KwaZulu-Natal, South Africa — A purpose-built gantry crane from Condra is set to streamline operations at the Ngwadini Dam, part of the Lower uMkhomazi bulk water supply project currently under construction in KwaZulu-Natal.
Rather than using multiple machines for different tasks, Condra’s Johannesburg design office proposed a single top-running portal crane equipped with two hoists on one platform—an innovative, compact solution that was selected over competing multi-crane proposals.
Simplifying Complex Lifting Operations
The gantry crane will span the dam’s 52-metre-high wall, with 31.5-metre-long girders and cantilevers on both ends. Its supporting legs are spaced 19.5 metres apart, while the overall height of the structure will reach 11.3 metres.
The crane’s two hoists—rated at 15 tons and 3 tons—will manage the installation and operation of sluice gates, trash racks, and stop blocks, as well as carry out all ongoing maintenance tasks post-commissioning.
Currently in final stages of manufacture at Condra’s Germiston facility, the crane is scheduled for delivery in May and commissioning in June.
Unique Engineering Features
One of the key technical highlights is the 45-degree orientation of the main hoist relative to the girder platform. This angled alignment ensures clear rope travel past asymmetrically positioned guide shaft access slots in the dam wall.
To accommodate this configuration, Condra engineers:
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Increased the rope drum diameter
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Reduced drum width
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Adjusted gear ratios and gearbox dimensions
These refinements were necessary to maintain proper rope lead angles and mechanical performance.
Advanced Positioning and Safety Systems
The crane will be equipped with:
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Proximity sensors on both girder and ground rails, providing real-time feedback via a display panel to ensure accurate positioning
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Floodlighting for night operations
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Storm brakes for high-wind stability
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Radio control with pendant backup
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A full-length walkway for safe access during maintenance
All components, including the full-length girders, are engineered for maximum 12-metre sections to allow road delivery over challenging terrain.
Innovative Girder Design
Each girder is spliced at two points, with bolted and welded steel plates on all internal faces of the male girder section. This eccentrically welded design delivers additional friction grip, enhancing strength and durability well beyond what standard bolting alone would offer. The result is a near-seamless joint with a projected operational life of over 20 years.
A Legacy of Dam Solutions
The Ngwadini crane adds to Condra’s portfolio of custom-engineered lifting systems for dam infrastructure across Southern Africa. This includes its earlier work on the Lesotho Highlands Water Project, where it supplied cranes with extreme lift heights of 158 metres—among the tallest in the region.
