bronze or brass

how can you tell bronze from brass by looking at it ? I have a casting that was for a traction engine front hub , I want to use it for boiler fittings , its a different colour from brass ,

regards Phil

It depends on the copper content.

Gunmetal, aluminium and manganese bronzes look a lot like brass.

Phosphor bronze like PB102 has a more coppery tinge to it, but is still yellower than pure copper.

However, AFAIK all brasses look roughly alike in bare metal, so if it doesn't look like brass I'd think it probably isn't.

Ramon gave a few examples on MEM, generally bronze and GM is darker and more towards orange than brass

Bronze should be used for all fittings that come in contact with heated boiler water because brass can corode and become brittle. (dezincification) Brass fittings can be used for the cold water and for the steam lines.

Bronze and gunmetal (a type of bronze) is normally a bit darker and redder than brass. Turning bronze produces long stringy swarf where brass tends to chip. Drill bits tend to dig in wnen drilling bronze.

Edited By Paul Lousick on 30/08/2019 14:35:43

Whilst not disagreeing that the use of bronze for "fittings" (e.g the bits you can unscrew from the boiler) is a good idea Phil - it's not actually mandated in the Southern Feds 'Orange' book. Nor in fact is it mandated for mountings & bushes (e.g. the bits permanently attached to the boiler shell) - although I would be very unhappy if told by a prospective new builder that they intended to use 'brass' for such bushes - it is very poor practice these days and I would find it unacceptable.

However, the SF test code simply states that "The constructor of a boiler to other than a recognised design available through the model engineering trade and/or press shall produce design drawings and demonstrate to the satisfaction of the Inspector, either by calculation or by well-proven example, that the design and materials used have adequate strength." So to a large extent it depends on the inspectors view of things and is therefore subjective - and of course it could also be subject to the age of the boiler design being used (many older ones are a bit suspect!).

For context - there are many G3 locomotives in current use that I'm certain have brass 'fittings' and that are perfectly safe provided the regular inspections/tests are undertaken. I'm not aware of any of our boilers being failed for this reason. I'd be a lot more nervous about finding a non-captive spindle, as these are very dangerous to the untutored - and personally I would strongly recommend that the owner changed it as soon as possible (for a captive type). However, the Orange book clearly states that a non-captive spindle should NOT be a reason to fail the boiler!

My advice to you Phil would be to certainly use "known" materials for the bushes (and all permanent boiler mountings) in accordance with the BoM of the boiler design that you are building and if possible use your 'unknown' material in areas away from the heated water. It will then be much easier for your inspector to give your boiler the go ahead if there is no room for doubt.

I'm not making these points to be contentious btw, simply to re-assure owners of existing (especially older) small boilers that brass fittings are certainly not the end of the world. Keep an eye on things and if in any doubt change them. Bushes are more problematic (it's very hard to know what material has actually been used for a start) but again, the owner should know his engine and be aware of any signs that things may be going south - and if in doubt - ask his local inspector for advice.

Regards,

IanT

Im not re-reading it all again but im sure the new regs state that boiler bushes have to be bronze. As for the fittings themselves, to the best of my knowledge all commercially availible are made from brass. At Pendle Steam Boilers we moved to Bronze bushes a few years back much to the frustration of our cnc parts maker who now has to change his tooling more frequently!

I am pretty sure this is bronze , different colour to brass and machines with "curly bits" not the spray you get with brass, but I will play safe and buy some known bronze for the bushes and use this for the fittings Thanks for the help

Regards Phil

Maybe it should Fizzy - but I can't find that reference if it does - happy to be proved wrong.

However, I feel that most boiler inspectors will be aware of the issue and will advise accordingly for new builds.

Regards,

IanT