This International Standard specifies the requirements for couplings for the transmission of power between the rotating shafts of two machines in special-purpose applications in the petroleum@ petrochemical and natural gas industries. Such applications are typically in large and/or high speed machines@ in services that can be required to operate continuously for extended periods@ are often unspared and are critical to the continued operation of the installation. By agreement@ it can be used for other applications or services. Couplings covered by this International Standard are designed to accommodate parallel (or lateral) offset@ angular misalignment and axial displacement of the shafts without imposing unacceptable mechanical loading on the coupled machines. It is applicable to gear@ metallic flexible element@ quill shaft and torsionally resilient type couplings. Torsional damping and resilient type couplings are detailed in Annex A; gear-type couplings are detailed in Annex B and quill shaft style couplings are detailed in Annex C. This International Standard covers the design@ materials of construction@ manufacturing quality@ inspection and testing of special-purpose couplings. This International Standard does not define criteria for the selection of coupling types for specific applications. This International Standard is not applicable to other types of couplings@ such as clutch@ hydraulic@ eddy-current@ rigid@ radial spline@ chain and bellows types.