JPS5924240B2 - How to change the paper machine and change the frame - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a paper changing and frame changing method in a paper machine.

In the papermaking process, the basis weight and moisture content of paper are important factors that determine the quality of paper, so the papermaking machine is controlled so that each of these satisfies predetermined standards.

When changing the paper standard, a paper change is performed.

The papermaking change is performed by continuously changing the basis weight and papermaking speed to new values without stopping the papermaking machine.

Along with paper changing, the take-up reel is replaced, that is, the frame is replaced.

Due to frame change, non-standard paper (waste paper) during the transition period
is assumed to be the lower winding of the new IJ/l.

This is to facilitate the work of dropping the waste paper portion into the break pit later.

The amount of paper waste depends on the time required for paper change, the time for the moisture content to stabilize after paper change, and the presence or absence of paper breaks. The paper machine is controlled in consideration of shortening the rate stabilization time and preventing paper breakage.

A paper machine and its control system are configured as shown in FIG. 1, for example.

That is, the raw material discharged from the head box HB is squeezed by passing through the wire part WP, dried by passing through the pre-dryer fDR1 and the after-dryer DR2, and wound onto the reel RL.

White water from the water pumping of the WP is received by the pit PT and is returned to the head box HB by the fan pump PMP.

The basis weight and moisture content are each measured by a measuring device BM immediately before the reel RLL, and are measured by a calculation controller CMT.
is input.

The calculation control device CMT calculates the seed flow rate operation amount and the steam pressure set value of each dryer based on the deviation between the measured value and the set value, and applies them to the seed port valve VLV and the steam pressure controller of each dryer. pRct and PRC2 to control the basis weight and moisture content to match their respective set values.

An operator controller OPC is connected to the calculation control device CMT, and through this, the operator and the calculation control device CMTO are connected.
This is due to the fact that information can now be exchanged between the two countries.

When performing a paper change, the calculation control unit CMT controls the head
Change the flow rate and machine speed of the seeds injected into the box HB, and the steam pressure settings.

Due to the distance between the seed opening valve VLV and the head box HBO, there is a dead time before the operation of the seed opening valve VLV affects the raw material concentration in the head box HB.

Therefore, in order to shorten the time required for paper changeover, the seed opening valve is operated prior to changing the papermaking speed by the amount of dead time.

In addition, the dryer system has a large delay time constant, and the steam pressure system that operates it is structured so that it cannot instantly generate a large output. In response to expected dryer load fluctuations, steam pressure control is performed prior to machine speed changes.

In that case, the lead time differs depending on the magnitude of load fluctuation.

It is economical to change the paper size and frame from the point where the paper of the specified length has just finished, as this will prevent unnecessary sections from occurring.

However, if there is a preceding operation whose time varies depending on the magnitude of the load fluctuation as described above, it is difficult to issue a start signal so that paper reshuffling and reframing can be performed at just the right point.

Conventionally, this has relied on the skill of the operator, but since it is done with safety in mind so that the specified length is not missed, there is a tendency for parts to be erected, and therefore it is very economical.

An object of the present invention is to provide a method that allows paper reshuffling and frame reshuffling from the point where a specified length of paper has just been completed, no matter how the preceding operation time changes.

In the present invention, the contents are discharged from a head box containing a mixture of seeds supplied through a seed opening valve and white water returned from a pit according to the machine speed, and the water is squeezed using a wire bart. This method uses a computer to control a paper machine in which white water is dropped into a pit, the remaining water is dried in a dryer, and then wound onto a reel, and paper and frame changes are performed.
In accordance with the goal of the paper change, find a paper speed change pattern that changes the paper speed from the speed before the paper change to the target speed, and a basis weight change pattern that changes the basis weight from the paper basis weight before the paper change to the target basis weight. , a production amount change pattern is determined based on these two patterns, and based on the basis weight change pattern,
The seed flow rate operation pattern including the lead time corresponding to the dead time LF according to the distance from the seed opening valve to the head box is determined, and the dryer load is determined from the machine speed change pattern, basis weight change pattern, and production amount change pattern. Predict the fluctuation and calculate the corresponding lead time LS based on this predicted load fluctuation.
Based on the distance between the head box and the reel and the speed-per-second change pattern, the dead time LR from the head box to the reel during the paper changing operation is determined, and the preceding time LF is determined. Convert the sum of the larger of LS and LS to the dead time LR to the length of the paper, and calculate the difference between the specified length of the paper to be wound on the reel and the current length of the paper wound on the reel. The above purpose was achieved by a method of reshaping and reframing, in which reshaping is started when this difference matches the above-mentioned conversion value, and the reel is reframed when the above difference becomes zero. be.

The present invention will be explained below with reference to the drawings.

FIG. 2 is an explanatory diagram of the operation when paper changing is performed according to the present invention.

Prior to the paper change, the operator sets new target values for speed per second and basis weight in the calculation control device CMT.

Then, the calculation control unit CMT creates a change pattern (solid lines a and b in Figure 2) for shifting the current speed per second and basis weight to the new target values, and an accompanying change pattern in production volume (Figure 2). Find C).

Then, the dryer flow rate operation pattern (Fig. 2 d) that causes the basis weight to change according to the change pattern is determined, and the change in dryer load (Fig. 2 e) is determined from the patterns of machine speed, basis weight, and production amount.
) and create a vapor pressure operation pattern (second
Find figure f).

The starting point of the seed flow rate operation pattern is preceded by the machine speed change starting point (to time point) by the dead time LF corresponding to the distance from the seed opening valve VLV to the head box HB (t-1
time).

The starting point of the steam pressure operation pattern precedes the machine speed change starting point (to time point) according to the dryer load variation pattern (t-2 time point).

The lead time Ls changes depending on the magnitude of load fluctuation.

The calculation control device CMT also calculates, based on the distance from the head box HB to the reel RL and the machine speed pattern,
Determine the dead time LR until the point of change in basis weight due to paper changing reaches the reel RL.

Leading time LF or Ls, whichever is larger, and dead time LR
The sum LT is converted to the paper length and displayed on the operator controller OPS.

This display value is calculated from the time when the paper whose basis weight has actually changed reaches the reel RL after paper change is started.
Represents the length of paper wound on.

The operator controller OPS also displays the specified length of the paper, the current length wound on the reel RL, and the difference between these specified lengths and the current length.

The displayed value of this difference becomes smaller every moment as the winding progresses.

When the displayed value of this difference matches the converted displayed value,
A paper change start signal is issued by an operator operation or automatically.

Accordingly, in this example, the steam pressure operation is first started, after the Ls-LP time, the seed flow rate operation is started, and further after the LP time, changes in the papermaking speed and basis weight are started.

In other words, the basis weight begins to change during the Ls waiting time after starting the papermaking change.

This change in basis weight reaches reel RL1 after LR time.

During this time, a length of paper equal to the converted value is wound on the reel RL, and the winding amount of the reel RL reaches the specified length.

At this time, the difference display value becomes zero, and the frame is changed by an operator's operation or automatically.

As a result, paper changes and frame changes occur from the point where the specified length of paper has just finished.

Note that the conversion value specifying the start time of sheet change may be expressed in time without being converted into distance.

In that case, the displayed value of the difference needs to be converted into time and displayed.

As described above, according to the present invention, no matter how the preceding operation time changes, paper reshuffling and frame reshuffling are performed from the point at which a specified length of paper has just been completed.

Therefore, there is less waste paper and it is economical.

[Brief explanation of drawings]

FIG. 1 is a conceptual block diagram of a paper machine and its control system, and FIG. 2 is an explanatory diagram of the operation of paper changing according to the present invention. SB... Seed box, VLV... Seed mouth valve, H
B...Head box, WP...Wire part, PT...Pit, PMP...
...Fan pump, DRl. DR2...Dryer, BM...Basic weight/
Moisture percentage needle, RL...Reel, CMT...
・Calculation control device, PRCI, PRC2...
・Steam pressure controller.

Claims (1)

[Claims] 1 The head box containing the mixture of seeds supplied through the seed opening valve and white water returned from the pit discharges its contents according to the speed of the second, and the wire part squeezes the water to drain the white water into the pit. A paper machine that uses a dryer to dry the remaining paper before winding it onto a reel is controlled by a computer to change the paper size and frame. Find a paper speed change pattern that changes the paper speed from the previous speed to the target speed, and a basis weight change pattern that changes the paper weight from the paper weight before paper change to the target basis weight, and change the production amount based on these two patterns. Based on the basis weight change pattern, a seed flow rate operation pattern including a lead time corresponding to the dead time LF depending on the distance from the seed mouth valve to the head box is determined, and based on the papermaking speed change pattern and the basis weight change pattern, The load fluctuation of the dryer is predicted from the volume change pattern and the production volume change pattern, and based on this predicted load fluctuation, the steam pressure operation pattern of the dryer including the corresponding lead time LS is determined. Determine the dead time LR from the head box to the reel during the paper changing operation based on the distance and the paper machine speed change pattern, and calculate the preceding time LF and L.
The sum of the larger of S and the dead time LR is converted into the length of paper, and the specified length of the paper to be wound on the reel and the current length of the paper wound on the IJ-reel are calculated. Find the difference,
A sheet changing and frame changing method that starts sheet changing when this difference matches the conversion value, and changes the reel frame when the above difference becomes zero.