Condra is set to deliver a purpose-built top gantry crane to service the Ngwadini Dam, part of the Lower uMkhomazi bulk water supply project in KwaZulu-Natal, South Africa.
The crane design, proposed by Condra’s Johannesburg design office, was selected over other tenders that suggested operating the dam’s trash racks, sluice gates, and stop blocks.
The proposed solution involves a single portal crane equipped with two hoists traversing the same platform, straddling the dam’s 52m-high wall.
The crane’s design includes 31.5m girders with cantilevers at both ends, supported by legs spaced 19.5m apart, and standing 11.3m high.
Two hoists, with capacities of 15 tons and three tons, will manage the installation of sluice gates and trash racks and handle all maintenance activities after commissioning.
Condra said the manufacturing at work at its Germiston facility is nearing completion, with delivery scheduled for May and commissioning in June this year.
A unique feature of the main hoist is its 45-degree orientation to the girder platform, ensuring the rope runs clear of asymmetrically oriented slots accessing the wall’s guide shafts.
The design includes an increased rope drum diameter and reduced width to achieve the necessary rope lead angle, with adjustments to gear reduction and gearbox size.
The gantry crane for Ngwadini Dam will include proximity sensors on the girder and ground rails, part of a positioning system with an integrated display panel.
The system ensures precise crane positioning for various lifting and lowering tasks.
Additional features include floodlights, storm brakes, radio control with pendant backup, and a full-length walkway.
All crane components, including the 31.5m girders, are designed with a maximum length of 12m to facilitate delivery via challenging access roads.
Each girder is spliced at two points, providing a smooth path for the crab wheels, with splices comprising bolts and welded steel plates to reinforce the girder beyond the splice bolts.
Earlier this year, Condra secured an order from Tronox Mineral Sands for a 35/12.5-ton overhead crane and two hoists for the Namakwa Sands East OFS Project in South Africa.
The crane, designed for mill maintenance, will be integral to the extraction of orange feldspathic sand (OFS) from deeper levels than previously mined at the Namakwa Sands.
