Annealing copper tube

[DanTribe]

I need to put a sharp bend in some 8mm OD copper gas pipe. It is old so I need to anneal it in order to get a decent bend.
I've looked on Google and come up with three different bits of advice.
1/ definitely quench it.
2/ definitely don't quench it.
3/ it makes no difference.
Any expert advice please?

 

[Boater Sam]

It is reckoned to make no difference with copper but quenching steel hardens so I always let copper cool slowly just in case.

 

[wingcommander]

It will probably kink anyhow if youare attempting to hand bend round your thumb , best use a proper

hand machine and formerhttps://www.screwfix.com/p/rothenberger-lever-pipe-bender-6-8-10mm/79571?tc=TB8&ds_kid=92700055262507126&ds_rl=1244066&gclid=CjwKCAjwsJ6TBhAIEiwAfl4TWKJ9udslO6lbTa56fUuGvk5HJCVJz0aFB5W0W2rMfQHGgPnT25zPbhoCnvIQAvD_BwE&gclsrc=aw.ds

 

[wingcommander]

Although personally I prefer these

Rothenberger External Bending Springs for Copper Tube: 8 or 10mm

 

[VicS]

I need to put a sharp bend in some 8mm OD copper gas pipe. It is old so I need to anneal it in order to get a decent bend.
I've looked on Google and come up with three different bits of advice.
1/ definitely quench it.
2/ definitely don't quench it.
3/ it makes no difference.
Any expert advice please?

It makes no difference.
There is no change in crystal structure with temperature like there is with steel.
You are just allowing the crystal structure to return to normal after it has been distorted by cold working

Quench it if you want to cool it quickly other wise just let cool naturally.
BUT
Dont overheat it or keep it hot longer than necessary or you may cause excessive grain growth

 

[Dan Tribe]

Thanks guys. Let it cool naturally seems to be the way to go.
"somewhere" I have a little bending machine, if I could only find it!

 

[Bilgediver]

I need to put a sharp bend in some 8mm OD copper gas pipe. It is old so I need to anneal it in order to get a decent bend.
I've looked on Google and come up with three different bits of advice.
1/ definitely quench it.
2/ definitely don't quench it.
3/ it makes no difference.
Any expert advice please?

You won't kill it whichever you do however for 70 years I have been the of the quench brigade. Always heat copper objects to red heat and drop into cold water. It is NOT carbon steel and does not harden. 8 jmm tube usually was soft in my time. If it has work hardened in the production process then doing this will certainly help and kinking should not be a problem if good copper tube

 

[Thistle]

If it really is a sharp bend you need, have you thought about cutting and soldering in an elbow?

 

[VicS]

I need to put a sharp bend in some 8mm OD copper gas pipe. It is old so I need to anneal it in order to get a decent bend.

Would an elbow fitting be a better choice

.

 

[Bilgediver]

If it really is a sharp bend you need, have you thought about cutting and soldering in an elbow?

Oh!!!!! Not a good idea. In fact as it is 8mm tube then most chandlers sell 90 deg elbows with compression firings.

I don't think we are allowed to have soldered gas fittings in Scotland. Fire hazard. Some years ago a gas engineer noticed that my cooker fitting was a soldered fitting and should be swapped for compression . He offered to swap at no charge if I popped down the road to get the fitting.

Flomasta Compression Equal 90° Elbow 8mm

 

[Norman_E]

Would an elbow fitting be a better choice.

It depends how sharp a bend is needed. Remember that a swept bend does not resist gas flow quite so much as a sharp elbow so if flow rate is an issue, perhaps when using hob and oven together, then a swept bend is preferable.

 

[wingcommander]

Soft solder is a big not advised on a boat . If you use compression make sure you use copper olives..not the brass one's..Most old pipe has a thicker wall so bends are less likely to kink .

 

[VicS]

If it really is a sharp bend you need, have you thought about cutting and soldering in an elbow?

According to the BSS all joints on copper tube should be compression fittings

From the version for privately owned and operated boats

All LPG pipe joints must be accessible for inspection. All LPG pipe joints must be compression fittings on copper pipework or compression or screwed fittings on copper alloy or stainless steel pipework.

And from the version for commercially operated boats

joints Inefficient joints will cause LPG to leak. To minimise the risk of this happening joints must be made with compression fittings. Soldered joints must not be used because of their low resistance to heat, such as that experienced in an initial fire.

 

[Daydream believer]

I would have thought that silver soldering would have solved that issue

 

[Boater Sam]

If you want to avoid a kink, seal one end, fill the tube completely with dry sand and seal the other end. Bend and then empty the sand out.

Old method but works.

Silver soldering or brazing is acceptable for gas fitting on boats. Note that this is not soldering with lead free silver based solder.

 

[Bilgediver]

Silver soldering a gas fitting on a boat is not the best place to learn. Especially if Swimbo refuses to let you have access to the Borax in the medicine cupboard

 

[Dan Tribe]

Would an elbow fitting be a better choice

.

Yes it would. Space is tight and I wanted to minimise the number of joints.
A bulkhead bend would be ideal but I couldn't find one in stock and without a large delivery charge. I will order one to fit later, but right now I need a cup of tea!