Mining equipment makes wide use of hydraulics technology because it packs so much power into such little space. Pneumatics, of course, also packs a lot of punch into a small space. However because most pneumatic systems operate at much lower pressure, hydraulics usually gets the nod to provide the power needs for digging, pushing, lifting, and crushing.
But there is certainly no shortage of pneumatics in mining. For example, mining operations involve a lot more than dealing with soil and rock. Water is prevalent in most mining operations, and moving it can pose a challenge because of the variety of solids it may contain.
Centrifugal and other rotating type pumps often can’t be used because solids suspended in the water could cause premature failure. Plus, electric motors typically used with rotating pumps are large, heavy, and pose safety hazards from electricity. Hydraulically powered pumps are often used, but unless the work site has portable hydraulic power units, finding a source of hydraulic power to tap into can be a challenge.
Sources of compressed air, on the other hand, are commonplace at most work sites, whether they be from work vehicles or portable compressors. One of the simplest pump designs that uses compressed air is the diaphragm pump. Diaphragm pumps have two pumping chambers that alternately pressurize and exhaust.
A directional valve shifts to route compressed air into the first chamber. Force from the compressed air pushes on a diaphragm, which pressurizes the liquid being pumped. A check valve at the pump’s inlet port prevents outflow, so the liquid is forced through the pump’s discharge port.
Expansion of the diaphragm causes pressure in the chamber to drop, which causes the directional valve to shift, so compressed air pressurizes the other chamber. Air pressure in the second chamber then pushes the fluid through the outlet port, and the cycle alternates from one side to the other.
Some pump designs can stall if differential pressure between the two chambers centers the directional valve. However, according to Ken Boyce, product specialist for Ingersoll Rand’s ARO diaphragm pumps, “The Pit Boss pump uses a patented unbalanced air valve to prevent stalling, sticking, centering or freezing during operation. The unbalanced valve has a large OD on one end and a smaller OD on the opposite end. This creates a pressure differential that always biases the valve toward one side. The force differential prevents the valve centering — even under low air inlet pressures — so stalling does not occur.”
Pit Boss pumps also use O-rings to provide positive sealing to reduce bypass air flow. This reduces compressed air energy consumption, which, in turn, lowers operating cost. The pumps are available in three sizes, the largest of which can move up to 217 gpm of fluid.
For more information, go to fluids.ingersollrand.com or visit Ingersoll Rand at MINExpo Booth 9075.
