Boiler Test specs. ??

[delaplume]

Hello all,

I've just been having a look at the current Boiler Test rules and I notice it calls for "Warm water" to be used.........What's the thinking behind this and, more importantly what specific temperature is "Warm" supposed to be ??

[uuu]

That's odd - can you please give the paragraph number? In amazement, I've had a quick look and have found 10.4 (b), which says "not lower than 7°C (45°F)". Volume 2 10.1 says cold water. I've not found mention of warm.

Wilf

[delaplume]

Hi Wilf,

First my apologies........ Somewhere in the recent past I thought I'd seen the word "Warm" written down in relation to a boiler test....I remember at the time thinking this was a bit odd compared to previous tests done over the last 40 odd years that I've been actively involved within the hobby where cold water was always used..

Later...at the my Club House a boiler was undergoing test and the Examiner said something to the effect that he was warming the water before use.......It was this comment that made me think about opening this thread ...BUT}--- just like a bad Sunday Fleet Street Editor I didn't verify my source before going to print !!.....Tut-tut !!

So I have rectified my error and read both Vol. 1 Boilers 3 bar litres to 1100 bar litres (Of which I have a printed copy ) and also Vol. 2 Boilers under 3 bar litres ( From an on-line copy ) ..........      www.sfmes.co.uk/ydrRoot/committees/boilerSC/Forms/testCode2018_volume2.pdf

and of course you are quite correct ie}---- no mention of "Warm water".....

However, as you also point out there appears to be a discrepancy between the quality of water required for the 2 Hydraulic Tests........I wonder what the thinking is behind the 7 deg C ( 45 deg F ) decision as opposed to cold water ??

In the past I think Cold water meant Domestic Tap Water  at ambient temp. ??

[d304]

Years ago I was told everything was standard at 20c. I even have a ruler that says standard at 20c.

David

[uuu]

I suppose if it squirts you in the eye during testing, it would be nice to have the chill off it.

Wilf

[d304]

Way off in Australia Wilf! Of course it wouldn’t be less than 20c.

[baldric]

I have heard a comment that a full size boiler may not pass as the weather was to cold in December to actually do the test, I am not sure if that was just a new inspector or a new requirement. I can't remember what the reason given was.

Baldric

[oldnorton]

There is some scientific logic to this. I was told by a senior boiler person that the lower temperature limit was because the copper becomes less flexible as temperature drops. I don't know, however, if there is a critical point at which the crystalline structure changes. For all materials, if you cool them enough the molecular structure becomes rigid (brittle) and if you stress them they shatter. Have you seen the films of flowers chilled in liquid nitrogen and then hit with a hammer?

[uuu]

I believe copper is OK at low temperatures, certainly way below those we're concerned with here (extreme subzero).

A relevant paper: Paper on behavior of metals at low temperature

Wilf

[houstonceng]

Mar 21, 2020 19:45:19 GMT oldnorton said:

There is some scientific logic to this. I was told by a senior boiler person that the lower temperature limit was because the copper becomes less flexible as temperature drops. I don't know, however, if there is a critical point at which the crystalline structure changes. For all materials, if you cool them enough the molecular structure becomes rigid (brittle) and if you stress them they shatter. Have you seen the films of flowers chilled in liquid nitrogen and then hit with a hammer?

The reason that the flowers shatter isn’t due to changes in molecular structure, just the ice formed in the petals.

[oldnorton]

Mar 22, 2020 14:03:24 GMT houstonceng said:

Mar 21, 2020 19:45:19 GMT oldnorton said:

There is some scientific logic to this. I was told by a senior boiler person that the lower temperature limit was because the copper becomes less flexible as temperature drops. I don't know, however, if there is a critical point at which the crystalline structure changes. For all materials, if you cool them enough the molecular structure becomes rigid (brittle) and if you stress them they shatter. Have you seen the films of flowers chilled in liquid nitrogen and then hit with a hammer?

The reason that the flowers shatter isn’t due to changes in molecular structure, just the ice formed in the petals.

Are you sure they shatter at -5deg?

[ettingtonliam]

Well you certainly wouldn't want to do it near freezing point, would you, which I imagine is where the 7 deg C comes from? I should think the ideal would be ambient (room) temperature, because when the test is at its hold point, the boiler and its contents are going to try to get to that temperature, and this can affect the pressure in the boiler, up or down depending on whether the boiler is trying to warm up or cool down. Do the rules say anything about not doing the test in bright sun? Years ago we were testing a largish polypropylene water main, prior to back filling the trench. We got it up to pressure and went off for lunch. When we came back, the pipe having sat out in the sun, under pressure, the gauge was nearly 'off the clock'

[houstonceng]

Mar 22, 2020 17:04:25 GMT oldnorton said:

Mar 22, 2020 14:03:24 GMT houstonceng said:

The reason that the flowers shatter isn’t due to changes in molecular structure, just the ice formed in the petals.

Are you sure they shatter at -5deg?

You implied that the flowers shatter after immersion in liquid nitrogen because of molecular changes. The liquid in them just forms super cooled ice and if you hit it with a hammer, it will shatter.