(a) The maximum allowable working pressure of a boiler carrying the ASME Code symbol or of a pressure vessel carrying the ASME or API-ASME symbol shall be determined by the applicable sections of the code under which it was constructed and stamped. Subject to the concurrence of the enforcement authority at the point of installation,
such a boiler or pressure vessel may be rerated in accordance with the rules of a later edition of the ASME Code and in accordance with the rules of the National Board Inspection Code or API 510, as applicable.
(b) The maximum allowable working pressure of a boiler or pressure vessel which does not carry the ASME or the API-ASME Code symbol shall be computed in accordance with the Inspection Code of the National Board of Boiler and Pressure Vessel Inspectors.
(c) This article shall not be construed as in any way preventing the use, sale, or reinstallation of a boiler or pressure vessel referred to in this Code section, provided it has been made to conform to the rules and regulations of the office governing existing installations and provided, further, that it has not been found upon inspection to be in an unsafe condition.