Paper machine: common faults and how to detect them

The paper machine is made up of hundreds of rollers and cylinders, attached to a large structure and driven by motors and gearboxes. It also has a number of shafts, pulleys and belts that allow it to move as required.

Its vibrational signature is made up of the vibration of these various components, which can make the analysis and detection of possible faults more complex. For example, a roller may show high levels of vibration caused by another component malfunctioning, making it difficult to determine the cause. For this reason, the analyst needs to have data on the machine as a whole and know the main signs of faults in this asset.

In this case, in addition to the faults common to rotating equipment such as looseness, misalignment and unbalance, the paper machine can present some very specific problems.

Common faults in paper machines 

The specific faults of these assets are linked to their components and their operation. The most common problems are therefore related to the rollers, drives, felts and screens, the structure and the process itself.

In structural terms, paper machines can present problems such as resonance and inadequate rigidity. These faults can often stem from incorrect installation or even be the result of lubrication issues. 

As far as the process is concerned, the main defects are pressure fluctuations in the presses, variations in paper thickness and inadequate operating conditions such as variations in speed, pressure, etc. These problems can be the result of errors in the machine’s configuration, or they can be caused by other problems such as a fault in a component. Thus, when it comes to components, the main problems are:

Faults in rollers

Rollers are subject to the typical failures of rotating components, the most common of which are related to surface quality and alignment. The following faults stand out:

• Defective bearings  

• Geometric eccentricity (or flattening)

• Axle End Warping 

• Coating deterioration

• Ovalização / Ondulação da Superfície 

Faults in drives

These components tend to suffer mainly from electrical problems in the motors and power supply. But in addition to these, it is possible to find mechanical faults and defects in the transmission (gears, cardan shafts, etc.).

Faults in felts and screens

Faults in felts and screens can appear as edge defects, seams or variations in thickness. And although they may seem like simple faults, they are responsible for major productivity losses in pulp and paper production.

Fault detection in paper machines

In order to be alert to the appearance of different failure modes, it is important for the maintenance team to have continuous monitoring of the equipment’s condition. The use of vibration sensors attached to the components of interest is therefore a solution for ensuring plant productivity. Through the signals collected, it is possible to detect and identify the evolution of faults in order to prevent unnecessary downtime.

Learn more about the analyses: Spectral analysis: how to apply it to analyze vibration in industrial assets. 

Check out a real case of fault detection with Dynamox technology:

Dynamox identifies fault in paper machine dryer cylinder

Dynamox’s monitoring of a paper machine’s dryer cylinder with vibration and temperature sensors enabled the detection of a fault that could have caused an unplanned downtime if left undetected.

In the images below, it is possible to see the speed vibration spectrum showing the fault and its severity:

In addition, the autocorrelation graph of the waveform was analyzed, making it possible to follow the distribution of the defect over the bearing:

When the fault was detected, the asset was scheduled for maintenance at an appropriate time. Thus, with preventive replacement, the machine was down for 6 hours. In a corrective action, the time would have been 15 hours. The loss of 76.5 tons of paper was avoided. Monitoring continued and a reduction in vibration levels was observed, proving that action was taken at the right time.

Read the full case: Dynamox identifies failure in paper machine dryer cylinder