New Standard for Design of Below-the-Hook Lifting Devices

The design, manufacture, testing, inspection, and use of below-the-hook lifting devices are standardized in the United States by ASME B30.20 Below-the-Hook Lifting Devices. Prior to the issuance of B30.20, there were no broadly applicable standards for the design and use of lifting devices used with cranes and derricks. This standard contained only a very basic structural requirement that lifters be designed based on a design factor of three with respect to yield strength. This requirement produced a number of requests to the B30.20 Subcommittee for clarification and a certain amount of confusion in industry as lifting equipment designers developed interpretations with respect to aspects of design for which yielding is not a practical limit state. ASME responded to these queries by developing the new design standard BTH-1-2005 Design of Below-the-Hook Lifting Devices. This paper documents the history of the development of B30.20 and BTH-1 from the inception of the B30.20 Subcommittee through the first issue of BTH-1 and documents certain key decisions made during the development of BTH-1. Particular emphasis is made on the structural design requirements for lifting devices.