Thermal expansion and 90 elbow end feed copper fittings

[doitall]

Much would depend on the actual length, the temperature rise, the system pressure and how well the lot is anchored down.

I have seen an 2" steam line push a concrete block wall over,

Is it at risk? Yes without a doubt.

As Chris has said an detailed drawing or photo would be good

 

[wavetrain]

Yes they are endfeed elbows. The worst case is as drawn. There is another size with a 170mm offset. There are a lot of this 135 - 170mm type of offset in the installation.

Here is the drawing showing the direction and extent of expansion. The 2mm expansion was measured but as it is a 2.5m run it is really 2.5mm with a 80C max flow temperature:

 

[doitall]

Its still at risk simply because the expansion has been allowed for.

At 2.5m, and I assume x 2 then expansion will be taken up in its length.

When you said long runs, I was assuming over 20m.

 

[wavetrain]

Yes long runs with a number of regular small offsets as drawn.

So with some trig, the 22mm end feed elbow is flexing around 1 degree. I think it might complain about that at some point in the future?

 

[doitall]

How is the heat controlled.

Is it a timed temperature say up to 80c twice a day or an permanent temperature as in a OPH, hospital etc.

 

[wavetrain]

It is 80C twice a day on Sundays only as a rule. With the odd extra days say 150 cycles per year.

 

[doitall]

How long they last is down to how good the solder is. I would get in though with the copper development Association and ask them for an opinion.

Other than that you can only advice the client that it's not ideal, with a strong chance of a joint cracking, more so if the pipes are well clipped

 

[wavetrain]

They are well clipped (metal type). I will contact the copper development Association, and point them to this thread.

 

[doitall]

Let us know what they say please.

 

[ChrisR]

A couple of millimeters of movement is likely to be taken up by pipe movement all over the place, but if it's tightly constrained that's bad, because the solder is going to do a lot of the deforming under stress.
It's half a dozen times less strong than copper (depending on alloys, state of hardening, etc) but has pretty horrible fatigue properties. It'll deform elastically + plastically + creep, but if you subject it to high strain (elongation divided by original length) a lot of times, it'll crack eventually. You see it on solder joints on pcb's a lot, where components get warm cyclically.
Quantifying the "trauma" is notoriously difficult, but it goes back to what was said above - don't use solder joints where they're the focus of thermal cycling. You're not just concentrating the stress, but onto a poor material as well.

 

[wavetrain]

Let us know what they say please.

There were 2 replies following a 2nd response by myself, they didn't tell me anything new however:

Dear xxxx

As you know there are a number of ways to accommodate expansion of pipework: loops, bellows, horseshoe. What is also important is where the anchor points are. I would recommend that you read the Installation Tip - Fixing Copper Tube, which covers clips/brackets, expansion devices.

http://www.ukcopperboard.co.uk/literature/pdfs/Installation-Tips/Fixing-copper-tube.pdf

If you have further questions please come back to us.


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Dear xxxx

I passed your enquiry on to a colleague for his thoughts. He has been in the plumbing industry for a long time, including many years as a plumbing teacher.

His first thought was to contact the fittings manufacturer. There are a great many variables in the installation and it may not be possible to say for sure whether a failure is about to happen or whether the joint will last for many years.

Unknowns include: how often does the temperature cycle, what type of solder was used, did the soldering/brazing process soften the fitting.

The fitting is probably either YF or IBP: http://www.yorkshirefittings.co.uk http://www.ibpconex.co.uk

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I haven't bothered to contact the manufactures and they will most likely say the same. I will advise my client that they may fail in the future

 

[doitall]

I think thats what they're saying in non committal way

Thanks for getting back