The Home Machinist!

I have one of the above lap seam, riveted boilers on an engine I am restoring. My question is, how to check the structural integrity of the rivets to know whether or not they are solid inside their holes or look like an hour glass and are just waiting the opportunity to become a high speed projectile when the boiler is put under steam pressure. Any thoughts?

I would be more concerned about the lap seam itself. You can use dye penetrant to check for cracking.

My question is how many rows of rivets are in the seam? As long as it's more than one, I would think a hydro test would be a good starting point

Bore scopes that you can use with a cell phone are cheap and can be used to inspect the interior.

How big of a boiler are you talking about? Steel or copper? What is the design (i.e., locomotive, vertical fire tube, or ?)?

Best test method is probably ultrasound.
I'm not sure what modern improvements offer, but "shear-wave ultrasound" used to be the chosen method for looking "sideways" into rivet seams.
~RN

All good info guy's! To fill in the blanks, the boiler is for an 18" gauge locomotive and is about 6 feet long (the pressure part) there are three rows of rivets on the engineers side of the boiler and they run the length of the boiler from the rear tube sheet to the smoke box front. I would guess the diameter of the rivets at a minimum to be 1/2" the heads are conical and about 1/2 dollar size. I will post some photos of the boiler seam tomorrow.