CASE STUDY-REXROTH
The reliability of the Rexroth AA11VLO pumps is especially critical in deep drilling applications requiring high pressure capacity and pullback force delivered by the drill rig.
T130XD was designed for drilling applications such as shallow oil and gas, deep water wells, geothermal exploration and... deep mine rescue.
A key component of the hydraulic system that powers the Schramm drill are the Rexroth AA11VLO variable displacement axial piston pumps, supplied by local Rexroth distributor Airline Hydraulics, Inc.( Bensalem, PA). Schramm selected the Rexroth AA11VLO130 pumps when designing the T130XD because of their proven performance, particularly in deep drilling applications requiring the high pressure capacity and pullback force delivered by the rig.
Rexroth’ s AA11VLO series of axial piston variable displacements pumps are designed for hydrostatic drives in open circuits. They offer high power capacity and displacement in a compact design, with nominal pressure of 5100 psi( 350 bar) and maximum pressure of 5800 psi( 400 bar.) The AA11VLO130 is equipped with a charge pump enabling high input speeds, which is especially important at high-altitude operation, like Chile. Its 130 cc / rev( 7.93 in 3 / rev) can operate at engine speeds up to 2,500 rpm.
When the Chilean government sent out the call across the country for assistance, it was determined that the T130XD rig offered several potential advantages for the rescue:
• The T130XD is well-suited for drilling with reverse-circulation down-the-hole hammers, making it especially ideal for drilling through the Chilean granite.
• Schramm’ s rig was designed to drill off a vertical axis, enabling it to utilize one of the existing pilot holes to drill a rescue portal, and would not have to be emplaced directly above the miners.
• The T130XD in Chile was equipped with Schramm’ s highest capacity top head, capable of drilling holes up to 28 inches in diameter.
• The T130XD is designed for fast teardowns and relocations, enabling it to make the 1,000 km trip in relatively short time.
Given the advantages offered by the T130XD, the Chilean mining authorities developed a“ Plan B” rescue plan: the T130XD would enlarge one of the 5.5-inch diameter initial probe holes, drilled with two passes. The first pass would increase its diameter to 12 inches and the second pass to 28 inches diameter, to allow a rescue rig to be lowered.
Putting Plan B into action Arriving at the San Jose mine on September 30, the T130XD was quickly set up and drilling on the
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| Global MDA Journal | NOV-DEC 2017
Schramm’ s drill uses four Rexroth AA11VLO130 pumps, which supply hydraulic pressure to the top mast head and mast cylinders. The top mast head is the mechanism at the top of the drill mast that provides the pullback force to manipulate thousands of feet of pipe down the hole; the mast cylinders support this function.
Photo courtesy of Schramm, Inc.
The variable displacement pumps on the T130XD supply hydraulic pressure to the top mast head for manipulating thousands of feet of pipe. www. ghmediabusiness. com