Heating equipment installation system

Disclosed is a method for installing a heater unit assembly in a reactor pressure vessel for performance of an annealing treatment on the vessel, the vessel having a vertical axis, being open at the top, being provided at the top with a flange having a horizontal surface, and being provided internally, at a location below the flange, with orientation elements which are asymmetrical with respect to the vertical axis, by the steps of: providing an orientation fixture having an upwardly extending guide member and orientation elements and installing the orientation fixture in the vessel so that the orientation elements of the orientation fixture mate with the orientation elements of the pressure vessel in order to establish a defined position of the orientation fixture in the pressure vessel, and so that the guide member projects above the pressure vessel flange; placing a seal ring in a defined position on the pressure vessel flange with the aid of the guide member; mounting at least one vertical, upwardly extending guide stud upon the seal ring; withdrawing the orientation fixture from the pressure vessel; and moving the heater unit assembly vertically downwardly into the pressure vessel while guiding the heater unit assembly along a path with the aid of the guide stud. 5 figures