Use of brass in Boilers

I am in the process of making fittings and plumbing a boiler, I understand that brass is not recommended for bushes as they can corrode from electrolytic action between brass and copper, but is it permissible to use brass inside a boiler such as the tube between the regulator in the steam dome to the header on the front tube plate, where the the brass is in contact with bronze.

The use of brass such as nipples and nuts for connecting fittings to copper tube seems to be common practice, would this not be more of a problem as the sections of material are smaller than that of bushes and would corrode faster?

Can a more experienced ME shed some light on the subject and recommendations?

Mike

Edited By Mike Palmer 1 on 09/01/2017 09:59:43

I thought I;d look this up for my own education and came across this **LINK**

I don't pretend to have read it all..just the introduction was enough to make my head start to ache.. but suffice it to suggest that the full electrochemistry is more complex than first impressions and it's probably easier just to avoid brass..

I will leave others to explain the places where the use of brass is acceptable BUT , before you proceed too far making fittings that require tapping, please consider using stainless steel screws for all 'flanged' fittings.

Make sure you can match the tapped holes ( metric/BA) with the availability of stainless screws you intend to use.

I would not use brass anywhere on a boiler. That way you don't have to explain to the boiler tester what you have done and why. I always use copper tube for any pipe work on or in a boiler. I don't understand all the science but I have built and had tested 8 boilers to date with no problems.

Michael

I think you will find that if the 'fitting' come into contact with the boiler water then gun metal or bronze if required and I personal would not use stainless fasteners on a boiler.

I've stripped an old boiler for examination, and the brass fittings snapped off like carrots. The zinc leaches out and you are left with a sort of Aero chocolate made of copper. I have always made my fittings of bronze since then. With one exception; I happened to have a small piece of brass hexagon, and rather than set up and make some little water gauge plugs (for rodding through to clear scale) out of bronze, I used the brass, screwed into the bronze fittings. The plugs lasted about a year before snapping off when trying to unscrew them. Since then, I really, really don't use brass on boiler fittings. Except for whistles or cold water feed valves...

Stainless steel will also corrode if it is below the water line of a copper boiler, but not as rapidly as brass. Bronze screws would be better, but they're not as strong a stainless, so you may need more of them or larger diameter ones.

The use of brass nipples and nuts for boiler fittings isn't such a problem, because it's usually either steam or cold water they're in contact with, and generally speaking that doesn't cause corrosion difficulties.

I would certainly advise against the use of an internal brass boiler component such as a steam pipe. What's the difference in price between copper/bronze and brass, and how long is it going to take you to change it when the brass fails?

It seems to me we are all in need of some serious education on this subject

Michael W

I've alway sgone by the ryle of thumb that if it is likely to come into contact with hot boiler water then don't make it from brass as it is impurities in the water that will attack the zinc when hot, which is the same as Harry's post.

So Brass is generally OK for nuts &nipples, injectors, globe valves, tender fittings etc as they only see water before it gets to the boiler or steam afterwards..

Boiler bushes, plugs or any fitting that fits into or onto the bushes don't use brass.

As for stainless some inspectors don't like it again if in contact with water so you may be OK using it in blind stud holes but not through holes into boiler.

As always if in doubt talk to whoever will be certifying the boiler etc.

J

I'm assuming that brass is ok for fittings on a boiler but not in contact with steam and water? I ask because I have just made up come brass brackets for attaching a water tank to a boiler. I will be using copper rivets, silver soldered, to attach the brackets to the boiler.

Brian

Edited By Brian Hutchings on 09/01/2017 15:20:38

I do wonder why you see a lot of antique boilers in brass.

It seems from frugal research I've done that there are work arounds if you do have brass, which either involve treating the brass or treating the water. There is brass you can get which by standard contains less than 15% zinc, or arsenic. The boiler can be treated with tin too. A stranger method appears to be using a cathodic device to allow the water to attack that, rather than the material in question, provided that it has a higher valency than the parent material we want to protect.

Having said that it's probably a better idea to avoid it if you haven't already used it. As people have said before, the end result is crumbly metal, but how long that takes, and where the brass was located has big effect on what happens.

Michael W

Edited By Michael-w on 09/01/2017 15:45:57

Thanks for all your comments and recommendations, the rule of no brass in contact with boiler water would seem to be sensible.

Interesting that Martin Evans specifies brass for the steam pipe!! I wonder how he and the other renowned designers such as Curly ran their engines?

Mike

Mamod / Wilesco

All suffer from dezincification !

Some suggest that you can use brass but you need to replace the fitting regularly, but as Jason said if the bouler is to be tested by a boiler inspector seek his guidance.

I would wager quite a bit of difference in price between brass and copper. I'm just saying.

Michael W

Well for a bit of sound advice from experience.

A few years ago I cut up a copper silver soldered boiler that also had structural sif bronzed joints.

This boiler was made professionally by Tom Goodhand in the very early 1960s for a medium sized 5"g loco that had seen a great deal of use in a hard water area.

The regulator of disc in type type was made of brass. It showed no sign of dezincification. It was 40 plus years old when I cut up the old boiler. It was re-used in the replacement boiler I made. The blowdown valves low down on the backhead showed bad signs of dezincification and the old ones were discarded. The bottom water gauge fitting showed some signs of dezincification, but in any event was replaced with a better design on the new replacement boiler.

My first boiler had a brass silver soldered regulator assembly for the body, and all but one subsequent boilers have had the same.

I remove the brass blowdown valves every 4 years for the hydraulic test. As clearly below the water line they are to a certain extent sacrificial. I give the bodies a life expectancy of 10 years.

Boiler bushes have to be of bronze due to the temperatures that occur when silver soldering boilers that brass would be prone to melt. Also the threads on such bushes, although finished later are far more resilient than that from a brass bush.

I hope this clears up any confusion.

Cheers,

Julian

Thanks for your post Julian.