Steam is used in abundance during the paper making process. Especially in the dryer sections, where heat is used to remove moisture from the sheet.

Steam is turned off during planned outages so millwrights can safely access the machine to perform regularly scheduled maintenance.

Once the maintenance has been performed, the steam is turned back on. If the steam is reintroduced to the system too quickly, rapid thermal expansion occurs.

Thermal expansion is natural during regular operation, but when it happens too fast, bearings can split like the example shown in Figure 1.

This defect was found in the dryer section of a paper mill, on the bottom pocket roll bearing.

SDT’s Senior Condition Monitoring Analyst, Gilles Lanthier first noticed impacting in the audio feedback during the measurement. The impacting was confirmed using the SDT340’s on-screen TWF & FFT, then later analyzed in UAS3.

By simply inputting the bearing make and model (SKF - 22312ECC), and then the rotational speed (669 RPM), fault frequency cursors can be lined up within the UAS3 software to indicate which type of bearing fault is occurring.

This failure was detected and then replaced shortly after. Visual inspection confirms an inner race split caused by improper steam up. Sometimes bearing splits like this are unavoidable, but to minimize the chances of them occurring, it’s important to reintroduce steam slowly to a paper machine after it’s been shut down.