Boiler fittings – is brass OK?

[Dennis RaynerParticipant @dennisrayner52782]

Is there a problem in using brass for boiler fittings rather than phosphor bronze? I seem to have heard somewhere in the past that it’s OK for fittings that are above the waterline? eg The turret and its associated valves. I have a good stock of brass sections but virtually no PB.

[Dennis RaynerParticipant @dennisrayner52782]

[ChrisParticipant @chris16039]

I’d have a word with whoever is going to do your boiler test when it is completed. I know the testers in the club I attend prefere bronze for fittings. In fact best advice is to talk to your potential testers anyway as many old drawings show parts which are now unacceptable. Also some parts cannot be seen once the boiler is completes so testers sometimes wish to see boilers at various stages of construction.

[SteambuffParticipant @steambuff]

My opinion is that if the part is in contact with the copper boiler/firebox then use Bronze.

 

For example, the safety valve bush that is soldered into the boiler must be Bronze, but the safety valve itself that screws into the bush can be Brass.

 

Dave

 

[JasonBModerator @jasonb]

I would say that if above waterline like the safety valve mentioned above then brass is OK but if its say a washout plug below water line then bronze. Both being fitted to bronze bushes.

 

J

[macmarchParticipant @macmarch]

Don’t forget that the bronze must be a lead free grade.

[BogstandardParticipant @bogstandard]

Dennis,

 

In all honesty, you should never have even asked the question if you had any doubts at all.

I made copper boilers for many years, and not only for myself, and always used bronze for ALL boiler fittings.

 

What you have to bear in mind is that after you have fitted brass bushes, it will always be in the back of your mind if you did the right thing and if they will ever fail, whereas if you spend just a few squid on bronze, you can forget about them.

 

Doing it right first time, rather than compromising to save a few pennies, is always the right way to go.

 

 

John

[Dennis RaynerParticipant @dennisrayner52782]

Thanks for all the replies received so far . I have purchased a commercially made boiler which has bronze/gunmetal bushes already silver soldered in before test. I am really referring to fittings which I will screw into these bushes such as blower/ injector valves etc.

 

Dennis

[BogstandardParticipant @bogstandard]

Sorry Dennis, got a bit muxed ip there, I thought your were referring to boiler bushes.

 

I actually bought a commercial copper boiler many years ago, ready fitted out with all the usual bells and whistles. Everything was fine for about 5 years, then leaks started to develop all over the place, even above the waterline.

 

Even though it was a very well respected supplier at the time (now gone the way of a lot of others), they had in fact used brass for ALL of their fittings, Galvanic action and de-zincing had taken over. Not only did I have to replace all the fittings, but it had affected some of the boiler bushes as well, it was a fairly big job at the time putting things right, hence my reluctance to use anything other than bronze.

 

If you are worried about the machining of bronze to make your fittings out of, which can be a bit harrowing at times, then Colphos will come to your rescue, it is almost as easy to machine as brass, and in reality, no more expensive than PB1 or PB2, just a little limited on sizes available. I have used it to make hundreds of fittings, some actually tiny ones with super fine threads, and it silver solders perfectly.

 

 

 

John

[bogusParticipant @bogus]

Hi all,

and how about copper bushings? Is copper ok for that?

[stan pearson 1Participant @stanpearson1]

Hi All

I have made the regulator body out of Naval Brass as per the drawings for my Less Warnett 9F, what are your thoughts on that

Stan

[Brian HParticipant @brianh50089]

Posted by bogus on 02/02/2016 10:14:57:

Hi all,

and how about copper bushings? Is copper ok for that?

I dare say that copper is ok from a materials compatability point of view but it does not take a thread easily and the threads tend to be weak, especially after brazing the bushes in and annealing the copper.

Much better to use PB, but not one with lead in it as mentioned by someone else.

[duncan webster 1Participant @duncanwebster1]

It's all a matter of how much lead. Gunmetal and Colphos both contain lead, but a lot less than leaded bronze. The BS for leaded bronze states that it can only be silver soldered with special measures, so even tho' I've got away with it in the past I wouldn't use it for boiler bushes. Manufacturers data sheet for Colphos says it can be readily silver soldered, which bears out my experience.

Whether the screw in bits need to be bronze depends on your water quality. This has been covered in ME in the past. For the little extra expense I'd use Colphos, drilling holes in drawn PB1 is a complete pain in the whatsit

[Paul HorthParticipant @paulhorth66944]

Hello all,

This question is of interest to me because I am nearing completion of a Trevithick Dredger engine to the design by Tubal Cain (see hpoto album). I hope to run the engine in steam, but not very frequently. The design has the entire end plate of the boiler in brass, and brass is also used for the cylinder, which is mounted submerged inside the boiler, and for parts of the flue tube. Tubal Cain (Tom Walshaw) did not mention dezincification in his articles in 1987 because I suppose,he considered it as a display model.

I was concerned about the problem, and managed to find a research paper in which measurements had been made of weight loss from brass samples of different compositions exposed to water under various conditions (heat, stirring and so forth). To summarise, there was a weight loss measured of 0.25%, increasing to 0.5% with galvanic contact with copper, in an exposure time of 2700 hours.

To me this is worth noting but does not prohibit running my boiler in steam, provided the duration is short and also that I drain it completely after each steam session. I doubt if I will ever approach as much as 20 hours exposure, never mind 2700 hours, for this small engine intended mainly for display with the occasional half-hour steam up. So, I think I will get away with it.. I have not yet pitched this argument to my club's boiler testers, though. I have used bronze for the bushes and fittings, Mainly for the better strength of the threads.

It would be quite different in an engine intended for regular longterm use, and I would not dispute that brass is best avoided in this kind of service.

Paul

Edited By Paul Horth on 05/02/2016 14:42:13

[AjohnwParticipant @ajohnw51620]

A little off topic but when people are silver soldering what melting temperature silver solder is usually used?

The reason I ask is that brazing to me means a gas plus blown air torch and temperatures up to circa 8 – 900C or more Approx as I just do it, or have done at work, school too. I see what is generally called silver soldering as being done at significantly lower temperatures and soft soldering even lower.

The question crops up from noting that many bronzes state excellent solderability and only good for brazing and wondering where silver soldering fits in. More like soldering I would have thought.

John

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[KWILParticipant @kwil]

Silver solders vary according to the % silver content, lowest melt temps are 630 degrees C + ranging up to around 800C. Typical Flux melting is just below 600 C.

You will be using the high silver (55%} at the lower temperatures. Either way it is still a brazing process.

[AjohnwParticipant @ajohnw51620]

I would still be interested to know what temperature silver solder people use on boilers.

John

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[bogusParticipant @bogus]

Regarding bushings:

the reason i'm trying to find alternative is the availability of bronze bars in small diameters (at least in my location). It is so expensive that i can't pass by the idea to use 20mm dia bar to turn 8mm dia bushings… such a waste!

Next idea is stainless steel – how about connection SS with copper? SS can be silver soldered, is strong and easily obtainable. Is there any unwanted galvanic phenomena stopping me from doing it?

As to brass bushings and thread strenght: i can make them longer and thus stronger…

Paul Horth – your input is very interesting! I'm not going to steam my boiler 8 hrs a day. Assuming occasional use and that 2700 hours you've mentioned it is good information for me. After all i can design bushings in such a fashion they can be re-threaded to the next size after that… 2700hrs and change fittings. Hey, this is insane

[Thor 🇳🇴Participant @thor]

Bogus,

I don't know where you live, but Chronos can supply bronze bar in small diameters and will ship orders outside the UK.

Thor

[JasonBModerator @jasonb]

Posted by Ajohnw on 05/02/2016 23:32:08:

I would still be interested to know what temperature silver solder people use on boilers.

John

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I thought KWIL answered that.

It is quite common especially on large boilers where there will be several heats of various sub assemblies to start off with a silver solder at the higher end of the temperature range and as the work progresses use lower melting point solders so that previously completed work does not melt so solders between 630 and 800deg melting point are used.

For small boilers one solder can be used and that would tend to be in the lower temperature bracket as its easier to reach the required temperature which is the 55% that KWIL said or old stock of Easyflo which melts at a similar temp.

J

[Ian S CParticipant @iansc]

Why would you bother using brass, that boiler etc will/may be around long after you have turned up your toes, and if it's passed on, it would be nice if it was 100%. A mate got a boiler, along with a Stuart Turner V10, it is pre 1930, and the bushes seem ok, but the safety valve bush is loose, I, suggested that it is probably best not to repair it, as I,m not sure of it's construction. Ian S C

[bogusParticipant @bogus]

My location is in Poland. Overseas delivery together with items price are beyond my hobby budget. So is SS ok for bushings? I can try to melt some bronze scrap i found on the junkyard and pour it in sand.
As to copper bushings: is it really an issue? The strenght?

[AjohnwParticipant @ajohnw51620]

Thanks Jason. I needed some clarification because where I come from silver solder would be a specific and not generally regarded as brazing. I have seen comments on the web that anything over X C is brazing which seemed a bit crack pot to me. I'd be inclined to regard silver soldering as hard soldering. I'm not the only one either.

Going back to the OP's question he needs to see dezincification as brass rotting. That might give him a better idea of what is likely to happen. If he has looked at older designs that use brass for fittings he might see the comment good brass. I have. Brass just like other metals can come in a variety of flavours that are intended for specific purposes and have varying analysis, some more controlled than others. I suspect the older sources were trying to avoid cast brass that might be any old thing. Gunmetal seems to be cast too though and is still about – copper, tin and pretty low zinc content. Sort of weak bronze. Many bronzes have zinc in them.

Bronze comes in many flavours too. Natural bronze can be found by searching tin bronze – what it should be but some use aluminium or silicon and other bits and pieces. Many suppliers give information on fabrication. Solderability is usually stated as excellent. brazing as good – even for tin bronze. All probably down to tin melting at circa 230C. Lead melts at circa 320C. Some pundits mention that it has the effect of making silver solder less fluid. I'd wonder if it alloys with silver.

Silver melts at circ 960C, bit hot for an ordinary gas torch so out of curiosity I tried to find out what is in sliver solder. Model engineering etc sources don't give any info but a major supplier does – interesting, lots of zinc.

**LINK**

This sort of area annoys me – myths that may or may not be fact depending on what is actually used what ever it is. Just saying brass for boiler fittings though is a no no without more information and now it has a bad name that info wont be available.

John

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[AjohnwParticipant @ajohnw51620]

If anyone needs to get a life like me there is a decent run down on brasses here

**LINK**

There are others about and other "brasses"

Data sheets on many here and also some bronzes

**LINK**

I was interested for other reasons once and still am a bit. The problem with all of them is in the eutectics area aspects and 'orrid things like valencies.

John

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[duncan webster 1Participant @duncanwebster1]

Avoid stainless steel like the plague if it is near the water in the boiler. Sounds daft I know, but unless you are certain you have the right grade, hot water under pressure can cause all sorts of problems. You are OK in superheaters as there shouldn't be liguid water

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