Some people think as you do and others consider silver soldering to be less safe as the stay may not be under tension if not straight or expand on heating and crack the joints on cooling.

I make no claims for which is best only that I have seen all viewpoints expressed in the past.

Those stays are so close to the central tube that they won't be doing a right lot. If it doesn't leak it's fine, if it does I'd try various sealants before soft or silver solder. Without any sizes/dimensions it's hard to tell what working pressure it is good for

The stays will get longer as they get warm, but so will the shell, and deflection due to pressure will tend to keep the stays in tension

Screwed ends on stays are common on full size boilers. Some have thicker tubes with screwed ends instead of solid stays. Tubes are normally expanded with a special roller to seal them into the end plates.

Pressure testing of a boiler should not be done with air.

Water should be used in case there a problem. It the boiler ruptures there could be an explosion as the compressed air expands. Water on the otherhand does not compress like air and the pressure is quickly repeased without a big bang. (If you must use air pressure because you don't have a pump, fill the boiler with water to reduce the volume of air inside of the bolier).

Paul

not a problem using air at a few psi to find leaks.

I did once have to pressure test a vessel which on no account was allowed to have liquid inside it ever. We found out which safety guy had a practical head, and pumped it up with air with the vessel and compressor in an old air raid shelter. It was only a small vessel, and not very high pressure. It was a containment for an induction heating coil which the boffins wanted to run at more than atmospheric pressure. Apparently it is less likely to arc, counter-intuitive really. The vessel was made from UHMWP, again not a material you'd normally choose, but it has very good insulation properties I'm told.

We live in an area with a lot of dairy farms (South Cheshire) and I understand the water pressure is high because the farms use a lot of water. We had to install a pressure reducing valve to reduce it to 3 bar as it was causing us problems. There are also a high number of water leaks in the distribution system that need to be repaired because of this.

Richard

Around here water pressure can be 80 PSI. I have seen a steam boiler in a lumber yard used for steaming timber at low to moderate pressure that was hooked to the mains water supply, directly through a check valve, so feed water relied solely on mains water pressure. The operator had a valve on the feed line he adjusted to match flow to water level in the boiler. Probably not strictly legal I should think. The boiler ran at a lower pressure than the water mains so it worked though.

I've even seen two-story houses fitted with a disability lift powered by water pressure from the mains. The water operated a large ram like a hydraulic ram set into a deep hole in the ground. Enough power to lift a steel platform and cage carrying two people and a wheelchair up to the upstairs floor. Also no longer legal but still a few in operation out the back of old timers' high-set houses in small towns. Horrendously dangerous with no safety interlocks etc in the hands of ageing operators and resulted in at least one death I know of. They used to be installed by local charity service clubs like Lions and Rotary etc.

Edited By Hopper on 19/05/2021 11:32:36

Edited By Hopper on 19/05/2021 11:34:58