Have a nice Halloween!
Elsmar Cove Forum Header Graphic The Elsmar Cove Wiki More Free Files The Elsmar Cove Forums Discussion Thread Index Post Attachments Listing Failure Modes Services and Solutions to Problems Elsmar cove Forums Main Page Elsmar Cove Home Page
NQA-USA
NQA-USA
Miner's MSA (Measurement Systems Analysis) Blog 
Go Back   The Elsmar Cove Forum > Manufacturing, Service, and Business Systems Processes > Reliability Analysis - Predictions, Testing and Standards
Forum Username

Search the Elsmar Cove
Search Elsmar
Monitor the Elsmar Forum
Follow Marc & Elsmar
Elsmar Cove Forum RSS Feed  Marc Smith's Google+ Page  Marc Smith's Linked In Page   Marc Smith's Elsmar Cove YouTube Page  Marc Smith's Facebook Page  Elsmar Cove Twitter Feed
Elsmar Cove Groups
Elsmar Cove Google+ Group  Elsmar Cove LinkedIn Group  Elsmar Cove Facebook Group
Donate and $ Contributor Forum Access
Courtesy Quick Links

Links that Elsmar Cove visitors will find useful in your quest for knowledge:

Howard's
International Quality Services
Marcelo Antunes'
SQR Consulting
Bob Doering's
Correct SPC - Precision Machining

NIST's Engineering Statistics Handbook
IRCA - International Register of Certified Auditors
SAE - Society of Automotive Engineers
Quality Digest Portal
IEST - Institute of Environmental Sciences and Technology
ASQ - American Society for Quality
Reply
 
Thread Tools Search this Thread Rate Thread Content Display Modes
  #1  
Old 8th November 2007, 10:28 AM
kctrinh kctrinh is offline
Inactive Registered Visitor

 
Registration Date: Nov 2007
Location: Texas
 
Posts: 14
Thanks Given to Others: 16
Thanked 0 Times in 0 Posts
Karma Power: 30
Karma: 10
kctrinh has less than 100 Karma points so far.
Let Me Help You MTBF (Mean Time Between Failures) Calculation

Please help!

I used this equation Fail Rate= # of failure/total running time.Therefore, MTBF is 1/fail rate.

The total running time= unit that does not fail running time + running time of the fail unit.

Question: Let say that one of my unit failed, we repair it then it will continue to run again. How do one input as a running time for this failed unit? Are you suppose to include only upto the time it failed or even after it is fixed and ran again?

Best regards,

Kenny

Last edited by kctrinh; 8th November 2007 at 10:55 AM.

Sponsored Links
  #2  
Old 8th November 2007, 11:06 AM
dna_leri's Avatar
dna_leri dna_leri is offline
Involuted - Posts

 
Registration Date: Sep 2007
Location: Ireland
 
Posts: 35
Thanks Given to Others: 10
Thanked 10 Times in 8 Posts
Karma Power: 32
Karma: 67
dna_leri has less than 100 Karma points so far.
Re: MTBF Calculation

Kenny,

In my opinion, you count the time before and after the repair.

If you only made one part and it first failed after 5 mins, you repaired it, and it fails again after 7 mins. At that point the MTBF (or average time between failures) is 6 mins.

See: http://www.vicr.com/documents/quality/Rel_MTBF.pdf
for a fuller explanation of the difference between MTBF and MTTF (Mean time to failure).

Last edited by dna_leri; 8th November 2007 at 11:07 AM. Reason: typo
Sponsored Links

  #3  
Old 8th November 2007, 11:11 AM
Jim Wynne's Avatar
Jim Wynne Jim Wynne is offline
Cross Forum Moderator

 
Registration Date: Jan 2005
Location: Southeast Wisconsin
 
Posts: 14,077
Thanks Given to Others: 2,051
Thanked 6,002 Times in 3,821 Posts
Blog Entries: 2
Karma Power: 1532
Karma: 42547
Jim Wynne is appreciated, and has over 1700 Karma points.Jim Wynne is appreciated, and has over 1700 Karma points.Jim Wynne is appreciated, and has over 1700 Karma points.Jim Wynne is appreciated, and has over 1700 Karma points.Jim Wynne is appreciated, and has over 1700 Karma points.Jim Wynne is appreciated, and has over 1700 Karma points.
Jim Wynne is appreciated, and has over 1700 Karma points.Jim Wynne is appreciated, and has over 1700 Karma points.Jim Wynne is appreciated, and has over 1700 Karma points.Jim Wynne is appreciated, and has over 1700 Karma points.Jim Wynne is appreciated, and has over 1700 Karma points.Jim Wynne is appreciated, and has over 1700 Karma points.
Re: MTBF Calculation

Quote:
In Reply to Parent Post by kctrinh View Post

Please help!

I used this equation Fail Rate= # of failure/total running time.Therefore, MTBF is 1/fail rate.

The total running time= unit that does not fail running time + running time of the fail unit.

Question: Let say that one of my unit failed, we repair it then it will continue to run again. How do one input as a running time for this failed unit? Are you suppose to include only upto the time it failed or even after it is fixed and ran again?

Best regards,

Kenny
Wikipedia reference-linkMean time between failures gives a good overview of MTBF and the calculations for it.

__________________

It is difficult to get a man to understand something, when his salary depends upon his not understanding it. --Upton Sinclair
  #4  
Old 20th November 2007, 11:31 AM
Randy Stewart's Avatar
Randy Stewart Randy Stewart is offline
VINI, VIDI, DORMIVI

 
Registration Date: Feb 2002
Location: Walled Lake, Michigan
 
Posts: 1,152
Thanks Given to Others: 20
Thanked 91 Times in 60 Posts
Karma Power: 170
Karma: 1541
Randy Stewart is appreciated, and has over 1500 Karma points.Randy Stewart is appreciated, and has over 1500 Karma points.Randy Stewart is appreciated, and has over 1500 Karma points.Randy Stewart is appreciated, and has over 1500 Karma points.Randy Stewart is appreciated, and has over 1500 Karma points.Randy Stewart is appreciated, and has over 1500 Karma points.Randy Stewart is appreciated, and has over 1500 Karma points.Randy Stewart is appreciated, and has over 1500 Karma points.Randy Stewart is appreciated, and has over 1500 Karma points.Randy Stewart is appreciated, and has over 1500 Karma points.Randy Stewart is appreciated, and has over 1500 Karma points.
Re: MTBF (Mean Time Between Failures) Calculation

The other part of your OEE is the Mean Time To Repair. When you decide to start the counter on either of them is something that should be understood by Maintenance, Production and yourself.
Normally, MTBF is from "start-up" to fail, MTTR may start at Maintenance notification and run until they return the machine to production (after prove out of the repair). I have seen some engineers track MTTR until the "Okay to Run" was issued from QA. I have also seen where scheduled downtime was not computed in MTBF because the machine wasn't running.
Decide what data is going to help. When to start or stop isn't the main issue. Getting data and being able to use it to make you better is.

__________________

"What this country needs is more unemployed politicians." Edward Langley
Thanks to Randy Stewart for your informative Post and/or Attachment!
  #5  
Old 8th January 2008, 03:46 AM
pinpin - 2009's Avatar
pinpin - 2009 pinpin - 2009 is offline
E-Mails Invalid or Rejected by Recipient System

 
Registration Date: Aug 2007
Location: NA
 
Posts: 169
Thanks Given to Others: 236
Thanked 17 Times in 14 Posts
Karma Power: 0
Karma: 36
pinpin - 2009 has less than 100 Karma points so far.
Re: MTBF (Mean Time Between Failures) Calculation

Quote:
In Reply to Parent Post by Randy Stewart View Post

The other part of your OEE is the Mean Time To Repair. When you decide to start the counter on either of them is something that should be understood by Maintenance, Production and yourself.
Normally, MTBF is from "start-up" to fail, MTTR may start at Maintenance notification and run until they return the machine to production (after prove out of the repair). I have seen some engineers track MTTR until the "Okay to Run" was issued from QA. I have also seen where scheduled downtime was not computed in MTBF because the machine wasn't running.
Decide what data is going to help. When to start or stop isn't the main issue. Getting data and being able to use it to make you better is.
Dear Randy,

TS clause 7.3.3.2 requires manufacturing process design output shall incluide "data for quality, reliability, maintainaility and measurability" and clause 8.2.3.1 also talks about "process capability, reliability, maintainability and availability". Can you give example of these metrics in relation to manufacturing process ?
Reply

Lower Navigation Bar
Go Back   The Elsmar Cove Forum > Manufacturing, Service, and Business Systems Processes > Reliability Analysis - Predictions, Testing and Standards

Do you find this discussion thread helpful and informational?


Bookmarks


Visitors Currently Viewing this Thread: 1 (0 Registered Visitors (Members) and 1 Unregistered Guest Visitors)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Forum Search
Display Modes Rate Thread Content
Rate Thread Content:

Forum Posting Settings
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Similar Discussion Threads
Discussion Thread Title Thread Starter Forum Replies Last Post or Poll Vote
Calculating MTBF (Mean Time Between Failures) for the whole Production Unit StressLess Reliability Analysis - Predictions, Testing and Standards 3 7th January 2012 05:19 AM
Mean Time Between Failures (MTBF) - SN 29500 Standards? Sherin MR Various Other Specifications, Standards, and related Requirements 5 30th October 2008 02:35 AM
Calculating MTBF (Mean Time Between Failures) of different Electronic Components. Sherin MR Reliability Analysis - Predictions, Testing and Standards 16 18th May 2008 07:43 AM
Graphing MTBF (Mean Time Between Failures) or Reliability Data of a System jag53 Reliability Analysis - Predictions, Testing and Standards 1 31st May 2006 06:52 AM
MTBF (Mean Time Between Failures) - Seeking help Mike Taylor Statistical Analysis Tools, Techniques and SPC 1 12th March 2003 05:23 PM



The time now is 05:52 PM. All times are GMT -4.
Your time zone can be changed in your UserCP --> Options.


   


Marc Timothy Smith - Elsmar.com
8466 LeSourdsville-West Chester Road, Olde West Chester, Ohio 45069-1929
513 341-6272
NOTE: This forum uses "cookies".