Abstract: A fluid-flow machine such as a steam turbine including an inner shell surrounding the rotor component of the machine and which is secured to the foundation, and an outer shell surrounding the inner shell and which is composed of three principal components, these being a support frame secured to the foundation, an exhaust duct for the steam or other motive fluid depending from the frame and leading to the condenser, and an exhaust cover above the frame. The inner shell is divided along a horizontal plane passing through the rotor axis into upper and lower hemi-cylinder halves. Each end of the frame includes a lower fixed part incorporating the lower half of the pass-through structure for the rotor shaft and a removable upper part in the form of a yoke beam incorporating the upper half of the shaft pass-through structure.