Elsmar Cove Forum Header Graphic The Elsmar Cove Wiki Sitemap 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
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

Wooden Line

How to calculate MTBF of a system based on subcomponents


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
Sponsor Links

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

Related Topic Tags
components, mtbf (mean time between failures), subcomponents and sub-assemblies, electronic components parts assemblies and products, mil-hdbk-217 - reliability prediction of electronic equipment
Reply
 
Thread Tools Search this Thread Rate Thread Content Display Modes
  Post Number #1  
Old 6th May 2008, 05:29 PM
JkelleyCDS

 
 
Total Posts: 51
Please Help! How to calculate MTBF of a system based on subcomponents

To provide better detail, our company has bid our product for a potential government contract. Their response has requested a MTBF of the system. I have the following questions?

1. If our product is a protoype, can a MTBF been performed?

2. Without official tests can MTBF be calculated?

3. If I have the MTBF data from our suppliers for subcomponents, what is the easiest way to calculate and combine these values to represent the system?

I can do the simple math of MTBF, but how can I compile these to reflect a system MTBF?

Thanks!

Sponsored Links
  Post Number #2  
Old 6th May 2008, 10:18 PM
Al Rosen's Avatar
Al Rosen

 
 
Total Posts: 3,546
Re: How to calculate MTBF of a system based on subcomponents

Quote:
In Reply to Parent Post by JkelleyCDS View Post

To provide better detail, our company has bid our product for a potential government contract. Their response has requested a MTBF of the system. I have the following questions?

1. If our product is a protoype, can a MTBF been performed?

2. Without official tests can MTBF be calculated?

3. If I have the MTBF data from our suppliers for subcomponents, what is the easiest way to calculate and combine these values to represent the system?

I can do the simple math of MTBF, but how can I compile these to reflect a system MTBF?

Thanks!
MTBF is a statistical prediction and actual performance may never match the prediction. Find yourself a copy of mil-hdbk-217 to do the system prediction.
Thanks to Al Rosen for your informative Post and/or Attachment!
Sponsored Links

  Post Number #3  
Old 16th February 2010, 08:04 PM
janedoe

 
 
Total Posts: 25
Re: How to calculate MTBF of a system based on subcomponents

Quote:
In Reply to Parent Post by JkelleyCDS View Post

To provide better detail, our company has bid our product for a potential government contract. Their response has requested a MTBF of the system. I have the following questions?

1. If our product is a protoype, can a MTBF been performed?

2. Without official tests can MTBF be calculated?

3. If I have the MTBF data from our suppliers for subcomponents, what is the easiest way to calculate and combine these values to represent the system?

I can do the simple math of MTBF, but how can I compile these to reflect a system MTBF?

Thanks!
The characteristic life parameter can not be added, from components, to determine system performance...but the reciprocal (hazard rate) can. So, add the hazard rates then determine the life parameter with this resulting number.
Thanks to janedoe for your informative Post and/or Attachment!
  Post Number #4  
Old 16th February 2010, 08:54 PM
Miner's Avatar
Miner

 
 
Total Posts: 3,597
Let Me Help You Re: How to calculate MTBF of a system based on subcomponents

Quote:
In Reply to Parent Post by janedoe View Post

The characteristic life parameter can not be added, from components, to determine system performance...but the reciprocal (hazard rate) can. So, add the hazard rates then determine the life parameter with this resulting number.
To clarify:
  • Lambda = 1 / MTBF
  • Lambda System = Lambda component 1 + Lambda component 2 + Lambda component n
  • MTBF System = 1 / Lambda System
Thanks to Miner for your informative Post and/or Attachment!
  Post Number #5  
Old 2nd March 2010, 05:32 AM
danwsc's Avatar
danwsc

 
 
Total Posts: 11
Re: How to calculate MTBF of a system based on subcomponents

1. Yes
2. Yes but they would only be Predictions (which may or may not satisfy your customer)
3. Yes but ...

Change MTBF (in hrs) to Failures In Time (number) by
Failures In Time = Time Period / MTBF
for MIL-217F, Time Period is 10^6 hrs.
for SR-332, Time Period is 10^9 hrs.

Add all FITs together,
Use same formula to calculate system level MTBF.

FITs (and therefore MTBFs) are also dependent on operating and environmental conditions. So you need more than just a single MTBF from your supplier.

Regards.

Last edited by danwsc; 2nd March 2010 at 05:51 AM.
Thank You to danwsc for your informative Post and/or Attachment!
  Post Number #6  
Old 5th March 2010, 08:01 AM
w_grunfeld

 
 
Total Posts: 231
Re: How to calculate MTBF of a system based on subcomponents

All of the previous answers you got are correct, however all assume that its an electronic system for which the exponential distribution is a good assumption. If however your system includes mechanical assemblies this may no longer be correct
Thank You to w_grunfeld for your informative Post and/or Attachment!
  Post Number #7  
Old 5th March 2010, 10:28 PM
Miner's Avatar
Miner

 
 
Total Posts: 3,597
Thumbs up Re: How to calculate MTBF of a system based on subcomponents

Quote:
In Reply to Parent Post by w_grunfeld View Post

All of the previous answers you got are correct, however all assume that its an electronic system for which the exponential distribution is a good assumption. If however your system includes mechanical assemblies this may no longer be correct
Excellent point that we all overlooked.
  Post Number #8  
Old 12th May 2010, 05:26 PM
vetes's Avatar
vetes

 
 
Total Posts: 4
Re: How to calculate MTBF of a system based on subcomponents

Depending on how the reliability of each component affects the others in the system as a whole may have an effect on the expected MTBF. In this case Reliability Block Diagrams (RBD) or Fault Tree Analysis may lead to a useful predictive answer to an overall MTBF. Pardon me as I cannot yet post links. Try searching for Reliability Block Diagram on Google or Wikipedia to get an idea of what this method provides.

There are also software packages that can be used for RBD simulation, the user can create one and assign failure and repair rates to the individual components and get an answer for Availability/MTBF of the system based on a simulated amount of time such as expected life or proposed deployment of a system. Relevant applications include:

ARINC Raptor
Relex OpSim
Reliasoft BlockSim
Thank You to vetes for your informative Post and/or Attachment!
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
ISO13485 application: can subcomponents or non-medical products be excluded? Eamon ISO 13485 and ISO 14969 - Medical Devices - Quality Management Systems 4 26th March 2008 12:17 AM
The difference between MTBF and MTBWSF and how to calculate MTBWSF of a system dsrelia Reliability Analysis - Predictions, Testing and Standards 2 31st January 2008 01:29 AM
MTBF to DPPM Calculation Based on the Unit's Typical Working Hours ravivangara Reliability Analysis - Predictions, Testing and Standards 9 7th September 2006 09:21 AM
Graphing MTBF (Mean Time Between Failures) or Reliability Data of a System jag53 Reliability Analysis - Predictions, Testing and Standards 1 31st May 2006 07:52 AM
20 Factors based QMS to TS 16949 Process based Quality Management System Link Xue ISO/TS 16949 - International Automotive Quality Systems Standard 1 10th March 2004 03:57 AM



The time now is 08:41 AM. 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".
no new posts