SOUTH AFRICAN SUPPLIERS
compliance , a SAHR braking system and a top speed of 38 km / h .
“ Designed by miners for miners , the Mine Scout XL has been specifically designed to cater for the gap in the market where more robust light duty vehicles are needed in bigger applications ,” GHH said .
Tapping deep mining expertise
Mines are getting deeper with every year that passes – 30 m deeper , if industry reports are correct .
With increased depth , comes increased ventilation and cooling needs , a fact Howden knows well from its experience of working with the deepest mines in South Africa .
Having entered the South African mining and power sectors in the 1950s , a decade later , it was helping equip the country ’ s deep gold mines with the ventilation and cooling products needed to extract ore safely and productively from kilometres below surface .
“ Initially mines used only ventilation as a method of cooling but , as mining depth increased , mechanical refrigeration was required to counteract the increasing heat loads in mines ,” Theuns Wasserman : Team Leader – Howden SA ’ s Mine Cooling and Compressor Division , told IM .
Howden introduced ammonia-based screw chillers into South African mines , which were initially employed in series after the existing surface centrifugal chillers . This enabled a step change in the amount of cooling that could be transported to these deep underground gold mines , bringing the average water temperature sent from surface down from 6-8 ° C , to 1 ° C . This enabled the use of the same shaft pipe infrastructure , which many of these mines had in place , while drastically increasing the amount of cooling sent to deep levels .
Some 20 years after their introduction , Howden , as a leading market player in the space , developed the WRV 510 – a large block screw compressor with a 510 mm rotor . This was , at the time , one of the largest screw compressors on the market , which suited the module sizes of the chillers required for refrigerating these deep South African mines . It also required the adaptation of safety codes around the use of ammonia , initially developed for other industries , to mining-specific standards that are still referenced in South Africa today .
Such success is evidenced by more than 350 MW of ammonia-based refrigeration capacity installed in the South African mining sector , believed to be the most of any country in the world .
The company has since added ice production plants on surface to its expanding mine cooling remit . These plants have a primary benefit of a reduction in pumping cost and positional efficiency close to the mining zone , with 1 kg / s of ice having the same cooling capacity of 4.5-5 kg / s of chilled water . The first plant was installed by Howden in 1985 at the ERPM ( East Rand Proprietary Mines ) mine , followed by an installation at Mponeng , the world ’ s deepest mine .
With more mines going deeper and space within the shaft at a premium , it is easy to see such a solution having applications in other parts of the world , as Wasserman hinted at .
MG Mynhardt , Howden ’ s current Manager of Compressors in South Africa and soon-to-be Head of Global Mine Cooling , said : “ Howden has been ‘ exporting ’ its South African deep mine cooling expertise for decades . Back in the 1990s , for instance , we provided a mine cooling solution for an underground gold mine in Nevada .
“ One interesting technology utilised by some South African mines is thermal ice storage that is used for load shifting – where thermal energy is stored in large ice dams . The ice is produced during peak periods and utilised in peak periods ,” he said . “ Conventionally , refrigeration plants are sized for maximum ambient temperature , which might be experienced for three hours a day in the summer months . Yet , if you have a facility to store your cooling energy , you could reduce this capacity .”
The parallels with battery energy storage for replacing excess spinning reserves are obvious here .
“ If you have an electricity tariff plan where you have quite high peak power tariff that you want to shift to a cheaper off-peak tariff , these ice plant solutions could make for a strong business case ,” he said . “ The upfront capital for the plant could be offset against the lower operating costs .”
At the same time as this , Bulk Air Coolers ( BACs ) used at mines in South Africa for decades are gaining prominence across the globe .
The newest generation BACs have higher thermal efficiency than their predecessors , lower limits on the shaft air temperature and a reduced footprint when compared with traditional BAC construction types . They are also embedded with the cooling on demand module within Howden ’ s Ventsim CONTROL platform where the temperature of the shaft collar air can be automatically modified to meet the demand below surface .
Howden supplied three of these newgeneration BACs in the past year to customers in Brazil and Burkina Faso .
The company can also manufacture customised solutions to deal with challenging operating environments ; a recent example being the “ unique BAC ” operating with ammonia chillers installed at the Carrapateena mine in South Australia for OZ Minerals .
“ Without any water available , the Howden Australia team installed dry condensers with Howden ammonia-based compressors along with a closed-loop dry bulk air cooler ,” Wasserman said of this installation . “ These coolers were engineered for ultimate efficiency considering it was a ‘ dry ’ plant as opposed to an open-headed spray cooler installed in applications where water resources are available .”
And the company is currently trialling an “ uptime ” condition monitoring solution at the 8 MW surface BAC plant it designed and engineered for Fortuna Silver ’ s Yaramoko mine ( previously Roxgold ) in Burkina Faso .
This system , monitored from Howden ’ s Johannesburg facility , allows the company to advise of potential efficiency gains and maintenance issues to ensure the plant is run as optimally as possible . The BAC installation at Ero Copper ’ s Caraiba mining complex in Brazil has also been designed to use such functionality .
This isn ’ t to say Howden is only focused on projects outside of South Africa – far from it .
Its Total Mine Ventilation Solution ( TMVS ) platform is continuing to build sustainable , value-adding relationships , which has seen the company carry out two ventilation on demand ( VoD ) feasibility studies in the country in 2021 .
Just over the border in Zimbabwe , it is working on a project that could see VoD-enablement of an automated door at an underground mine , to allow it to open at different increments and supply the required quantity of cooled air based on specific vehicle demand .
Such technology developments – using existing available mine infrastructure and readily available data feeds – will become part and parcel of the Howden offering in the future .
Winding up
UVB ’ s home country also happens to be the place where Dymot Engineering Company is looking to deploy two “ world class ” pre-sink single drum winder systems for mining contractor United Mining Services at a mining project .
These winders , designed and manufactured by Dymot , have successfully passed performance testing , according to Jorick Snyman , Mechanical Engineer at Dymot .
“ The systems incorporated a 130 kN winder complete with containerised 315 kW variable frequency drive ( VFD ) control system and drivers desk ,” Snyman explained . “ A 250 kW motor is installed to the drive train to achieve a rope speed of 1.5 m / s on the first layer .”
All required safety devices are fitted to the system , including over-speed devices , while the winder includes an incremental encoder on the motor for a closed-loop speed reference to the VFD , as well as an absolute encoder on each end of the drive shaft for depth measurement and cross referencing .
This winder is fitted with two SIBRE Siegerland Bremsen braking systems supplied by
24 International Mining | JANUARY 2022