Metal detector and iron removal device

First, the main technical performance

The main technical performance requirements are as follows:

(1) HQ-5 metal detectors can find various metal objects in magnetic or non-magnetic ore. The detector adjustment device can overcome the influence of different magnetic ores on the detector.

(2) Sensitivity: Generally, steel balls equivalent to 30 to 60 mm in diameter can be found. The sensitivity decreases as the coil size increases, as shown in Table 1. The sensitivity is higher in the coil plane close to the coil winding, and the center sensitivity is the lowest. Sensitivity can be adjusted as needed within the specified maximum range.

(3) The belt speed is 0.5 to 2.0 m/s.

(4) Output: In addition to the light signal of the instrument itself, a set of normally open normally closed contacts can be connected, and the contact capacity is 220 volts and 3 amps.

(5) Structure type: The instrument box is wall-mounted on-site installation, and the coil is a flat type or X-shaped assembly method for wearing a belt, which can be installed continuously.

The outer dimensions and weight of the coil vary depending on the width.

Second, the principle and structure

In an alternating electromagnetic field, a metal object absorbs the energy of a part of the electric field due to eddy current, hysteresis and dielectric loss. This part of energy is converted into heat energy, which is equivalent to increasing the electromagnetic field and coil resistance. In the inter-frequency range, the difference in eddy current loss is more prominent due to the difference in electrical conductivity between metal objects and magnetic ore. The eddy current not only increases the equivalent resistance of the coil, but also the magnetic flux generated by the eddy current is inverted from the magnetic flux of the original electromagnetic field to take a role of weakening the electromagnetic field. This is equivalent to reducing the inductance of the coil that produces this electromagnetic field. On the other hand, the magnetic permeability of the object increases the inductance of the coil. Combining the above effects, it is obvious that a metal object with better conductivity causes a significant increase in the electric resistance of the coil, and the inductance is increased little (for the conductive magnetic metal) or reduced (for the conductive non-magnetic metal); The magnetic ore with poor conductivity only slightly increases the equivalent resistance of the coil, and the increase of the inductance is more obvious. The HQ-5 magnetic ore metal detector is designed according to this principle.

The LC self-excited oscillator is used as the detection circuit of the detector, and the belt coil generating the electromagnetic field is used as the inductance element in the oscillator resonance circuit. Thus, the coil is both an element of the oscillation source and a sensitive element. When a metal object enters the belt coil, under the action of the alternating electromagnetic field, the good electrical conductivity of the metal produces a large eddy current loss, which reduces the amplitude of the oscillator. When this condition is detected, it can be known that there is a situation. The outer metal object passes through the belt loop. When the magnetic ore enters the coil, the ore magnetism causes a significant increase in the inductance of the coil, which increases the amplitude of the oscillator to compensate for the effect of the oscillator amplitude due to the energy consumption of the ore itself. As a result, the amplitude of the oscillator is compensated when appropriate. It remains the same, overcoming the impact of magnetic ore on the detector's operation. The HQ-5 block diagram is shown as 1.

The oscillator outputs a constant-amplitude AC voltage under normal conditions, and after detection, it is a constant DC voltage, so the output differential is zero. When the metal object passes through the circle, the amplitude of the oscillation decreases and then recovers. The detected DC voltage produces a reduced fluctuation through the differential circuit, and a pulse signal is output. This pulse is amplified, pushes the relay to operate, and outputs a contact signal to control the metal object take-out device to take out the metal object.

The principle circuit of HQ-5 magnetic ore metal detector is shown in Figure 2.

Figure 2 HQ-5 metal detector

Third, installation and commissioning

The instrument case can be hung on the wall near the belt coil. The external wiring of the instrument box adopts the CA type 20-way plug-in to facilitate the removal of the instrument box for inspection and replacement.

The line of the power line should be routed to the coil line. The connecting coil wire should be laid through the steel pipe or the core shield wire.

According to the site requirements, the sensitivity of the instrument can be adjusted to protect the safety of the crusher. Generally, medium and fine crushers are separately protected and different sensitivity is specified. The sensitivity adjustment is achieved by a potentiometer W ₂ mounted on the board inside the instrument. And send the steel ball into the coil for inspection. The steel ball has the lowest sensitivity when it is in the middle position of the coil plane. The higher the sensitivity of the coil is, the higher the sensitivity of the coil can be determined according to the scene. The potentiometer W _{3 is} used for zero adjustment, and is generally adjusted to a position of 5 μA.

A concentrator that contains a large amount of magnetic ore must carefully adjust the effects of magnetic ore. This adjustment is not necessary for concentrators of non-defective ore. When adjusting the effect of the magnetic ore, connect the μA meter to the output of FC2 (K3 is placed in a position where the μA meter is connected in parallel with R ₂₀ ). When a metal object enters the coil, the μA meter current decreases. This indicates that the instrument is normal. When the magnetic ore (preselected as a representative magnetic ore, as large as possible) enters the coil, the μA meter current also increases, indicating that the ore has the same effect as the metal object. At this time, the resistance of the potentiometer W ₁ that adjusts the influence of the magnetic ore should be increased. Conversely, if the magnetic field of the μA is reduced when the magnetic ore enters the coil and has the opposite effect when the metal object enters the coil, the resistance of W ₁ should be reduced. This is repeated until the effect of the magnetic ore entering the coil is minimal. Then, determine the sensitivity of the instrument's operation and proceed to observe the use. Due to the difference in shape, size, grade, etc. of the magnetic ore, the adjustment of the influence on the magnetic ore should be appropriately corrected in actual use.

Fourth, automatic iron removal device

There are many types of iron removal devices. Only the type of electric iron and iron removal trolleys will be introduced here. It is combined with a metal detector to form an automatic iron removal device. In addition to metal detectors, the device generally consists of a trolley, an electromagnet suspended on a trolley, an electric motor (JQ41-6, 1 kW), a worm gear reducer (PYII-120-315, i=22.2), and a drum and traction trolley. The wire rope is composed so that the electromagnet can be controlled to move back and forth in the track in the direction of the transverse belt. Electric iron is MZZ3-535 type. The rated voltage is 220 volts and the power-on continuation rate is 40%, which is powered by a silicon rectifier. The electromagnet is 160-175 mm high from the belt surface at the top of the belt (the specific data should be determined according to production requirements, this data is for reference only). The metal detector detection coil is mounted in front of the ore direction of the iron take-up device.

The control circuit is shown in Figure 3. M is an electromagnet, D is the motor of the drive trolley, 1QZK is the position control switch of the upper point of the belt of the electromagnet, 1FZK is the position control switch of the electromagnet stopped at the unloading point B outside the belt, 2QZK, 2FZK is the corresponding limit switch. JTQ is a metal detector control contact. SJ is a time relay that controls the residence time of the electromagnet at point A on the upper part of the belt. QCQ and FCQ are the contactors that drive the electromagnet motor forward and reverse (go to point A and return to point B). V is a DC power source that is excited by an electromagnet.

Figure 3 Automatic iron removal device circuit diagram

When there is a metal piece passing through the metal detector detection coil, the motor is decelerated by the reducer, and the drum is driven by the drum and the wire rope to drive the trolley to move from the point B of the outer side of the transport belt to the center of the belt, and is said to stop at the upper part of the belt and put the iron. The piece is sucked out of the ore stream, then returns from point A to point B, stops and unloads the iron pieces in the scrap iron box to complete an automatic iron removal cycle.

If the car takes the first piece of iron and leaves point A, but does not return to point B before the second piece of iron passes through the detector coil, the car is again controlled by the time relay and returns to point A, which will be second. The pieces of iron are sucked up and then returned to point B in the original order. Unload the first piece and the second piece of iron together in the scrap iron box. Complete the removal task of two iron pieces, the car needs to work for up to two cycles. When multiple pieces come to iron, and so on.