The CICA technical committee has developed a guidance note on single crane multi-hook lifting to address key risks with planning and conducting lifting operations with a single crane and dual hook.
This guidance note 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.
Single crane dual hook lifts are those that use both the main and the 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 instructions found in the crane operators manual developed by the OEM. Not all cranes 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 designed lift – which considers the crane design limitations in the lifting operations – shall be planned for the specific lifting operation.
Specific manufacturer’s instructions should be addressed during the planning stages. The main and auxiliary hook controls should be operated independently. The load on the main and auxiliary hooks should ideally be monitored separately to ensure no overloading of either winch arrangement, hook, rigging and load. In practice, many cranes will not have independent hook load monitoring. Risk control measures should be in place (i.e. load share calculations). It is recommended that Flow Chart 1 be adopted by the industry for the lift planning.
In basic terms:
If the entire weight of the load and deductibles is lifted within the minimum rated capacity of both the main and the auxiliary hook in configuration, load share calculations are not required for the lift plan. However, a lift procedure is still required, and the lift procedure should specify the risk management process of the entire operation.
If the entire weight of the load to be lifted exceeds either the minimum rated capacity of the main or the auxiliary hook, the lift should be treated as a Designed Lift. Risks mentioned in this guidance note should be considered as part the lift plan.
Single crane two hooks lifts must be performed in accordance with AS 2550.1:2011 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.
CICA technical committee* has developed a guidance note on single crane multi-hook lifting to address key risks with planning and conducting lifting operations with a single crane and dual hook. 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
The following topics were discussed in the guidance note to identify risks that should be considered as part of the lift plan if a Designed Lift is needed for the single crane multi-hook operation:
Physics and geometry: the lift plan should consider aspects including off-lead and side-lead effects, the importance of centre of gravity, in-plan (recommended) and out-of-plan lifts (should be avoided), stability during the lift process, the influence of keeper pins/minimum radius/geometry and the influence of wind.
Crane structure considerations: the lift plan should consider crane capacity ratings and crane line pulls, in plane angle limitation, and the load effects on crane structures caused by rigging arrangements (main hook erection rigging vs auxiliary hook erection rigging).
Crane features: this part discussed the features that the crane should have for the single crane multi-hook operation. Simultaneous use of both main and aux hooks should only be done in accordance with instructions provided by the crane manufacturer. Cranes that are not designed for simultaneous hoist operations should not be used (unless performed as designed lift).
Rigging design and load design: the lift plan should consider how the lift operation can be safely performed by riggers and doggers on site. There are many sling types available for lifting jobs, select the right sling for the job based on load capacity, frequency of use, mass of rigging gear, head room and site limitations, cost versus efficiency and environment factors.
Planning considerations: single crane multi-hook operation can be complicated; a number of planning considerations are required. Lift engineers should be clear on why you choose to have multi-cane or multi-hook operation, when you would choose single crane dual hook over two crane lifts and when you would choose a dual crane lift, these matters are all discussed in this part. Other planning considerations may include, for example, at the planning stage, consider whether the design of the load (e.g. lift point locations in precast) allows the selected crane to perform a clean lift from the delivery vehicle.
Load share between the main and the auxiliary hook is an important factor that can assist the risk control process. Forces from load rotation need to be 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 hoist line system would be drastically increase after initial pick position.
In the guidance note, sample calculations on main and auxiliary hook load share during the entire lift operation were given to assist the load share monitoring. On the previous page 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 degrees. Refer to the guidance note for detailed calculation on the whole panel rotation process and detailed calculation for rotating a slender shape load.
The full “Guidance Note for a Multi-Hook Lift” is available to CICA members. Contact alice@cica.com.au for more information.