New VFT boiler for Frøya

[froya66]

After a long time I finally got back in the workshop. I managed to find the Ø22 x 1.5 mm copper tubes in Denmark - 2700 DKK for 19 kg. I have made a tube expander fit for the tubes. I got my barrel turned at Vølunds "baby" lathe to reduce the thickness from 13 to 8 mm. I got my tube plates drilled with 55 x Ø21.5 mm holes. Soon the boiler is ready for welding.







Best regards
Jørgen

[cyberbadger]

Very nice Jørgen!

-CB

[Lopez Mike]

From the looks of that shell, you will be able to use your new boiler for a scuba tank. Stout!!

[froya66]

From the looks of that shell, you will be able to use your new boiler for a scuba tank. Stout!!

Mike - I'm sure that your post is funny, but my knowledge of English slang is quite rudimentary. Could you please explain?

By the way - I do love your slogan

Best regards
Jørgen

[Lopez Mike]

'Stout' means very strong.

I am joking that your boiler looks like it will be strong enough to hold perhaps a pressure of over 100 atmospheres and thus could be used for a diving air tank.

[S. Weaver]

North American English is my native tongue and I still don't understand Mike half the time ...

[Lopez Mike]

Neither do I.

At least first thing in the morning.

[froya66]

After a long pause, the boiler works has finale come to live again. One of my very welding skilled colleagues has started to TIG all the bottom strings and I finish with the less complicated cover welding with shielded basic electrode. First, the tube plate was welded to the firebox. Fire door coaming was welded to the outer barrel and finally the firebox was fitted in place and the fire door coaming was welded from inside. Inspection hole coaming, upper tube plate and all nozzles are still to be fitted ad welded. The fire door coaming will of cause be shortened once it is finally welded.





[imghttp://i229.photobucket.com/albums/ee293/froya/IMG_0916.jpg][/img]


Best regards
Jørgen

[froya66]

Hi steam boaters

Long time no post, but now it’s time to roll in the copper tubes. This raise a discussion among the Danish steam boaters about copper versus steel when it comes to heat transfer.

All of us are of cause aware of the increased heat conductivity when using copper, but it seems to play a minor role compared to what else influence the heat transfer through the wall such as border layers and dirt on both sides.

However, in a vertical fire tube boiler I have the feeling that the copper is able to drag more flue gas heat down into the water from the uncooled/steam cooled area above the water surface, due to the much better capability to let the heat travel in the axial direction of the tube.

Proof – if you hold a tube in your hand, and heat it up say 200 mm from your hand, you will burn your fingers on the copper tube, but not on the steel tube.

Any comments to this? Any known comparisson test between two similar boilers with steel respectively copper tubes? It may well be described and discussed elsewhere, but I did not succeed with a search.

Best regards
Jørgen

[cyberbadger]

Nice looking boiler

I *believe* Fred said that it is indeed only makes a small difference even though basic heat transfer tells us that copper is a great thermal conductor. I think Fred even had some calculations to prove/explain it but I can't seem to find the post.

My first boiler of ill repute had 36 copper tubes. The only comparison I can make personally is to my new boiler that has steel tubes. There are so many aspects of this new boiler, which I had built for Nyitra, that make it more efficient that I don' notice that it has steel tubes and not copper.

-CB