance no longer really applies and with the cost of fuel the savings are enormous.

Just a couple of notes on posts above. Steam ships are excellent unmanned and have been for many years.

Diesel engines originally ran on blast injected pulverised coal!!!!

spongebob
3rd June 2009, 23:49
Satanic, You are right about the design and management advances with both diesel and steam powered sources.Land boilers have long been built and equipped to the British and other unattended codes while diesel engines , their design, fuel management systems and construction have made quantum leaps.
They at least parallel the humble car engine's progress as we think back to the rust buckets of 30 years ago that did less than 30,000 miles without needing a valve grind whereas today's Toyota and others will clock up 100,000 miles without needing the cylinder head off.
One big advance has been the arrival of Computer Numeric Controlled machine tools that have allowed manufacturing accuracies to the Nth degree.

Bob

Peter Short
4th June 2009, 04:26
Diesel engines originally ran on blast injected pulverised coal!!!!

Satanic,

Sorry, but that is a myth. But in the strange way of myths it is one 'fact' that everyone knows! (I hear it quite often).

The first tests were made with petrol, which gave all sorts of problems. Then kerosene was used. Quite some time after (years? I need to re-read the history, not even the first engine) a series of tests were made with many different fuels including gas. Right at the end coal dust was trialled (they knew it would damage the engine) and results were taken. Others went on to develop the coal burning engine, not Diesel.

Another generally unknown feature of Diesel's first engine - he used solid injection. In other words Diesel knew exactly what he wanted from the beginning, but because of injector troubles he went to blast injection as a workable solution.

All this and huge amounts more in the excellent Diesel's Engine by Lyle Cummins, a must-read for anyone interested in the development of the Diesel engine up to 1919.

Satanic Mechanic
4th June 2009, 06:13
Satanic,

Sorry, but that is a myth. But in the strange way of myths it is one 'fact' that everyone knows! (I hear it quite often).

The first tests were made with petrol, which gave all sorts of problems. Then kerosene was used. Quite some time after (years? I need to re-read the history, not even the first engine) a series of tests were made with many different fuels including gas. Right at the end coal dust was trialled (they knew it would damage the engine) and results were taken. Others went on to develop the coal buring engine, not Diesel.

Another generally unknown feature of Diesel's first engine - he used solid injection. In other words Diesel knew exactly what he wanted from the beginning, but because of injector troubles he went to blast injection as a workable solution.

All this and huge amounts more in the excellent Diesel's Engine by Lyle Cummins, a must-read for anyone interested in the development of the Diesel engine up to 1919.

erm - lost me on this one

Peter Short
5th June 2009, 03:37
First of all, I have enjoyed finding this forum recently and reading some excellent threads. I guess I have got off to a bad start by offering a different opinion, but I better keep at it :) . No offense intended, I hope I can contribute something of interest. Also it does touch on the steam/diesel question so hopefully of interest to the original poster.

I have re-read a bit of the early Diesel test history, and think I see where the coal dust story comes from. In Diesel’s original patent of 1892 he mentions several fuels (gas and liquid) but a preference for coal dust. However almost this entire patent was botched and was never followed up, it was a patent for an engine which wouldn’t work, e.g. cylinder pressures of 250 atm, no need for cylinder cooling etc. (None the less it contained the vital invention that alone was his and makes his name famous – an engine for maximum heat usage, one that would make maximum use of its fuel).

It was not until Diesel greatly modified his ideas that he managed to make an engine that could be built, including the intention of running on crude oils and possibly coal gas. Thus in 1893 the first engine was built by MAN, operating on probably less than 30 atm and with a completely revised constant pressure combustion principle.

The first tests were run with gasoline in Feb 1894, the engine finally ran for about 1 minute.
Coal gas was tried in Nov 1894 (because partner Krupp was interested in an engine that would burn furnace gas etc).
By the end of 1894 the engine would still barely idle, and could produce no usable power.
The first vaguely successful test run was made in 1895, using gasoline.

It was not until Feb 1897 that the engine actually ran well, using lamp oil or kerosene. The engine was still not in a saleable state however (although sales and licensing began), and much work was still needed to make the design work away from its protected laboratory.

In 1897-99 a series of tests were run to try as many different fuels as possible. There was no hope of demanding a special fuel for any engine at this time – one had to burn the fuels which were available if any design was to be a success.

Also a Diesel engines sell cost was about twice that of a comparable steam engine, its improved fuel economy was not enough to make it pay its way, it also had to burn a cheaper fuel than the expensive lighting fuels (kerosene).

Thus the tests determined which oils were suitable (e.g. including coal-derived oils and mixtures with crude oils etc), then in 1899 at the end of all the fuel tests, coal dust was tried. MAN did not want to try coal dust, but Diesel most likely wanted to have it on record that his engine followed his original patent.

Initially powdered coal was fed into the intake of the engine by hand. Later an automatic feeder was fitted and the engine ran for about 5 minutes before being dismantled for inspection. Coal dust was found all over the piston and cylinder walls. Later another 7 minute run was made in which almost normal power was obtained, but once again engine parts were covered with a thick layer of coal dust.

In total there was 12 minutes of running. At no time was coal dust blast injected, it was added to the intake via vibrating and rotating sieves driven from the camshaft. Ignition was given by injecting a pilot charge of kerosene with the usual blast air, and the engine always started on oil.

Thus Mr Cummins notes No doubt it is this brief test series, combined with the patent disclosure, which gave rise to the myth of his engine running on a solid fuel. Coal was a finale not a debut.
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From a different source – I have just been reading a little about ship building in Scotland (Workshop of the British Empire by M Moss & J Hume). When discussing ship building and diesel engine building by John Brown and Fairfield in the 1920’s, it reckons that motor ships cost 20-30% more to build than steamers. Because freight rates remained low at this time, it was hard to justify the building of motor ships.

Discussing the relative merits about steam and diesel, a good read is The Marine Turbine Part 3 1928-1980 by Ingvar Jung which although giving a historical review of steam and gas turbine development, also considers the improvements and competition coming from the marine diesel.

spongebob
5th June 2009, 09:33
Steam versus Diesel

Although this tread applies to the relative overall costs of a ship’s propulsion via steam engine or oil fuel fired engines the proof of the pudding is in the fact that fuel oil fired engines as a marine prime mover are used in the vast majority of vessels today however once outside of this watery domain there are many instances where steam holds sway due to a boilers ability to be designed and built to burn a very wide range of fuel many of which are “free”.
Among the many examples are;

The Sugar industry- Bagasse fired solid fuel boilers burn the cane waste and generate steam for power and process

The Timber industry – Again wood waste from milling, including bark, sawdust, wood chips and even small logs are burnt in a variety of boiler designs to produce power and process steam

The panel woods plants- composite particle board made from wood chips is bonded and sanded for
a variety of uses and the sander dust waste is used to fire both steam boilers and thermal fluid heaters

The pulp and paper industry- this process delivers bark and sawdust plus black liquor from the chemical pulping process and this is burnt in boilers which recover the process chemicals while generating power and process steam

The freezing industry- Paunch contents, the various stomach contents of ruminant animals are blended with coal to provide supplementary energy and in some cases a coal bed is used as a filter medium to clean up all sorts of plant effluent thus enhancing the coal heat value and getting rid of the waste

At one time during New Zealand’s more difficult marketing periods such as when Britain went into the common market and curtailed the purchase of NZ butter some over stocked dairy factories even considered firing the boilers with butter ex long term storage especially when fuel oil hit its peaks.
We did experimentally fire lanoline from the wool scouring process once when the markets for this oil dropped to near the price of imported fuel oil.
I know that since I have retired the success of burning waste products for generating steam has gone ahead in leaps and bounds especially in the design of firing grates including fluid bed combustion and also in flue gas cleaning equipment.

Apart from dedicated power stations including nuclear, the age of steam is indeed alive and well and there are a few little compound steam engines such as “Tange” and “Stuart Turner” still whispering away at some remote little mill.
Out of context to the thread but worth a post

Bob