Paper machine common failure analysis

Analysis of common faults in paper machines

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

From the principle to understand and then according to the phenomenon to make analysis and judgment, is the basis for correctly distinguishing the cause of the failure: one look, two tests, three tests.

Common failures are:

1. Electrical failure

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

2) The motor heats abnormally, or even smokes, or the current is large and the motor does not rotate or the torque is small, which may be a line failure or an internal failure of the motor;

3) Operation failure, acceleration and deceleration do not move, or reflect abnormal when it is good and bad; The load distribution is unbalanced, can be adjusted but the degree of change is unstable, etc. These may be related to failures such as line contact or communication interference.

2. Mechanical failure

1) Bearing heating;

2) The equipment rotation sound is abnormal, obvious periodic sound and can observe the mechanical cycle;

3) The common mechanical failure of the mesh part is the slippage of the net driving roller, which is manifested as the load distribution is good and bad, especially abnormal acceleration. For example, the friction resistance of the net drive roller suddenly decreases after slipping, the load current decreases, and the programmed action of load reduction is acceleration, thus causing the net drive roller to continuously accelerate Z and then fly.

In this case, the net can be tensioned simply, if not, it can only reduce the current limit of the roller or increase the wrapping angle of the net driving roller.

It is difficult to confirm the failure of the source of the failure

For obvious faults, it can be solved directly from the point of failure, and there are often some abnormal phenomena that are difficult to determine the source of the fault in the actual operation of the paper machine.

There are three common reasons:

1. Unstable speed

1) The speed sensor has poor mechanical connection, and the coupling should be checked;

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

3) The speed regulator parameters are not suitable, check and adjust the speed regulator parameters;

4) In the case of the wet part of the paper machine driving the paper thread, there will often be a high moisture content of the paper web, and the weight of the sagging part of the paper web will lengthen the paper web when the paper is threaded, so it is always thought that the speed of the rear branch is too slow, in fact, the faster the speed of the rear division, the more serious the phenomenon of sagging, and the dehydration of the corresponding part should be checked.

2. Sudden changes in speed

1) The mechanical connection of the speed sensor is poor, the coupling should be checked.

2) The line connection point 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 poor, the coupling should be checked.

2) The load fluctuation of mechanical equipment is large, and the coupling of mechanical equipment should be turned on to run only the motor to judge whether the interference comes from mechanical equipment.

Broken paper inside the dryer

This obviously cannot be regarded as the cause of vehicle speed, but must be related to process parameters such as steam pressure, paper quantification, and slurry composition. Even though there may be speed fluctuations, it is not the main thing. Therefore, the process personnel should be assisted to find other causes.

Broken paper in the press section

Paper breakage in the press section is a relatively difficult fault to judge. Generally speaking, it is first necessary to analyze and judge according to the pressing form and the broken part. If it is a compound press, there may be errors in load distribution control related to electrical, and the balance of force between the rollers is lost, so that the paper page is subjected to abnormal tension or pressure, resulting in a decrease in strength and an increase in breakage. 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 from the ammeter, the empty vehicle should be debugged first 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 pressing part of the multi-point load stop the suspected problem point and observe whether it is stable. In order to find out the cause of the instability of the individual rolls first.

The specific inspection parts are:

1) Whether the connection lines have poor contact, especially the associated signal lines, such as feedback lines, communication lines, input and output lines between load distribution points, etc.;

2) PLC program inspection, whether the upper and lower limits of the parameters are appropriate, whether there are errors in the calculation program, whether the program execution is correct, etc.;

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

4) Common faults of the paper machine analysis whether the motor is normal, whether there is abnormal sound and abnormal heat. If the above is normal, preliminarily conclude that the electrical is normal, and observe the reasons for the process and raw materials.