# Mean Time Between Failures (MTBF) Basics - Thoughts on Product Life Cycles

A

#### Armtzcor

I need your help. Our company (within the field of manufacturing of electronic components for pc-boards, power supplies) have to implement Mean Time Between Failures (MTBF) but don't know anything about about how to start.

Do somebody there outside knows where can we find information about this or some formula, standard procedure (MIL, ANSI, etc...), method, etc...?

Regards,
Arnulfo

B

#### Bill Ryan - 2007

Arnulfo,

"Reliability Statistics" by Robert Dovich (considered one of the "gurus" in the reliability field) is available from Quality Press (for \$20-25 - US). This book contains just about every formula you may ever use with some explanation for each application (I recommend this book in any company's library involved in reliability testing!)

Another good reference (IMO) is "Reliability, Maintainability, Availability Assessment" by Michael Locks (from \$61 to \$75 - US).

Bill

R

#### Randy Stewart

Here's a tip

MTBF can be determined by dividing the number of failures occuring over a given period into the operating time during that period. It is the average time that the equipment will operate without failure. Similarly, maintainability is expressed using Mean Time to Repair (MTTR). Using MTBF and MTTR and estimates of downtime costs, the Cost of Corrective Maintenance can be determined over the life of the equipment. Lets say Plant ABC estimates downtime costs of \$300.00 per hour in machining operations and as high as \$3,000 per hour in assembly. These costs account for the cost of maintenance manpower, the cost of lost productivity and increased cost due to additional overtime required. These \$ figures can then be used in your MTTR calculations.

By using these figures along with the ones listed below you will be able to determine the "Life Cycle Cost" of any equipment. This can be very useful in justifying more cost for a new piece of equipment.

Life Cycle Cost Relationships

Life Cycle Cost (LCC) = Acquisition Cost + Ownership Cost

Acquisition Cost = F & T Cost

Ownership Cost = Cost of Operations + Cost of Maintenance

Cost of Operations = Cost of Manpower + Cost of Expendables

Cost of Manpower = Operator Cost x Number of Operators

Cost of Expendables = Cost of Electrical Power + Cost of Tooling + Cost of Lubricants, etc.

Cost of Maintenance = Cost of Preventive Maintenance + Cost of Corrective Maintenance

Preventive Maintenance Cost = Maintenance Labor Cost + Cost of Materials + Cost of Logistics Support System + Cost of Lost Productivity

Corrective Maintenance Cost = Maintenance Labor Cost + Cost of Failed Item + Cost of Lost Productivity + Cost of Logistics Support System

Maintenance Labor Cost = Cost of Maintenance x Number of Maintenance Actions

Hope this helps.
:thedeal:

A

MTBF

Hey Guys,

Best Regards,
Arnulfo

#### Manoj Mathur

##### Quite Involved in Discussions
I was just thinking to start a new discussion and just through search I found this article on MTBF.
My Question to you is "IS MTBF ALWAYS CHANGING PHENONMENON?" In the year 2001 I had Three Brake Downs . I have calculated MTBF for that In the Year 2002 this M/C was so bad and troubled 8 Times. My MTBF was reduced. While In this Year It has never gone Down?
Can you please tell me What Is MTBF of this M/C?

Manoj Mathur

#### Marc

##### Hunkered Down for the Duration
Staff member
MTBF is an estimate or prediction. A component rated at 10,000 hours MTBF can fail 1 minute after it is first turned on. OR it could last for 30,000 hours.

The attached is from a paper from 1988 (scanned from my copy - can't find the disk file off hand) and presented to US Army TACOM in Warren, MI. that year. It's a typical life cycle 'bathhtub' curve. When you do a MTBF calculation, it gives you a location on the curve.

The original for this was derived from data from various aerospace (jet and turboprop) LRUs and found to be similar no matter what the LRU. It also correlated with manpack radios we made for field use and the early field computers.

The important part is to understand this is an estimate or prediction.

Just wondering - anyone have any current thoughts?

#### Attachments

• 3.2 KB Views: 629

#### Al Rosen

##### Holed-up in a Hotel in South Florida
Staff member
Super Moderator
Marc said:
MTBF is an estimate or prediction. A component rated at 10,000 hours MTBF can fail 1 minute after it is first turned on. OR it could last for 30,000 hours.

The attached is from a paper from 1988 (scanned from my copy - can't find the disk file off hand) and presented to US Army TACOM in Warren, MI. that year. It's a typical life cycle 'bathhtub' curve. When you do a MTBF calculation, it gives you a location on the curve.

The original for this was derived from data from various aerospace (jet and turboprop) LRUs and found to be similar no matter what the LRU. It also correlated with manpack radios we made for field use and the early field computers.

The important part is to understand this is an estimate or prediction.

Just wondering - anyone have any current thoughts?
Marc:

I wanted to add that a reliability prediction is a way to compare designs for reliability and as you pointed out only a statistic.

I have MIL-HDBK-217F, RELIABILITY PREDICTION OF ELECTRONIC EQUIPMENT (14MB) and MIL-HDBK-472, MAINTAINABILITY PREDICTION (5.6MB).

If anybody wants a copy of either, send me a PM with your e-mail address and I will be glad to send them to you. They are too large to attach.

mtbf (mean time between failures) calculations of an assembly Reliability Analysis - Predictions, Testing and Standards 10
S Calculating MTBF (Mean Time Between Failures) for the whole Production Unit Reliability Analysis - Predictions, Testing and Standards 2
S MTBMF (Mean Time Between Mission Failures) vs. MTBOMF - Differences Reliability Analysis - Predictions, Testing and Standards 6
S Mean Time Between Failures (MTBF) - SN 29500 Standards? Various Other Specifications, Standards, and related Requirements 5
S Calculating MTBF (Mean Time Between Failures) of different Electronic Components. Reliability Analysis - Predictions, Testing and Standards 16
K MTBF (Mean Time Between Failures) Calculation Reliability Analysis - Predictions, Testing and Standards 4
J Graphing MTBF (Mean Time Between Failures) or Reliability Data of a System Reliability Analysis - Predictions, Testing and Standards 1
M MTBF (Mean Time Between Failures) - Seeking help Statistical Analysis Tools, Techniques and SPC 1
MTBOMF ("Mean Time Between Operation and Mission Failure") - How to Calculate Reliability Analysis - Predictions, Testing and Standards 9
A Mathematical difference between mean Deviation and Standard Deviation Statistical Analysis Tools, Techniques and SPC 3
M Mean Time Between Failure (MTBF) Data for a New Design Customer and Company Specific Requirements 9
What does AS9100 mean when it says you must establish a process to do X? AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 0
General Motors and Honda Alliance - What does this mean to suppliers? IATF 16949 - Automotive Quality Systems Standard 3
What does this sentence "this symbol shall be used in the orientation shown" mean in ISO 780:2015? Other Medical Device Related Standards 4
What is mean by Oxygen Rich Environment as per the IEC 60601-1 clause no 11.2.2 IEC 60601 - Medical Electrical Equipment Safety Standards Series 5
Definition Open Audit - What does an Open Audit mean? Definitions, Acronyms, Abbreviations and Interpretations Listed Alphabetically 3
EU MDR Annex XIV - Clinical Evaluation Plan - What do these methods mean? EU Medical Device Regulations 12
What does UPH/m² mean? Quality Tools, Improvement and Analysis 3
"IATF-Compliant" IATF 16949:2016 certification? What does this mean? IATF 16949 - Automotive Quality Systems Standard 13
Circled-Z symbol on a syringe — what is it for, what does it mean? China Medical Device Regulations 21
What does "Class" mean in an FMEA? FMEA and Control Plans 16
What does % study variation of 20% mean in GRR? Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 17
GHTF Incidents - What does unlabeled and labeled mean? Japan Medical Device Regulations 9
When a deviation is opened but what does it mean to close a deviation? Misc. Quality Assurance and Business Systems Related Topics 1
Definition Intended Results - What does "Intended Results" mean? Definitions, Acronyms, Abbreviations and Interpretations Listed Alphabetically 4
What does "Gap" and "Flush" in ASME Y14.5 mean? Inspection, Prints (Drawings), Testing, Sampling and Related Topics 1
ISO 9001 Cl. 4.1 and 4.2 - What does monitoring and review mean? ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 13
What does "factional and failure dependencies“ mean? FMEA and Control Plans 1
What does 8.2.2.1, Determining the requirements related to products and services,mean IATF 16949 - Automotive Quality Systems Standard 1
E Uncertainty of Mean - Test rig that measures water temperatures Measurement Uncertainty (MU) 3
J What does "If required by the customer" mean? IATF 16949 - Automotive Quality Systems Standard 4
What does "Corporate stewardship" mean? IATF 16949 - Automotive Quality Systems Standard 6
W Using MPE (Mean Percentage Error) for Linearity and Type-1 study Measurement Uncertainty (MU) 1
Does the word "claim" in ISO 9001 Clause 8.2.2 mean "requirement"? ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 7
What does "effective implementation of quality management system" mean? ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 7
S IEC 60601-2-27: What does "linear within ±20% of the full scale output" mean? IEC 60601 - Medical Electrical Equipment Safety Standards Series 6
I ITSM and Orchestration - What does this mean? IT (Information Technology) Service Management 2
A How to calculate Mean and standard deviation without sample size in Minitab Using Minitab Software 5
FDA 21 CFR 820.250 - Does "valid statistical" always mean math? 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 6
Standard Deviation vs. Standard Deviation of the Mean (Standard Error) Measurement Uncertainty (MU) 7
What does B, M1 through M5 and the black triangle mean in MDD ? EU Medical Device Regulations 5
M What do the terms "Lessons Learned" and "Best Practices" mean ? Preventive Action and Continuous Improvement 2
Would compliance with ISO/TS 16949:2009 mean also compliance with ISO 9001:2015? IATF 16949 - Automotive Quality Systems Standard 1
E Callout of a length dimension and then P.I at the end - What does that mean? Inspection, Prints (Drawings), Testing, Sampling and Related Topics 2
What does "review" of records actually mean? US Food and Drug Administration (FDA) 12
Definition What does Engineering Judgement mean in MSA? Definitions, Acronyms, Abbreviations and Interpretations Listed Alphabetically 1
Definition Comply - What does 'comply' mean to you? (Definition) Definitions, Acronyms, Abbreviations and Interpretations Listed Alphabetically 3
What does "other APPLIED PARTS" mean in IEC 60601-1 ed 3.0 8.7.4.7 b) IEC 60601 - Medical Electrical Equipment Safety Standards Series 5
M How to calculate MTTF (Mean Time to Failure) Reliability Analysis - Predictions, Testing and Standards 1
C 95% CI vs Mean +/- sample standard deviation 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 1