From Concrete Slab to Working Crane

Lifting equipment company Condra is to manage as a turnkey project the manufacture of a 70/5-ton electric overhead travelling factory crane and the construction of its gantry.

The newly-received order is for the design and supply not only of the crane itself, but also for the erection of the gantry from concrete slab up, and thereafter delivery, installation and commissioning of the crane to complete the project.

Condra’s initial 3-D site scan during the tender phase gave it an edge in being able to work from plans accurate to one millimetre in 50 000mm (50 metres), allowing for the design of the most cost-effective gantry possible.

After commissioning, the manufacturing company’s 21-metre span double-girder electric overhead travelling crane will be used to move and position injection moulding heads. It follows delivery to the same customer of three similar cranes over several years for various applications.

An industry source reports that the reliability record and low maintenance costs of these three prior machines, as well as rapid service response, had been key to Condra’s success in securing the latest order.

Machine uptime through robust design and readily available spare parts is a core philosophy at this Johannesburg-based crane company.

The order for the previous three cranes was placed principally because of dissatisfaction with long periods of downtime experienced with a competitor’s machine, the result of having to wait up to two months for the arrival of spares from Europe.

Condra manufactures locally within South Africa and delivers parts anywhere in the country by overnight courier. Robustness within the product range is achieved by designing to allow operation beyond specified limits rather than designing as close as possible to them.

The result of overly tight design among foreign crane manufacturers, while sometimes achieving a lower selling price, also often results in a higher overall lifetime cost, because even slight over-stressing of the machine results in breakdown and a long wait for spare parts to arrive.

Condra’s machines are more forgiving because they are designed to permit momentary operation beyond specified limits in the pressure of the moment.

The manufacturing customer’s new 70-ton crane will be a dimensionally large machine with comparatively nimble operating speeds. Cross-travel speeds of up to 12,5 metres per minute will be possible, with 25 metres per minute achieved on the long-travel.

The main and auxiliary hoists will have lifting heights of 9 and 10,73 metres respectively, with frequency drives delivering lifting speeds of 1,5 and 6 metres per minute.

An interesting decision taken during the design phase was to place increased focus on precise positioning. A frequency drive was incorporated in the main hoist to deliver absolute accuracy at very slow speed. The auxiliary drive, which will do most of the fetching and carrying, will lift at a higher speed of 6 metres per minute.

Delivery of the crane is scheduled for March 2021, immediately after completion of gantry erection.

www.condra.co.za