The tool consists of a 2-m-long rod which is mounted immediately behind the drill bit. Hydraulically actuated steering runners provide directional control by applying pressure to the walls of the drill hole. An inclinometer inside the rod is capable of detecting a deviation of one angular minute from the vertical. Once a deviation has been detected, the inclinometer system generates a signal which activates small clamping cylinders. These cylinders push the steering runners of the drilling rod against the wall of the drill hole. Pressure is applied until the correction is completed.
But how does the driller know the system is working? An electro-hydraulically operated pulse transmitter in the unit produces 11 brief pressure pulses in the drilling rod flushing system every five minutes. A differential pressure receiver on surface then generates pulses of electric current which are fed via a cable to a data terminal. The data is decoded into eight independent measuring value channels and displayed as actual values on digital indicators.
“This method of data transmission and the resulting continuous monitoring of the drilling process guarantees a high degree of reliability,” a company brochure says.
Another feature of the directional drilling tool is an independent electric generator within the unit, which supplies all power requirements. The unit rotates at 60 r.p.m. and weighs about 300 kg. The recommended drilling pressure is about 18 tonnes. Ground Support Mesh
A company first chartered in Italy in 1879 and which has nibbled ocassionally at the mining market is now ready to tackle Canadian mines. Maccaferri Gabions of Canada has decided to try to market its special brand of ground support mesh.
The mesh, a common sight wherever gabions have been built to support river banks and roadway hillsides, is a non-ravelling, triple-twist wire that is heavily galvanized and remarkably strong.
According to Joseph D’addario, president of the Canadian subsidiary, it surpasses in strength standard wire mesh and chain link configurations. In tests, a 9×3-ft mesh withstood a weight of 48,000 lb. The mesh’s special hexagonal construction distributes weight far better than traditional meshes.
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