Shanahan Engineering was successful in securing an erection only contract to erect Secondary and Tertiary Structural Steelwork for Kusile Boiler 3 for Mitsubishi Hitachi Power Systems Africa in 2013.
Shanahan delights in providing well supervised and productive construction crews for all of our customers. This positive attitude during the execution of our contract at Kusile quickly led to the company securing the erection contracts for Kusile Boilers 4 and 6 as well as the Primary Coal Feed Conveyor for Kusile Boiler units 4, 5 and 6, the Steel Erection contracts for PJFF units 4 to 6 and the Coal Bridge between Boilers 5 and 6.
As the name suggests, the Coal Bridge feeds coal into the Boiler Mills for use in the boiler combustion process. The coal travels up to Boiler 4 via the Primary Coal Feed Conveyor and then across two bridges from Boiler 4 to 5 and then from Boiler 5 to 6 before being fed into the Boiler Mills.
The bridge is assembled at Ground Level before being lifted as a single piece construction, to its final resting place, 50 m above ground level. The total weight of the bridge is 450 tons and is therefore too heavy to be lifted by means of a Mobile or Lattice Boom Crane.
The Engineers therefore designed a system of strand jacks comprising of a series of winches, and cables that are fixed to the 4 corners of the Coal Bridge. When all necessary load and safety checks have been checked and double-checked, the winches are activated in a controlled manner to lift the Coal Bridge up before being fixed by means of bolted connections, into position.
The lift can only be performed in near perfect weather conditions. This is due to the large surface areas that are in play which would make windy and wet conditions more hazardous for the lift.
Prior to the Coal Bridge being ready to lift, the Shanahan Construction Team had to request for all the necessary components to be delivered to the erection site for the bridge to be assembled at Ground Level. The erection drawings are reviewed and a parts list was made that comprised 1556 steel sections and 11863 bolts and nuts. Some of the steel sections were quite light whilst others weighed tons. These parts lists were passed onto the Materials Handling Contractor who delivered the requested components to the erection site. On any mega – project like Kusile, there will be parts that are either incorrectly fabricated or missing, this invariably delays the process of erection due to the engineering queries that result. This process was managed closely by the Construction Team together with the Materials Handling Contractor and the Main Contractor so as to ensure the minimum possible impact to project schedule.
In this case, the Shanahan Construction team spent 10968 manhours to complete the assembly of bridge to be ready for lifting into position. The Strand Jacks were then fixed to the 4 corners of the coal bridge and the Construction Team were ready to erect by the afternoon on 7 December 2018. Weather conditions were checked and due to a favourable forecast (dry conditions and little wind), it was decided to perform the lift early the following day, 8 December 2018.
The lift started at 08h23 on 8 December 2018 following a special safety briefing which started at 06h30 earlier that morning. In the picture below you can see the 450 ton bridge section still on its trestles at Ground Level. By 15h40 on the same day, the Bridge had reached its final position. The lift took just under 7 hours and 20 minutes to complete which was just under 5 hours faster than any of the previous Coal Bridges.
Shanahan achieved a perfect Safety record during the Assembly and lifting of the Coal Bridge with no incidents having been recorded from start to finish.
|Completion date of steelwork||08/12/2018|
|Completion date of full project||In progress|
|Tons of structural steel used||450|
|Structural profiles used||Miscellaneous|
|SA content – if this is an export project|