Author Topic: pits in copper tube  (Read 3290 times)

Offline daveclm

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pits in copper tube
« on: October 13, 2016, 03:45:58 PM »
hi
i am just on with building a marine boiler, and have found some pits inside the copper tube. is there any one that can advise me if they will be ok or put some silver solder on them, or get a new copper tube.
thanks dave.......

« Last Edit: October 13, 2016, 03:54:07 PM by daveclm »

Online Jo

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Re: pits in copper tube
« Reply #1 on: October 13, 2016, 04:35:07 PM »
Hi Dave,

Are you a member of a model engineering club? If so I would take that tube along and show it to the boiler inspector and get their advice.

Jo
Enjoyment is more important than achievement.

Offline daveclm

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Re: pits in copper tube
« Reply #2 on: October 13, 2016, 09:30:54 PM »
hi jo
thanks for replying. im not a member off any club. just to be on the safe side im going to order another piece.

cheers dave......

Offline Robert Hornby

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Re: pits in copper tube
« Reply #3 on: October 13, 2016, 09:53:46 PM »
Dave, it looks like mechanical damage, wise to not use it.
Robert
Age and treachery will always overcome youth and skill

Offline engjas

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Re: pits in copper tube
« Reply #4 on: October 14, 2016, 10:18:17 AM »
Have a careful look at the boiler drawings. There are three thickening pads on the Minnie boiler, one (internal) for the cylinder mounting, one (internal) for the valve gear support saddle and one (external) for the feed pump. These are all silver soldered to the boiler tube. If your luck holds one or more of these might coincide with the thickening pads (or the thickening pads could be slightly enlarged locally) and if so then the tube might be of use.

Offline wheeltapper

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Re: pits in copper tube
« Reply #5 on: October 14, 2016, 11:03:40 PM »
He said a marine boiler, not a Minnie boiler.

Roy.
I used to be confused, now I just don't know.

Offline engjas

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Re: pits in copper tube
« Reply #6 on: October 15, 2016, 09:37:20 AM »
Apologies for wasting everyone's time. Brain fade is becoming more  frequent I'm afraid.

Offline wheeltapper

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Re: pits in copper tube
« Reply #7 on: October 15, 2016, 10:35:06 AM »
Don't worry about it, it happens to us all. :old:

Roy.
I used to be confused, now I just don't know.

Offline Florian Eberhard

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Re: pits in copper tube
« Reply #8 on: October 15, 2016, 01:18:05 PM »
Hi Dave

Well - these pits are ususally where corrosion starts, so it is not wise to use that tube as it is right now. Except where the endcaps are soldered in, those will be filled with silver solder and therefore not cause any problems.

I would probably try to fix the pittings by filling them with silver solder. Silver solder has a highter tensile strength than copper has, so it is at least as good as it would be if there was only copper (the fusion zone between solder and copper is also stronger than copper itself)

There is still the risk that there are some other particles in the material which could cause electrochemical corrosion.
Because of this I would recommend to grind those pits and then fill them with silver solder.

If you don't feel good about that, you could also drill some holes and then solder in a copper rivet with its head on the inside.
Then remove the excessive Material on the outside of the shell.

I have to mention aswell that I don't know anything of that is legal considering the pressure vessel regulations in your country! (I assume the copper rivet soultion is though)
So you may first find out if thats ok and then decide what you are going to do.

Cheers Florian
« Last Edit: October 15, 2016, 01:22:39 PM by Florian Eberhard »

Offline daveclm

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Re: pits in copper tube
« Reply #9 on: October 18, 2016, 09:16:51 PM »
hi
just like to thank you all for all the advise. i have now got a new tube, no pits in this one. will use the old tube for water tank.

thanks dave.....

 

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