Locate problematic machine elements using Tapio MD Analysis

In paper, board, and other continuous production processes where the product is formed by rolling or pressing, every rotation of any mechanical element affecting the web — such as a roll, felt, wire, or pump — leaves a repeating pattern related to quality variation on the final product. These periodic patterns can manifest as variations in thickness, basis weight, ash content, density, porosity, gloss, brightness or other appearance

Tapio Machine Direction (MD) Analysis

Tapio MD Analysis is a powerful, high resolution tool designed to detect and analyze these periodic patterns. By measuring the product properties along the machine direction and applying spectral (frequency domain) analysis, Tapio MD Analysis can pinpoint repeating defects with high precision.

When roll diameters or rotational speeds are provided, our world-leading open-source software Tapio Analysis will automatically suggest which spectral peaks (wavelengths and frequencies of variations) most closely match the given machine elements. This feature makes it much faster and more intuitive for operators and engineers to locate the mechanical sources behind recurring defects.

Diagram showing a web passing through rolls with quality variations and geometry errors, illustrating how machine direction frequency stays at 1 Hz even as velocity and wavelength change.

Figure: “One Hertz in Paper”. The diagram illustrates the relationship between machine speed, defect wavelength, and temporal frequency. As the web speed changes — due to acceleration or stretching along the production line — the wavelength of periodic defects increases proportionally. However, the temporal frequency — the rate at which defects pass a fixed point — remains constant. Understanding this behavior is essential for correctly linking detected patterns to machine elements.

 
Frequency spectrum chart of a machine direction sample, showing a distinct peak at 1.42 1/m, with annotated red dashed lines marking the roll frequency and its harmonics.
Screenshot of Tapio Analysis software showing machine direction (MD) paper machine roll frequencies, wavelengths, and grouped roll types.

Figure: Machine element matching in Tapio Analysis

 When given roll diameters or rotational speeds, Tapio Analysis can automatically suggest which spectral peaks (rotating frequencies and wavelengths) have the closest match to the provided machine elements. This speeds up troubleshooting and enables targeted maintenance actions by pin-pointing the rolls which most contribute to the quality.

 
 

Pinpointing the problem using Tapio Analysis

Beyond just identifying the frequency, deeper analysis is possible by using the channel-specific information available from Tapio Measurements. Tapio Analyzers measure the same point in paper with multiple sensors with small apertures and high resolution.

 

Available sensors include:

  • Basis weight
  • Caliper
  • Ash content (absolute and relative)
  • Gloss (both sides)
  • Transmission
  • Remission (optical brightness)
  • Porosity

Additional calculated channels based on combining the data from multiple sensors, such as density, bulk, relative ash.

By analyzing in which measured property (channel) the fault appears, and studying correlations between channels, it becomes possible to narrow down the likely source of the problem, using reasoning that depends on knowledge of the specific production line:

 

  • Basis weight defects typically originate from the wet end of the paper machine, where the basis weight is formed.
  • If ash content is not evenly distributed relative to basis weight (poor correlation), the source may lie in the coating stations.
  • Gloss variations that occur at the same frequencies as thickness variations usually indicate problems originating from the calendering sections.

By combining frequency and correlation analysis with reasoning based on the defect type and measurement channel, maintenance and troubleshooting efforts can be much more targeted and effective.

 
 

Key Benefits of Tapio MD Analysis

  • Fast identification of periodic defects.
  • Direct display of fault frequency (Hz) for easy matching to machine components.
  • Automatic suggestions for likely problematic machine elements based on size and speed data.
  • Improved maintenance efficiency and reduced downtime

 

 
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Phone: +358 40 089 1413 

Email: info@tapiotechnologies.com

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