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Tube-tubeplate joining - soldering

Tube-tubeplate joining - soldering

Tube-tubeplate joining - soldering

(OP)
Dear all

Advice on oil coolers tube to tupeplate expansions.

We are currently preparing drawings for the manufacture of oil coolers to replace existing ones.  The oil is on the shell side and the cooling water flows through the tubes.

The tube plate is 48 mm thick rolled naval brass and the current tubes are Al brass, which will be replaced with 90/10 copper nickel tubes.  The tube outer diameter is 12.87 mm and the minimum pitch is 15.18 mm.

We have had some problems in the past with tubes leaking at the tube plate.  

The current design calls for a lightly expanding tube in the tube plate and the back is then filled with solder.  

We do not have any expertise in the field but were wondering whether it would be preferable to fully expand the tubes and not solder or continue with the existing method of lightly expanding followed by soldering.  Any thoughts would be much appreciated.

RE: Tube-tubeplate joining - soldering


  KCLIM

Please elaborate, oil pressure???, solder type???,
flux etc. Have you considered brazing??? What are
the conditions in the field??? Are you investigating
a mechanical "Swedge" fitting???

                                  Cosmic Pigg

RE: Tube-tubeplate joining - soldering

(OP)
I have been told the oil pressure will be about 220 kPa. The proposed solder type is a 60/40 tin-lead solder, with a temperature of 150C. Brazing has not been considered as the temperatures during brazing are considered too high.

The oil should enter the tubes at about 60C, and exit at around 30-40 C. Cooling is provided in the form of bore water (30C).

What we're looking for are guidelines specifically regarding the attachment of tubes to tube plates, by expansion or soldering means. If no such standards/guidelines exist, I guess we go to a manufacturer with plenty of experience with these things to help draft a procedure.

What exactly is "Swedge" fitting? I've never heard of it myself.

RE: Tube-tubeplate joining - soldering

kclim
 You may want to contact Haydenauto.com, they've been in
the oil cooling business for years.

P.S. I quit using solder that contained lead many moons
 ago. A "Swedge-Fit" refers to the mechanical bonding
 by interlocking devices. Invision a cone being forced
 inside a cylinder, an inverted crimp of sort.

                                      Later

                                      Cosmic-Pigg

RE: Tube-tubeplate joining - soldering

Silver based braze alloys at 1300 - 1400 ?

Try Lucas Milhaupt 800 558-7006 get their free brazing book - it does a beautiful job of addressing your issues of joint design -

contact Kim Brandenberg - Prince & Izant 800 634-0437

You can also see www.carbideprocessors.com - our work is geared towards materials much harder to braze, much more temperature sensitive and needing much more strength.

My first thought on leaking is cleanliness (surface condition).  See the section in my book on plate cleaning for some ideas.  

Tom   

RE: Tube-tubeplate joining - soldering

I do not think any of the heat exchanger manufactures use soldering any more. At least all of our suppliers use tube expanders. Such as

http://www.mcmaster.com/catalog/108/html/1815.html

and then pressure test at a higher than rated pressure.

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