HRP Expanding Tubes

The holes in the tubeplates for the boiler tubes should be reamed or at least have a good machined finish, and the two tubeplates should be kept parallel with each other when welding up.

When fitting the tubes, leave them protruding at either end by 3/16" and then expand them in with a proper roller expander,so that the tubes will fit correctly all over the area of contact with the tubeplates. Do not fully expand one tube at a time, but go generally over the lot, expanding enough to take up the slack, the idea being that the tubeplate will then not be distorted. Do not over-tighten, but expand the tubes sufficiently to seal only; it is best to give an initial tighten all over at both ends, and then to finally tighten up where required, as indicated during the hydraulic test. A simple universal joint can be made for ease of expanding tubes in the firebox. Take a short piece of rod, and secure this in the tommy bar hole of the expander spindle. This can be fitted by knurling the short tommy bar; now take a piece of tube of similar size to that of the steel boiler tubes, and drill or end-mill two 'U' slots in the end of this tube diametrically opposite. In the other end, drill a hole to take a tommy bar of normal length, and then it will be possible to put this extension tube through the firehole door, and to locate it over the expander spindle, and expand the tubes very readily.