Firetube vs Watertube boilers and full speed


Rancor

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Dear all,

Got a couple of quick questions for the brainstrust.

1) Why did the Olympic Class use firetube boilers and not watertube? Watertube boilers had been around since the late 1800s and were well established in warships. Was the cost vs performance just not worth it?

2) I have been following some naval podcasts recently and it is mentioned time and again that vertical triple expansion engines could not run at full speed for any length of time due to vibrations causing damage. Therefore a vessel with a top speed of 20 knots could only run at that speed for a short period of time. I would however note that the Olympic class seemed to have no problems ploughing at full speed across the Atlantic for days at a time with no detrimental effect. Can anyone confirm/deny?

Many thanks!
 

Rancor

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Hey Sam, thanks for your reply.

So it would seem the naval historian who can tell his audience how many blades HMS Hood had on her port inner turbine is incorrect?!

I shall do some further research myself before taking him on over it though!
 
Nov 14, 2005
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Dear all,

Got a couple of quick questions for the brainstrust.

1) Why did the Olympic Class use firetube boilers and not watertube? Watertube boilers had been around since the late 1800s and were well established in warships. Was the cost vs performance just not worth it?

2) I have been following some naval podcasts recently and it is mentioned time and again that vertical triple expansion engines could not run at full speed for any length of time due to vibrations causing damage. Therefore a vessel with a top speed of 20 knots could only run at that speed for a short period of time. I would however note that the Olympic class seemed to have no problems ploughing at full speed across the Atlantic for days at a time with no detrimental effect. Can anyone confirm/deny?

Many thanks!
In case you haven't been thru it this thread below has a lot of info. Sort of long thread...16 pages.
I think the firetube was a better choice IMO for the application. Especially from a performance and maintenance aspect. They both have their advantages. But from my experience with boilers the watertubes had their problems. Granted I worked on power plant boilers but the basically the same as ships systems (thats why most of our operators were ex-navy). My plant was a super critical once-thru watertube type. We needed that sytem to make the 1000* at 5000psi steam to run the monster turbine generator sets we had (750+MW). If we lost fires we were off line where the drum type could keep running awhile because of reserve thermal capacity. Also we had to have ultra pure condensate conditioning for feed water or it would eat the turbine blades because of water going thru the tubes. Lots of equipment to make the ultra pure water. Like I said its just my opinion but I think the engineers made the right call going with what they did for the Olympic class ships.
 
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Doug Criner

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I think firetube boilers are a bit easier to maintain and clean. The tubes can be cleaned by running brushes through the tubes. Watertube boilers typically use steam or air sootblowers to clean the firesides. Watertube boilers tend to be more compact.
 

Rancor

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In case you haven't been thru it this thread below has a lot of info. Sort of long thread...16 pages.
I think the firetube was a better choice IMO for the application. Especially from a performance and maintenance aspect. They both have their advantages. But from my experience with boilers the watertubes had their problems. Granted I worked on power plant boilers but the basically the same as ships systems (thats why most of our operators were ex-navy). My plant was a super critical once-thru watertube type. We needed that sytem to make the 1000* at 5000psi steam to run the monster turbine generator sets we had (750+MW). If we lost fires we were off line where the drum type could keep running awhile because of reserve thermal capacity. Also we had to have ultra pure condensate conditioning for feed water or it would eat the turbine blades because of water going thru the tubes. Lots of equipment to make the ultra pure water. Like I said its just my opinion but I think the engineers made the right call going with what they did for the Olympic class ships.

I'll definitely have to take you out for a steak and chips one day, you must have some excellent stories regarding your power station work!

Makes sense what you say about the firetube boilers being more robust. Further research tells me that the main reason for Water Tube boilers in warships of the time was their ability to quickly respond to changing speed requirements which were not really an issue on an ocean liner.

Thanks all for your detailed replies thus far. I'll see what other info I can find on triple expansion engines and what limitations they had regarding maxiumum permissible RPM over long time periods.
 
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Thanks. I'm sure everybody here who's had a long career has some good stories. The plant I worked at had a lot of unique challenges because it was built as an experiment. Only slurry fed coal fired plant I know of in the western hemisphere. I understand China is looking into using it. Our pipeline was around 280 miles long that pumped coal to us. When we shutdown that pipeline was used by company to run fiber optic cable underground...pretty smart...280 miles of conduit. As a side note your comment about speed changing requirments for a warship makes sense. But my plant was a base load station. We ran up to full load and stayed there for 95% of the time. We couldn't handle large swings in load or would trip. I still remember the first time I saw a gas turbine powered warship. It was impressive when she pulled up next to us and put on a little show. When they kicked her in the ass and took off it was like wow. It was a Soviet missle frigate or something. Anyway she was fast fast. But I digress...back to Olympic class.
 

Rancor

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I assume this was the Mohave power station? Quite an interesting history according to wikipedia, including some very unfortunate events early on its service life.

From what I understand water tube boilers enable much higher pressures and higher efficiency compared to firetube boilers. There's a new video on YouTube explaning the basic history of naval boilers if anyone is interested..

 
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Yes as I stated before we were a super critical boiler. Our steam was processed to 1000 degrees at 5000psi. According to our engineers it wasn't even classified as steam at those values. They refered to it as "stuff". Because of the entropy and enthalpy charateristics it was almost a plasma according to them. Sort of an in-between state of matter. But that was over my head. I was Instrument and Control technican. I measured the stuff and fixed the controls that ran it but the physics of "the stuff" was beyond me. That looks like a good video. I will have to watch it later. Thanks for the link.
Oh yeah...it was the Mohave Generating Station. We did have some bad days over its lifetime but I really liked working there for the most part. It was said that we had approximatley 3 times the equiptment to maintain than a typicle power plant because of its unique design. I learned a lot at that place.
 
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Rancor...I try my best to stay on topic of Titanic on this site but sometimes its easy to get sidetracked. But since you asked about the Mohave power station it does have sort of a connection to Titanic. Besides both burning coal to make steam (Titanic burned 600 tons per crossing. We burned 600 tons per hour) the two have another connection in the engineering world. I've seen various lists where the 2 were mentioned on the same list. They are lists of engineering screw ups. Not a good list to make but it is what it is. Titanics problems everyone here knows. Mohaves problem was something that hardly any would know outside the buisness. It had to do with sub synchronous resonance on our turbine gen sets. We snapped 2 turbine/gen shafts. Thats a big deal on 2 million H.P. machines. But like Titanic after the problems were corrected and solutions found it made both industries safer to run and operate. Mohave No. 15 and Titanic No.18 on the list below. So thats the connection. Sort of a six degrees of seperation thing.
 
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Yes you right about that. I got that wrong. According to this thread below if I read it right Mark Chirnside says she could burn even more than 700 tons a day under different conditions.
 
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J Sheehan

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Well, watertube boilers are not as successful as firetube boilers.

A prime example of that is the LNER W1 4-6-4 designed by Sir Nigel Gresley, which was equipped with a watertube boiler when first built.

As here:
1581092070354.png


It had many problems and was eventually rebuilt into a shape similar to Gresley's A4 Pacifics with a more conventional firetube boiler, which was a lot better.

This is:
1581092306259.png
 

Rancor

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Good info, thank you.

Interesting though, if firetube boilers are the way to go, why is every modern steam plant where efficiency is the number one priority such as the coal plant Steven spoke about above a water tube setup?
 
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Water tube setups allow for higher temps and pressures where their needed like the really big turbine gen sets. Today I don't know of any coal burners being built in the USA with the exception of one tiny plant (17 Mw) in Alaska. China is building them like crazy. Most now here are combined cycle (gas turbine-steam generator sets. But most of these also use a water tube setup for the steam generator part of the plant. The design with the watertube setup using exhaust waste heat is about 50% more efficient for the same amount of fuel burned. With natural gas costing around 30% of what it did 10 years ago its the way to go. Nat gas is so cheap right now they are practically giving it away. 1.85 spot price today.
 
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J Sheehan

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Just an interesting fact about the LNER W1, nick named the "Hush Hush".

It's corridor tender has survived and is coupled behind preserved A4 60009 Union of South Africa.
 
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