| http://www.w3.org/ns/prov#value | - This top drive unit enables several lengths of standard pipe to beassembled above ground in a short drill rig.FIG. 3 depicts the top drive power swivel assembly 28 on the derrick 15 secured to the hoist means 103 in a side view showing tubular 14.FIG. 4 is a detailed front view of the top drive power swivel assembly secured with eight extensions secured to the top drive, eight extensions secured t
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