The International Organization for Standardization (ISO). First edition, 1999-11-01. 32p. This International Standard specifies the requirements for couplings for the transmission of power between the rotating shafts of two machines for general purpose applications in the petroleum and natural gas industries. Such applications typically require couplings to transmit power at speeds not exceeding 4 000 r/min, between machines in which the first lateral critical speed is above the running speed range (stiff-shaft machines). It may, by agreement, be used for applications outside these limits.