The present invention relates to a control method for an opener for a blast furnace taphole.
In the operation of a blast furnace to produce pig iron, a taphole is opened, using an opener, to tap hot metal from the furnace. Japanese Unexamined Patent Publication No. 6-322420, for example, describes a taphole opener as shown in FIG. 4. According to the figure, the taphole opener opens a taphole 6 of a blast furnace, using a drilling rod 2 held by a drill unit 1, by giving impact and rotation to the drill unit 1, and drives the drill unit 1 forward and backward using a feed motor 5 installed on a guide cell 3 and driven by hydraulic power supplied from a hydraulic unit 4. A pulse generator 7 is connected with the rotary shaft of the feed motor 5. An arithmetical unit 9 is provided for counting output pulses of the pulse generator 7 upon receiving a tapping commencement signal. The driven distance of the drill unit 1 is counted by the pulse generator 7 in the form of the number of pulses, and the hydraulic pressure during the taphole opening operation is continuously monitored by a pressure gauge 8 to measure the depth of the taphole 6.
FIGS. 5(a) and 5(b) are flowcharts showing the control flow of the aforementioned taphole opener. Once the taphole opening operation begins (step 1), the pressure gauge detects hydraulic pressure (step 2).
The detected hydraulic pressure is input to the arithmetical unit, which judges whether the detected pressure B is equal to or higher than a set pressure A (step 3). If the detected pressure B is lower than the set pressure, the tip of the drilling rod has not reached a plugging material in the taphole and, then, the control flow returns to steps 1 and 2 and the forward driving of the drilling rod is maintained until the tip of the rod reaches the plugging material in the taphole.
When the tip of the drilling rod hits the plugging material in the taphole during the forward driving of the rod, the detected pressure B exceeds the set pressure A and, at that time, the value of the position detected is set to zero (step 4) and the counting starts (see FIG. 5 (a)).
The rod is driven forward under visual monitoring to determine whether the forward movement proceeds normally and whether any bend occurs in the drilling rod (see FIG. 5(b)). In the meantime, the number of the pulses is accumulated, and when the taphole opening is completed, a tapping commencement signal is turned on (step 6), the drilling depth of the taphole is calculated from the accumulated number of pulses (step 7), and the calculated result is shown on the output (step 8).
In the above-mentioned taphole opener, however, the forward movement speed of the drilling rod is controlled manually so that the rod may not buckle and, for this reason, the control is imperfect when the hardness and strength of the plugging material in the taphole change resulting in large drilling resistance. As a result, the drilling rod sometimes suffers bending and its tip tends to wear very rapidly.
In addition, since the impacts are also controlled manually, visually monitoring if the forward movement is sufficient, an impactor of the drill unit sometimes hits idly when the resistance against the forward driving is small, resulting in shorter service life or damage to the equipment.
Further, after the commencement of the taphole drilling is detected, detection of the drill depth in the taphole and rapid increase in the forward driving speed are confirmed also visually, and therefore accurate measures may not always be taken due to a slow reaction time.
Further yet, since the taphole opening operation is one of the cast house operations wherein the taphole opener is manually operated by a worker visually monitoring its forward movement speed, there is a problem that work environment of the operator is hot, dangerous and dirty with much dust.
The present invention provides an automatic control method for a hydraulic taphole opener, whereby a drilling rod of a drill unit can be prevented from buckling and idle hitting, the taphole opening time can be shorter, and taphole depth can be measured more accurately, making remote operation possible through automatic operation of taphole opening work to liberate workers from a foul work environment.
The gist of the present invention is as follows:
(1) An automatic control method for a hydraulic taphole opener for opening a taphole by giving impact and rotation to a drill unit holding a drilling rod and driving the drill unit forward and backward by a hydraulically driven feed motor, which method comprises the steps of:
detecting the driving load in the form of detected hydraulic pressure;
stopping the driving but maintaining the rotation when said detected pressure reaches an upper limit set value beyond which buckling may occur; and
resuming the driving when said detected pressure falls to a lower limit set value or below.
(2) An automatic control method for a hydraulic taphole opener for opening a taphole by giving impact and rotation to a drill unit holding a drilling rod and driving the drill unit forward and backward by a hydraulically driven feed motor, which method comprises the steps of:
detecting the driving load in the form of detected hydraulic pressure;
maintaining the impact when said detected pressure is equal to or higher than a set value to commence the impact; and
stopping the impact when said detected pressure is lower than said set value.
(3) An automatic control method for a hydraulic taphole opener for opening a taphole by giving impact and rotation to a drill unit holding a drilling rod and driving the drill unit forward and backward by a hydraulically driven feed motor, which method comprises the steps of:
detecting the driving load in the form of detected pressure;
setting the count of position detection to zero when the detected pressure exceeds an upper limit set value for detecting that the drill unit has reached a plugging material in the taphole, commencing position detection from this position, and calculating the depth of the taphole;
stopping the driving of the drilling rod when the taphole depth according to the position detection becomes equal to or deeper than a set value and the detected pressure becomes equal to or lower than a lower limit set value for detecting that the taphole has been perforated;
stopping the driving but maintaining the rotation when, during the forward driving of the drilling rod, said detected pressure reaches an upper limit set value beyond which buckling may occur; and
resuming the driving when said detected pressure falls to a lower limit set value or below.
(4) An automatic control method for a hydraulic taphole opener for opening a taphole by giving impact and rotation to a drill unit holding a drilling rod and driving the drill unit forward and backward by a hydraulically driven feed motor, which method comprises the steps of:
detecting the driving load in the form of detected pressure;
setting the count of position detection to zero when the detected pressure exceeds an upper limit set value for detecting that the drill unit has reached a plugging material in the taphole, commencing position detection from this position, and calculating the depth of the taphole;
stopping the driving of the drilling rod when the taphole depth according to the position detection becomes equal to or deeper than a set value and the detected pressure becomes equal to or lower than a lower limit set value for detecting that the taphole has been perforated;
maintaining the impact when, during the forward driving of the drilling rod, said detected pressure is equal to or higher than a set value to commence the impacts; and
stopping the impact when said detected pressure is lower than said set value.
(5) An automatic control method for a hydraulic taphole opener for opening a taphole by giving impact and rotation to a drill unit holding a drilling rod and driving the drill unit forward and backward by a hydraulically driven feed motor, which method comprises the steps of:
detecting the driving load in the form of detected pressure;
setting the count of position detection to zero when the detected pressure exceeds an upper limit set value for detecting that the drill unit has reached a plugging material in the taphole, commencing position detection from this position, and calculating the depth of the taphole;
stopping the driving of the drilling rod when the taphole depth according to the position detection becomes equal to or deeper than a set value and the detected pressure becomes equal to or lower than a lower limit set value for detecting that the taphole has been perforated;
stopping the driving but maintaining the rotation when, during the forward driving of the drilling rod, said detected pressure reaches an upper limit set value beyond which buckling may occur;
resuming the driving when said detected pressure falls to a lower limit set value or below;
further, maintaining the impact when, during the forward driving of the drilling rod, said detected pressure is equal to or higher than a set value to commence the impact; and
stopping the impact when said detected pressure is lower than said set value.