brass dezincification

[ukjimoo]

Hi all

Im sure this question has been covered here before but i cant seem to find it in the archive.

I need to make some simple threaded steam pipe couplers which will not be used below the water level.
I have plenty of hexagon brass bar that i could use but am not sure if its wise to use brass for steam fittings.
I realise that dezincification would occur in the water but how about in the steam?

On inspecting some steam fittings that i have purchased in the past, the colour leads me to suspect they may be brass. Funny i would have expected them to be bronze.

Thanks in advance for any help on this one.
Jim

[Jo]

Having seen a spectacular fracturing of a fitting earlier this year: I'm sticking to bronze into the boiler.

Jo

[Shawki Shlemon]

Hi ukjimoo
Bronze is best for all fittings wherever they are but brass is OK for all fittings that are not silver soldered or permanently attached to boiler . they are cheaper and if kept clean will last for long time.
Most commercially made fittings are made of brass .

[davidimurray]

Bronze bronze bronze. I've had a brass fitting fail in my hand on a full size engine and it was rather scary! As a result there's no brass near my boilers.

Cheers

Dave

[baggo]

As mentioned in a previous post, there is now some doubt about the suitability of brazing in copper boiler construction due to the same problem of dezincification. Not all brazing materials contain zinc but a lot do contain very high percentages. Some brazing materials are basically just brass!

Although most people do use bronze for fittings, I have wondered about using stainless steel instead? Most boiler fittings such as valves, regulators etc. have at least one part made from stainless so why not make all of the parts from it. I am sure there must be a reason for not using it as no-one seems to. Just a thought as stainless hex bar is considerably cheaper than bronze!

John

[havoc]

I tought the thing about stainless is that there are some questions about embrittlement.

[chris vine]

Stainless bodies for fittings.

I wonder if it is that a stainless valve seating on a stainless seat would tend to pick up and score. The softer bronze might make a better seat.

I think the high quality commercial fittings are made of bronze, a free cutting variety. However unless you know what you are doing I think there is a problem with some bronzes which I read about years ago in ME. High phosporous content?

And some bronzes have quite a high percentage of lead which can make them difficult to silver solder. I once made a blast pipe nozzle with internal passages for blowers etc. After silver soldering it, there were lots of little leaks around my joint. Re did it and it was worse. After the third heat the leaks were coming straight through the parent metal. I think it must be that the lead had burnt out, leaving it porous......

I find that good old PB102 is the best. People complain about it being a piglet to machine but I find that with a good supply of cooland, a tipped tool and a really high speed that it is a joy to work with. For tapping I use Rocol. One thing I discovered, and which surprised me, about PB102 is that its tensile strength is a bit higher than mild steel.

Chris.


I

[greasemonkey]

I seem to remember there being some issue with certain grades of stainless suffering from stress fatigue and cracking caused by exposure to chlorine. May be wrong though.

Andy

[Shawki Shlemon]

I agree with Andy . That is why stainless steel is not allowed to be used as stressed parts on boilers ( such as bushes, stays ,tubes etc.. ).It is OK for valves ,operating rods, bolts not in direct contact with steam etc.. It is not the water or steam that causes the problem, but the chemicals in the water that causes the embrittlement .

[steammadman]

as old LBSC WOULD HAVE SAID "Inspector meticulous at it again."