FR2573809A1 - PROCESS FOR REDUCING THE RISK OF FIRE STRIKES DURING THE OPERATION OF A TRIMMER FOR DRAWING - Google Patents

Abstract

PROCESS FOR REDUCING THE RISK OF GRAY STROKES DURING THE OPERATION OF A TRACING FELLING MACHINE PROVIDED WITH A RISING AND LOWERING ARM ROTATING AROUND A VERTICAL AXIS AND AT LEAST A HAVING DRUM ARMED WITH AT LEAST 30 PEAKS OF HAVING OF WHICH THE EXTERIOR ENDS MOVE AT A CUTTING SPEED OF 2 TO 3MSEC BY FELLING THE ROCKS, BLEEDS IN THE FRONT OF THE GALLERY, THE REFRIGERANT SUPPLY DUCTS 4 AND INJECTORS 5 OF REFRIGERANT BEING ASSOCIATED WITH EACH PIC OF HAVING USING COMPRESSED AIR AND WATER AS REFRIGERANT AND INJECTING INTO THE VARIOUS BLEEDS A MIXTURE JET 6 OF AIR AND WATER. FOR EACH PEAK OF HAVING, 0.25M TO 1M OF AIR AND 0.2 TO 0.5L OF WATER ARE INJECTED EACH MINUTE, THAT IS AT A FLOW SPEED ABOUT A FACTOR TEN ABOVE THE SPEED OF ADVANCEMENT. THE MIXING JET IS DIRECTED, FROM THE BASE FOR FIXING THE VARIOUS HAVING PEAKS AND AT AN ANGLE OF 40 TO 70 WITH RESPECT TO A RADIUS OF THE ROTATION CIRCLE OF THE DIFFERENT HAVING PEAKS, IN THE ANGLE SHAPED BETWEEN THE TIP OF THE PIC AND THE SAIGNEE.

Description

The invention relates to a method for reducing the risk of strokes.

  firedamp during the operation of a trimming cutter for tracing provided with an up and down arm rotating around a vertical axis which is equipped with at least one cutting drum armed with at least cutting peaks, the outer ends move at a cutting speed of 2 to 3 m / sec by making, by the felling of the rocks, grooves in the gallery front, refrigerant supply conduits and injectors of

  refrigerant being associated with each peak of cutting in use

  sant as a coolant for compressed air and water and by injecting a jet of air and water mixture into the various grooves. Such cutting drums generally have a maximum diameter of about 450 to 900 mm for

  an axial length armed with cutting peaks of 500 to 1000 mm.

  In general, the cutting peaks are arranged along a helix on a suitable rib. The lifting drum can be mounted on the movable arm in a way as a mushroom and coaxially with the movable arm or else, its axis being oriented orthogonally to the axis of the arm.

  mobile, it can project from either side of the

  mite said arm. The mixing jet can come out of the refrigerant injectors during the entire rotation path or else the refrigerant can only be brought in when the peaks

  of havage slaughter the rche at the gallery front.

  In the context of well-known measures (EP-A 00 10 534, introduction), it is sought to obtain cooling of the peaks and of the surface of the grooves and, for this, water is used first as a coolant. Air is used to spray water. This does not prevent with sufficient security the ignition of firedamp during the

  operation of the drum cutters described, in particular

  bind in case of release of firedamp from the "blowers", which frequently occurs in geological layers containing firedamp. Particular parameters preventing such ignition with sufficient safety have not been proposed in the context of well-known measures. In fact, the inflammation of firedamp during the operation of a drum cutter of the aforementioned kind constitutes a complex phenomenon which has been studied often and in depth, but without result as regards a reliable prevention of blows of firedamp during the practical use of such a machine (cf. "Gl1ckauf- Forschungshefte", 1980, p. 17 to 21). It goes without saying that an ignition occurs only in the presence of a flammable mixture and that it is necessary to introduce into the flammable mixture an energy corresponding at least to the ignition energy necessary for setting

  fire. Furthermore, the flammability of the mixture depends

  thermodynamic parameters, such as pressure and temperature, and a combination of these parameters which is

  predetermined by the corresponding thermodynamic potentials

  which control the firing. In addition, it is necessary

  take into account the geometric and thermal marginal conditions

  modynamic as well as aerodynamic conditions which prevail in the vicinity of the flammable mixture or which determine the aerodynamic behavior of the flammable mixture. In addition, the surface of the incandescent particles released during the operation of this type of drum cutter and the trajectory of these particles. It is therefore easy to understand that hitherto no indication has been given to allow technical action to prevent with sufficient safety, for the processes considered,

inflammation of the firedamp.

  The object of the present invention is to indicate a way of carrying out the process of the aforementioned kind to prevent, under all operating conditions of the drum cutter of the aforementioned kind and with sufficient safety,

inflammation of the firedamp.

  According to the invention, this object is achieved by the fact that each minute 0.25 m3 to 1.0 m3 of air and 0.2 to 0.5 1 of water are injected for each peak in the form of a mixing jet. in the associated tapping, namely at a flow speed approximately tenfold higher than the indicated forward speed, and the mixing jet is directed, from the fixing base of the different cutting peaks and at an angle of 40 to 70 relative to a radius of the circle of rotation of the different cutting peaks, in the angle formed between the tip of the peak and the tapping made. In a preferred embodiment of the invention, the flow rate per minute is approximately 0.4 m3 of air and 0.3 1

of water per peak of havage.

  In a preferred embodiment of the invention, the mixing jet is sent at a flow rate of from 35 m / sec, preferably approximately 30 m / sec, into the respective associated groove, namely preferably under an angle of about 50 relative to a radius of the circle of rotation. The flow speed of the mixing jet is understood to mean the speed of the air flow of the mixing jet at the outlet of the refrigerant injectors. In general, the water dispersed in drops entrained in this area has the same speed, but it is also possible that individual drops move more slowly. In a preferred embodiment of the invention, the drops of water contained in the mixing jet have a mass large enough to reach, thanks to inertial forces, the surface of the groove, and this independently of the diffusion of the air component of the mixing jet in

before bleeding.

  The technological measures described are very easy to carry out, to maintain and to carry out when the jet of mixture leaves the injector with a diameter of approximately mm. In this case, the air from the mixing jet can: be taken in a compressed air line which has an overpressure

  from i to 2 bars compared to the atmosphere.

  In the context of the invention, the compressed air on the one hand and the water on the other hand can exit via separate refrigerant injectors, then be combined in a mixing jet. But it is also possible to already perform this meeting inside the refrigerant supply conduits. In this context, a proven embodiment of the invention is characterized in that, at least in the area of the refrigerant injectors, the compressed air and the water are brought together in the refrigerant supply pipe and that the water is dispersed in drops on detachment edges in the coolant supply pipe, upstream of the injector. Water can be added with a wetting agent, and air can be

2S73809

  mixed with an inert gas, for example with nitrogen.

  The advantages obtained reside in the fact that if the teaching of the invention is carried out, a

  firing of firedamp is prevented with sufficient security

  health during the operation of a drum cutter for tracing galleries of the kind described. The invention is then based on the discovery that preventing this inflammation requires separate measures which, however, cooperate in a functional fusion, namely on the one hand with the supply of a sufficient quantity of air into the space capable of containing a flammable mixture of air and firedamp and, on the other hand, with this quantity of air supplied with sufficient kinetic energy which depends on the cutting speed of the cutting peaks and is equal to approximately ten times the cutting speed . In addition, it is necessary to mix with the air jet a sufficient quantity of water, but not too large. The quantity of water must be large enough to ensure sufficient cooling of the surface of the groove. But the amount of water should not be too large

  otherwise the effect of the air circulation will be compromised.

  The drops should not be too small to be certain that they actually arrive in the manner described, thanks to the forces of inertia, on the surface of the groove, which can be obtained and ensured without difficulty by ensuring that, in addition to controlling the size of the drops, the mixing jet is directed, at the angle indicated, into the angle formed between the tip of the cutting peak and the bleeding. However, this angle is at the same time important for the influence of the air supplied-on the prevention of setting

over the firedamp.

  The following description, next to the drawings

  appended by way of nonlimiting example, will make it possible

  understand how the invention can be put into practice.

  Figure 1 shows a side view of a cutting peak mounted in the peak support of a drum cutter of the structure described, Figure 2 shows, in section and on a larger scale compared to Figure 1 , detail A of the object

of figure 1.

  The figures relating to a trimming cutter with a rising and falling arm rotating around a vertical axis represent a part of the cutting drum 1 to which is attached a support called peaks 2 comprising a peak havage 3. At the peak of havage 3

  associated with a refrigerant supply pipe 4 which is

  mine by injector 5. As refrigerant, compressed air and water are used. A mixture jet 6 comes out as indicated from the injector 5 and enters the corner

  formed between the point 7 of the cutting peak and the groove 8.

  In Figure 1, this groove 8 has been indicated, as well as the direction of rotation. For each cutting peak 3, approximately 0.25 m3 to 1.0 m3 of air and 0.2 to 0.5 1 of water are injected every minute. The arrangement was chosen in such a way that the mixing jet 6 leaves the injector 5 at a flow speed approximately a factor of ten greater than the forward speed. The angle of the jet a is within a range of 40 to 70, in the embodiment fairly exactly 50, measured relative to the radius r of the circle

  of rotation of the individual cutting peak 3.

  In the exemplary embodiment and according to a preferred embodiment of the invention, the compressed air and the water are led together in the supply duct of

  refrigerant, i.e. at least in the injector area 5.

  Figure 2 shows a detachment edge 9. This per-

  puts to get, inside the refrigeration supply duct

  rant, immediately before exit 10, the dispersion of

  water in drops whose size is not too large.

  In conclusion, the process works with drops of water in the mixing jet 6 whose mass is large enough for them to reach the surface of the groove 8, and this independently of the diffusion of the component

air from the mixing jet 6.

Claims (10)

  1. Method for reducing the risk of blows of firedamp during the operation of a trimming cutter for tracing provided with an ascending and descending arm rotating around a vertical axis and at least one cutting drum armed with '' at least 30 cutting peaks, the outer ends of which move at a cutting speed of 2 to 3 m / sec, by slitting rocks   in (3 gallery front, refrigeration supply ducts M (5to   rant / and injectors? e refrigerant being associated with each peak of the havage using compressed air and water as refrigerant and injecting into the various grooves a jet of mixture / air and water, characterized in that, for 0.25 m3 to 1.0 m5 of compressed air and 0.2 to 0.5 1 of water are injected each minute as a mixing peak in the form of a jet of mixture into the associated groove, namely at a speed ten times more at the indicated forward speed, and the mixing jet is directed from the fixing base of the different cutting peaks and at an angle of 40 to 70 relative to a radius of the rotation circle of the different cutting peaks, in the angle formed between the tip of the peak and the bleeding performed.   2. Method according to claim 1, characterized in that the flow rate per minute is approximately 0.4 m3   of air and approximately 0.3 1 of water per peak of cutting.   3. Method according to one of claims 1 or 2,   characterized by the fact that the mixing jet is sent into the groove at a flow speed of 25 to 35 m / see,   preferably around 30 m / sec.   4. Method according to any one of the claims   1 to 3, characterized in that the mixing jet is directed into the groove at an angle of about 50 per   relative to a radius of the circle of rotation.   5. Method according to any one of the claims   tions 1 to 4, characterized in that it works with drops of water in the mixing jet whose mass is large enough for them to reach, thanks to inertial forces, on the surface of the groove , and this independently of the diffusion of the air component of the   mixing jet in front of the bleeding.   6. Method according to any one of the claims   1 to 5, characterized in that the mixing jet   comes out of the injector with a diameter of about 5 mm.   7. Method according to any one of the claims   1 to 6, characterized in that the mixing jet is taken from a compressed air line which has   an overpressure of i to 2 bars compared to the atmosphere.   8. Method according to any one of the claims   1 to 7, characterized in that, at least in the area of the refrigerant injectors, the compressed air and the water are brought together in the refrigerant supply pipe and that the water is dispersed in drops on a separation edge in the coolant supply duct, upstream of the injector.   9. Method according to any one of the claims   1 to 8, characterized in that a wetting agent is added to the water.   10. Method according to any one of the claims.   tions i to 9, characterized in that an inert gas is added to the air.