Boiler fittings – is brass OK?

[bogusParticipant @bogus]

Wow. I read somewhere some attempts were made to make SS boilers and weld them. If my memory serves me right the conclusion was cracks can occur because of warm up and cool down cycles under stress (pressure).

Duncan – do you know what is the 'right grade'?

At work I have a lot of equipment made out of 304, 316, 316L grades.

See Table. 1: here:

http://www.parker.com/literature/Instrumentation%20Products%20Division/Catalogs/Bul%204200-TS%20-%20Feb2010%20-%20Final%20Low%20Res.pdf

Ajohnw – so SilverFlo55 contains 22% zinc but is ok. Is it ok because of no galvanic action?

[duncan webster 1Participant @duncanwebster1]

I think we need a real metallurgist to comment on this one, I just take it from one that I knew at work (before I retired) that austenitic and hot water under stress is a problem. Presence of chloride ions makes it worse, and tap water contains traces of chloride, which get concentrated in a boiler as the water bois away leaving the chloride behind.

[bogusParticipant @bogus]

You provoked me to google this subject For the curious ones:

http://www.parrinst.com/wp-content/uploads/downloads/2011/07/Parr_Stainless-Steels-Corrosion-Info.pdf

https://en.wikipedia.org/wiki/Stress_corrosion_cracking

and some HSE report:

http://www.hse.gov.uk/research/rrpdf/rr902.pdf

[michael darbyParticipant @michaeldarby61557]

I dont know if it helps, but "stainless steel" is just a generic term like "car" the range and diversity are almost limitless. from cutlery to aerospace ,mot only the nickel and chrome content can vary ,but other elements are added which completely change the characteristics of the material. so unless it is purely decorative,it useage needs to be specified and the correct grade obtained

[bogusParticipant @bogus]

so true

[AjohnwParticipant @ajohnw51620]

My son reckons that stainless corrodes – he looks at stainless saucepans which do and he lacks a technical education. School part covered it under the heading of resistant materials which seems to only exclude plastics.

Stainless is a broad field as are copper alloys and many other things.

John

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[julian atkinsParticipant @julianatkins58923]

for making a proper silver soldered boiler out of copper there should be no 'short cuts' and only the proper materials used for bushes and stays.

when one considers the cost of the copper and silver solder the small extra to obtain the correct grade bronze for the bushes is very small.

if a jobs worth doing….

cheers,

julian

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