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Acceptance test

The customer purchased a new felt stretcher for the press section. In the supply contract, it was noted that no disturbing vibrations may occur in the stretcher within the paper machine’s production speed range of 800 – 1000 m/min. To ensure this, the acceptance test of the stretcher was carried out by CMT Solutions.
The acceptance test:
The acceptance test included the following vibration studies to determine the vibration properties and vibration behavior of the stretcher at the speed range of 800 – 1000 m/min.
 1. Speed trials
 2. Modal analysis
Results of the speed trial showed that the stretcher vibrated over the acceptable level in the axial direction at the speed range of 860 – 960 m/min.
Modal analysis of the stretcher revealed that the stretcher’s vibration in the axial direction was due to the lowest axial natural frequency of the stretcher (9.5 Hz), which, when excited, resonated at the rotating frequency of the stretcher roll (Ø 513mm).

Because the demands of the delivery contract were not fulfilled, the supplier changed the stretcher’s axial direction stiffness unconditionally. This eliminated the resonance of the stretcher at the speed range of 800 – 1000 m/min.