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Boiler fittings - is brass OK?

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Dennis Rayner30/06/2011 18:09:58
124 forum posts
8 photos
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.
Chris03/07/2011 18:46:16
87 forum posts
13 photos
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.
Steambuff03/07/2011 19:15:21
534 forum posts
7 photos

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.
JasonB03/07/2011 19:21:42
22751 forum posts
2653 photos
1 articles
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.
macmarch03/07/2011 21:46:49
147 forum posts
1 photos
Don't forget that the bronze must be a lead free grade.
Bogstandard03/07/2011 22:15:12
263 forum posts
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.
Dennis Rayner03/07/2011 22:38:40
124 forum posts
8 photos
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.
Bogstandard04/07/2011 11:44:28
263 forum posts

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.

bogus02/02/2016 10:14:57
31 forum posts
54 photos

Hi all,

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

stan pearson 103/02/2016 10:16:36
135 forum posts
2 photos

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


Brian H03/02/2016 10:31:55
2312 forum posts
112 photos
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 webster03/02/2016 12:06:27
3989 forum posts
65 photos

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 Horth05/02/2016 14:34:11
66 forum posts
18 photos

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.


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

Ajohnw05/02/2016 16:36:19
3631 forum posts
160 photos

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.



KWIL05/02/2016 17:00:33
3554 forum posts
70 photos

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.

Ajohnw05/02/2016 23:32:08
3631 forum posts
160 photos

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



bogus07/02/2016 06:20:56
31 forum posts
54 photos

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 🇳🇴07/02/2016 06:54:47
1630 forum posts
46 photos


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


JasonB07/02/2016 07:27:45
22751 forum posts
2653 photos
1 articles
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.



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.


Ian S C07/02/2016 10:22:38
7468 forum posts
230 photos

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 Cdsc01138 (800x600).jpg

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