Underground mine piping systems

Service water is used during drilling, wall washing and other operations. As mentioned earlier, this water must reach every level of the mine and all active work areas. Grooved piping systems are often used to simplify installation. One of the challenges with water distribution is regulating pressure, because pressure increases the deeper we go, roughly 15 psi (1 bar) per 10 metres of depth. In mines that reach depths of up to 3,200 metres, proper pressure management is critical for both for worker safety and equipment protection. To control pressure, operations may use pressure-regulating valves, depressurization basins at level entrances and heavy-duty piping and components. While grooved piping can handle high pressures, it’s important to select the right components. Some couplings can withstand pressures of up to 2,700 or even 4,000 psi, as needed. It’s crucial to adjust the piping system to each mine’s reality. Some prefer to keep piping components simple to manage inventory, while others prioritize installation optimization by using components adapted to each part of the mine.

Compressed air is used as an energy source to operate certain production equipment and to clean floors before onsite drilling begins. One of the challenges with air distribution is leakage in the supply lines. In one study, a mine air distribution system had lost as much air as a 500 HP compressor could produce, wasting energy and reducing system capacity. Insufficient air pressure and poor flow also make mining equipment less efficient, hindering production.

Grooved piping is usually used for compressed air distribution in mines, as it’s well suited to this type of work and very easy to install.

However, workers don’t always have the proper training to make sure piping is installed according to manufacturer specifications. Humidity, low lighting and dust can also affect installation quality and system performance. Carefully selected components such as pre-lubricated, quick-install grooved couplings have been shown to reduce leaks in some pilot systems. It’s also been proven that calculating system consumption can help reduce pressure drops and improve distribution and efficiency. Proper maintenance also minimizes losses in distribution systems, since losses are generally caused by poor installation, equipment impact, rust, and valves being leaky, clogged by debris or improperly closed.

Water management varies greatly from one mining operation to another, depending on the operating environment. It involves managing water that comes in from the rock (infiltration or seepage) or from mining operations (run-off). If it isn’t properly managed, this water can disrupt operations, limit access and even affect the mine’s viability. This water is routed to low points called sumps, typically located at level entrances, and through service holes that channel water to a collection basin, usually at the mine’s lowest point (shaft bottom or accumulation basin). Ideally, efforts are made to separate clean water (without suspended solids) from dirty water (with suspended solids) to reduce pump purchase and maintenance costs. If water quality permits, it can be reused in mining operations (drilling, dust control, cleaning, etc.). There’s a growing trend in the industry toward reusing water to reduce surface water consumption.

Bringing water to the surface generally requires high-pressure pumps to overcome the massive hydraulic head found in underground mines (as deep as 3,200 m). Water lift can be staged over several levels to reduce hydraulic load. The dewatering system must be designed to withstand high pressures and heavy flow rates. Flanged piping is a good alternative for vertical lines exposed to high pressures, while grooved piping is better suited for lower pressures.

Paste backfill is a mixture of ore-processing residue and cement used to fill mined-out stopes to ensure long-term rock mass stability. It’s highly abrasive, denser and more viscous than water. As such, concrete pumps are often used to pump the paste through downhole pipes to underground stopes. Pump discharge pressures can exceed 2,175 psi (150 bars) and often experience repeated water hammer effects, which cause both frictional and fatigue wear on the piping system. It’s important to use piping that can withstand these stresses, e.g., Class 900 flange, 5D elbows and Schedule 80 piping. Because paste backfill is so dense, its pressure increases rapidly as it descends into the mine. To control this, pressure-reduction loops are required to prevent overloading the piping. If there’s a risk of clogging the line, a flushing pump can inject water and dilute the paste backfill mixture. Flushing piping must also be built withstand pressures equal to or greater than those produced by the concrete pump.

Fuel that powers underground mining equipment must be delivered to a fuel storage room. Transporting fuel down the ramp would be slow and dangerous and cause traffic jams. Instead, fuel is piped underground through a supply line that can pass through either the shaft or a borehole drilled in the rock. This line is fed from a storage tank, passing through a measuring tank before descending underground. Since the line is usually vertical, fuel velocity must be controlled to prevent auto-ignition. The system cannot have any low points and must rely on gravity to drain properly. Moreover, when the fuel reaches its destination, it’s measured again to ensure the entire volume has been delivered without any losses. A single supply line can feed multiple fuel rooms on various levels using a series of automated, remote-controlled valves. Measurements also need to be taken to slow the fuel down before it enters the destination tank. Several standards must be met to ensure worker safety.

CSA B139: Installation and safety standards for fuel storage systems, including in industrial and underground environments

NFPA 122: Fire safety standard specific to underground mines, including guidelines for underground fuel systems and mechanical facilities

For more information, contact our experts.