Show dra drilling ng shot holes in in utah coal BY B B E R M while the drilling of shot holes in coal with rotating hammer drills such as the sullivan rotator and ingersoll jackhammer Jack hamer has been quite common in other fields it r is comparatively new in utah the average coal in utah is slow drilling because of its hardness and its woody character which causes it to pulverize in drilling instead of chipping and hand drilling with auger steel is extremely slow in some cases two four or even aven six hours is required to drill the four noles six feet deep required in each room when this is done by hand the detail of undercutting coal is familiar to almost everyone interested in the production of coal and involves cutting a channel under the coal at the bottom to a depth of six feet in utah in other fields to a greater or less depth and about five e t 2 j r COAL TOP VIEW A OAL r SIDE VIEW views of drill mounting 1 faches high this permits the coal to be shot down with comparatively little powder and makes a product high in lump percentage method in rooms where the coal is from six to ten tell feet high there are usually four I 1 shot holes drilled about two t wo feet from the r roof two at each side or rib of the room and two equidistant from the rib all drilled horizontally and practically parallel to the salt lake city cut furnished by sullivan machinery co Chica chicago gd straight sides of the room all to a depth equal to the undercut in some cases where special con conditions diGons exist the channel is cut at varying from the bottom or even close to the roof of the coal where the cut is made at varying heights from the bottom it is necessary to drill the coal above the cut and shoot it out the lower bench being drilled and shot afterwards when cut at the top usually one set of shot holes is sufficient electric drills failed electric drills have been tried in utah coal and found wanting because of slow drilling speed and high upkeep cost and the operators turned to the question of air drills for this work such companies as the utah fuel company united states fuel company and the cameron coal company being equipped with sullivan WK 2 portable electric driven air compressors for rock tunnel and other work found it easy to experiment with self rotating air hammer drills with the portable compressor the procedure is to run the compressor either to the entrance of the room into the room or locate it in a nearby crosscut simply connecting it to the leads for the electric under cutters in some cases the air is coil conducted to the face of the rooms by sending it through the sprinkler system water pipes temporarily drained in the section being drilled drill is light the hammer itself weighs about forty pounds and in drilling holes of reasonable height can be held in the hands of the operator however where the holes are drilled at from six to eight feet from the bottom it was found that some sort of light easily handled mounting greatly facilitated the work the mounting shown in tile the accompany ing cut was first built by the writer and officials of the utah fuel company at castle gate utah the mounting this consists of two rear legs or feet joined at the top by a crossbar having a tee in the center in which is secured a horizontal bar or leg the rear legs have a telescoping feature formed by drilling holes at regular intervals in the pipes of two diameters composing the leg and a pin is inserted to hold the leg at the height desired this mounting is made of ordinary pipe one inch or one and a quarter in diameter and fittings it is set at the height desired and the rotator drill is hung under the horizontal bar or leg on oil two hooks one on oil the drill handle the other at the bit end of the steel this makes it unnecessary to hold the steel while collaring the hole the operator merely steadies the drill and thrusts it forward to ito work in the setting shown holes were put in about six and one half feet above the floor in eight foot coal and the drilling was done rapidly and easily in this mine where the coal was fairly hard miners with hand augers drilled about ten holes per manber shift holes being five to five and one half feet deep it required two four or even sometimes six hours to drill the holes for a single room results in trying out the new mounting several rooms were drilled one of these will serve as an example of the results secured five holes were drilled for a total of feet in thirteen minutes ten seconds drilling time an average aldrage of 21 feet per minute the drill and mounting were then pulled down moved to a nearby crosscut aset beset and three holes drilled for a total of feet in a total time of seventeen minutes the actual drilling time on these three diree holes was eight minutes two seconds the drill was the standard sullivan DP 33 rotator with hollow piston using seven eighths inch hollow hexagon steel and Z bit on the first hole two lengths of steel were used on all others one six foot length only the great time and labor economy of such a coal drilling rig will be evident to all stationary compressors other companies in utah are using hammer drills with stationary compressors and one large company is running a mechanical entry where all operations are by machine the coal is cut by electric chain machine drilled with air drills operated by WK 2 compressors and the coal loaded in cars with electrically driven loading machine air drills are no longer a mystery to the coal digger and the hard rock man has no edge on these men in the operation of machines which until campara were unknown in coal mines |