Page 275 - Advanced Mine Ventilation

252 Advanced Mine Ventilation

Figure 15.2 The auxiliary unit for in-mine horizontal drilling.

Figure 15.3 The gas and water separation system.

The water (mud) circulating pump is a triplex, reciprocating pump with a capacity
of 70 gpm at 900 psi. In the rotary mode, an annulus fluid velocity of 3 ft/s is usually
sufficient, but in nonrotary mode, the annulus velocity must be increased to 5 ft/s. The
pump is driven by a 50 hp electric motor.
The hydraulic power pack consists of a number of hydraulic gear motors capable of
delivering 80 gpm of hydraulic fluid at 2500 psi. The working pressure in the system
seldom exceeds 2000 psi. Petroleum oil is the recommended fluid for the entire
hydraulic system.

15.2.1.3 The Guidance Systems

When a horizontal hole is started in the middle of a relatively flat, 5e6 ft thick seam
the drill bit usually ends up in the roof or floor before reaching 200 ft. To drill a deeper
hole, it is imperative to guide the bit up and down as needed. In most cases, it is also
necessary to guide the bit in the horizontal plane.