The Crane Industry Council of Australia (CICA) recently released guidelines relating to single crane dual hook lifts.
Single crane dual hook lifts use both the main and auxiliary hooks of a single mobile crane to simultaneously lift a load and, in general, rotate to a different orientation to the initial lift.
These are similar to multi-crane tailing lifts but have additional unique considerations which should be factored in during the planning stages.
Single crane dual hook operations must be undertaken in accordance with instruction found in the crane operators manual developed by the OEM, as not all crane configurations are designed for single crane dual hook operations. In the absence of OEM manual coverage of single crane dual hook operation, guidance can be sought from the OEM, or a lift engineer.
- The main auxiliary hook controls should be operated independently.
- The lifting points and rigging need to be designed to take the load in direction orientation that will occur during the rotation process.
- The load on the main auxiliary hooks should ideally be monitored separately to ensure no overloading of either the winch arrangement, hook, rigging and load. In practice many cranes will not have independent hook load monitoring. In the absence of independent load monitoring, load share calculations can help control the risk of excessive load through each hook.
- If the entire weight of the load and rigging (deductions) is lifted within the rated capacity of both the main and the auxiliary hook configuration, load share calculations are not required for the lift plan. However, a lift procedure should specify the risk management process of the entire operation.
- If the entire weight of the load to be lifted exceeds either rated capacity of the main or auxiliary hook, the lift should be treated as a Design Lift. Risks mentioned in the guidance note should be considered as part of the lift plan.
Single crane two hook lifts need to be performed in accordance with AS2550.1:2011 and AS2550.5:2016. If there is any doubt as to the capabilities of the crane or conformity of the lift planning in relation to applicable standards, then the lift planning should be considered as a Designed Lift.
The CICA Technical Committee is developing a guidance note on single crane multi-hook lifting to address key risks with planning and conducting lifting operation with a single crane using dual hooks.
This guidance note also provides further guidance and position for the industry where current guidance material is either conflicting, silent or has multiple references. Considerations in this guidance note include manufacturer’s requirements, applicable standards and industry regulations and requirements.
CICA has produced for members a simple Excel calculation tool to demonstrate the load is transferred during rotation from the auxiliary hook to the main hook. Load share between the main and the auxiliary hook is an important factor that can assist the risk control process. Forces from the load rotation need to ne carefully considered at all stages of the lifting operations.
Particular consideration is required for loads that are relatively slender in nature with significant differences between main and auxiliary lift points, where operational percentage of the hoist line system would be drastically increased after the initial pick-up position.
In the guidance note, sample calculations on the main auxiliary hook load share during the entire lift operation were given to assist the load share monitoring.
The illustration is an example of a lift operation for concrete panel rotation. The drawing shows the load share for the main and the auxiliary hook when the panel is rotated at 63°.
This CICA Guidance Note is available to CICA Members or by contacting Alice Edwards (firstname.lastname@example.org)