Crane manufacturer Condra recently delivered a Class III grab crane to Impala Platinum. Operating speed of this latest heavy duty design has been increased by some 50% over its predecessors, with travel and lift speeds of 6.4 and 20 metres a minute respectively.

The 10 tonne double-girder overhead travelling crane is fitted with two KSeries hoists incorporating slip-ring motors instead of the usual squirrel-cage induction motors with variable speed drives.

Slip-ring motors deliver a higher torque, making it easier for the operator to control grab movement, particularly closure. Motor resistance is managed so that close-rope tension is greater than lift-rope tension during lifting, ensuring that the grab stays shut.

Impala Platinum will use the Condra unit to augment existing grab capacity at its mineral processes refinery.

Condra, which has been manufacturing Class I and Class II designs for some time, is undertaking its foray into heavy-duty Class III with caution, selecting subcontractors with care to ensure that they comply with the necessary qualifications and experience needed for this specialised field.

Late last year, Condra delivered four Class I and II workshop maintenance cranes worth some R6.0 million to Impala Platinum’s Number 17 shaft.

The units comprised two 60 tonners, one 40 tonne unit and a 30 tonne crane.

The 60 and 40 tonne cranes had spans of over 20 metres, while the 30 tonne crane was a very high lift maintenance machine designed with a 14 metre span to service the mine’s headgear.

Lift height of this crane was 81 metres, or more than three times the 25 metre lift classified by international standards as very high.