SU441376A1 - A device for regulating the moisture of the paper web - Google Patents

Description

one

This invention relates to the field of controlling the moisture of a paper web on a paper machine.

A device for controlling the moisture of a paper web on papermaking machines is known, which includes a humidity sensor, a differentiation unit, the outputs of which are connected through an adder to the input of a humidity controller connected to the input of a vapor pressure regulator in the drying group of cylinders, and a vacuum gauge in a gauge shaft.

Such a device does not provide a sufficient reduction in the dynamic error of the process of controlling the moisture of the web from introducing pre-emptive, its correction of its signal from the vacuum in the gauch-shaft, and thereby the regulation accuracy.

The purpose of the invention is to improve the accuracy of pei-lining.

To achieve this goal, the device is equipped with a paper sheet air permeability sensor, a constant multiplication unit and a unit for calculating the difference between two signals, the paper sheet air permeability sensor output being switched on a constant factor multiplier input, the output of which, together with the vacuum sensor output, is the shaft is connected to a difference calculator

two signals connected to the input of the differentiation unit.

The drawing shows a schematic diagram of the described device. The device contains a humidity sensor 1 located in the dryer part of the machine, a vacuum sensor 2 (absolute pressure) in the camshaft chamber (not shown), a sensor 3 for air permeability of the dried

paper web, multiplying unit 4 by a constant coefficient, unit for calculating the difference of two signals (adder) 5, differentiation unit 6, adder 7, main humidity controller 8, generating, charging the controller 9, steam pressure in the cylinder group (in the drawing not shown), to the input of which the vapor pressure sensor 10 is connected. The output of sensor 3 is connected to the input of multiplier 4, the output of which, together with the output

The vacuum sensor 2 is connected to the adder 5. The output of the latter through the differentiation unit 6 and the output of the humidity sensor are connected to the adder 7, the output of which, in turn, is connected to the input of the regulator 8. The output 11 of the vapor pressure regulator 9 is connected

with actuator (in drawing

not shown) installed on the supply line

pair into a cylinder group.

The device works as follows.

The signal from absolute pressure sensor 2 in a crouch shaft, which is functionally dependent on the humidity of the moving paper web, as well as on parameters not related to moisture (billing factors) - weight 1 m2 of absolutely dry fiber, grinding mass, composition, etc. , arrives at the adder 5. At the same time, the input from the adder 5 through the multiplication unit 4 receives a signal from the air permeability sensor 3 of the dried web, which is functionally not dependent on humidity, but proportional to the above-mentioned displacement factors.

Since the signal from gauge shaft absolute pressure sensor 2 is in fact an indicator of the air permeability of the wet web, the signal at the output of the adder 5, equal to the difference between the air permeability of the wet web and the dried one, is proportional only to the absolute moisture content of the web.

The signal from the adder 5 is fed to the differentiation unit 6 and further, proportional to the rate of change of the moisture content of the web above the gauch shaft, as a forward correction signal, to the adder, where it is summed with the signal from the humidity sensor 1 of the dried web, and the result, in turn, is received to the input of the main controller 8 humidity. The latter acts on setting the steam pressure regulator 9, the output 11 of which, depending on the signal from the sensor 10, controls the steam supply to the cylinder group, thereby changing the drying rate.

A change in the moisture content of the web on the gauch-shaft causes a change in the signal from the absolute pressure sensor 2 in its chamber and acts as a useful correction signal on the task of the controller 8 with a advance equal to the time the canvas travels from the gauge shaft to the location of the humidity sensor 1. This change in humidity is not perceived by sensor 3.

air permeability during the passage of the canvas place its installation at the end of the essential part.

When a false correction signal appears from sensor 2, caused by a change in the moving factors, without changing the wetness of the web, its preemptive action lasts only during the period the canvas travels from the gauch shaft to the air permeability sensor 3, and then the signal from sensor 3 compensates for impact on the drying mode caused by the signal “false correction. In the absence of compensation from sensor 3, the “false correction” signal would continue to act on the vapor pressure regulator 9 for a period equal to the passage time of the main control channel signal: the vapor pressure in the group is the humidity of dried paper, which is significantly longer than the distance from the canvas Gauch-shaft to roll.

Subject invention

A device for controlling the moisture of a paper web, including a moisture sensor, a differentiation unit, the outputs of which through an adder are connected to the input of a humidity controller connected to the input

a vapor pressure regulator in the drying group of cylinders, and a vacuum gauge in the camshaft, characterized in that, in order to increase the control accuracy, it is equipped with a paper air permeability sensor

a cloth, a constant multiplication unit and a unit for calculating the difference of two signals, the output of the air permeability sensor of the paper web being connected to the input of the multiplying unit on a constant

the coefficient, the output of which, together with the output of the vacuum sensor in the caster shaft, is connected to a unit for calculating the difference of two signals connected to the input of the differentiation unit.

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