876 EXPLORATION GEOPHYSICS 



the rods is sufficient to provide the necessary pressure on the bit. If hard 

 ground conditions are encountered, the drive rod can also be equipped with 

 a chuck in addition to the drive bushing so that hydrauHc pressure can be 

 appHed to the Kelly if needed. 



Figure 547 shows the mast or derrick raised to its vertical position after 

 the drill has arrived at the location for the hole. The Kelly or the drill pipe 

 (Q) is in position in the drive rod (L) and is connected to the swivel hose 

 (R) by means of the water swivel (S). The water swivel (Figure 549-K) 

 is a hollow packed joint that provides the connection between the swivel 

 hose, which does not rotate, and the Kelly or drill pipe, which does rotate. 

 The swivel is equipped with a bail (U) for hoisting or lowering the drill 

 pipe with the hoisting drum or draw works. The wire rope from the hoist- 

 ing drum passes over the sheave wheel mounted in the top of the mast and 

 is attached to the bail of the water swivel or the bail in the hoisting plug by 

 means of a safety hook (V). After each 10-foot advance in the depth of 

 the hole the water swivel is disconnected, and a new 10- foot piece of pipe 

 is picked up with the hoisting plug (Figure 549-L) and screwed in place.* 

 The hoisting plug is then removed and the water swivel again attached to 

 the top of the new rod. When disconnecting or connecting the rods or Kelly, 

 the string of rods remaining in the hole is suspended either from the drill 

 chuck (A) or from a safety clamp set on the ground (Figure 549-M). Do 

 not allow the tools to rest on bottom for more than a few minutes, without 

 being rotated to circulate the mud; the tools may become stuck, because 

 the rock cuttings settle fast when the mud is not circulating. 



The mast or derrick is usually about 25 feet high, which allows sufficient 

 height above the top of the drive rod for a 10-foot section of drill rod or 

 the 14-foot Kelly plus the length of the water swivel, the length of the safety 

 hook, and an additional two or three feet for spudding or reciprocating the 

 rod string. At the top of the mast is mounted the sheave wheel (G, Figure 

 551) for guiding the wire line from the hoist. This sheave wheel is placed 

 so that the pull in the hoisting rope will be directly in line with the center 

 of the hole being drilled. If the drill is equipped with a cathead (C, Figure 

 547), a second sheave wheel is mounted in the fop of the mast for guiding 

 the soft line (manila rope). The cathead is frequently used for picking up 

 each new rod, as it is added to the rod string, rather than using the hoisting 

 line for this purpose. 



The mud pump (/, Figure 547) is usually a two-cylinder, double acting, 

 reciprocating-type pump with 4"-diameter pistons and a 5" stroke. It is 

 equipped with abrasion-resistant valves, valve seats, cylinder liners and 

 piston rods. The suction hose connected to the pump intake has a check or 

 foot valve on the other end. This foot valve is submerged in the mud sump 

 or pit, which may be merely a shallow hole or trench dug in the ground adja- 

 cent to the hole being drilled. However, better practice is to use a "two- 



* Pipe wrenches are not recommended for "break-out" purposes. Use the special 

 wrenches provided, to minimize chances of personal injury. 



