Abstract: A method of and an apparatus for shot peening an inner surface of a stainless steel tube. A set of at least two electromagnets is arranged around the stainless steel tube and has an iron core with an air gap adjacent to the stainless steel tube. At least one magnetic shot particle is provided inside the stainless steel tube. A controller controls the activation of the electromagnets according to a predetermined sequence, so as to cause the at least one magnetic shot particle to repeatedly hit the inner surface of the tube so as to shot peen the inner surface.

Abstract: A test apparatus for testing the tube-to-header connections in a heat recovery system in which a plurality of tubes is connected to a header via tube-to-header connections. The test apparatus includes a source of test gas, a shroud surrounding the tube-to-header connections and a test gas detector in communication with the chamber within the shroud. The invention also relates to a method of testing the tube-to-header connections by forming a test chamber surrounding the tube-to-header connections, introducing a test gas into the chamber and then detecting the level of test gas in the chamber.