JPS5815025B2 - How to monitor vibrating sieves - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vibrating screen monitoring method that automatically and quantitatively displays the vibration state of the vibrating screen.

As is well known, in steel works, many vibrating screens are used for sizing steel raw materials, sorting coke or sintered ore, and the like.

The configuration of a typical vibrating sieve is schematically shown in FIGS. 1a and 1b.

In the figure, 1 to 14 are support springs, 2 to 24 are brackets, and the cylindrical body 3 is supported at four points by these.

Vibration is applied to this cylinder body 3 from a vibrating device.

In the illustrated example, the vibration device includes motors 41 and 42, shafts 61 to 63 provided in the center of the cylinder body 3 whose rotations are transmitted via the gear box 5, and shafts 6□ to 63. Unbalanced weights 7□~76 attached to each end
It is composed of.

The operation of the vibrating sieve used in the steel raw material processing process is a reciprocating (
It is roughly divided into linear motion and circular motion.

In either case, it goes without saying that a certain amplitude and period (frequency) are required.

Generally, the natural frequency fn of a vibrating sieve is given by the following equation, and it is normally excited at a frequency of f=2fn to 3fn.

7v fn= - 2π However, n: Number of support springs ・ g: Gravitational acceleration (980α152) k: Spring constant (kgf/cm) W: Machine weight (kyf) This forced frequency is determined by the motor rotation speed and reduction ratio. is determined, and this rarely deviates significantly from the predetermined value.

However, the amplitude can easily change due to factors such as poor adjustment of the main body support frame and unbalance.

In unstable operating conditions, abnormal loads act on various parts of the main body in a very short period of time, causing cracks due to repeated stress.

If it continues to operate as it is, it will eventually break and cause significant operational and equipment damage.

For example, a vibrating screen that moves in a circular motion takes various operating modes as shown in FIG.

FIG. 2 shows the four support positions A of the vibrating sieve main body 3 in FIG.

This figure shows vibration trajectories in the xy plane (the direction in which the material travels, and the perpendicular direction is the X direction) at points B, C, and D.

■ indicates a state in which the four points are moving normally in a circular motion with a predetermined amplitude.

■ indicates a state in which the four points are performing circular motion with large amplitude as shown by the broken line, compared to the regular circular motion shown by the solid line (the same applies for ■ to ■ below), and this is because the weight is too heavy. The cause may be that the cylinder body has become lighter due to wear, etc.

On the other hand, ■ is a state in which the four points are moving in a circular motion with a smaller amplitude than the normal circular motion, and the weight is too light, or the cylinder body has become heavy due to additions or deposits, or processing This may cause the amount to become excessive, etc.

In case (2), point A is moving in a large circular motion, and the remaining three points are moving in a normal circular motion.This is due to an abnormality in the support spring at point A, an imbalance in the weight of the main body, etc.

■ indicates a state in which the four points are moving in an ellipse, and this is because the upper part of the cylinder body has become lighter due to wear or cracks have occurred.

This is caused by

■ is in a state of elliptical motion opposite to ■, and this means that the lower part of the cylinder body has become lighter due to wear or a crack has occurred.
etc. are the causes.

To monitor the operating status of various vibrating screens,
Conventionally, this has been done by manually tracing the operating trajectory or by using a visual observation device.

The former is the side surface (xy
A measurement paper is pasted on a flat surface, and maintenance staff presses a pencil against the measurement image to record the vibration trajectory.

be.

However, although it is possible to quantify the vibration state to some extent with this method, it is difficult to objectively and accurately grasp the vibration state because it is greatly influenced by the skill level of the maintenance personnel.

On the other hand, the latter is also on the xy plane, as shown in Figure 3.
Mark points P1°P2.corresponding to the amplitude values. ... are plotted on a horizontal straight line, and each point P1... is plotted above each point. P2. The landmark points Q1゜Q2... are located at a distance equal to the amplitude value of . ... is plotted, and the locus due to the circular motion is observed. In the case of Figure 3, the scale 12r is the position where the two upper and lower circular loci touch.
It is determined that nvt is the amplitude value.

However, with this method, even if the amplitude value of the circular motion is known,
Actually, it is not possible to quantitatively understand the most common elliptical motion.

Furthermore, since either method requires inspection by maintenance personnel, it can only be carried out intermittently, and is insufficient for preventing breakdowns.

Whether it is a linear motion or a circular motion, if the operation of the vibrating sieve becomes unstable, it becomes an elliptical motion.

Therefore, it is sufficient to know the amplitude values in at least two perpendicular directions, x and y, and the phase difference between vibrations in each direction, and a method for automatically and quantitatively measuring these is desired.

The present invention provides a vibrating screen monitoring method that satisfies the above-mentioned needs.

In the present invention, the vibrating sieve body is provided at a plurality of locations, for example, the support spring positions A, B, and C shown in FIG.

A pair of vibration detectors that detect vibrations in the X and X directions, which are orthogonal to each other, is installed at each point of D, and the output of each vibration detector is extracted through a low-pass filter to display the vibration status of each part. It is characterized by automatic and quantitative monitoring of the vibrating sieve.

FIG. 4 shows the main part of one embodiment of this invention.
A pair of vibration detectors 11 x t 11 y for detecting vibrations in the X direction (direction of movement of the material) and the X direction (vertical direction) is attached to point A of the vibrating sieve body 3 in the figure.

For example, piezoelectric vibration detectors are used for these vibration detectors 11x and 11y.

The outputs of the vibration detectors 11x and 11y are passed through preamplifiers 12x and 12y, respectively, and are horizontally swept by the synchroscope 14 through low-pass filters 13x and 13y to remove noise components.

Input to the vertical sweep input terminal.

This causes the synchroscope 14 to draw surge waveforms 15 corresponding to the vibrations in the X direction and the X direction.

Note that the low-pass filters 13 x and 13 y are
In order to clearly detect the operating state of the vibrating sieve, components other than the operating frequency, that is, noise components are removed.

Usually, the frequency of the vibrating sieve is often in the vicinity of 5 to 20 Hz, and in this case, a filter is used to extract only vibration signals of 20 Hz or less.

Further, if low frequency noise of less than 5 Hz is present, a band type filter is used so that it can be removed.

In any case, the low-pass filters 13x and 13y only need to have a function of cutting noise components other than the vibration frequency of the vibrating sieve.

In addition, the Lissajous waveform 15 is a waveform representing the locus of the composite motion of two vibrations in mutually perpendicular directions, as shown in the JIS Terminology Dictionary (published by the Electric Mortar Standards Association).

In FIG. 4, only point A is shown, but similar devices are installed at other support positions B, C, and D.

In this way, the surge waveform force can be dynamically displayed according to the vibration state of each part of the vibrating sieve as shown in Figure 2, and it can be easily and quantitatively displayed without requiring the skilled work of maintenance personnel. You can know the operating status of the vibrating sieve.

By the way, in an example of a vibrating screen in a sintering factory, a clear surge waveform was obtained for vibrations with a frequency of 12 Hz and an amplitude of 12 mm, and the accuracy was (12 ± 0.7) mrn, which is sufficient for practical use. It was confirmed that there is.

In the above embodiment, only the vibrations in the x and X directions are monitored.

Normally, this is sufficient, but vibration detectors are also installed in the two directions orthogonal to these directions, that is, the width direction of the vibrating sieve.

If a Lissajous waveform is drawn using a combination of y--z, etc., it is more useful for determining abnormal vibrations, etc.

Further, in the above embodiment, the vibration state is displayed as a Lissajous waveform, but it is also possible to quantitatively grasp the vibration state by displaying the amplitudes of each vibration in the x and X directions and their phase differences.

For example, as shown in FIG. 5, a low-pass filter 13x,
The vibration signal output in the x and X directions taken out through 13y is
The data may be input to an arithmetic circuit 16 such as a microcomputer and digitally processed to calculate vibration amplitudes in the x and X directions and their phase differences, and these may be displayed on the meter 17.

More specifically, when the vibrating sieve is vibrating in a normal circular motion, the lengths of the long and short axes are equal and the phase difference between them is 90°.

On the other hand, when the vibration is abnormal, it becomes an ellipse, but in this case, the major axis>minor axis, and the phase difference is 90° or less.

Therefore, when the vibration components of the vibrating sieve are detected separately in the X and Y directions, the long and short axes are related to the maximum amplitudes in the X and Y directions, so After the component analog signals are converted into digital signals by A-D conversion circuits 161x and 161y, the digital values are sampled by sampling circuits 162x and 162y.

After that, if the peak hold circuits 163x and 163y detect and hold the maximum value from the sampled signal,
The hold values become the amplitudes in each of the X and Y directions.

This is displayed on a digital display meter 17. lx. 171Y
Display in .

On the other hand, the phase difference θ is determined from the time difference between the maximum values of the X and Y direction component signals.

Therefore, a clock circuit 164x measures the time of the signal sampled by the sampling circuits 162x and 162y.

164Y, and the time difference circuit 165 calculates the time difference t, then the phase difference circuit 166 calculates θ-2πf·Δt to determine the phase difference.

172 is a meter that displays the phase difference.

f is the frequency.

Next, FIG. 7 shows an example of analog calculation processing.

In this case, the X output from the filters 13x and 13y
, a peak hold circuit 16 holds the peak value of the Y direction component signal.
If you hold at 3x and 163y, the hold value becomes the amplitude, so use this as the analog display meter 173x.
, 173y.

On the other hand, the phase difference can be determined by converting the outputs of the filters 13X and 13Y into pulses using the pulse conversion circuits 167x and 167y, and finding the pulse difference width of these pulses using the pulse difference width circuit 168. This pulse difference width corresponds to the phase difference. Therefore, it can be displayed by this phase difference display meter 172.

Furthermore, instead of the combination of vibration amplitude and phase difference, the lengths of the short and long axes of the ellipse that depicts the vibration locus and the angle between the long axis and the reference axis are similarly calculated and calculated. It is also possible to quantitatively understand the vibration state by displaying the vibration on a meter.

Furthermore, permissible limits are set for the vibration amplitude in the two directions of X and Y, or their ratio, vibration phase difference, etc., and when abnormal vibration exceeding the permissible limit occurs, an alarm is automatically issued or a vibration The sieve may be automatically brought to an emergency stop.

In this case, it is also useful to divide the permissible limit into two levels, issue only an alarm at the first set value, and control the vibrating sieve to automatically stop at the next set value.

As explained above, according to the present invention, the operating state of the vibrating screen can be automatically, constantly, and quantitatively monitored without requiring the skilled work of maintenance personnel, and It can contribute to improved sieve reliability and operational stability.

[Brief explanation of the drawing]

Figures 1a and 1b are schematic perspective views and plan views of the vibrating sieve;
Fig. 2 is a diagram showing an example of the vibration state of each part of a vibrating sieve that moves in a circular motion, Fig. 3 is a diagram showing the principle of a visual observation device for the vibration state, and Fig. 4 is a diagram showing the main part configuration of an embodiment of the present invention. , FIG. 5 is a diagram showing a main part configuration of another embodiment, and FIGS. 6 and 7 are diagrams each showing a specific configuration of the arithmetic circuit shown in FIG. 5. 3... Vibrating sieve body, Ilx, 11y...-
・Vibration detector, 12x, 12y...Preamplifier, 13X. 13y...Low pass filter, 14...
- Synchronoscope, 15... Lissajous waveform, 16... Arithmetic circuit, 17... Meter.

Claims (1)

[Scope of Claims] 1. Pairs of vibration detectors for detecting vibrations in two mutually orthogonal directions are provided at each of a plurality of locations on the vibrating sieve body, and the output of each vibration detector is taken out via a filter to A method for monitoring a vibrating sieve, characterized by displaying the vibration state of the vibrating sieve. 2. The method for monitoring a vibrating sieve according to claim 1, wherein the means for displaying the vibration state is a graphic display that draws a Lissajous waveform by inputting outputs in two directions horizontally and vertically. 3. The means for displaying the vibration state takes the maximum value of the output in two directions as the respective amplitude, and also calculates the phase difference from the time difference between the outputs in the two directions or the pulse difference width of the converted pulse of the output, and calculates the amplitude of each of the above. A method for monitoring a vibrating sieve according to claim 1, wherein the phase difference and phase difference are displayed on a meter. 4. A patent claim in which the means for displaying the vibration state is one that displays the lengths of the long and short axes of an ellipse drawn by the vibration locus obtained from outputs in two directions, and the angle formed between the long axis and the reference axis using a meter. A method for monitoring a vibrating sieve according to item 1.