History of Diesel Displacing Steam in U.S. Merchant Marine

we have jumped the tracks here again…

can we stay on topic please?

I have a theory. It may be a bit of an off one, but consider this. Maybe the government was hoping for an advanced nuclear future, brought on by boundless atomic energy. Certainly there were factions within the government who thought this was rediculous, however there were also groups that took the idea very seriously. It would of course all require steam power. After all the NS Savannah was ordered in 1955. Ft. Schuyler had a mini-nuclear reactor installed for the purpose of training Nuclear USMM Officers, they still graduate engineers that end up going into Navy Nuke school. Many other sectors of government were experimenting with what we could do with nuclear power. The Navy stuck with it of course. However everyone else gave it up because of environmental concerns. I they may have lost out on building a stronger diesel industry because many in the tech and engineering world may have thought it was “so 1944”.

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Kind of interesting to note that in the next few years most of the US flag steamships will be retired as their replacements are delivered. The last vestiges of steam plants requiring licensed engineers may not be US ships but foreign flag LNG tankers.

When I was in Korea in 2006 one of the companies I worked closely with was a Greek outfit. They decided to get into LNG’s and had one built that was delivered in 2007. It was built with steam plant. I asked them why they didn’t go diesels since that is what powered their tanker fleet. They said it was proven technology when they signed the new construction contract. This goes back to my earlier statement about companies being conservative and reluctant to adopt new technologies. Their next LNG tanker delivered in 2016 was diesel.

They probably also used boil-off gas to fire the boilers when loaded??

That was the prevailing technology at the time. Nowadays they can re-liquefy the boil-off or burn as fuel in the diesel plant. The engineering plant in the Greek company’s 2016 LNG tanker is described as Tri-Fuel diesel-electric.

hardly…how many steamplants remaining in the RRF? 28 was my last count

so this is a conundrum if there are no steam plants in the active commercial fleet, where are the engineers going to be found to operate these RRF ships should they be mobilized? I suppose all the RRF ships could keep a full engineering force aboard but even then, these ships don’t have their boilers fired when at the dock which means they will need to be kept underway and if that is the case, why not just use those ships to move DoD cargoes? Way better than using foreign ships even if these old time steamers are not so efficient to operate

or scrap them all which would be a pity because the government has invested a mountain of money into them (especially the FSSs!)


Sunk costs are sunk.

I was speaking of active ships but you are right and to some extent that is a conundrum. At least once a year there is a steam course offered at the MEBA school to allow diesel to steam crossover. So there is always a way to get the licenses. When motorships came into play they got manned.

There are a few Preposition ships that are steam but most RRF steamships are laid up, and as such, are inactive. They are kept in various stages of ROS where some are routinely broken out, others not so much. Some may never again move under their own power. Ultimately they will be phased out.

I am very familiar with the FSS ships. Yes, the government put a lot of money in converting them as well as maintaining them. But they are 45 years old. In some ways technology had passed them by (container size in addition to type of prime mover) when they were delivered.

The tanker I referred to was built in Japan and had an air conditioned control room as you described. It also had an office at the top of the engine room where all the ship’s drawings were in cabinets where the drawings hung vertically from rods. The rods had diagonal lines on them to ensure that the drawings were returned in the correct order. A kitchenette, conference table and independent aircon with easy access from the main deck and engine room completed an arrangement that I have never seen again. More is the pity.

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Amazing how some plants were designed so well and others so poorly. It is like some who thought by redesigning the wheel adding square edges would make it roll better. Naval Arch’s either liked and understand marine engineers or disliked them. By plant design it was easy to tell what they thought.

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This post (hogsnort’s) belongs in a “real” ship of the future thread. These among many other useful features would make a better ship of the future than AI, autonomous operations, augmented reality etc. This is not a blanket condemnation of new technologies but merely lamenting the simple things that can make work more efficient and higher quality are often too quickly shunted aside.

As to why,how when the US fleet transitioned it is really not a mystery is it? Well established and large base of the existing technology. De Laval and GE making things in our own backyards. A supplanting (though not nonexistent in US) technology comes along with lower operating costs (on average) market forces, shrinkage of the fleet in total. We were lagging in this area and that is not implying it was by choice. That was just the circumstances at the time. Sure the Navy aspects being mentioned are part of circumstances but to think there is a single hidden cause out there doesn’t seem plausible.

To think it’s any different now is delusional too. A long time ago shipping companies may had some familial ties and management was involved in an industry because they wanted to be and were good at it. So about this time period you are talking about what was happening in US corporate culture? Were they looking ahead? Were they planning for the fleet size reductions? Placing contracts enough to support a large US based manufacturing or transitioning the existing companies to the new products? No, much easier to shift some numbers around on a ledger, divorce the company from the operation, become a shipping absentee slumlord. “Hey why mess around with those messy ship things when we can just farm out the actual objects and crews and sit back and whine.”

As long as we are still making broad general statements it just seems the history of diesel replacing steam is merely evolution - in slow motion in the case of the US.


Boiler efficiency is in the high 80 to low 90 percent range, reduction gears are around 98 percent and turbines around 80 percent. Overall plant efficiency is around the mid to high 20s.

Modern slow speed diesels reach above 50 percent. Condensers do a great job of heating the ocean.


if the major components have such high efficiency, why does a steam plant as a whole operate at such poor numbers? certainly all the piping and ancillary equipment can’t rob the whole of so much energy? I would have thought the greatest loss would be in the uptakes because any flue gasses going up the stack above ambient is energy which did nothing. Wouldn’t a perfect boiler actually not put out any gasses above ambient temps?

lastly why did they never develop a turbine set with a third intermediate rotor as a triple expansion reciprocating engine had? yes, the reduction gear would have been more complicated but certainly buildable?

but in the case of the US, we had an industry once which built slow speed marine propulsion diesels but while the merchant fleets over the remainder of the globe switched to diesels for their ships, the US scrapped its own diesel industry and kept on going with steamships right up until the early 80’s…nobody here has yet to answer the question why did we do this?

we evolved and then just as fast devolved in a span of a mere 2 decades. Was any single US build merchant ship built after WWII ever fitted with a slow speed direct drive engine? Yes, certainly many medium speed but they don’t have the efficiency of a slow speed engine.

To get plant efficiency you multiply the efficiencies of the component pieces. in other words; .85 (boilers) x .95 (turbines) x .98 (reduction gears) x .80 (condenser) x .95 (pumps) etc. I thought a well designed & run steam plant was up in the mid 30% range but I can’t recall where I got that number.
If there is fouling in the boiler or combustion controls are not trimmed properly, the efficiency drops. If you are running less then design pressure, the efficiency drops. If the condenser and coolers are dirty or vacuum less that it should be, the efficiency drops.


I made a quick look-up in IHS Sea-web database with engine type set as “turbine”. I found 336 extant ships ranging from 1942-built laker Alpena (IMO 5206362) to seven LNG carriers currently under construction in Japan. However, some of the ships are either listed or otherwise known to be laid-up and/or awaiting scrapping, and some may have gas turbines instead of steam turbines (there’s no option to exclude one or the other).

In all, 271 of the vessels (including newbuildings) on the list are LNG carriers. Eight are lakers. About two dozen are old tankers repurposed as F§SOs. There’s nine container ships, all of which are US-flagged (out of 25 American ships in total, which includes a handful of naval logistics and training ships as well as SS United States). The Russian nuclear-powered icebreakers are of course on the list together with the lone atom-smashing cargo ship.

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[quote=“c.captain, post:75, topic:49485”]
lastly why did they never develop a turbine set with a third intermediate rotor as a triple expansion reciprocating engine had? yes, the reduction gear would have been more complicated but certainly buildable?
[/quote]There were a number of ships built with three rotors. However, expansion in a turbine takes place through each row of blades, not in each rotor, so, for example, a turbine with fifty rows would have fifty stages of expansion.


Even a perfect boiler with perfect combustion will put a pound of water up the stack for every pound of fuel burned and that water is going to be very acidic from fuel sulfur. Stack temp has to be kept above condensation temperature so there is excess hot air to do that and reduce smoke from incomplete combustion which is impossible for practical purposes.
With regard to overall efficiency, remember a motor boat doesn’t burn any fuel in the mains when docked, boilers never shut down. Also motor boats use heat recovery techniques to run auxiliaries, make water and run some hotel and other services. Steam boats, especially tankers use nearly as much power to offload as they do running to the offload port. Also, making water, huge amounts of water, uses a lot of steam and the fuel to make that steam shows up on the bottom line of the beancounter’s efficiency page.

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A company looking to build a ship is going to look at all costs. Not just fuel. TOTE went with steam for a 1976 build while Waterman went with diesel for a 1970 built LASH ship.

On short coast-wise runs I would assume fuel would be a lower percentage of total costs than a ship making long ocean passages.

Union Castle were early adopters of diesels, the Capetown Castle having twin 14,000hp B & Ws,in 1938, whilst the Carnarvon was not far behind.