For a crane to work it’s necessary that the entire mechanism and load is kept stable. Any slight alterations of the stability of the crane, especially at the base can cause other sections to move unnecessarily, or even topple.
The stability of a crane is calculated by measuring the sum of all moments about the base of the crane. These must be close to zero or the crane will overturn.
The stability-limited rated load for a crawler crane is 75% of the tipping load. The stability-limited rated load for a mobile crane supported on outriggers is 85% of the tipping load. These requirements, are set by the American Society of Mechanical Engineers.
Because of the dynamic nature of water, standards for cranes mounted on ships or offshore platforms are somewhat stricter due to vessel being in motion. This means that, the stability of the vessel or platform must be considered also.