Not sure what a small boiler like that would get up to for psi, but i suggest a face protector visor at least and a few feet away, when you get it fired up. Safety first always. Not that a visor would stop a chunk of…brbum, it looks like? i sure hope you didnt just take sheet brbum and weld a seam in it to make a tube, i dont think plain welds will hold that pressure, not with the added heat. also those end welds look suspicious…i hope you just exercise caution, thats all.