Sisson Triple

[MGMarine]

Thanks for the comments. This is getting a bit like a ping-pong game!

First, we don't luxuriate with "a curator" at Markham Grange Steam Museum. The Museum is operated by volunteers, in an Association, of which I happen to be the Honorary Secretary. So I guess it falls to me to start a search for early magazines! I was hoping someone would say, "there is such an archive freely available; just look at ...." But I suppose I'm an incurable optimist (otherwise I wouldn't tackle the restoration of steam engines), which leads me to -

I admire gondolier88's faith in engine builders, but I don't heartily share it. As one works with steam engines of various makes and types, one is regularly coming across features that could well have been better thought out. The Sisson triple is one of the best, but some of the engines we have collected have been awful, in concept, in design, and in construction. A digression on this subject would not be relevant to this Sisson Triple topic, and would fill a book. However I will stick my neck out and suggest that reciprocating steam engine development and thinking largely came to a grinding halt in the early years of the 20th Century, whereas steam turbine development grew wings and flew. Too many firms just ceased thinking, ignored the practical problems arising in operation and maintenance, but carried on producing what they had always made - until they deservedly went out of business. The unavoidable problem of latent heat loss, only partially recoverable by condensing plant didn't help steam's case. Neither did the invention and rapid development of the (nasty!) internal combustion machine which, for example, displaced steam on the whole Thames fleet of Salters of Oxford some 50 years ago. Even the most efficient and high-tech steam turbine generating stations can only extract barely half the energy from the fuel. Not that IC engines are all that efficient, but they are self-contained and somewhat less complicated than mega steam plant. And they don't need vast quantities of water in operation. But I must stop. And I still prefer steam.

[Scotty]

.... Even the most efficient and high-tech steam turbine generating stations can only extract barely half the energy from the fuel. ....

Large power station steam plants run with appr. 45 to 48 % efficiency.
Combined cycle plants reach 55 to 65 %.
Try this with Internal Combustion.

ps: ever looked at a Spilling steam motor - 40 bar / 400 °C ?

Scotty

[MGMarine]

OK, 45 to 48 per cent is, as I said, barely half. Yes?! Combined cycle is "cheating"; in fact it's steam plus a bit of internal combustion in a gas turbine. So the steam on it's own is still that same barely half. However, if you have a need for process steam heat (eg Bowaters for papermaking) then the overall efficiency is very good, because the latent heat which would be dumped in a straight condensing cycle is directly used in the process. The electricity is a sort of by-product!, and a very good one too.

Yes, I was aware of Spilling (German) and they kept going after pretty well every other steam firm had finished, basically by pushing the design limits, ie continuing to apply their brains to the subject. However, I have, as yet, no details of their engines. I'll try an Internet search - now.

So goodbye - and search.

[Scotty]

"barely half" is the theoretical maximum for the process.

There are now some plants with a superheat of 720 °C but they are plagued by material problems
- technology beyond the limit.

Scotty

[MGMarine]

I have just made a trawl on the Internet (Google) for Spilling inverted vertical steam engines. There are several entries, of a "sales" type, but I cannot find any technical "meat", other than one small cross-sectional diagram, not very informative. In other words, they are playing their cards very close to their chest.

The engines are assembled in one to six cylinder form, using standardised jig-made components - very sensible. They say they run without cylinder lubrication (good), which implies a special piston ring material, not iron-based. I trust they have overcome the nuisance of condensate / gland leakage entering the crankcase (always a problem with Belliss and Morcom and Sisson enclosed engines, never properly tackled and solved, so far as I am aware), and this implies appropriate gland packing - let's hope it is easy to adjust / replace in the fairly confined space between cylinder and crankcase. The valves seem to be driven from a separate shaft (camshaft?), implying gearing. About balancing, bearings, materials, piston construction, piston valve design, lubrication, and so forth - nothing. As to looks, about as pretty as a diesel, just a box with nothing to see. But they are both just doing a job - aesthetic elegance? artistic pleasure? these went out long ago.

But we still have a few surviving beautiful Sisson triples to enthuse over. Let's be thankful for small mercies.

[fredrosse]

“Large power station steam plants run with appr. 45 to 48 % efficiency.”
I don’t know where you are getting your data, but I have been a power plant thermal performance engineer for many years, and have never seen any actual steam plants with this high level of efficiency.

“Combined cycle plants reach 55 to 65 %.”
Again, 65% efficiency in a combined cycle is unheard of. Some claim 60% efficiency, but the combined cycle plants use the lower heating value for the fuel, which allows them to publish a higher efficiency claim. Using the lower heat value for fuel when talking about efficiency is just not proper, but the advertising campaign to draw in money is at work here. They even advertise heating furnaces with efficiency of over 100%, which any reasonably knowledgeable person should understand as a ridiculous statement.
“Try this with Internal Combustion”
Combined Cycles are indeed internal combustion engines. Two thirds of the power they make comes from firing an internal combustion engine(s) with natural gas or fuel oil. The hot exhaust duct from these engines goes thru a heat recovery steam generator, and that steam runs a steam turbine, making the final third of output power.
“I have just made a trawl on the Internet (Google) for Spilling inverted vertical steam engines. There are several entries, of a "sales" type, but I cannot find any technical "meat", other than one small cross-sectional diagram, not very informative. In other words, they are playing their cards very close to their chest.”
I have tried to get some Spilling Information for years, but they have never responded to inquiries. It appears that the Spilling Reciprocating Engines have expander efficiencies similar to typical 100 year old engines, but they can take high superheat, with claimed non-lubricated cylinders. I understand they use tungsten carbide for wearing surfaces.

[MGMarine]

I am curious.

How come that what I wrote on 27 August at 9.38 pm has changed from, if I remember correctly, "internal combustion engine" to "smelly long-chain hydrocarbon" which I definitely did not write? Let's discuss our subject in a spirit of amicability and occasional fun, by all means, and try to "spread the word" about our steam engines, but do please refrain from altering somebody else's text. That is not at all acceptable.

Just another word on the "barely half" topic. When I followed CEGB power station efficiency figures (claims) regularly (but many years ago), my recollection is that those at the top of the league were hitting just over 40%. So, allowing for a bit more squeezing of the pips in the intervening years, a possible extra percent or two, so I generalise that steam makes effective use of barely half of the calories (or rather BThUs!) in the fuel. That's fair is it not? It was not so long previously that 30% was reckoned to be pretty good.

There is a bit of an anecdote here, again from long recollection. Many CEGB sites had several separate stations; I recall that Drakelow (on the River Trent), Ferrybridge (Yorkshire) and Littlebrook (Kent) all had three, and many sites had two. Now it used to be said, in truth or jealousy or otherwise I am unable to confirm, that "fictitious coal" (the term used) was transferred (on paper) from the newest station to the earlier one(s), so enabling the newest station to show (on paper) a somewhat higher efficiency than the reality figure. An interesting speculation, which might perhaps affect my recollected efficiencies. It is certainly true that high tech power plants did use every possible technique to push efficiency as high as possible; a point or two of improvement at say 2000 MW represents a worthwhile amount of coal, or oil, or gas saved. I guess marine steam plant had quite a long way to go in efficiency terms.

Have we about exhausted (or condensed) this subject?

[MGMarine]

An abject apology.

In my post at 7.51 pm on 27 August, second line, I typed "it's" for the possessive of "it", instead of "its", an error by others that I regularly complain about or, perhaps pedantically, an error by others about which I regularly complain. Consider my knuckles rapped with an ebony ruler. "It's" = "it is".

In shame is my head hung (but fortunately not hanged).

[TahoeSteam]

The forum is programmed to automatically alter swear words in to more acceptable words I.E. Dies'l (intentionally misspelled) into diesel. No one was playing with your text, you can settle down before you have a wobbly.

[fredrosse]

Yes, we must refer to those compression ignition reciprocating internal combustion engines as "Dissel" engines or something similar, for if you spell it correctly it gets automatically changed. When talking about the typical fuel for such engines, perhaps the term "light distillate oil" or "No. 2 Fuel oil", although that is certain to leave less clarity for most people trying to get some information here.