The practical aspects of rear pick arrangements on boom-type tunnelling machine cutting heads, investigated during long-term underground trials with the use of ...
Mining Science and Technology, 10 (1990) 221-230 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands
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Practical aspects of rear pick arrangement on boom-type tunnelling machine cutting heads O.Z. H E K I M O G L U 1 and R.J. FOWELL 2 I Turkish Coal Enterprises, Beypazari Lignite Mine, Cayirhan (Turkey) 2 Department of Mining Engineering, University of Newcastle upon Tyne, Newcastle upon Tyne NE1 7R U (U.K.) (Received June 21, 1989; accepted August 17, 1989)
Abstract Hekimoglu, O.Z. and Fowell, R.J., 1990. Practical aspects of rear pick arrangement on boom-type tunnelling machine cutting heads. Min. Sci. Technol., 10: 221-230. The practical aspects of rear pick arrangements on boom-type tunnelling machine cutting heads, investigated during long-term underground trials with the use of various types of picks and cutting heads are described. The results indicate that with improperly positioned rear picks the cutting rate is significantly reduced, and that progressive wear develops both on tool holders and cutting boom components. It is also emphasised that the cutting head connection to the boom is greatly influenced by excessive depth of sump, and the flange-type cutting heads are much more prone to wear.
Introduction
Cutting head and drum design is recognised as a vital factor in the successful application of rock and coal-cutting machines [1]. A considerable amount of laboratory research work has been carried out on the fundamental aspects of rock and coal excavation. The significance of these studies is inevitably more distinct in practice, because the effect of any parameter associated with cutting is likely to be reflected by the behaviour of the machine. Because they are very expensive, particularly those requiring long-term observations, the number of practical studies in this field is, however, not large. It would be, therefore, very convenient to conduct in-situ investigations during an actual tunnelling operation where suitable conditions for a particular trial 0167-9031/90/$03.50
are available during normal delay periods. Important aspects of cutting head and drum design can be investigated using in-situ trials to estabfish practical design principles. Extensive and long-term underground investigations for improving the performance of rock- and coal-cutting machines in terms of cutting head design have been carried out during various tunnelling operations in Beypazari lignite mine. The validity of the basic principles of cutting-head design based on laboratory studies has been investigated, together with some practical problems which would have been difficult to investigate under laboratory conditions. The effect of the arrangement of the rear picks is one of the factors which may be investigated in practical terms. It is understood that very few manufacturers consider the rear pick arrangement.
© 1990 Elsevier Science Publishers B.V.
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Nearly all efforts are directed towards the tool lacing at the nose section of a cutting head because this is where the picks are in continuous contact with the material to be cut and, therefore, more prone to damage. Due to its corner cutting action, when the correct lacing is not employed, the front most pick is the only one which is subject to heavy loading and severe wear. The same situation may also apply to the rear most picks. From a theoretical viewpoint difficulties arising from cornercutting action would not be the case for the rear picks if they were only partially embedded into the face within the nominal depth of sump of the cutting head. In this situation, the rear tool benefits from relieved cutting. This situation is, however, not always seen as being attainable in practice owing to rock and machine features. Some problems are, therefore, to be expected from improperly designed rear pick arrangements. This paper explains and discusses the resuits obtained from long-term underground trims carried out in Beypazari lignite mine on the effects of rear pick arrangement on machine performance and cutter boom components.
General aspects of rear picks Rear picks, as the name suggests, are those which are found at the rear part of a cutting head or a drum when viewed from the operator's position. The duty of rear picks varies according to the depth of sump and hence they are likely to act as corner-cutting picks or as ordinary picks under different cutting conditions. It is therefore useful to first point out the relative duty of the tools on a cutting head in order to provide a comprehensive definition of the rear pick assembly. Cutter tools disposed on a cutting head or a d r u m are required to cut in concert in such a manner that they all perform relieved cutting, a process in which the action of a tool is
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