Vibration is a well-known technics used to distinguish between operation and mechanical defects for decades.  For polymer pellets extrusion, with variable viscosities to meet customized receipts (some are very hard to push through, whereas, the others are much easier), not to mention feed rate yet, to tell the normal process change from any abnormal equipment health change is a definite challenge for condition monitoring in its kind.

In this case study, an extruder was changed out with new gear sets, output shaft was upgraded to high speed (from 226 to 265 RPM) to maximize capacity (Note : new motor and new coupling were replaced during the same T/A as well).

Both portable analyzer (for Operation Deflection Shape test) & online scanning system were deployed & cross check each other.   It is interesting to note:

(1) Vibration synchronously responds to process with wide variation range.
(2) With DCS data, to specify the major contributor (either viscosity or feed rate)
to high vibration is possible & predicative.
(3) Consequence by hard start up (vibration trending with associated DCS data)
without following proper SOP on long term reliability is also discussed.

Han-Chian Gee is a registered PE in Texas. He works as Chief Reliability Engineer for Formosa Plastic Corp. at Texas for more than 25 years. He is a ISO 16436.2 & ASNT SNT-TC-IA certified analyst. He ever published several articles on prestigious magazines during his past professional career. He always enjoys life with families, with his wonderful wife and two bright kids (both graduated from Ivy League School).