Page 567 - Air and Gas Drilling Manual

Chapter 11: Specialized Drilling Equipment 11-5
working clearance. This clearance allows the rig to be classified as a double (can
pull a stand of two drill pipe, see Chapter 1). Figure 11-4 shows three hoses in the
mast. One hose is the rotary hose that allows the drilling fluid to flow to the top
drive power swivel mounted below the traveling block. The other two hoses are the
hydraulic supply lines for the top drive power swivel.
These unique drill rigs are used throughout the world principally for oil and
natural gas recovery drilling operations. These rigs can also be skid mounted for
offshore platform operations.

Figure 11-4: Trailer mounted slant capable deep drilling rig (courtesy of George E.
Failing Supply Company, Limited).

11.1.2 Power Swivels
The top drive power swivels are hung from the traveling block of a typical
conventional drill rig. The power swivel is an auxiliary to the normal complement
of drill rig equipment. The power swivel can be utilized on any conventional drill
rig. When a power swivel is used, the rotary table must be removed. The power
swivel works in much the same way as a top head rotary drive on smaller drill rigs.
The power swivel is hydraulically actuated and can be used to rotate the drill string
at speeds of a few rpm to normal drilling rotary speeds of about 100 rpm. Figure
11-5 shows a typical power swivel with an elevator bail at the top (attaches to the
elevators on the traveling block) and the rotating stem at the bottom (which makes
up to the top of the drill string). This example power swivel is a Bowen Tools
Model S-1 with 30 ton lift, 0 to 75 rpm rotating, and 1,875 ft-lb torque capabilities.