Thanks Ian, just dipping a toe into the very different world of steam. I've been trawling around on the net and getting info and a very long way from even considering firing anything up!! I wasn't sure about air and the responses have clarified that one ! It seems that owning and operating requires significant commitment!
I need to test the solder first I guess to see if it's hard or soft, is this as simple as just scratching it with a blade or similar?
This is clearly an important point which begs the question if it's soft soldered should the boiler be disposed of?
Roger, If you have washed the casing will be O.K. and it will be safe enough.
The boiler layout with the 2= tubes at the bottom is an indication of it's age, in the past there was all sorts of configurations made but after K.N. HARRIS published his books things became a bit more rational.
The 2- tubes in my opinion are superfluous as the fire hole in the casing is very small and would allow only a small burner which wouldn't apply direct heat to the tubes only to the underside of the boiler..
Be careful with the boiler as it would appear to be soft soldered, another indication of age, if you can scratch it it's soft soldered.
I must agree with the other comments and don't put your compressor on it to test it as it could come apart with serious consequences.
I am reluctant to write the following but if treated with respect ,it's safe enough.
I have made many boilers in the past and for a first test on them I made an adapter from the valve from my high pressure cycle tyres and screw it into a bush, put a bicycle pump on it and with the boiler at the bottom of a water filled bucket, the deeper the better, apply about 2-3 stroke of the pump which is enough to show any air bubble leaks, and I do mean 2-3 strokes which will give about 3-4 p.s.i.
IF IN DOUBT GET SOME BODY TO DO A HYDRAULIC TEST ON IT.
I don't think this has been a school project as in the time scale when it was made schools didn't have lathes or mills and not some botched up kitchen table job.
Some of the parts are turned, the pistons and their oil grooves, the main shaft has been turned in one piece, con rod ends have been turned so somebody has known what they were doing with a lathe..
I am quite sure when you have cleaned up the engine it will look the part but whether you steam it is up to you. Don't be afraid of working with steam but a great deal of common sense is required.
Regarding your question on working pressure I wouldn't go as High as that without having a proper hydraulic test on it