November 25 - Finland headquartered crane services company Havator has used a Terex CC 6800 lattice boom crawler crane to replace an old riding ring with a new one at a pelletising plant in Kiruna, Sweden.

The original riding ring at the plant, owned by LKAB, had begun showing cracks and appeared difficult to repair, so the owner decided to replace the old model with a new one rather than risk a delay in prodyction.

Weighing 192 tonnes and measuring 8.6 m high by 3.6 m wide, the riding ring was located in the 42 m long rotary kiln. The only way to access the ring was by crane, descending 19 m from an opening in the plant's roof.

The Terex CC 6800 crane was equipped with a 48 m main boom and 48 m luffing jib in a super lift configuration. In addition, the crane features a Vario-Superlift system, which means that the radius can be adjusted from 15 m to 24 m, said Terex.

Havator used a maximum of 320 tonnes of counterweight on the superlift tray, while the crane itself was balanced with 170 tonnes of counterweight on the superstructure. Terex explained that this enhanced the machine's stability and manoeuvrability at the LKAB site, as well as enabling Havator's crews to work more easily in the plant's space-restricted areas.

"The crane had been working on a project in Hammerfest, Norway, when we realised it had the right capacity and set-up for the LKAB project," said Havator manager Bengt Hedlin. "We dismantled it and transported it 650 km to Kiruna. Using 38 trucks, we had the crane in place and ready for use in six days..

Before the project began, Havator worked with LKAB to plan how the lifts could be achieved in the shortest amount of time possible. LKAB also stressed to Havator the importance of job security and maintaining a safe working environment on site.

Once all the preparations were in place, Havator's operations crew - comprising three crane operators and riggers - used the Terex CC 6800 crane to remove the old riding ring from the kiln at a 42 m radius, before picking up the new ring at a 20 m radius, lifting it 47 m from the ground, turning 45 degrees and lowering it by 19 m into the kiln.

"Both lifts were carried out at night because the timetable was short, and it was necessary to do them as soon as the opportunity arose," explained Hedlin. "In addition to the two riding ring lifts, ten more lifts were undertaken to remove smaller units of equipment from inside the kiln for other maintenance repairs."