From 1910.180(c) and underlined by Crane Tech to indicate important points: OSHA makes a couple of important statements about crane ratings which govern crane design and use. Although the reserve is not for the operator’s use, this factor does provide a margin between the actual tipping moment of the crane and the maximum safe rating of the crane within the area of stability. In the standards, the margin of stability is provided as a percentage of the tipping load. These standards provide an acceptable stability rating and outline the reserves a crane must have to allow for the variables of operation. Manufacturers must adhere to the American Society of Mechanical Engineers (ASME) standards in their design and fabrication of mobile cranes. In its most basic sense margin of stability means, for areas of operation that are limited by stability, there must always be greater leverage on the crane side of the tipping axis than on the load side of the tipping axis. So, the industry developed a suitable “margin of stability” that is applied to all cranes. It would be like hoisting 2,000 pounds with a sling that is known to have a breaking strength of 2,000 pounds. As we’ve discussed earlier in this series, it would not be safe to operate a crane that didn’t have reserve stability.

Working radius of crane