Brass or bronze

[Garry Coles]

Hello again
I'm just in the process of finishing the axle driven water pump, and was wondering if the drawings are correct to use 10 BA brass screws that are used to stop the two s/s balls from lifting to far. I thought that all materials that come into contact with water should be of bronze. If this is the case, who sells bronze fasteners of this size.
Cheers once again from a sunny Jersey
Garry

[alanstepney]

For that, I would use brass. Or stainless steel.
It only has cold water rather than boiler pressures and temperature, and they are quite easy to check and change should that be required.

Dont know of anyone (but someone may prove me wrong) that can supply them in bronze so you would have to make them yourself.

[spurley]

Hi there

Whilst I must defer to Alan's greater knowledge I understand the fear with brass is 'de-zincification' which is more prevalent when exposed to steam. It seems to occur with boiling/boiled or hot water and once this process reaches a certain point the material will fail thus any boiler bushes or fittings in direct contact with steam should be of bronze to avoid this possible failure. I personally would think that items in the feedwater circuit, such as the pump that you are asking about would be OK in brass as the rate of failure is insignificant. Also the risk to you or anyone operating the engine should any failure occur is very low indeed.

Cheers

Brian

[Garry Coles]

Thanks for that comment Brian.
I had a feeling it was only when the water was boiling hot and under pressure.
Thats whats so good about this forum. If you don't know or not sure, just ask.
Cheers
Garry