John,
In essence what you need to do is have a measurement frequency which in the
worst case will just give you time to plan and carry out remedial action in
a way that has a small impact on the business. (production or repair costs)
If you know how long it takes from a detectable condition to failure then
with the data on how long you need to prepare to make the repair without
impact on production, you can set the frequency.

Having said all that the equipment criticality related to its business
impact becomes the second factor. If the impact is very high you will do the
business risk calculation based on probability that the failure could occur
more quickly and /or the detection probability. If that is a concern then
you will test more frequently.
Typical frequencies I have seen vary from say 4/6 weeks for critical
equipment to six months where it is acceptable for a proportion not to be
detected. Averages tend to be in the 2/3 months.

If the equipment is super critical then you should consider installing on
line monitoring.

Regards Tony Ramshaw
Head of Maintenance
Kvaerner Facilities Management
* Tel +61 8 9429 5800
* Direct + 61 8 9429 5378
* Fax +61 8 9429 5241
* E-mail mailto:tony.ramshaw@...
Kvaerner, Level 20, 250 St George's Terrace, Perth, WA, 6000


> -----Original Message-----
> From: John Isaac [SMTP:John@...]
> Sent: Tuesday, 17 July 2001 0:57
> To: plantmaint@...
> Subject: [plantmaint] Condition Monitoring
>
> Dear group,
> A question for the experts.
> We are embarking on an improved system of CBM. Utilising Vibration
> monitoring, Oil analysis and Thermography.
> We are a multi product Food factory with 24/7 production. At the moment we
> do Vibration Monitoring every 2 months. Up until now it has proved quite
> successful at capturing potential problems.
> We do Thermography once a year.
> The question is.
> Is there a "Bench Mark" for the frequency of CBM? It has been suggested
> that we should do Vibration Checks every month and Thermography every 3
> months.
> Your thoughts and opinions are welcomed.

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