Analysis of common failures of paper machine

Analysis of common failures of paper machine

      The performance of the paper machine control system is the prerequisite for determining whether a paper machine can produce high efficiency and high quality. For a normal paper machine, in order to ensure its continuous high efficiency and high quality production, the transmission system The maintenance is particularly important.

Finding out the principle and then making analysis and judgment based on the phenomenon is the basis for correctly distinguishing the cause of the failure: one look, two tests, three tests.

      Common faults are:

1. Electrical failure

1) The inverter cannot be started, and the load is not stuck or blocked;

2) If the motor heats up abnormally, or even smokes, or the current is large but the motor does not rotate or the torque is small, this may be a line failure or an internal failure of the motor;

3) Operation failure, acceleration and deceleration does not work, or the reflection is abnormal when it is good and sometimes bad; the load distribution is unbalanced and can be adjusted but the degree of change is unstable. These may be related to faults such as line contact or communication interference.

2. Mechanical failure

1) Bearing heat;

2) The equipment's rotating sound is abnormal, with obvious periodic sound and mechanical cycles can be observed;

3) A common mechanical failure in the wire section is the slippage of the screen drive roller, which manifests itself in the ups and downs of load distribution, especially abnormal acceleration. For example, after the screen drive roller slips, the friction resistance suddenly drops and the load current drops, and the action of the load drop in the program is to accelerate, which causes the screen drive roller to continuously accelerate and finally speed.

In this case, it is simple to tighten the net, if not, you can only reduce the current limit of the roller or increase the wrap angle of the driving roller.

It is difficult to identify the source of the fault

For more obvious faults, you can directly solve the problem from the point of failure. In the actual operation of the paper machine, there are often some abnormal phenomena that are difficult to determine the source of the fault.

There are three common reasons for :

1. Unstable speed

1) The mechanical connection of the speed sensor is poor, and the connector should be checked;

2) The load of mechanical equipment changes greatly. Open the connector with the mechanical equipment and only run the motor to determine whether the interference comes from the mechanical equipment;

3) The speed regulator parameters are inappropriate, check and adjust the speed regulator parameters;

      4) When the paper is threaded in the wet part of the paper machine, the moisture content of the paper web is often too high. The weight of the sagging part of the paper web during threading will stretch the paper web, so it is always considered that the speed of the rear section is too slow. In fact, the faster the speed of the rear part is adjusted, the more severe the sagging phenomenon, and the dehydration of the corresponding part should be checked.

2. Sudden speed change

1) The mechanical connection of the speed sensor is not good. Check the connector.

2) The connection point of the circuit is in poor contact, and the wiring should be checked.

3) Mechanical equipment failure, such as bearing damage.

3. Large load fluctuations

1) The mechanical connection of the speed sensor is not good. Check the connector.

2) The load of the mechanical equipment fluctuates greatly. The coupling of the mechanical equipment should be opened and only the motor is operated to determine whether the interference comes from the mechanical equipment.

       Paper break inside the dryer

Obviously, this cannot be regarded as the cause of the vehicle speed. It must be related to the process parameters such as steam pressure, paper basis weight, and slurry composition. Even if there may be speed fluctuations, it is not the main thing. Therefore, we should assist the craftsman to find other reasons.

Paper break in the press section

Paper break in the press section is a difficult fault to judge. Generally speaking, it is necessary to analyze and judge according to the pressing form and the broken paper position. If it is a compound press, there may be errors in load distribution control related to electricity. The balance of force between the rollers is lost, and the paper is subjected to abnormal tension or pressure, resulting in a decrease in strength and an increase in broken ends. The method of judgment is mainly to observe whether the current indication is normal and the size of the swing. If a serious imbalance or abnormal swing is found on the ammeter, you should first perform empty vehicle debugging to find the cause of the imbalance and adjust the parameters to stabilize the system. A simpler way is to stop one or two motors if the load distribution allows, that is, let the squeezing part of the multi-point load stop the suspected point and observe whether it is stable. In order to find out the cause of the instability of a single roller first.

       The specific inspection parts are:

1) Whether each connection line has poor contact, especially related signal lines, such as feedback lines, communication lines, input and output lines between load distribution points, etc.;

2) Check the PLC program, whether the upper and lower limits of the set parameters are appropriate, whether the calculation program is wrong, whether the program execution is correct, etc.;

3) Check the parameters of the inverter, whether the torque compensation setting is reasonable, and whether the default parameters are consistent with the motor parameters;

4) For common failures of paper machine, analyze whether the motor is normal, whether there is abnormal sound or abnormal heat, etc. If all of the above are normal, it is preliminarily determined that the electrical is normal, and the reasons for the process and raw materials are observed.