This 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 will typically be in large and/or high speed machines, in services that may be required to operate continuously for extended periods, are often unspared and are critical to the continued operation of the installation. By agreement, it may be used for other applications or services. Couplings covered by this 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. It is not applicable to other types of couplings, such as clutch, hydraulic, eddy-current, rigid, radial spline, chain and ellows types. Torsionally 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 standard covers design, materials of construction, manufacturing quality, inspection, and testing of special-purpose couplings. This standard does not define criteria for the selection of coupling types for specific applications.