Walz Group was awarded the coveted CICA Lift of the Year: Over 20t for several Triple Crane Lifts completed to extract the 60m-long DN500 Jacketed Pipe Units (JPUs 141, 143 and 144) requiring repairs within the internal pipework at an alumina refinery in Central Queensland.
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Three cranes, two hydraulic all terrains and one lattice boom crawler, were concurrently employed to perform the extraction operations,to allow for the assemblies (lifted one at a time) to be set-down onto repair beds at grade, and for the repairs of the inner pipework to be completed prior to lifting the units back in position.
The project was undertaken on the repair beds since, due to the extreme heat present at the top level of the Digestion Area (where the JPUs are located), Walz Group personnel were not allowed to complete the works in-situ. The assemblies had to be extracted and then re-instated at completion of the integrity repair works.
Due to its shape (two 60m long DN500 pipes, connected by a larger DN750 U-shaped spool), three cranes were employed to pick up the load at spaced locations via dedicated spreader bars.
The cranes involved were a Tadano Demag AC350 350t capacity all-terrain, a Grove GMK 7450 450t capacity all-terrain and Walz’s Kobelco CKE 2500G-II 250t capacity lattice boom crawler. The Demag AC350-6 was de-rated to 26.2t at 22.1m with 36.2m boom operating at 91.8 per cent of capacity.
The Grove GMK7450 was de-rated to 31.1t at 26m with 41.5 m of boom operating at 97.4 per cent of capacity and the Kobelco CKE2500G-2 lattice boom crawler was de-rated to 25.7t at 24m with 39.6m of boom operating at 93.7 per cent of capacity.
Due to the characteristics of the load, the three-crane scenario was adopted to allow pick up of the unit at 12 locations via dedicated spreader bars and restrain frames. The lift methodology, crane configuration and staging aspects of the lift were planned and executed by Walz Group.
Lift Details & Methodology:
The exact position of the cranes was calculated via 3D modelling in order to ensure the best configuration and crane reach throughout the operations.
The lift sequence considered that the three cranes had not direct sight of the load during the initial stage of the lift and that the existing facility presented physical obstacles that had to be overcome with a combination of hoisting, luffing and slewing, while maintaining the appropriate clearance to the crane booms.
Additional spotters were employed to allow the cranes to manoeuvre the load safely and to carefully coordinate the pick & carry operations of the lattice boom crawler crane.
Since scaffolding was not able to be erected due to the extreme heat present in the area, and due to the short intervals that personnel were allowed to access the top level of the Digestion Area, rope access rigging specialists were employed to connect the load to the cranes via chain slings.
The rigging involved 12m, 9.5m and 8m spreader bars set-up along the length of the JPU to ensure support of the unit while being lifted and lowered to grade. Six purposely designed restrain frames were utilised at the nominated pick-up points to brace the two DN500 pipe sections comprising each JPU assembly to avoid lateral buckling when being lifted.
Risk Control & Solutions Adopted:
An initial structural assessment was completed to identify suitability of the three-crane configuration in order not to compromise the integrity of the JPU assemblies.
Since the cranes had to be positioned over the access road, dedicated traffic management measures had to be employed for the lifting operations.
Due to the presence of existing underground electrical cabling and services running directly under the crane set-up positions, large crane mats and steel plates were set-up under each crane to reduce the overall ground pressures.
The presence of three cranes concurrently lifting each JPU unit, resulted in complex coordination activities performed in the field. Radio communications on a dedicated Walz Group channel were utilised to coordinate the lifting operations and avoid interferences between the three cranes.
The Critical Lift Plan form was completed by Edwards Heavy Lift with the assistance of Walz Group for the development of the lift sequence, the rigging arrangements and the positions of the cranes and the repair beds.
Three-dimensional modelling of the lifting sequence at the different stages was completed by Walz Group and its engineering team to determine the optimal crane locations, crane configurations and rigging gear to be utilised for each one of the three cranes.
The rigging configurations were simplified to the highest extent possible to reduce the rigging gear load as well as to streamline the rigging activities (completed in an unfavourable area).
Walz Group engaged Edwards Heavy Lift to complete the structural analysis associated with the identification of the best pick-up point locations and the design of the restrain frames.
No chainblocks/complex rigging was used for the cranes in order to avoid complications associated with the mechanical aids (chainblocks, snatch blocks, etc.).
Radio Communications were used to ensure constant communication of the Walz Group specialised team involved in the lifting operations. A dedicated Walz Group radio channel was used by the lifting team throughout the works.
Several spotters and dedicated personnel were employed to ensure the crane and load movements were controlled and the set-down position was calculated.
Thanks to this crane configuration and lift of the JPU units, the extent of works performed on the top level of the Digestion Area of the plant where extreme heat is present were minimised.
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