Help needed on plugging cylinder

Hi. I have a cylinder made of bronze that someone has drilled two holes in the side and tapped. I think that they may of been inspection ports. These two holes are in the valve part of the cylinder not the piston. I have made some plugs for these holes but I have hit a problem. I can’t silver solder the plugs into position has I can’t get enough heat into the cylinder.
so what can I use to seal these two plugs that will not allow steam to bypass. I don’t think that loctite will work given the location and the heat involved.
anyone have an idea. Thanks

JB Weld will withstand the heat and pressure, just make sure it is the "original formula" one not rapid or marine. Red and black labels. Just coat both threads and screw in the plugs, allow to set for a couple of days.

Ordinary soft solder would work too. Steam will not melt that.

Comsol ! higher melting point ! Noel.

Thanks chaps. I can’t use Comsol as I can’t get enough heat into the cylinder to allow its use. I forgot about soft solder which melts at around 180 to 240*c so it will not melt from the steam. I think that given the fact that the plug threads will deal with the pressure just leaving the solder to fill any caps. I will try this first and hope it works. Thanks

why not start a taper tap in the hole and thread a piece of bronze bar and screw in it should tighten onto the taper and seal it ,cut off and dress back.

Before trying to plug it permantly I would take a closer look at their possible role. You mentioned inspection holes and this is most likely the case, their role considering their position in the steam chest is most likely to help set the valve timing. If so they will be positioned so that you can set the valves to the ports. These can be sealed by suitable plugs and perhaps some loctite steam sealant. It can be very helpful having such viewing ports to help set the timing.

Pete

Boss white. Then you can disassemble if you need to.

Neil

lead babbit? tin babbit?

If they are just inspection ports and don't interfere with the piston or valve bores, then I'd use PTFE tape. Just make sure it is on the threads, not overhanging the end, then you don't get whiskers of tape into the system. Most of the time they just blow through, but they can get caught up and cause problems

Loctite will be fine too. Have you ever tried getting it apart by heating? Steam at the temperatures we use won't remove it. I've loctited liners into cylinders more than once in steam engines. I've had to do this when a blowhole appeared in the bore. You can also loctite small screws into boilers for say holding the firedoor on though I prefer not to drill holes in a finished boiler to fit things like support brackets but they won't leak or come out.

I'd vote for Comsol as well. It only melts at 300 degC, but that's plenty enough for cylinders. Being a higher melting point than 60/40 it retains more strength at higher temperature.

The only problem you might have with Comsol is that it requires a different flux from 60/40 and pure tin. Most leaded and lead free fluxes only just make it to 230 degC. For Comsol you need "Bakers Fluid" which is otherwise described as a Zinc Chloride flux.

Don't get the flux on anything other than the work. It rots just about anything it comes into contact with, and is a devil to get rid of. It will dilute in water. On steel it somehow penetrates into the surface, such that reoccuring rust appears where none did before.