Boiler stays

[Michael CallaghanParticipant @michaelcallaghan68621]

Hi, just want to make sure this is ok. I have a boiler that has the firebox wrapper held in place with copper rivets and brass nuts. The brass nuts are inside the firebox. I have never seen this before. Is it an acceptable method. Thanks

[noel shelleyParticipant @noelshelley55608]

The only certain way to find out is to consult with your boiler inspector. Are the copper rivets threaded into the inner fire box ? Brass is always suseptable to zinc loss, the more so in the fire box where heat and acidic fumes are present. Soldering the rivets and nut is one way to seal the assembly. But the world we live in has changed. Good luck. Noel.

[Paul LousickParticipant @paullousick59116]

This is a copy of the types of stays that are allowable in the Australian AMBSC code for copper boilers.  I would query the use of using brass nuts because boiler water can de-zincify brass fittings.

[duncan webster 1Participant @duncanwebster1]

I think we need a metalurgist to give a definitive answer, but I think you need liquid water in contact with the brass to get dezincification.  I suppose liquid could work its way down the threads.

[JasonBModerator @jasonb]

Plenty of Minnie traction engines running around with Mason’s specified brass nuts inside the firebox on bronze or GM stays. As the whole lot is silver soldered you should not get any water contact with the nuts if the solder flows into the gap between stay and boiler plate.

Though the commercially made one tend to just have a copper rivit with head on the inside and all soldered in without nuts.

[JAParticipant @ja]

Looking at Paul’s illustration from the Australian boiler code, why is silver soldering stainless steel to a boiler not allowed?

JA

[Nigel BennettParticipant @nigelbennett69913]

Despite its name, stainless steel will corrode when exposed to hot tap water and in contact with copper. There is also the problem of corrosion of silver-soldered joints in stainless steel in these conditions. There was an article in ME  about why silver solder and stainless are not best friends by Graham Astbury, in September and October 2023.

[Paul LousickParticipant @paullousick59116]

Stainless steel is not recommended for boilers because high temperatures combined with even low levels of chlorides can break down stainless steel’s passive chromium oxide layer, causing sudden, brittle, and cracking.

[duncan webster 1Participant @duncanwebster1]

Stainless steels come in a wide range of compositions, some are more resistant to the above mentioned problems. The problem is knowing and proving which one you’ve got, the more exotic ones are probably only available in large sheets.

Even tap water has trace amounts of chloride, and as it is boiled into steam the concentration in the boiler increases.

I’m not sure why you’d bother with nuts on the inside if you’re going to silver solder stays.

[JasonBModerator @jasonb]

Depends where in the world you are if stainless is OK or not. I see it used quite a lot in mainland Europe and our Friend LukeR down in South Africa has no problems building his (welded) boilers from it.

[Michael CallaghanParticipant @michaelcallaghan68621]

Thanks chaps. Apart from the treaded stays I have a bigger problem. After disconnecting every boiler fitting I could find. Removing the rear frame foot plate and rear axle I still cannot get the boiler out. I don’t want to start using a hammer. The pipes in the smokebox are free. As anyone removed a boiler from a Jenny Lind. Is there something hidden holding it on. I can’t remove the smoke box as it’s been riveted in place.

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