2 manual cutting
Under manual cutting , the operator utilizes two basic actions to control the miner, the track pads,and the side jacks. The forward advance rate and direction are both controlled by the track pads. The operator has two independent levers, one for each track. By adjusting these levers, the miner can be made to cut in the proper direction and with the optimum advance rate, which is determined by torque on the cutting heads. A reliable method of determining torque is to measure the amperage required by the four head motors. If the amperage is too low, the operator moves both tram levels forward, which in turn increases the pressure applied to both tracks ; if the amperage is too high, the pressure is reduced
As the miner is cutting, the face shears away in sections and causes the miner ti surge forward and then cut heavily as a full face is again encountered, which requires adjustments every few seconds. This function leads to much of the operator fatigue. After a few hours, the operator’s natural tendency is to allow for larger surges or cut at a reduced raye so the peak of the surges is within an acceptable range, thereby requiring fewer adjustments. If large surges occur, more maintenance on the miner is required. If cutting is done at a reduced rate, productivity of the miner is reduced.
The other function of the tram levers is to determine the heading of the miner. In the first pass, the heading is determined by a laser mounted on the back and pointed toward the miner. To control the heading, the operator maintain the laser dot on a predetermined location on the miner. To adjust the heading, the operator changes the ratio of the left tram to the right tram whlie maintaining the overall average so as to maintain the penetration rate.In the second and third passes, the heading is determined by following the wall of the first pass. The object in the second and third pass is to cut as wide as possible while producing an even back.
The second major function controlled by the operator is the front trim cylinders. These independently controlled cylinders raise and lower either side of the gearcase, which is connected to the cutting heads, which then determines the pitch and roll of the miner. In the first pass, the pitch of the miner is determined by the lay of the ore body. An on-board ore analyzer provides the operator with a graphical reptesentation of the cross section of the ore body and adjusts the front trim cylinders to adjust the pitch of the gearcase to follow the ore body and maximize the ore grade mined.
In the second and third passes, the pitch of the miner is set so the backs of the first and second or third pass are at the same elevation. In all three passes, the miner cuts a level back. An angle sensor on the gearcase indicates the roll of the gearcase. To maintain the level back, the operator moves one trim cylinder in one direction and the opposite one in the other direction until the angle sensor indecates zero roll, at which time the trim cylinders are equalized.
The operators are also responsible for controlling the backup equipment. In the first pass the tub (figure 14.2) follows the miner. The extensible belt is drawn from the take-up by the tub,which positions the belt immediately behind the miner. The tub serves to align the belt behind the miner and drills holes for posts in the backup operators, who install the extensible conveyor structure and ventilation brattice. In the second and third passes, the tub is removed, and a cross conveyor is attached behind the miner. The cross conveyor takes the ore from the rear of the miner and conveys it onto the extensible belt installed during the first pass