Abstract: A frame structure is provided for a bed vessel in an energy plant with higher or lower pressure in the bed vessel in relation to the surrounding space. The walls of the bed vessel are stiffened by surrounding horizontally extending, continuous frames with stiff corners, beams in the frames are built up from rolled standard beams and each individual frame is supported and guided by devices applied to the bed vessel wall. The devices make possible axial movements of the frame beams in relation to the devices. Anti-twist bars for each frame are arranged by means of crossbars rigidly attached to each frame. The crossbars extend to the adjacent frame. The ends of the crossbars mounted in a web of the adjacent frame, the ends of the crossbars at the mounting point being freely axially movable.