15 April 2008
PT Freeport Indonesia, a subsidiary of Freeport-McMoRan Copper & Gold Inc., operates the Grasberg copper and gold ore open cast mine on West Papua. It ships the resulting milled concentrate from the deep water port of Amamapare to smelters around the region. To maximise loading operations at the port the ship loader needed an upgrade during a routine shutdown of the mill.
This meant that only an 18 day window was available to dismantle the old loader and install a new unit designed by Vancouver, Canada-based Sandwell Engineering. Initial plans to carry out the work in 2005 had to be shelved due to a lack of personnel and planning capability on site.
Additional specialized staff were recruited by Freeport for the job, which was completed last year. To provide additional lift capacity, Tiong Woon Marine Pte Ltd, based in Singapore, was contracted to provide additional lifting capacity.
The remote location of the port was a major concern – it is 50 km from the nearest settlement, Timika, and from any support facilities in the Freeport mining area. In addition it is in a huge inaccessible swamp area without any independent infrastructure. As a result, contingency planning for any likely event had to be undertaken to ensure that no delays would result from the unavailability of parts, spares or any other missing items.
Freeport decided to pre-assemble the main loader components in the port area, test them and then install the new loader in four sections, as opposed to carrying out piecemeal assembly. An adjacent dock was designated for the boom and bridge assembly.
The routine shutdown scheduled to begin on 5 July (although this was delayed for two days due to adverse weather conditions impacting scheduled shipments) so all shipments of equipment and additional lifting were planned around this date.
Work on the ship loader began six months prior to the replacement start date. It consisted of structural alterations and the addition of a new electrical house containing the controls and switchgear for the replacement unit. During this period, piling work was carried out and a new pile cap constructed as the base for the new sill beam, all without interrupting scheduled shipments.
Tiong Woon dispatched the additional floating lift capacity from Singapore. This consisted of a tug and a 5,000 tonne dead weight static ballast barge carrying a 1,000 tonne capacity Demag CC 6400 lattice boom crawler crane with 54 m of boom, which took 18 days to cover the 1,500 miles between the two locations. On arrival it took less than 24 hours to deploy the Demag ready to start lifting operations.
While the tug and barge were en route, Freeport was not idle. It placed a maintenance tower that was transported fully assembled from the LIP Fabrication Yard where the new boom was also fabricated in two parts. It was moved to the cargo dock where it was lifted upright and then transported by barge to the loader site where it was lifted into place using a Manitowoc Model 4100 Series 2 lattice boom crawler crane. The same crane was used to place the new sill beam, also fabricated at the LIP yard. The beam was shipped to the site and stored onboard a barge.
The main components of the new ship loader were all transported to the dock area and it took five weeks to carry out the assembly of the main component – the two sections of the boom.
The 1,000 tonne Demag then began the serious lifting. It was used to lift the old loader boom and placed it on a KPI cargo barge, positioned so as to leave sufficient space to accommodate the existing top tower on the same barge. The lift weight was 60 tonnes, instead of the pre-calculated 66 tonnes, and the centre of gravity was accurately laid on the barge alongside the old boom. This load was slung by the day shift, with the nightshift then taking over to carry out the removal.
The crane and barge then moved to the cargo dock to lift the bridge assembly, which weighed 131 tonnes, 3 tonnes less than originally calculated. The assembly was placed on the crane barge at 11 m radius and safely secured for transport.
On arrival at the loader site, the barge was moored between dolphins in line with the centreline of the existing tower at slack high tide. The bridge assembly was then lifted off the barge during the outgoing tide and installed in an operation that took two hours to complete. During the lifting operations, the Akjwa cargo vessel was moored alongside to reduce the effect of the outgoing tide on the crane barge, and to allow a more favourable angle for the mooring ropes to reduce tension on the ropes and maintain a permissible safe load.
Attention then moved to the new boom. It had been assembled in a horizontal position at the cargo dock but had to be orientated to an 8 degree angle to allow installation and to set it at its final 6 degree orientation on the maintenance tower. Both the Manitowoc and the Demag were used for this operation. To maintain the angle during transport aboard the crane barge, an engineered system consisting of a half-height container, steel flat racks and hardwood blocks was assembled on the deck of barge to support the boom. Welded stoppers were used to prevent any lateral movement during transport. Around 30 tonnes of the weight of the boom was released by the Demag during the move.
The new boom was erected one day late because of engineered weight and centre of gravity differences according to the rigging studies carried out under RS-004RH-1 to 4 Rev B. The work was completed within two hours.
The rotating spout and hydraulic system had been preinstalled and tested prior to boom erection. The Banana spout was installed in a convenient position after the maintenance tower was placed and fitted to the rotating spout immediately after boom placement.
The hydraulic luffing cylinders were positioned at 12 degrees and prepared for immediate connection to the boom to avoid any delays, as well as to create a safe working environment.
Finally, the BC 3 conveyor was erected. This had been transported from the LIP yard and placed aboard the crane barge to avoid congestion at the cargo dock.
The whole operation was completed four days ahead of schedule and to the satisfaction of all concerned.
Illustrating the difficulties of operating in such a remote site, for the last three days of the operation, the road to the port site was unusable after it was washed away. This meant that personnel and small items had to be flown in by helicopter. In addition, no mobile phone network was available for several days, complicating a number of daily routines, such as food re-supply.