1.1 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. 1.2 Couplings covered by this standard are designed to accommodate parallel (or lateral) offset, angular misalignment and axial displaceme