ASME Committee Updates Below-the-Hook Device Design Document
ASME BTH-1-2011 “Design of Below-the-Hook Lifting Devices” is now available, reports Dave Duerr, of 2DM Associates, Houston, Texas. Though there are no major changes to the structural design chapter of the new document, a number of changes were made to the mechanical design section of the document.
“It’s not a big change for construction crane and rigging people,” said Duerr. “We added a section on fluid power, hydraulic and pneumatic systems used in lifting devices,” he added, referring to the ASME BTH-1 committee. Whereas BTH-1-2011 document is a design standard for below-the-hook lifting devices, the ASME B30.20 volume ("Below-the-Hook Lifting Devices") serves as a safety standard for these devices.
“Each one references the other,” explained Duerr. “They need to be used together by people who design and manufacture lifting devices, such as spreader bars and lifting beams. B30.20 also includes requirements for inspection, markings, etc.”
When B30.20 came out in 1986, it was the only standard that had anything to do with below-the-hook devices, said Duerr. The document included basic design requirements which proved confusing to the industry, and necessitated the creation of BTH-1 as a design standard. “The first edition of BTH-1 in 2005 was oriented to the structural design issues because that’s where most questions about B30.20 came from,” he explained. “Since then, we have been migrating other design issues, getting them out of B30.20 and into BTH-1. This time we worked on fluid power; next we’ll work on magnet lifters. As we do this, provisions in B30.20 are deleted and added to BTH-1.”
That process, said Duerr, is more the way other B30 standards are structured. For example, industry standards exist for the design of overhead and gantry cranes, so ASME’s B30.2 doesn’t include that type of information. “There are design standards for major components of mobile cranes, so B30.5 doesn’t get into design issues. Up until 2005, we didn’t have a design standard for BTH devices that we could site in B30.20. Now we do.”