Oil burner consumption

A special section just for steam engines and boilers, as without these you may as well fit a sail.
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fredrosse
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Re: Oil burner consumption

Post by fredrosse » Tue Aug 06, 2019 3:45 am

"I don't then think that feed water heaters or economisers are worth the extra complexity"

I just put a small exhaust feedwater heater on Margaret S, with atmospheric exhaust, and it allows nearly 12 percent more steam generation, due to sending 194F (90C) water into the boiler rather than 70F (21C) water without the exhaust feedwater heater. It is a simple copper tube, 1 inch nominal diameter (25mm) carrying steam exhaust, about 12 inches (305mm) long, with an outer copper tube about 1-1/4 inches (32mm) diameter, and feedwater travels in the annular space between the two copper tubes. Simple enough to install, and I think 12% extra output here is worthwhile.

Installing an economizer will give even more output, but an economizer runs in hot flue gas, which is often well above 450F, and this can lead to some complications. If continuous feedwater flow is not always occurring, the economizer will overheat, and produce steam at very high pressures. Therefore an economizer relief valve is required if there are isolation valves in the economizer water circuit, and materials must be good for the maximum stack temperature that might be experienced. Copper is prohibited for any service above 406F, so a copper economizer would be considered unsafe if Code compliance is being followed.
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DetroiTug
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Re: Oil burner consumption

Post by DetroiTug » Tue Aug 06, 2019 5:31 pm

Quote: "I don't then think that feed water heaters or economisers are worth the extra complexity, and I can't prove it at the moment"

Not worth the complexity? This is flabbergasting to read. After working with systems with and without economizers and exhaust feedwater heaters, the differences in performance are stark in contrast. My Tug which I just took on a 20 mile run on Saturday up the Saint Clair river, will barely run without an economizer, That was the first thing I added back in 2010. Without it, take on feedwater and watch the steam gauge drop.

Just recently I was getting considerable water out of the exhaust on my Locomobile, so I bypassed the exhaust feedwater heater as a test, I could not believe how poorly it ran disconnected. I would estimate a 30% drop in performance. (small sensitive system)

The US Navy had as many as five feedwater heaters on some of their steamers.

Without feedwater heaters. you're throwing heat away that could be converted to horsepower.

-Ron
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DetroiTug
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Re: Oil burner consumption

Post by DetroiTug » Tue Aug 06, 2019 5:44 pm

Quote: ""Installing an economizer will give even more output, but an economizer runs in hot flue gas, which is often well above 450F, and this can lead to some complications. If continuous feedwater flow is not always occurring, the economizer will overheat, and produce steam at very high pressures. Therefore an economizer relief valve is required if there are isolation valves in the economizer water circuit, and materials must be good for the maximum stack temperature that might be experienced. Copper is prohibited for any service above 406F, so a copper economizer would be considered unsafe if Code compliance is being followed."

On the Locomobile, I have an economizer 40' of 1/4" (too small) copper tubing which is really only about 12" above the fire, and I have a "muffler" with 12' of 3/8" copper tubing wound, I seem to get more out of the exhaust fw heater. The coil is exposed to steam and condenses on the cold feedwater line. I've not had any issue with the temp limits on the copper, and that burner on kerosene gets extremely hot. On the tug it takes about an our to fire up with no feedwater moving, I do hear the economizer make some squealing noises etc, but it has remained intact.

-Ron
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Lopez Mike
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Re: Oil burner consumption

Post by Lopez Mike » Sat Aug 10, 2019 12:54 am

Good thoughts.

My engine is a 3 x 4 single and moved the old hull along quite nicely at around five knots. More power wasn't needed and going for a smaller compound seemed like more trouble than it would be worth.

Right now my summer has been consumed with other projects so no steaming at all. When I get my power plant transplanted into my new hull we'll see how things go.
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Re: Oil burner consumption

Post by RGSP » Sun Aug 11, 2019 9:44 am

Lopez Mike wrote:
Sat Aug 10, 2019 12:54 am
Good thoughts.

My engine is a 3 x 4 single and moved the old hull along quite nicely at around five knots. More power wasn't needed and going for a smaller compound seemed like more trouble than it would be worth.
If it ain't broke, don't fix it!

The Clyde puffers were very successful little craft, for about a century, and the great majority had single cylinder engines with absolutely no frills, not even a superheater in most cases. One point about them is worth making in the present context: they were usually crewed by two men, sometimes three, and the engine and boiler etc. were run and maintained by an untrained stoker (whatever he called himself), so the simpler the better. Neil Munro was exaggerating in the Para Handy tales, but not by that much, and having the whole crew inebriated was certainly nothing unusual. There were remarkably few serious accidents or fatalities, but the puffers were small enough, strong enough, and slow enough, to be be run straight up the beach at full speed without serious damage, even if it was a bit rocky. Boilers were often run dry, or nearly dry, but extremely few failed with a major bang.
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Re: Oil burner consumption

Post by malcolmd » Sun Aug 11, 2019 11:52 am

"The Clyde puffers were very successful little craft, for about a century, and the great majority had single cylinder engines with absolutely no frills, not even a superheater in most cases. "...

However, they were all condensing engines....
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Lopez Mike
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Re: Oil burner consumption

Post by Lopez Mike » Sun Aug 11, 2019 12:29 pm

Reading over the various responses brings up even more questions.

So Fred is picking up about 12% from an exhaust feed water heater. I might notice a 12% reduction in fuel consumption. I'm not sure. That would be one bag less of wood in a long day's steaming about. And Ron is really noticing a difference. I will give this more thought as neither is a giant project.

On a related subject, how do we think that total boat weight is related to fuel consumption? My reflexive response is that is should be directly related. 10% more tonnage? 10% more consumption. I've had this assumption in mind as I build and equip my new launch. Any thoughts please?
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Re: Oil burner consumption

Post by RGSP » Sun Aug 11, 2019 2:36 pm

malcolmd wrote:
Sun Aug 11, 2019 11:52 am
"The Clyde puffers were very successful little craft, for about a century, and the great majority had single cylinder engines with absolutely no frills, not even a superheater in most cases. "...

However, they were all condensing engines....
Up to a point Lord Duckett. The VICs were, I believe, all built with condensers, and that probably means all of the present survivors. However, very few puffers were built between 1920 and 1936 (when the VICs started), and before 1920 condensers were an optional extra fitted to the seagoing vessels only. Pre-1900, puffers tended to be significantly smaller vessels, and many of them stayed on freshwater with only occasional short forays onto the salty stuff. They were the delivery vans of the day, and a day's steaming was often only 10 or 15 miles, so picking up water from every dropping-off point was quite feasible, if a bit tedious, even on salt water.

By repute, the Knoydart estate supply boat pre WW2 was a true puffer, with home port Mallaig, but large fresh water tanks available at Barrisdale and Tarbert Loch Nevis. There was certainly a huge fresh water tank at Barrisdale in the early 1970s. A very elderly old boy who I met in a bar at the end of Mallaig Pier (as you do) claimed you could hear it puffing at Mallaig when it was at the head of Loch Nevis. He lived off the calories in whisky cadged off visitors though.
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Re: Oil burner consumption

Post by DetroiTug » Sun Aug 11, 2019 10:03 pm

Speaking of the Clyde Puffers, if any of you haven't seen it, try to find a copy of the movie "The Maggie". That was made at Ealing Studios, they made several really good movies, another one is "Titsfield Thunderbolt", it's about a train but equally as good. Both are must-sees for any fan of steam.

Hard to find as they are not released in video format for here in the states. Have to find a ripped copy.

Took the tug on another run yesterday, still running flawlessly. Gave her a fresh coat of Epifane's varnish on the exterior, she's never looked better.

-Ron
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Re: Oil burner consumption

Post by DetroiTug » Sun Aug 11, 2019 10:23 pm

Quote: "On a related subject, how do we think that total boat weight is related to fuel consumption? My reflexive response is that is should be directly related."

In my personal experience and observation, they are directly related, more work requires more fuel and water. You and I came at the problem from different directions, you are designing in fuel economy, I built a big heavy boat and had to make improvements to the system to improve performance and economy. My boat with it's hull design can't be built light, it needs so much ballast to get the deep belly of the hull down in the water. The first time I launched it, it was like a fishing bobber/float on the water, I was seriously concerned about it rolling right over, I've added enough weight to it over the years that it is siting about right and stable for rough water. The Tug weighs around 8000 pounds, when I pull in, the trees shiver :)

-Ron
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