The structural design of the Ngezi Portal 3 was completed by FL Smidth. Appointed by the Client, Zimbabwe Platinum Mines (Pvt) Ltd. ZIMPLATS is one of the three Platinum mines in Zimbabwe with a total of five mines in production, and the sixth mine in the construction phase.
The structure consisted of twelve main boxed gantries, 2.5m deep x 2m wide x 54m long. The twelve boxed gantries are welded to base plates on the concrete plinths at the base and bolted to a 7m dia center ring at the top. This structure covered the Mine’s main ROM stockpile with a capacity of 13 000t. All work was carried out around the already-installed Stockpile Feed Conveyor. The Mine and Stockpile Feed Conveyor continued to operate during night shift operation throughout the installation period. Safety measures were of paramount importance as the Mine enjoys an excellent safety record.
Shop detailing was completed in Tekla. Detailing and model reviews were done at regular intervals to ensure the design intent was understood and carried into the shop detail drawings.
During the shop detailing phase, numerous meetings were held to optimize the constructability of the structure. Safety of the site installation crew was of prime importance, with access walkways being added to ensure their safe transit up and down the structure during installation.
During the constructability reviews, a few concerns regarding the installation sequence were highlighted by the team. A decision was taken to trial assemble two main gantries with the lattice and infill steelwork between the two. The trial assembly was completed without a single modification having to be made. Trial assembly was assembled and disassembled in two weeks. Once the trial assembly was completed, the green light was given for full production to proceed.
Manufacturing was done at Viva Engineering’s workshop in Spartan, Kempton Park.
The CNC and preparation department cut their teeth on the structure and were excited to make use of the newly acquired FICEP SP16T6 CNC Anglematic which had been commissioned two weeks prior. This machine worked its way through the structure and resulted in the CNC department completing material preparation three weeks ahead of internal planning. Repetitive gantry sides were assembled in jigs which were inspected and signed off by Viva’s Quality Department before assembly work started. Welding Process utilized was GMAW and was done with the AMIGG 500PM pulse arch welding machines, resulting in superior weld quality with 90% less spatter and minimal cleaning.
Cross-Border Exports and Logistics
The structures were expertly packed by the Viva dispatch and logistics team, ensuring that the structures were safely secured and vehicles across the border were optimized. In total there were 31 vehicles dispatched to site. Vehicles were cleared through Beitbridge Border post and on average were on site within nine days from dispatch. The center ring, whilst split, fell outside normal transport gauge and needed abnormal transport to site.
Installation on site at Bimha Mine, Ngezi, Zimbabwe, was carried out by Hogarths Engineering; a Bulawayo based Structural/Mechanical Engineering Company.
Overall, three cranes were used during installation – 250t, 90t and 55t units. Initially, large base plates were bolted onto the cast-in plates, on top of the concrete plinths. The erected gantries would be welded to these base plates once levels were checked and confirmed. The 12 main gantries were pre-assembled on the ground in positions convenient for lifting. The 90t lattice boom crane was positioned on top of the stockpile, where it lifted in and held the center ring in position ready to receive the main gantries.
The twelve gantries were lifted into position by the 250t crane and bolted to the center ring being held by the 90t crane. This crane continued to hold the center ring whilst intermediate cross gantries, bracing and purlins were lifted in and fitted. Both the 150t and 55t cranes were in service feeding these members. Overall installation of steelwork took 3.5 months, with completion in early December 2019. No major site alterations or repairs were necessary. Thankfully there were no safety incidents during the installation period.
Roof Sheeting is 0.8 IBR Chromadek, Traffic Green colour. Total is 5500 square meters, with 8000 fixings. Sheeting installation started shortly after the first three bays of steelwork were completed. Completion of the sheeting was a week after completion of the steelwork.
ISO 9001-2015 (Certification body – TUV)
Viva Engineering obtained their ISO Certification in August 2019 and Hogarths in February 2020. Certification was at the same time as this work was being completed in our workshop and site, showing that simultaneous production and continuous improvement initiatives are possible.
Structural mass – 380T
Radius – 50.2m
Diameter / Distance between supports – 100.4m
Coverage – 7 914m2
Top of structure height – 36.520m
Northgate Dome – 11 000m2
Viva Engineering and Hogarths Partnership
The Viva-Hogarths partnership was formed in 2010. Since then, this partnership has developed into a dynamic and energetic partnership which has successfully completed a number of complex projects in Zimbabwe over the last 10 years. This partnership is of great value to clients looking to execute turnkey supply and installation work in Zimbabwe.
Project motivation editorials are provided by the project nominator. If any technical details, company names or product names are incorrect, please notify the SAISC so that the error can be corrected.
|Completion date of steelwork||Last load to site 01/07/2019|
|Completion date of full project||December 2019|
|Tonnage and steel profiles used||380t|
|Project Team Role||Company|
|Nominator||Viva Steelfab Engineering|
|Client/ Developer||Zimbabwe Platinum Mines|
|Main Contractor||Hogarths Engineering|
|Steelwork Contractor||Viva Steelfab Engineering|
|Steel Erector||Hogarths Engineering|
|Cladding Manufacturer||ClassEcon Roofing & Tiles|
|Cladding Supplier||ClassEcon Roofing & Tiles|
|Cladding Contractor||PWR Roofing Services|
|Photographer, Photo competition|
|Photographer, Other submitted images|
If you were a part of this project, and your company details are incorrect or missing – please notify the SAISC so that the error can be corrected.