Construction World December 2015

B

Specialist Contractors or Suppliers

Special

Mention

Sasol Process Water Cooling Tower

50

Aveng Grinaker-LTA’s specialist concrete repairs team to carry out the repairs to the first tower in need of the most repairs, with the possibility of more towers being awarded at a later stage. Providing safe access to the top of the tower and work face provided the most complicate challenge – especially with the complex shape of the structure. The Process Water Cooling Towers at Sasol Secunda are 140 m high, 65 m in diameter at the top and 105 m at the bottom. The structural raking columns take up the bottom 20 m and prop up the structure. Access is provided by a means of Alimak and 24 Temporary Suspended Platforms. These comprise of 16 x 8 m wide working platforms and 8 x 4 m wide shuttle platforms. Alimak is installed to the profile of the Process Water Cooling Tower. The vertical level was controlled with a theodolite. Mast sections were running parallel to the tower surface and anchored to the concrete. Initially the anchors were chemical anchors which changed over to

Project information • Company entering: Aveng Grinaker-LTA • Project start date: 28 May 2014 • Project end date: 28 February 2016 • Client: Sasol Synfuels • Main contractor: Aveng Grinaker-LTA • Project manager: Aveng Grinaker-LTA • Consulting engineer: Wynand Louw & Associates • Project value: R66 037 396,82 Repeat client, Sasol Group Technolo- gies, required urgent repairs to their eight rapidly dilapidating concrete process water cooling water towers. The scope would entail the removal of spalled concrete, replacing of reinforcing, reinstating with structural grout and sealing of the entire structure with polyurethane coatings. Sasol engaged the services of

express anchors due to the 150 mm thick- ness of the wall. The profile against the tower was achieved by installing spacers to the mast sections to allow the sections to curve. This is only done every second section. Special brackets were designed to accommodate the walking platform on the top rim of the cooling tower. A monorail section is installed with brackets to allow a temporary platform to suspend from the brackets while still being able to transverse horizontally. The move- ments (vertically as well as horizontally) of the temporary suspended platforms (TSPs) were the main concern of the project as this is where the most time would be lost. As the project kicked off into the construction phase, extra methods were adopted and innovated to achieve a higher efficiency. These included a trap door design to allow the team to enter from the top platform to reduce the lost time of access to the system. This eliminated the time lost by using the shuttle platforms to access the work area from ground level.

2 15 BEST PR O JECTS

CONSTRUCTION WORLD DECEMBER 2015