African Mining January 2023 | Page 29

MINING INDABA •

Thorough standards are in place at all mines indicating the requirements of what the standard installation should look like , along with the associated signalling systems . However , after the installation , people must operate these winches . There are also people that need to move in the same paths where scrapers must run when the winch is in operation . Thus , the complexity of this system lies in the human element and arrangements , the understanding of what is happening and then knowing when and where what will stop and what will start at what point .

It is important to note that during scraping operations the winch operator cannot physically see where the scraper is running . Thus s / he operates this winch blindly and relies on signals given by a winch operator assistant , who is positioned closer to the face and is able to observe the scraper at certain points . The face winch operator therefore operates the winch in accordance with the signals given by the assistant .

Again , where the face scraper tips into the gully , the operator of the gully winch cannot see the full length of the pull of the scraper . Typically , s / he can see about 15m down the gully , and s / he is operating this winch with the scraper running to and from the winch blindly . Then , if there is centre gully scraping taking place , another set of scraper ropes are introduced to an already complex arrangement of ropes and scrapers that run independently of each other , but with scraper ropes crossing one another . The winch operators react on signals given by persons they cannot even see , as those persons giving signals must be close to where the scraper runs to see the collection of the broken rock .

Thus , for this arrangement , there is a critical requirement that everybody in the vicinity understands what can happen , and at what moment . Clear indication is required when a scraper is going to be activated to be pulled either forward or backwards as these are strong machines and the winch operators do not really have control over the amount of energy exerted when the drum is engaged to turn and coil up the rope . With the extreme tensions , moving scrapers , moving scraper ropes and high energies present , if a person comes into contact with any part of the scraper winch system , the outcome in many cases can be detrimental .

The design of using double drum winches , with ropes attached to it , with scrapers attached to the ropes and these ropes pulling at different angles on the snatchblock to move broken rock from the stope face is inherently unsafe . Through the risk assessment processes applied at mines , operations apply the hierarchy of control by firstly examining the process to see if this design can be eliminated . In the industry currently , if a mine is not using mechanised mining , the use of winches and scrapers is the only tool available to do the job of moving high volumes of rock from the blasted faces to the ore-passes . Thus , this methodology cannot be eliminated or substituted at this stage . There are some mines that do apply water jetting on the face area for cleaning . Again here , the type of ore mined will dictate if one can add water to the broken rock – some ore turns into clay with the addition of water .

If a winch is essential , the next step in the controls is to apply a barrier . There are some barriers that have been applied over the years to reduce the risk associated with this operation . Some are physical barriers , like winch barricades positioned in front of the winch installation . If a rope snaps , just like a steel cable snaps under tension – it coils up – at least this winch barricade gives some protection to the operator . There are also drum guards around the winches , to protect the operator from the rope when it coils up loosely . As a separation control , signalling systems are installed to instruct the winch operator and those in the vicinity of the winch operation . Before a winch start up , a warning signal is given . That signal is a warning to all in the vicinity to move out of the scraper path and rope positions for winch start-up . However , the person giving the signals also has limited view of the full scraper path . From the moment the signal is given , going forward the team relies on the correct behaviour from all in the area to ensure the job can be done in a safe manner .

The current legislation in South Africa related to the installation and use of machinery like double drum scraper winches is adequate . However , legislation cannot possibly address all applications and operational possibilities at different mines . The law and related regulations supply minimum requirements . There are numerous scenarios where a person can accidently come in contact with a part of the winch system while the winch is in operation and other mining activities are taking place .

Winch development Although the double drum winch itself has not changed through the years , several systems have been re-designed around winch installation to enable safer operation . Dedicated scraper paths where the workforce and machines are separated ; automated pre-start warning systems and automated proximity detection systems have been introduced to address some of the reliance on human beings ‘ to do the correct thing .’ As double drum scraper winches are not going to be phased out any time soon in the South African mining industry , mines must reduce the reliance on the administration controls .

Mine standards are very clear when it comes to the physical conditions of the winch installation . Mining procedure on ‘ the dos and don ’ ts ’ around winches have become overly complex . We talk about : ‘ no-go ’ zones ; where to sit for protection from a snatchblock that inadvertently comes loose and what to do when the signal is given and one cannot get out of the way immediately . Although individuals are generically trained on where s / he must be when there is a winch in operation there are many iterations of that same situation while mining , and the individual is exposed to an immediate situation where s / he must make the final decision on the action to follow . The individual at that moment must decide where the safest point is .

Although the winch is a stationary installation , the ropes and other attachments are constantly moved and adjusted to enable efficiencies . So , where the safest position was the last time , is now no longer safe to be . The findings of investigations following unforeseen incidents involving a winch usually involve an error in judgement . The person may have assumed that the position s / he took up was safe , or the person assumed it was safe to enter the

Thus , the complexity of this system lies in the human arrangements , the understanding of what is happening and then knowing when and where what will stop and what will start .