Boiler bushes studs material.

Hi all!

I was searching forums hoping to find an answer but no luck. Subject has been discussed here before but not in details I'm after.

Soon I will have to source the material to make studs that goes into a steam dome and regulator bush. Bushes are made of bronze I believe. Someone mentioned in another thread that bolts shouldn't be used on the boiler and the way to go is studs with washers and nuts. Stainless 316 has been recommended.

Problem is that 316 aka marine grade only comes in metric sizes (some imperial can be found on Ebay but what is the guarantee that this is going to be 316?)

I got a feeling that 316 wouldn't be easy to machine from 4mm to 1/8 (holes in bushes are tapped 5BA) so my question is, would 303 stainless be OK to use?

Same will be with washers and nuts, I couldn't find 316 grade in any online shops and hex bar in 5ba size is also impossible to find if I would decide to make nuts myself.

I'm guessing that bronze could be used as well but what grade? And if I to go for a bronze, what material could I use for nuts? Or isn't nuts and washers that important since they're outside and easy to inspect for any corrosion.

Also while I'm on it, what people use to seal steam dome to a bush?

Thanks, Tom

try here if you use stainless don't expect it to pass a club steam test.

Thanks Dave. I must say I'm a bit surprised that stainless would fail boiler test. Link after reading this thread I thought it is the material to go for.

Could I use PB102 bronze round for studs then?

Can anyone recommend supplier of bronze 5BA nuts?

PB102 should be fine for studs but I couldn't find anyone doing 5BA bronze nuts, you may have to make your own.

Can I just ask exactly what the nuts are holding?

It may be worth asking your boiler inspector for advice.

Brian

Edited By Brian H on 12/10/2020 19:17:01

I have read that it is a good practice to use studs and nuts instead of screws on boiler.

These will be used to fix inner dome and regulator to their bushes .

I was thinking about making nuts myself but closest hex bar i found is 4BA. This wouldn't work though as holes drilled in inner dome flange are to close to dome tube and there is just enough clearance for 5ba size.

Tom, I have sent you a PM.