WATER JET CONFERENCE - Waterjet Technology Association

immediately mounted onto the contemporary customary and widespread basis equipment
namely the coach, as the upper part of Figure 1 shows . The motorized vehicle
represented is the first motor car from Daimler in 1886, proceeding from the basic
equipment of a "coach". The only concession to the new technology was the removal of
the redundant draw bar and its substitution by another steering system . In 1903, just
about two decades later it had been realized, that in order to retake full use of the new
technology, the negligibly altered coach was obviously not the optimal basic equipment
for the internal combustion engine, as the basic conception of a motor vehicle resembling
today ' s automobile, in the lower half of the Figure (Figure 1(b)) shows.
In the first decade of our century the suggestion was made for tie first time and
the attempt undertaken to install percussive compressed-air tools in mining (Figure 2). As
the upper half of the picture demonstrates, the new technology "percussive
compressed-air tools were at first adjusted to the basic equipment at that time current in
coal winning, namely the pick. The equipment was thus also called "mechanized pick
ax". In this form, the new technology could however not be rendered fully effective,
because it was mounted on the basic equipment of a pick. It was also 20 years later with
the discovery of a new basic equipment for the new technology, i.e. the pneumatic
pickax, that compressed-air tools directly came to be distributed world- wide above all in
coal mining. There are almost endless examples of this sort.
To apply this basic principle of development theory to the high pressure water jet
technique (Figure 3), we must next look at the inherent advantages and disadvantages of
the physical and technical processes of this technology. In the context of such a general
coverage, these must be reduced to a very simplified level. Significant advantages to be
cited are the extraordinarily high energy density in the area of impact in the mineral and
rock and above all the high destruction and crushing effect, dependant on the formation
and composition of the mineral and resulting from the complex processes in the area of
impact and underlying mineral area. A further advantage is that at the point in the area of
impact where the energy is introduced into the mineral, there is no wear or the tool. As
disadvantages we must mention, above all in the basis of experience up to now, the
relatively high specific energy input per volume unit of cut material as well as the
technology specific input for equipment e.g. driving motor, pump, pressure controller,
steering and control equipment, jet nozzle and movement mechanisms for jet nozzles.
From this it can already be deduced that the high pressure water jet technique is probably
only technically meaningful and economically feasible for high-grade crushing and
winning tasks, which could be done by conventional tools and for operations, where the
specific energy input per unit volume of cut mineral is not of primary importance.
In the next step, both the possible applications in mining and the point at which
the machines and equipment hitherto employed have reached their limits or have been
unable to realize or solve specific tasks within the existing methods and systems, must be
examined. The requirements profile for such application possibilities will have to be
precisely formulated and drawn up in detail with regard to technical and economic
considerations as well as the optimization of the coal winning method or of the overall
system.