On Mark6, in last 3 days observed strange behaviour of vibration readings in HMI where few vibrations readings observed frozen while few changing normally, and in 24hrs this behaviour changes among different vibration readings. At the moment on turbine bearing#1 X probe is varying normally while Y probe reading is frozen in last 24hrs. In toolbox view, R & S were observed frozen while T is varying.
There are no diagnostic alarms on system. Oil analysis also performed which indicated higher acid #.
GE issued PSIB (Product Service Information Bulletin) PSIB 20160913A-R1 back in 2016 for this same issue. At the time the PSIB was released GE was still in the discovery stage of identifying the issue. The PSIB refers to TIL-1623 about frozen analog inputs related to a bad batch of A/D converters which I have seen. Lastly the PSIB mentions Knowledgebase Article KB0022185 which gives instruction on adding logic to the MKVI application code that will detect the frozen vibration signals. I would urge you to find these documents or get in touch with your GE representative to have them provided if you do not have them.
Please let us know what you find.