The completion of Impala Platinum’s new deep level 16 Shaft is a major milestone in the mine’s history. It boasts Africa’s tallest concrete headgear (108 m) writes Laura Cornish.

Impala Platinum’s (Implats) 16 Shaft project, launched in 2004, is one of three critical new greenfields replacement shaft developments (the others being 17 and 20 Shafts), which must meet production start and ramp-up timelines to ensure the company’s platinum output remains stable.

Nine years down the line, one of the final activities outstanding before commissioning the shaft infrastructureroping up – is under way. This means that production start-up remains on schedule for 2014, with ramp up to its 226 500 tpm nameplate capacity expected in 2018. This is a great achievement for both Implats and Read, Swatman & Voigt (RSV), and a testament of a successful and supportive EPCM and client relationship under the guidance of client representative Frikkie Hὅll, general manager at 16 Shaft.

The Implats 16 Shaft complex comprises of a vertical man/material and rock hoisting shaft (main shaft) using tower-mounted Koepe winders, with an upcast ventilation shaft. The main shaft (sunk by Shaft Sinkers) is a 10 m diameter (inside concrete lining) shaft with an ultimate depth of 1 682 m below surface.

“What makes this project unique to the Implats asset portfolio is the interesting design factors for the winders and hoisting technology that has been implemented inside the concrete headgear,” says Torra Engelbrecht, group construction manager for RSV. RSV is the EPCM contractor for the 16 Shaft project and will forever be recognised for its commitment to technological advancement and innovative approach.

“Unlike the more traditional headgear installation methods in South Africa – such as steel headgears and ground mounted Koepe or Blair multi-rope winder systems, which usually suffer significant wear and tear – we believe our use of a tower-mounted Koepe friction winder system, together with the associated rope handling equipment, will showcase an international tried and tested methodology encompassing the most advanced technology, practises and techniques. Even more impressive is the fact that this suite of rope-up equipment application is a ‘once in a decade’ event. The last roping-up of Koepe winders using the modern friction winch and clamp lifting device application in South Africa took place at the Palabora mine in 2001,” Engelbrecht explains.

Due to the headgear’s proximity to surrounding communities, the headgear accommodates an internal tipping arrangement to reduce noise levels – another impressive and unusual project element. There are two 25 t skips that will tip into a 350 t capacity bin situated in the headgear on the conveyor level, which will carry the ore from the headgear to the silos. The first ore from underground is scheduled toward the end of July 2013.

With so many elements situated inside the headgear at various levels, a 60 t overhead crane mounted in the top section of the headgear was used to ensure all components were placed safely within the correct areas.

The speed of this project can also be attributed to the simultaneous activity of headgear equipping and shaft sinking. “We built the sinking headgear inside the concrete headgear structure, which was fully functional, with ground-mounted kibble and stage winders.”

The main headgear elements

  • two identical 6.5 diameter friction Koepe drum winders, 91 m above bank elevation, each with a 4 300 kW motor – supplied by ABB and sub-contractor FLSmidth
  • mobile friction winch (the heart of the rope-up technology)
  • clamp and lifting device  59 m above bank elevation – same level as permanent deflection sheaves
  • permanent deflection sheaves (in the headgear)
  • ground-mounted rope reelers
  • messenger winches
  • ground-mounted deflection sheaves and compression beams.
Why the tower-mounted Koepe friction winder system?

A lot of time and effort was spent evaluating the best methodology for the project. “We evaluated winders and rope-up systems from around the world, performing trade-off studies with installations (and ropes) in Germany, Canada and South Africa.”

“The result of our decision was based on numerous additional benefits.” Not only is the implementation timeframe to completion much faster, but the lifespan and wear and tear on the components, particularly the ropes, is lengthened considerably. In fact, less maintenance on the winder ropes is required – impressive considering they will travel at 16 m/s and must be in operation 19 hours a day, 23 days a month,” Engelbrecht notes.

The men and material Koepe winders will support one 32 t cage, comprising two decks capable of transporting 150 people per deck. Shift capability includes 2 488 people every hour. Two service cages will run on a ground mounted conventional double drum winder.

A global first

Designed in conjunction with RSV and Winder Controls, a member of the shaft hoisting specialist Siemag Tecberg Group, the scale of the rope system (installing four tail ropes from surface) is a first for South Africa and, according to Engelbrecht, is currently the most advanced methodology in the world.

The only double-faced clamp and lifting device in the world, the system allows for safe handling of all ropes simultaneously, e.g. for rope attachments and conveyance replacement and maintenance. It will also allow the mine to return to production quickly after routine maintenance procedures.

The 150 t mobile friction winch is used for the simultaneous installation of all ropes and will ensure fast and safe changing of all the winding ropes.  Because it is mobile, the machine will be transported to the nearby Impala 17 Shaft to perform the same tasks.

Both Winder Controls and Engelbrecht were involved in the first and only other tower-mounted Koepe winder friction winch rope-up system in South Africa, which is at Palabora Mining Company – the concrete headgear is 3 m shorter than 16 Shaft. Next to Palabora Mining Company, 16 Shaft is only the second project to use this suite of rope-up equipment in South Africa.

Additional technology benefits include:

  • Koepe-type winders have lower rotational inertias and less out of balance mass to accelerate and consequently require less power to deliver the same output.
  • Koepe winders are cheaper to manufacture, install and commission.
  • Koepe maintenance and operating costs are lower (the costs are based on 20 years at full production)
  • Terrace layouts take up considerable space for conventional winder buildings.
At the bottom of the headgear, below the bank level, a closed-off tunnel passageway for personnel loading for shifts has been incorporated at sub-bank level. This has been incorporated for safety reasons and will ensure proper monitoring of every individual starting or ending a shift, Engelbrecht notes.

Abbreviated rope-up sequence:

  1. reeve the head ropes up through the headgear
  2. attach a conveyance to the head ropes
  3. lower conveyance to rope separation level in the shaft bottom
  4. reeve tail ropes through the friction winch
  5. attach tail rope to the bottom of the conveyance
  6. install the second conveyance
  7. connect the tail ropes to the second conveyance.
Interesting facts and project highlights

  • the first application of concrete pumping in a slip-forming application of a headframe in South Africa
  • the first shaft at Implats to successfully sink through major water intersections
  • the first shaft at Implats to traverse the Hex River fault, without any incidents
Keeping it on record

Engelbrecht indicates that due to the high success already achieved on the project, Implats, together with Rio Tinto, BHP Billiton and Siemag Tecberg are jointly investing in the compilation of a DVD on the headgear rope-up technology. It will be used to train artisans and technical personnel without requiring the presence of an RSV consultant.

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