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Enterprise Asset Management (SAP EAM):MTTR, MTBR, Failure Rate, Availability andReliability

Posted by Jogeswara Rao Kavala Jul 21, 2014

The objective of this post is to bring clarity in understanding the two often confused terms viz, Availability and

Reliability, by explaining in simple perspective for the purpose of understanding by a common maintenance

man.

Let’s try to understand through this picture.

This is the time-line of a particular Equipment where U is Operating time (Uptime in Hrs), D is Repair time

(Downtime in Hrs). A total period of 6 weeks has been taken for analysis.

Two cases have been depicted here .

Case1:

No. of Failures = 6 (Denominator for MTTR, MTBR Calculations)

Total Uptime = U1 + U2 +U3 + U4 + U5 + U6 + U7. = Say 900 Hrs.

Total Downtime = D1 + D2 + D3 + D4 + D5 + D6. = Say 108 Hrs.

We know that MTTR (Mean Time to Repair in Hrs) = ( D1 + D2 + D3 + D4 + D5 + D6 ) / 6 = 18 .

Enterprise Asset Management (SAP EAM): MTTR, MTBR, Failure Rate, Availability and Reliability

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Similarly MTBR (Mean Time Between Repairs in Hrs) = ( U1 + U2 +U3 + U4 + U5 + U6 + U7 ) / 6 = 150 .

Now,

Equipment Availability (%) is: UpTime / Total Time = (900 / 1008) * 100 = 89.2

Another formula for Equipment Availability in practice is [MTBR / (MTTR + MTBR)] * 100 = (150 / 168 )*100

= 89.2

Case2:

No. of Failures = 2 (Denominator for MTTR, MTBR Calculations)

Suppose here too we get the same total values like:

Total Uptime = U1 + U2 +U3 = Say 900 Hrs

Total Downtime = D1 + D2 = Say 108 Hrs

MTTR (H) = ( D1 + D2) / 2 = 54 .

MTBR (H) = ( U1 + U2 + U3) / 2 = 450 .

Equipment Availability (%) is: Uptime / Total Time = (900 / 1008) * 100 = 89.2

Through other formula for Equipment Availability : [MTBR / (MTTR + MTBR)] * 100 = (450 / 504 )*100 =

89.2

We have seen the Availability, Now let’s see the Reliability. What is Reliability?

Reliability can be broadly defined as the probability that an Equipment will perform its intended

functions continuously for a specified duration.

How do we measure Reliability1. MTBR (H) value is a direct measure of Reliability. More the MTBR more is the Reliability.2. The Failure Rate (ʎ): In simple expression this can be calculated as No of Failures / Total Time

Now Let’s tabulate the results

Case Duration (H) Failures Downtime(H)

Availability(%)

MTBR (H) FailureRate (ʎ)

1 1008 6 108 89.2 150 0.00595

2 1008 2 108 89.2 450 0.00198

We have clearly seen that for the same amount of Equipment Availability, Equipment Reliability changes

drastically. So our Equipment in Case2 is more reliable.

Enterprise Asset Management (SAP EAM): MTTR, MTBR, Failure Rate, Availability and Reliability

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Here I want to share a screen-shot ( used in one of my previous documents ) . This has a realtime data of an

Equipment with performance relevant to present discussion. See this picture.

The Equipment03 in Year 1314 has Availability of the order 99.58% but lowest Reliability (MTBR) of 95.57

Hrs. Compare this with the 2nd line: Equipment02 has lowest Availability 99.39% but good Reliability (MTBR)

around 400 Hrs.

So, we understand that

A Highly Reliable Machine is Highly Available Machine too, but the converse need not be true.

Lastly, let’s try to understand the practical significance of the term Reliability. In processindustries if a chain of machines run without any problem for several hours then a stage comesfor the final equipment deliver the finished product. Often paper industry is quoted  as anexample. If a machine breaks down like case1, the finished paper will never come-out of thepaper machine.

Then, a question might arise, that 'Why Reliability can not be directly based on the No. of Failures?' The

answer could be 'Yes, it is ! But it is calculated as a function of No. of Failures per a Specified period , where

this period might differ from process to process and hence the acceptability of Reliability Index'.

Hope members will be benefited by this post.

Thank you & Regards

KJogeswaraRao

Enterprise Asset Management (SAP EAM): MTTR, MTBR, Failure Rate, Availability and Reliability

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Note:

The formulae used here in this post are in their simplest form for understanding purposes. They might not

exactly match with those mentioned in different contexts like OEE calculations etc.4280 Views Tags: quality, plm7.02, eam

Jogeswara Rao Kavala in response to Pavan Kocherlakota on page 4Aug 13, 2015 3:48 PM

Thanks Pavan

Pavan KocherlakotaAug 13, 2015 3:32 PM

Very Nice and clear explanation sir.

Regards

Pavan

Jogeswara Rao Kavala in response to Kaushik Ghosh on page 4Aug 8, 2015 10:00 AM

Thank you Mr. Kaushik

Regards

KJogeswaraRao

Kaushik GhoshAug 8, 2015 9:24 AM

Mr Rao, the document is well articulated and cogent, thanks for sharing

regards

Kaushik

Piyush GuptaJul 24, 2015 7:01 AM

Dear Sir.....your document made the concept really simple and understandable. I always look forward to your

documents. Thanks, Piyush.

Kunal Shukla in response to Jogeswara Rao Kavala on page 4Jul 22, 2015 10:28 AM

Thank you for providing the link I shall check all your sharings!!!

Regards,

Kunal

Jogeswara Rao Kavala in response to Kunal Shukla on page 5Jul 21, 2015 10:38 AM

Enterprise Asset Management (SAP EAM): MTTR, MTBR, Failure Rate, Availability and Reliability

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Thank you Kunal !

You can have my other contributions here: MyContent

Regards

KJogeswaraRao

Kunal ShuklaJul 21, 2015 9:41 AM

Good post Sir,

Kindly keep posting such knowledge.

thanks.

Kunal

Prasad VMay 7, 2015 11:48 AM

Short of words ....

Jogeswara Rao Kavala in response to Nagaraju Nandipati on page 5Apr 9, 2015 2:16 AM

Thank you Nagaraju

Nagaraju NandipatiApr 8, 2015 6:26 PM

Thank you Mr Jogesswara Rao. It is an awesome explanation of reliability and Equipment Availability.

Best regards,

N.Nagaraju

Jogeswara Rao Kavala in response to ganesh patil on page 5Apr 8, 2015 2:06 PM

My pleasure.ganesh,

And thank you

ganesh patilApr 8, 2015 11:49 AM

Sir,

it s very nice document to understand availability and reliability of machine.

Thanks sir for sharing such valuable documents,

Regards,

Ganesh

Enterprise Asset Management (SAP EAM): MTTR, MTBR, Failure Rate, Availability and Reliability

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Jogeswara Rao Kavala in response to swapnil rajane on page 6Dec 8, 2014 12:40 PM

Thank you swapnil ,

Very glad to know that the content is useful to you.

Regards

KJogeswaraRao

swapnil rajaneDec 8, 2014 12:35 PM

Dear Mr Jogeswara,

Keep it up for another one document,Really its very important.

Regards.

Swapnil

Jogeswara Rao Kavala in response to pramod balanagendra on page 6Dec 8, 2014 11:18 AM

Thank you pramod !

Glad you found it useful

Regards

KJogeswaraRao

pramod balanagendraDec 8, 2014 11:15 AM

Thank you very much sir for providing such a valuable document.

Its very helpful to all.

Jogeswara Rao Kavala in response to Govardhan Maile on page 6Dec 8, 2014 10:53 AM

Hello Govardhan,

I am glad this post helped you. Thank you for the compliments.

Regards

KJogeswaraRao

Govardhan MaileDec 8, 2014 9:16 AM

Thank you so much sir for your valuable explanation.... it helped me a lot

Jogeswara Rao Kavala in response to Christophe Sturzel on page 7

Enterprise Asset Management (SAP EAM): MTTR, MTBR, Failure Rate, Availability and Reliability

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Sep 11, 2014 2:45 PM

My pleasure Christophe Sturzeland thanks for appreciation.

Christophe SturzelSep 11, 2014 2:35 PM

Thank you for this document

J S S PRASAD in response to Jogeswara Rao Kavala on page 9Aug 23, 2014 9:24 AM

DS,

Greetings. Thanks for the info. I promose to educate my co-workmen about this matter.

Thansk again.

Jogeswara Rao Kavala in response to T C on page 7Aug 12, 2014 1:44 PM

Hello Taurai Chitsiga,

That is very kind of you.

Thank you for the great compliments and

Best Regards

KJogeswaraRao

T CAug 12, 2014 1:23 PM

Nice document, I agree with all other members , you have contributed immensely to SCN. WHEN CREDIT IS

DUE IT MUST BE GIVEN!!

Chintan Budhbhatti in response to Jogeswara Rao Kavala on page 7Aug 7, 2014 7:06 AM

Jogeswara,

You really deserve that sir.

Chin2.

Jogeswara Rao Kavala in response to Chintan Budhbhatti on page 7Aug 6, 2014 3:28 PM

Chintan,

I feel honored to receive such appreciation.

Thank you

Regards

Chintan Budhbhatti

Enterprise Asset Management (SAP EAM): MTTR, MTBR, Failure Rate, Availability and Reliability

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Aug 6, 2014 2:53 PM

Jogeswara,

Very nice document... very helpful and self explanatory.

Your document always encourage me for trying new areas in Plant Maintenance.

You are directly/ indirectly a role model to me.

Thank you so much.

Chin2.

Jogeswara Rao Kavala in response to sunil kumar boya on page 8Aug 1, 2014 1:35 PM

Thank you Sunil

KJogeswaraRao

sunil kumar boyaAug 1, 2014 1:08 PM

Very Nice Document to understand MTTR and MTBR.

Thank you very much sir such a nice document.

Thanks ,

Sunil Boya

Jogeswara Rao Kavala in response to Anand M on page 8Jul 25, 2014 9:34 AM

Anand,

That was a deveopment. No standard Tcode is there for Availability % in SAP. As the formula indicates it will

be easy to compute through Infoset Query or a simple ABAP program using table S070 (Inostructure).

Thank you for the review.

Jogeswara Rao K

Anand MJul 25, 2014 9:29 AM

Hi Jogeswara Rao,

Really good document explained complex thing in simple and easy to understand manner .Please give Tc code

where we can see availability percentage

Regards

Anand

Enterprise Asset Management (SAP EAM): MTTR, MTBR, Failure Rate, Availability and Reliability

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Jogeswara Rao Kavala in response to Muhammad Ali Asim on page 9Jul 25, 2014 8:12 AM

Thanks Muhammed Ali Asim, for your review.

Muhammad Ali AsimJul 25, 2014 8:08 AM

Dear Rao,

The document is really nice and simple.

Kind regards,

Muhammad

Jogeswara Rao Kavala in response to Jogeswara Rao Kavala on page 9Jul 25, 2014 4:25 AM

Jogeswara Rao Kavala in response to Patrick S. on page 9Jul 24, 2014 4:40 PM

I constantly feel your presence and resounding inspiring words towards such work, though you do not

communicate through alphabets. But when you find time to do so, I am really glad. Thank you very much for

your motivating words Patrick!

Bye

Jogeswara Rao K

Patrick S.Jul 24, 2014 4:29 PM

Dear Jogeswara,

thanks for putting so much effort in this oustanding business case description.

My compliments, you achieved again to outline a rather complex topic in a well structured and understandable

( ! ) way.

I'm sure many followers like me, can take some inspirations from your documents and try to adapt the shown

functions in their own company landscape.

Keep going!

Bye,

Patrick

Enterprise Asset Management (SAP EAM): MTTR, MTBR, Failure Rate, Availability and Reliability

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Jogeswara Rao Kavala in response to Thyagarajan Krishnamurthy on page 10Jul 22, 2014 7:05 AM

Dear Sir,

I am grateful to you, for posting the biggest compliment ever. Active participation started from June last year,

with sole idea in mind that 'Let me return some to SCN'. Initially encouraged by you (I do not forget) afterwards

by space itself and also the moderators.

Best Regards

Jogeswara Rao K

Thyagarajan KrishnamurthyJul 22, 2014 6:54 AM

hi

Clearly I am running out of words to appreciate your efforts in clarifying the doubts and the amount of time you

are spending for the same

From behalf of all our SDN members many thanks for the same and hope the same will continue.

Regards

Thyagarajan

Jogeswara Rao Kavala in response to hitendra saini on page 10Jul 22, 2014 6:45 AM

Thank you hitendra for your encouraging words

Jogeswara Rao Kavala in response to Kalyan Chakravarthi on page 10Jul 22, 2014 6:44 AM

Thank you Kalyan,

Always motivated by your reviews

hitendra sainiJul 22, 2014 6:29 AM

awesome document.... thank you so much sir

Kalyan ChakravarthiJul 22, 2014 6:24 AM

Another good document, thanks for sharing Sir...