Reliability Training Lesson 1 Basics
description
Transcript of Reliability Training Lesson 1 Basics
1
Reliability – Lesson 1
The Basics
Overview: Application of Reliability in different
industries Importance of Reliability – Cost Impact Bathtub curve Predictability vs. Failure Mode Avoidance P-Diagram Strategies for Improvement
2
“A man who lacks reliability is utterly useless.”
Confucius (551-479)
“Engineering is the science of economy, of conserving the energy, kinetic and potential, provided and stored up by nature for the use of man. It is the business of engineering to utilize this energy to the best advantage, so there may be the least possible waste.”
Willard A. Smith (1908)3
Wikipedia - the ability of a system or component to perform its required functions under stated conditions for a specified period of time.
ASQ – the probability that an item can perform its intended function for a specified interval under stated conditions
4
Products: Design for Reliability Software
Equipment: Reliability Centered Maintenance
Medical – Survival rate
5
6
Reliability field
Nuclear Aerospace Medical Consumer Products
Reliability Criteria
# units in field 00 000 00000000 00000000
Quality of field records:
Failed units excellent excellent Reasonable>good fair
Unfailed units excellent excellent none none
Units lost to follow-up no no often yes
Noise space simple moderate complicated complicated
Competing risks no no yes yes
Key Reliability redundancy, redundancy, intervention robustness,
Strategy intervention intervention some intervention
Key reliability measure probability probability cure rate and side effects distance from failure modes
Memo: Design improvement yes yes no yes
Safety Customer Satisfaction Warranty Costs Reputation Repeat Business Cost Analysis Customer Requirements Competitive Advantage
7
Set goals & requirements (customer driven)
Perform an assessment Testing Data collection Failure reporting, analysis and
corrective action system (FRACAS)
8
Mean Time to Failure (MTTF) Mean Time Between Failures (MTBF) Hard Failures – product function ceases Soft Failures – degraded to unacceptable
level Failure rate Hardware Breakdown Structure FMEA – Failure Modes, Effects & Analysis SPC – Statistical Process Control DOE – Design of Experiments
9
“It’s unwise to pay too much, but it’s foolish to spend too little”— John Rustin
Present Value vs. Future Value of money Acquisition Costs Sustaining Costs Cost Breakeven Include Cradle-to-Grave costs
converted to NPV models
10
http://www.barringer1.com/pdf/LifeCycleCostSummary.pdf
11
Product B has a lower acquisition cost but needs repaired more often and at greater expense
12
Prevention activities - intended to ensure that processes work without fail, such as failure mode and effects analysis, training and preventive maintenance
Appraisal activities - how well processes such as product and process approvals are actually working via activities such as inspection and testing
Failure costs - related to failures that do occur and are further classified as internal (failure identified before it reached the customer) or external (detected after reaching the customer). The time and expense of reprocessing failed products or services and investigating failures could fall into either failure category, depending on when the event occurs. Warranty costs are decidedly external failures.
13
Number of
failures
Time
Infant Mortality
14
Number of
failures
Time
Infant Mortality
Useful Life
15
Time
Infant Mortality
Useful Life
WearoutNumber
of failures
We do not have access to all products in the field, particularly those that have not failed
We cannot specify a period of time to measure reliability
We cannot specify a set of operating conditions
16
Reliability is the probability that an item can perform its intended function for a specified interval under stated conditions, However:
Reliable products are robust and mistake free
Failure modes of our products are primarily that something breaks or performance degrades
Avoiding failure modes will decrease the probability of failure
Reliability prediction is not easy for many industries
We need to reduce variation and the sensitivity to noise (ie. Six Sigma and P-diagram)
17
18
P-DiagramNoise Factors123
Input Signal Ideal Function
System
Error StateControl Factors 1
1 22 3345
Ideal Function – primary intended function of the design
Input Signal – energy which is put into the system to make it work
Error State – undesirable output of the system
Control Factors – features that can be controlled by design or process
19
Product variations Changes over time/usage Customer duty cycle External environment System interactions
20
Sources of disturbing influences that can disrupt ideal function, causing error states which lead to quality problems
21
P-Diagram
Self contained jet pack Noise Factors
1. Fuel volatility
2. Wind
3. Temperature
Input Signal
Ideal Function
Throttle position
System
Lifts person off ground
Error State
Control Factors 1. No ignition
1. Material properties 2. Flame too large
2. Design
3. Manufacturing process
4. Assembly process
Bring P-Diagram List error states (potential failure
modes) Ties together P-Diagram and Testing Living and changing document Discovery, legal document Ultimate failure mode avoidance
document
22
Captures the effects of noise factors over useful life
Generates a measurable event Generates a failure of degradation of the
ideal function Generates results which are directly
correlated with real-world performance Can be accelerated for reliability
improvement experiments (HALT, HASS)
23
24
HALT testing
Change the design concept Make basic current design assumptions
insensitive to the noises (beef up design, use Design of Experiments, redundancy)
Reduce or remove the noise factor(s) Insert a compensation device Send the error state/noise elsewhere else
where it will do less harm (disguise effect)
25
Failure Reporting, Analysis and Corrective Action System
Prioritizes field failures Root Cause Investigation Teams Needs input from Team members Drives problems to closure Documentation in central location Closed Loop System
26
27
Application of Reliability in different industries
Importance of Reliability – Cost Impact Bathtub Curve Predictability vs. Failure Mode
Avoidance P-Diagram Strategies for Improvement
Reliasoft - http://www.reliasoft.com/ RIAC -
http://src.alionscience.com/src/training.do Hobbs Engineering -
http://www.hobbsengr.com/ ASQ Reliability Div. -
http://asq.org/reliability/ SRE - http://www.sre.org/ You’ll find many more on the web….
28
29
Dr. Tim Davis -“Science, engineering, and statistics”. Applied Stochastic Models in Business and Industry, 2006, Vol. 22, Issue 5-6, pp. 401-430
Dr. Vasiliy Krivstov Dr. Paul Barringer Reliasoft