<p>A gas flow diverter receives large volumes of hot gazes from a gas turbine and has a blade adapted to close either the outlet port to a heat recovery steam generator or the outlet port to the stack. Each port is surrounded by an open channel the two side walls of which are each provided with a seal with both exposed, one beyond the other. The surfaces of the blade are stainless steel cladding and are connected through insulation to a reinforcement in a manner permitting but confining the expansion of the cladding. The frame has a border providing first and second ledges on each side which are spaced and positioned so that each may engage a different one of the two seals bordering an outlet port when closed thus establishing the channel as a closed passageway surrounding the closed port which may be sealed against leakage by die-charging sealing air into it. The blade is shifted between its two operative positions by means of a reversible drive including toggle joints connected to the blade reinforcement by a unit which is shiftable in response to forces exerted by the expanding or contracting toggle joints. <IMAGE></p>
