JPH0630254Y2 - Instrumentation around screen - Google Patents

Description

[Detailed Description of the Invention] (a) Field of Industrial Use The present invention relates to an instrumentation screen around a screen, for example, in a paper and pulp plant, in a stock material preparation process, impurities are removed to select only necessary ones. The present invention relates to a screen-surrounding instrument device for detecting and processing blockages or clogging around a screen used in a selective process.

(B) Prior Art FIG. 3 is a block diagram of the configuration of a conventional example.

In the figure, 1 is a screen, 2 is a chest or tank, 3 is a pump, and 4 is a liquid cyclone. The raw material charged into the est 2 is pumped up by the pump 3, passes through the liquid cyclone 4, and is input to the screen 1. A selected, predetermined amount is output through the valve VB. On the other hand, impurities and the like pass through the valve 5 and a predetermined amount passes through the valve VC to be excluded or rejected from the selection.

The clogging of the screen (clogging) means a state in which the self-cleaning action of the screen 1 cannot remove the clogging phenomenon of the raw material and the foreign matter which are going to pass due to the pressure difference between the inlet and the outlet of the screen 1.

When the screen 1 is clogged, the inlet pressure PI changes to the pump 3
Clamping pressure rises to near P, outlet pressure P0 is 0 kg
/ It goes down to near cm ² . If the operation is continued as it is, the screen 1 is clogged, the motor 6 rotating the screen cylinder trips, and the operation of the system is stopped.

In order to prevent this, a method is taken to detect a condition where the screen is slightly clogged (normal, intermediate between occlusion and transition period), and take measures.

PIC-1 is a controller that detects the pressure PT1 and adjusts the valve VA so that the inlet pressure PI of the screen 1 becomes a set pressure.

HC-1 is a manual operation device that adjusts the valve VB so as to output a predetermined selection amount, and HC-2 is a manual operation device that adjusts the valve VC so as to output a predetermined rejection amount, and PIA-
2 is the outlet pressure P0 for detecting clogging of the screen 1.
Is a pressure alarm that detects
PdIA-3 is screen 1 inlet pressure PI and outlet pressure P
It is a differential pressure alarm that operates when the differential pressure of 0 is above the set pressure.

In the screen clogging removal method, when the screen 1 is in the transitional period of clogging, the differential pressure between the inlet pressure PI and the outlet pressure P0 becomes large, the differential pressure alarm PdIA-3 operates, and the solenoid valve MV1 operates. , Valve VB closed. At this time, the self-cleaning action of the screen 1 works to eliminate the clogging. Then, the differential pressure between the inlet pressure PI and the outlet pressure P0 returns to normal, the solenoid valve MV1 is returned, and the opening degree of the valve VB is returned.

The other method is to detect the outlet pressure P0 of the screen 1 with the pressure detector PT2, and when the pressure falls below the set pressure, the pressure alarm PIA-2 operates, and from that time on, the solenoid valve MV1 is operated and the valve VB is turned on. close. During this time, the self-cleaning action of the screen 1 eliminates the clogging, and after the timer time elapses, the outlet valve VB is returned to the original opening degree.

(C) Problems to be solved by the invention The screen is increased in selection amount, and the opening degree of the outlet tail valve 5 of the screen 1 is narrowed down so as to reduce the amount of rejection.
Operate by reducing the opening of the valve VC.

However, the pulp content of the lysate component is about three times higher than that of the carefully selected component, and the operation is often stopped even if clogging occurs at the impurity outlet part in addition to the screen clogging. This is a problem.

In the prior art, clogging of the screen outlet is also erroneously detected as clogging of the screen.

An object of the present invention is to provide an instrumentation device around a screen that can detect clogging of an impurity outlet portion of a screen and eliminate clogging of the screen and clogging of the impurity outlet portion without error.

(D) Means for Solving the Problems The above-mentioned purpose is to feed the raw material to a screen having two outlets, to allow impurities to flow out from one outlet via a predetermined amount control valve, and to select from other outlets. Minute, the differential pressure between the inlet pressure of the screen and the outlet pressure of the selected portion or the output pressure of the selected portion is detected, and when this detected value reaches the set value, the control valve that intervenes on the output side of the selected portion. In the instrumentation device around the screen for closing the screen and removing the blockage (clogging) of the screen, a high-pressure cleaning water source connected to the screen outlet side via a high-pressure cleaning water valve for flowing out impurities, A detector for detecting at least one of the flow rate of impurities flowing out through the predetermined amount control valve and the screen outlet pressure of impurities, and the high pressure washing water valve and the predetermined amount control valve when the detected value reaches a set value. Both of It is achieved by including a control means for releasing.

(E) Action Detects clogging at the impurity outlet of the screen by detecting its flow rate, pressure, differential pressure, or any combination, and when it exceeds the set value, opens the high pressure washing water valve, the specified amount control valve, or both. There is a clogging release control.

(F) Embodiment A preferred embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the structure of one embodiment of the present invention, and FIG. 2 is an illustration of the control means according to the present invention.

The main parts added to the conventional constituent elements shown in FIG. 3 will be described.

MV3 is a valve for opening and closing the high pressure cleaning water for cleaning the clogging of the impurity outlet of the screen 1, PT4 is a pressure detector at the outlet of the tail valve 5, PIA-4 is its pressure (indication) alarm device, FT is a reject flow detector, FIA-1 is the same flow rate (indication) alarm device, and PdIA-5 is the difference (indication) between the output of the detector PT1 and the output of the pressure detector PT4 of the inlet pressure PI of the screen 1.
The alarm device, MV2, is a solenoid valve for fully opening the reject control valve VC.

When the impurity outlet portion of the screen 1 starts to be clogged, the amount of reject decreases. Flow rate alarm FIA if the flow rate falls below the set level
Work -1. Further, the pressure behind the tail valve 5 also decreases. The pressure detector PT4 goes down, and the pressure alarm PIA-4 is activated below the set pressure. The inlet pressure PI of the screen 1 is constant because it is detected by the pressure detector PT1 and adjusted to be constant by the adjuster PIC-1.

The pressure difference between the pressure detectors PT1 and PT4 is
As 4 goes down, it tends to increase. Pressure difference alarm PdIA-
5 works above the set value. In this way, the clogging of the impurity outlet can be detected even if the flow rate, the pressure, the differential pressure, or the combination is detected.

There are two methods for clearing this blockage: a method in which the control valve VC is fully opened and the amount of the resist is rapidly increased to release it, a method in which high-pressure washing water is injected and the method is released, and a method in which both are combined.

The alarm / indicator FIA-1, PIA-4, PdIA-5 or any combination thereof may be associated with the valve MV2 / VC or MV3 or a combination of both. FIG. 2 shows an example of control operation of three combinations and two combinations.

L1 is an OR logic circuit, and alarm indicators FIA-1, PIA
-4 and Pd2A-5 work, the OR circuit L1
Output becomes "1". L2 is a flip-flop, and when the input on the set side becomes "1", the output is held at "1". When the output of the circuit L1 becomes "1", the output of the circuit L2 becomes "1", and the valve MV2 operates.

Between the valves MV2 and VC, the valve VC is fully opened by the operation of the valve MV2. When the output of the circuit L2 becomes "1", the valve VC is fully opened, and at the same time, the valve MV3 is also opened. L
3 is a timer whose output becomes "1" after the set time T seconds when the input becomes "1". When the circuit L2 becomes "1", the timer L3 operates and the output becomes "1" after T seconds.
Enter the reset input of. Circuit L2 is reset input "1"
The output returns to "0".

Therefore, after T seconds, the valve MV3 is closed, the valve MV2 also stops operating, and the valve VC returns to the original opening degree.

That is, when any of the alarm indicators FIA-1 or PIA-4 or Pd2A-5 is operated, the reject valve VC is fully opened for a period of T seconds and the valve MV3 is opened to inject high pressure cleaning water to release the clogging.

The operation example shows a combination of the removal of clogging of the impurity outlet of the screen 1 and the removal of the clogging of the screen 1 main body. Since they are individually detected, the clogging release operation at the impurity outlet becomes a disturbance for the clogging detection of the main body. Therefore, in the case of combination, the clogging removal operation of the screen 1 main body is executed only when the impurity outlet portion of the screen 1 is not clogged.

(G) Effect It is possible to eliminate clogging at the screen impurities outlet, which has a high pulp concentration, and thus prevent the clogging of the screen main body due to clogging at the outlet, and at the same time not overloading the screen cylinder drive motor. Higher screen efficiency can be maintained by increasing the operating rate and lowering the reject rate.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention, FIG. 2 is an exemplary diagram of a control circuit according to the present invention, and FIG. 3 is a configuration block diagram of a conventional example. 1 is a screen, 2 is a tank, 3 is a pump, and 4 is a cyclone.

Claims (1)

[Scope of utility model registration request] 1. A raw material is fed to a screen having two outlets, impurities are discharged from one outlet through a predetermined amount control valve, and a selected fraction is selected from the other outlet, with the inlet pressure of the screen at that time. The pressure difference between the selected pressure and the outlet pressure of the selected portion or the output pressure of the selected portion is detected, and when this detected value reaches a set value, the control valve interposed on the output side of the selected portion is closed to close the screen ( In the instrumentation device around the screen for removing (clogging), a high pressure cleaning water source connected to the screen outlet side through a high pressure cleaning water valve for outflowing impurities, and an outflow through the predetermined amount control valve. A detector for detecting at least one of the flow rate of impurities and the screen outlet pressure of impurities, and a control means for opening both the high pressure washing water valve and the predetermined amount control valve when the detected value reaches a set value. That Wherein, the screen around instrumentation equipment.