Over the past decade, mine owners have increased the use of backfill systems to manage waste and enhance ore recovery in underground mining operations, and automated systems are now playing a significant role in effecting efficiency gains and improving worker safety.
Historically, mine owners were slow to adopt paste reticulation systems due to the cost of backfilling equipment and the amount of time required for manual operation. Owners opted for mining top-down in some cases, using cemented rockfill to stabilize stopes even though this approach is less effective than backfill paste for ensuring full confinement of hanging walls.
There is no question that manual backfilling is a time-consuming process. In reticulation systems where there are no diverter valves, a worker must travel to the lockout location, perform the lockout (which in some mines takes place on the surface), travel to the switching location, manually switch the pipe, and return to the lockout location to remove the locks. Performing this can take a team of three paste operators anywhere from two to five hours, depending on the layout of the mine and the lockout procedure employed.
Switching to an automated system eliminates these 2- to 5-hour delays, allowing paste filling to begin quickly and enabling rotation to occur during otherwise nonproductive times, such as shift changes. There is no need for physical intervention, which makes it possible for workers who were previously required for paste operations to perform other tasks on site. This gain in productive time has a significant impact on the bottom line.
Unfortunately, many owners operating under the assumption that automated equipment is cost-prohibitive, have not yet adopted this technology. And that means they not only miss out on the financial benefits, but they also miss the opportunity to improve worker safety.
New thinking delivers better design
The Victaulic Series 725T 4-way diverter valve was designed for remote actuation to simplify backfill operations and optimize labor efficiency. The internal rotating plug has three flow positions, with two primary outlets for directing paste or hydraulic backfill through the reticulation system to fill the appropriate stopes and a third, clearly marked, drain outlet for flush water diversion and emergency backfill dumping. The 90-degree rotation to the tapered drain port enables quick diversion of flow to mitigate water hammer during flush water diversion.
The valve is compact, so it is easy to install even in tight underground environments and can be configured with several styles of grooved end connections. Manufactured with high-performance, resilient materials, it can accommodate pressures to 1,500 psi. A polyurethane seat provides long-life wear resistance, and martensitic stainless-steel wetted surfaces prevent premature erosion and corrosion.
Proving value through performance
In a recent installation, this automated diverter valve replaced manual diversion in a reticulation system. The mine had been using an open stope, retreat mining method that used backfill to extract gold ore. The open stopes ranged from 500 cu m to 2,700 cu m, with an average size of 1,500 cu m, requiring between 100,000-110,000 cu m of backfill per year. Because of the relatively flat dipping nature of the orebody, the hanging walls required topping up with a flowable mixture of sand, cement, and water to prevent hanging wall failure. Although this manual backfill method was effective, it was slow, and operating costs were high.
The decision to switch to paste backfill was made to ensure that the backfill achieved full confinement of hanging wall voids while allowing the mine to attain higher productivity, lower dilution, and reduced operating costs. The installation employed automated diverter valves in the reticulation system that could be monitored and actuated from an above-ground control room. This solution increased site safety while enhancing the efficiency of the paste reticulation system, which could be operated during shift changes to reduce system downtime. The installation of an automated diverter valve streamlined the paste reticulation process, minimizing nonproductive time and moving workers out of harm’s way.
The enhanced design of the diverter valve itself eliminates all exposed moving parts, which further improves worker safety. In the unlikely event of seal wear on the valve, all media remain contained within the valve body. This feature offers advantages over other diverter valves that rely on exposed compression seals between the body and sliding plates or rotating discs that expose operators to high-pressure media spray and seal leakage if there is a failure during operation or during the flushing process.
Should the system require it, the valve design also allows for local actuation. An operator can travel to the level of the mine where work is to be performed, change the diverter control unit to local actuation, switch the valve away from the line that is being worked on, and lock out the actuator to isolate the line. This functionality provides the highest level of safety for operators because it allows them to manage the process without relying on someone else to ensure isolation.
Facilitating efficient operations
Today, valves developed specifically for backfill are more compact and safer to operate underground than ever before, and as backfill systems continue to evolve, so does the development of automated diverter valves. The results gained by installing these advanced valves prove that functionality and worker safety can be improved through automation and that better designs can deliver greater efficiencies and better economics for facility owners.
ART: Victaulic – Series-725T.jpg
CAPTION: The internal rotating plug of the Victaulic Series 725T 4-way diverter valve has three flow positions, with two primary outlets for directing paste or hydraulic backfill through the reticulation system and a third, clearly marked, drain outlet for flush water diversion and dumping. (Image courtesy of Victaulic)
ART: Victaulic – Installed Diverter Valve
CAPTION: Designed for either manual operation or remote actuation, the automated diverter valve enables mines to quickly and easily divert paste and dump backfill in the event of a blockage. (Photo courtesy of Victaulic)
