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Dear Paul,
If a provision for continuous vibration monitoring is being given in the design, then the detectability should naturally decrease as the onset of failure can be detected well in advance. If there is no continuous monitoring facility available on the machine, then it depends on the type of application and the frequency of the measurements that are being taken. The failure rate for a heavily loaded equipment will naturally be different from that of an equipment that is lightly loaded. The failure mode would need to be explored for the specific type of application in that case. For getting a reduction in the risk, then a combination of daily checks and PM would normally be the case. 
Regards,
Srihari

------------------------------
Srihari R ramasubramanian.srihari@gmail.com
------------------------------

Original Message:
Sent: 11-01-2019 09:18 AM
From: Paul Bamforth
Subject: FMEA - RPN calculation

Hello all.

Firstly thank you for all your posts, there is some great material in there.

My question is a follows:-

During an FMEA, when performing the RPN rating rating for failure mode (for example bearing siezes due to fatigue), the residual rating for Detectability will be reduced using vibration analysis as the method of detection. However vibration analysis by itself does not reduce the likelihood (Occurence) even though you would expect the results of the vibration analysis to lead to early detection and therefore reduced likelihood of failure. Am I correct in saying that occurence is not affected by vibration analysis. Is there a rule of thumb here as to how this should be  interpreted?

Looking forward to hearing back.

Paul Bamforth, CMRP

Melbourne Australia

Thanks Srihari and Sundar for your replies.

Let's assume that the vibration monitoring is online (real time), and the P-F interval is 3 months for this particular failure mode.

The point at which the failure initiator is detected by vibration monitoring (P) and the functional failure (F) are 3 months apart. Now isn't the (residual) likelihood of the failure (function failure) occurring going to be reduced?

I just want to be clear in my mind if this is the correct interpretation. Although there are many other factors involved such as lead time, availability of spares etc...


regards Paul

------------------------------
Paul Bamforth
ALTONA
------------------------------

Original Message:
Sent: 11-01-2019 09:30 AM
From: Srihari R
Subject: FMEA - RPN calculation

Dear Paul,
If a provision for continuous vibration monitoring is being given in the design, then the detectability should naturally decrease as the onset of failure can be detected well in advance. If there is no continuous monitoring facility available on the machine, then it depends on the type of application and the frequency of the measurements that are being taken. The failure rate for a heavily loaded equipment will naturally be different from that of an equipment that is lightly loaded. The failure mode would need to be explored for the specific type of application in that case. For getting a reduction in the risk, then a combination of daily checks and PM would normally be the case.
Regards,
Srihari

------------------------------
Srihari R ramasubramanian.srihari@gmail.com

Original Message:
Sent: 11-01-2019 09:18 AM
From: Paul Bamforth
Subject: FMEA - RPN calculation

Hello all.

Firstly thank you for all your posts, there is some great material in there.

My question is a follows:-

During an FMEA, when performing the RPN rating rating for failure mode (for example bearing siezes due to fatigue), the residual rating for Detectability will be reduced using vibration analysis as the method of detection. However vibration analysis by itself does not reduce the likelihood (Occurence) even though you would expect the results of the vibration analysis to lead to early detection and therefore reduced likelihood of failure. Am I correct in saying that occurence is not affected by vibration analysis. Is there a rule of thumb here as to how this should be  interpreted?

Looking forward to hearing back.

Paul Bamforth, CMRP

Melbourne Australia

​Thanks Paul for initiating this discussion. Sharing my thoughts on your query...

In the example that you've provided, the RPN is calculated for Failure Mode of Bearing (cause) and is different from the Functional Failure (Failed State) of the Equipment. Once the bearing failure manifests, the failure mode can only be detected at some stage in the P-F Interval by Condition Monitoring. Depending on the stage at which it is detected, we get the time to plan and carry out the corrective maintenance to prevent the functional failure of the equipment (this action does not change the likelihood of the failure mode detected). 

Improved detectability helps to reduce the Risk (as ranked by RPN) as we assign a lower value for high detectability.
It'd be good to see some more responses on this. Thanks

------------------------------
Sundar Naranammalpuram P.
Navi Mumbai
Maharashtra
India
------------------------------

Original Message:
Sent: 11-03-2019 11:48 PM
From: Paul Bamforth
Subject: FMEA - RPN calculation

Thanks Srihari and Sundar for your replies.

Let's assume that the vibration monitoring is online (real time), and the P-F interval is 3 months for this particular failure mode.

The point at which the failure initiator is detected by vibration monitoring (P) and the functional failure (F) are 3 months apart. Now isn't the (residual) likelihood of the failure (function failure) occurring going to be reduced?

I just want to be clear in my mind if this is the correct interpretation. Although there are many other factors involved such as lead time, availability of spares etc...


regards Paul

------------------------------
Paul Bamforth
ALTONA

Original Message:
Sent: 11-01-2019 09:30 AM
From: Srihari R
Subject: FMEA - RPN calculation

Dear Paul,
If a provision for continuous vibration monitoring is being given in the design, then the detectability should naturally decrease as the onset of failure can be detected well in advance. If there is no continuous monitoring facility available on the machine, then it depends on the type of application and the frequency of the measurements that are being taken. The failure rate for a heavily loaded equipment will naturally be different from that of an equipment that is lightly loaded. The failure mode would need to be explored for the specific type of application in that case. For getting a reduction in the risk, then a combination of daily checks and PM would normally be the case.
Regards,
Srihari

------------------------------
Srihari R ramasubramanian.srihari@gmail.com

Original Message:
Sent: 11-01-2019 09:18 AM
From: Paul Bamforth
Subject: FMEA - RPN calculation

Hello all.

Firstly thank you for all your posts, there is some great material in there.

My question is a follows:-

During an FMEA, when performing the RPN rating rating for failure mode (for example bearing siezes due to fatigue), the residual rating for Detectability will be reduced using vibration analysis as the method of detection. However vibration analysis by itself does not reduce the likelihood (Occurence) even though you would expect the results of the vibration analysis to lead to early detection and therefore reduced likelihood of failure. Am I correct in saying that occurence is not affected by vibration analysis. Is there a rule of thumb here as to how this should be  interpreted?

Looking forward to hearing back.

Paul Bamforth, CMRP

Melbourne Australia

Hello Paul,

My thoughts on your question, taking the example of bearing, is as follows. Though the failure mode can be detected (unlike hidden failures) by Vibration Analysis, the likelihood/occurrence itself is not changed, as initiation of bearing failure has already happened (when detected by Vibration Analysis) and any timely detection only helps us to plan and execute the maintenance work (the window available for this depends on how early the failure is detected). The ease of Detection would depend on the available monitoring and analysis (type/effectiveness), periodicity of analysis. Depending on the overall Risk the Detectability could be further improved by a combination of Condition Monitoring Tasks (Continuous or Periodical Monitoring with its frequency, PM/Inspection Tasks).

It would be great to hear from others on this...

------------------------------
Sundar Naranammalpuram P.
Navi Mumbai
Maharashtra
India
------------------------------

Original Message:
Sent: 11-01-2019 09:18 AM
From: Paul Bamforth
Subject: FMEA - RPN calculation

Hello all.

Firstly thank you for all your posts, there is some great material in there.

My question is a follows:-

During an FMEA, when performing the RPN rating rating for failure mode (for example bearing siezes due to fatigue), the residual rating for Detectability will be reduced using vibration analysis as the method of detection. However vibration analysis by itself does not reduce the likelihood (Occurence) even though you would expect the results of the vibration analysis to lead to early detection and therefore reduced likelihood of failure. Am I correct in saying that occurence is not affected by vibration analysis. Is there a rule of thumb here as to how this should be  interpreted?

Looking forward to hearing back.

Paul Bamforth, CMRP

Melbourne Australia

Agree with Sundar, Bruce and others that vibration analysis does not prevent the failure mode but only gives early warning and thus prevent unscheduled downtime.​ 

Paul, you are correct in that vibration analysis can affect the detection probability but not the occurrence probability. 


------------------------------
Randy Riddell, CMRP, PSAP, CLS
Reliability Manager
Essity
Cherokee AL
------------------------------

Original Message:
Sent: 11-01-2019 11:14 AM
From: Sundar Naranammalpuram
Subject: FMEA - RPN calculation

Hello Paul,

My thoughts on your question, taking the example of bearing, is as follows. Though the failure mode can be detected (unlike hidden failures) by Vibration Analysis, the likelihood/occurrence itself is not changed, as initiation of bearing failure has already happened (when detected by Vibration Analysis) and any timely detection only helps us to plan and execute the maintenance work (the window available for this depends on how early the failure is detected). The ease of Detection would depend on the available monitoring and analysis (type/effectiveness), periodicity of analysis. Depending on the overall Risk the Detectability could be further improved by a combination of Condition Monitoring Tasks (Continuous or Periodical Monitoring with its frequency, PM/Inspection Tasks).

It would be great to hear from others on this...

------------------------------
Sundar Naranammalpuram P.
Navi Mumbai
Maharashtra
India

Original Message:
Sent: 11-01-2019 09:18 AM
From: Paul Bamforth
Subject: FMEA - RPN calculation

Hello all.

Firstly thank you for all your posts, there is some great material in there.

My question is a follows:-

During an FMEA, when performing the RPN rating rating for failure mode (for example bearing siezes due to fatigue), the residual rating for Detectability will be reduced using vibration analysis as the method of detection. However vibration analysis by itself does not reduce the likelihood (Occurence) even though you would expect the results of the vibration analysis to lead to early detection and therefore reduced likelihood of failure. Am I correct in saying that occurence is not affected by vibration analysis. Is there a rule of thumb here as to how this should be  interpreted?

Looking forward to hearing back.

Paul Bamforth, CMRP

Melbourne Australia

Original Message------

Hello all.

Firstly thank you for all your posts, there is some great material in there.

My question is a follows:-

During an FMEA, when performing the RPN rating rating for failure mode (for example bearing siezes due to fatigue), the residual rating for Detectability will be reduced using vibration analysis as the method of detection. However vibration analysis by itself does not reduce the likelihood (Occurence) even though you would expect the results of the vibration analysis to lead to early detection and therefore reduced likelihood of failure. Am I correct in saying that occurence is not affected by vibration analysis. Is there a rule of thumb here as to how this should be  interpreted?

Looking forward to hearing back.

Paul Bamforth, CMRP

Melbourne Australia

​Paul,
Bruce took the words out of my mouth. Vibration analysis will only notify you there is a issue. It may help you stave off a production stoppage, but it will not change your occurrence likelihood.

------------------------------
Scott Fortner
Reliability Engineer-Asset Management Specialist
Honda of America Manufacturing
Marysville OH
------------------------------

Original Message:
Sent: 11-04-2019 07:16 AM
From: Bruce Hawkins
Subject: FMEA - RPN calculation

Paul, unless anything is being done to reduce the incidence of fatigue in the bearing, then the frequency of occurrence for that failure mode will not change.

Bruce

 

Bruce Hawkins, CMRP, CAMA | Director | Operational Certainty Consulting

Emerson Automation Solutions | 1100 Louis Henna Blvd.| Round Rock | TX | 78681 | USA

M 843 743 5962  

Bruce.Hawkins@Emerson.com

 

The information in this electronic mail message, including any attachments, is intended solely for the use of the individual(s) to whom it is addressed and may contain information that is privileged, confidential, or otherwise exempt from disclosure.  Access to this Internet electronic mail message by anyone else is unauthorized. If you are not the intended recipient, any disclosure, copying, distribution, or action taken or omitted to be taken in reliance on it is prohibited and may be unlawful.  If you have received this communication in error, please destroy this communication and notify the sender immediately.  Thank you.

 

Original Message------

Hello all.

Firstly thank you for all your posts, there is some great material in there.

My question is a follows:-

During an FMEA, when performing the RPN rating rating for failure mode (for example bearing siezes due to fatigue), the residual rating for Detectability will be reduced using vibration analysis as the method of detection. However vibration analysis by itself does not reduce the likelihood (Occurence) even though you would expect the results of the vibration analysis to lead to early detection and therefore reduced likelihood of failure. Am I correct in saying that occurence is not affected by vibration analysis. Is there a rule of thumb here as to how this should be  interpreted?

Looking forward to hearing back.

Paul Bamforth, CMRP

Melbourne Australia

Paul,
When generating a RPN for all your assets. I recommend doing based on Severity, Occurrence, Detection. Severity should be set by impact of Safety, Delivery, Environmental, Cost, Morale, and Quality. Occurrences based on time till failure mode, hourly, daily, monthly, quarterly, semi-annually, annually, and etc. Detection be it based condition monitoring. Continuously, hourly, daily, weekly, monthly, quarterly, semi-annually, annually and etc.
In saying this, what ever your weights and measures be, use same scale for all assets. Even if rotating equipment, electrical panels, and etc.
After you have mitigated risk to lower your asset RPN, then do a RPN(B) a new FMEA. These assets will always change on RPN scale. So it is recommended to schedule a review of these or even when equipment is modified. If you are are using a CMMS like Maximo, the RPN will constantly change due to break downs, PMs, meter readings, and condition monitoring.

------------------------------
Shaun Dick
Equipment Reliability Engineer/ MES SME
Honda of America Manufacturing
Greensburg IN
------------------------------

Original Message:
Sent: 11-01-2019 09:18 AM
From: Paul Bamforth
Subject: FMEA - RPN calculation

Hello all.

Firstly thank you for all your posts, there is some great material in there.

My question is a follows:-

During an FMEA, when performing the RPN rating rating for failure mode (for example bearing siezes due to fatigue), the residual rating for Detectability will be reduced using vibration analysis as the method of detection. However vibration analysis by itself does not reduce the likelihood (Occurence) even though you would expect the results of the vibration analysis to lead to early detection and therefore reduced likelihood of failure. Am I correct in saying that occurence is not affected by vibration analysis. Is there a rule of thumb here as to how this should be  interpreted?

Looking forward to hearing back.

Paul Bamforth, CMRP

Melbourne Australia

Vibration monitoring that detects the bearing fault frequencies can reduce the consequence of the bearing failure by giving adequate warning so corrective action can be planned before the failure becomes "catastrophic".  Vibration monitoring that detects an adverse operating condition (for example, excessive misalignment) can reduce the "likelihood" of a failure by allowing correction of the problem before the bearing itself is damaged.

------------------------------
Edward Spyhalski PE/CMRP
Deployment Leader
Advansix
Chester VA
------------------------------

Original Message:
Sent: 11-04-2019 08:47 AM
From: Shaun Dick
Subject: FMEA - RPN calculation

Paul,
When generating a RPN for all your assets. I recommend doing based on Severity, Occurrence, Detection. Severity should be set by impact of Safety, Delivery, Environmental, Cost, Morale, and Quality. Occurrences based on time till failure mode, hourly, daily, monthly, quarterly, semi-annually, annually, and etc. Detection be it based condition monitoring. Continuously, hourly, daily, weekly, monthly, quarterly, semi-annually, annually and etc.
In saying this, what ever your weights and measures be, use same scale for all assets. Even if rotating equipment, electrical panels, and etc.
After you have mitigated risk to lower your asset RPN, then do a RPN(B) a new FMEA. These assets will always change on RPN scale. So it is recommended to schedule a review of these or even when equipment is modified. If you are are using a CMMS like Maximo, the RPN will constantly change due to break downs, PMs, meter readings, and condition monitoring.

------------------------------
Shaun Dick
Equipment Reliability Engineer/ MES SME
Honda of America Manufacturing
Greensburg IN

Original Message:
Sent: 11-01-2019 09:18 AM
From: Paul Bamforth
Subject: FMEA - RPN calculation

Hello all.

Firstly thank you for all your posts, there is some great material in there.

My question is a follows:-

During an FMEA, when performing the RPN rating rating for failure mode (for example bearing siezes due to fatigue), the residual rating for Detectability will be reduced using vibration analysis as the method of detection. However vibration analysis by itself does not reduce the likelihood (Occurence) even though you would expect the results of the vibration analysis to lead to early detection and therefore reduced likelihood of failure. Am I correct in saying that occurence is not affected by vibration analysis. Is there a rule of thumb here as to how this should be  interpreted?

Looking forward to hearing back.

Paul Bamforth, CMRP

Melbourne Australia

Original Message------

Vibration monitoring that detects the bearing fault frequencies can reduce the consequence of the bearing failure by giving adequate warning so corrective action can be planned before the failure becomes "catastrophic".  Vibration monitoring that detects an adverse operating condition (for example, excessive misalignment) can reduce the "likelihood" of a failure by allowing correction of the problem before the bearing itself is damaged.

------------------------------
Edward Spyhalski PE/CMRP
Deployment Leader
Advansix
Chester VA
------------------------------