damaged or the gas pressure has droppedabnormally due to a gas leakage.Pay attention to the yawing of the drillmounting. Violent yawing of the drill mountingis caused by improper feed pressure. Adjust thefeed force by using the feed pressure adjustingvalve.NOTE: Improper feed pressure shortens the life ofthe feed chain, the rod, the sleeve, and the shank. It alsoresults in poor penetration rates.ADDING EXTENSION RODS.— Components ofthe rock drill, used when adding or removing extensionrods, are shown in figure 14-26.Adding extension rods, commonly called drill steel,is performed as follows:1. Feed the drifter down and hold the coupling ontop of the centralizer. Engage the drifter hammer untilthe coupling is loose.2. Reverse rotate and allow the drifter to back outof the coupling, then run the drifter to the top of the drillguide. Be sure to grease the drifter shank or tamper bar,and ensure the coupling remains on the drill steel downin the borehole.3. Attach another coupling to the drifter shank ortamper bar. Add additional drill steel; forward rotateuntil all is coupled.4. Lift the coupling off the centralizer. Then openthe centralizer and continue drilling until the couplinghas completely passed the centralizer. Once thecoupling has passed, close the centralizer around thedrill steel.REMOVING EXTENSION RODS.— Once therock drill has reached the desired depth, removing theextension rods is performed as follows:1. Clean the hole completely before removing thedrill steel.2. Move the rotation control lever to the neutralposition to stop rotation.3. Place the coupling on top of the centralizer, andallow the drill to hammer on the shank to loosen thecoupling threads.4. Shut off the drill.5. Reverse rotate the steel from the coupling.Figure 14-26.-Components of the drill guide.NOTE: Keep an eye on the coupling that connectsthe drill shank to the drill steel. This coupling will workloose faster than the lower coupling and could fall.6. Run the drifter down to the coupling that isresting on the centralizer.7. Forward rotate the drifter into the coupling.8. Run the drifter with the attached coupling anddrill steel to the top of the drill guide. To remove14-21
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