A new, R98-million floating caisson is to be fabricated for the Sturrock Dry Dock in the Port of Cape Town, which will enable one of the biggest dry dock facilities in the southern hemisphere to double its productivity, the Transnet National Ports Authority (TNPA) announced on Thursday.

TNPA stated that the new caisson forms part of a multimillion-rand overhaul of the port’s ship repair facilities under South Africa’s Operation Phakisa programme, through which ship building and ship repair have been identified as a strategic competence for the port.

The caisson is a large steel gate structure that acts as a secondary seal and subdivides the dock, allowing for the simultaneous docking of multiple commercial vessels within the facility. 

The old, defective caisson had been out of commission since December 2016. The 74-year-old dry dock was first commissioned in 1945 to repair American and British war vessels.

Refurbishment of the old caisson cost TNPA R2.7-million and covered a condition assessment and finite element analysis, as well as stabilisation of the old caisson prior to the new one being introduced.

Phase 1, completed by Southey Co between July and August last year, entailed the installation of special greenheart timber to seal water leaks around the old caisson.

Phase 2 was completed in November and comprised the replacement of shut-off doors and three sinking tank valves, as well as the addition of ballast weights to make up for lost weight owing to corrosion, as well as blanking off valves that would not be used going forward.

During the initial commissioning of the refurbished caisson, there were challenges as the floating caisson was not sinking sufficiently at high tide. This compelled the naval architect to go back to the drawing board.

There were also minor leaks between the floating caisson steel structure and the sealing timber as a result of uneven steel structure surfaces. This was resolved by inserting a special sealant that is compatible with sea water.

Civil infrastructure at the Sturrock dock has also received attention, including concrete repairs and replacement of corroded tunnel piping.

Twenty-nine capstans – rotating machines that assist in pulling the vessels into position inside the dock – are being replaced in Cape Town at various locations which include the Sturrock Dry Dock, the Robinson Dry Dock and the Synchrolift.

In line with Operation Phakisa’s intention to fast-track delivery, while being respectful of governance, TNPA took a decision to execute the replacement of capstans at its dry docks as a national project for the benefits of standardising the ship repair equipment and achieving economies of scale by procuring these capstans in large numbers.

Under Operation Phakisa, the port’s Robinson Dry Dock is also undergoing a major upgrade. While the Robinson Dry Dock’s floating caisson was recently refurbished, the intention is ultimately to replace this structure with a modern, fit-for-purpose caisson structure.

TNPA said the design process will start in the near future and will include replacement of the floating caisson that seals off the dry dock from the basin.

TNPA noted that it is investing significantly to restore ship repair facilities, including an investment of R950-million to modernise the Port of Cape Town’s ageing facilities, such as the Robinson Dry Dock, the Repair Pier, the Sturrock Dry Dock and the Synchrolift.