Reliability Analysis

1

• Reliability Analysis
• Sample Study
• October 2000

Jahan Alamzad 1250 Aviation Avenue Suite
200M San Jose, CA 95110 Tel [phone] Fax
408-280-5700 Email jahan.alamzad_at_ca-advisors.com
CA Advisors
2
Objectives

• Present a sample study for reliability analysis
  applicable in the electric power utility industry
• Provide a general framework for reliability
  analysis
• Suggest the structure of a detailed project

3
Introduction

• Reliability analysis approaches have been
  successfully applied in the airline industry with
  impressive results
• optimizing maintenance program
• forecasting for maintenance events
• planning resources for maintenance requirement
• A decision was made to explore the possibility in
  apply similar techniques in the electric power
  utility industry
• To investigate applicability, this pilot study
  was conducted to understand various issues
• data
• analytical models
• outputs

4
Collected data

• Extract of maintenance records, dating 1990
  -1999, for one part, provided by a utility
  company
• Breakers
• Model 15VHK500
• Key data
• Workorder Class
• Type
• Mode
• Serial No.
• Date
• Workorder No.

5
General framework
Probability of failure before t p
one-parameter approach
two-parameter approach
ln-ln scale
ln scale
Slope beta parameter
f(p)
f(p)
Slope failure rate
Characteristic Life
ln scale
t
t

• Analysis process
• identify Scheduled vs Unscheduled events
• determine inter-event time
• build probability distribution function (pdf)
• transform data points
• do regression analysis
• determine parameters

6
Results

• One-parameter
• Failure rate 0.00149
• R-Squared 95.9

• Two-parameter
• Beta 1.06067
• Characteristic life 703.30
• R-Squared 98.0

• Application
• Input
• next scheduled maintenance 400 days
• time since last maintenance 120 days
• Output
• probability of failure beforescheduled
  maintenance
• expected time until next failure (days)

one-parameter
two-parameter
0.4488
0.4360
301
306
7
Considerations

• Maintenance records
• availability
• content
• quality
• Maintenance event identification
• scheduled
• unscheduled
• Influencing factors
• analysis unit
• unit relationships

8
Applications

• Similar to the airline industry, using
  reliability-based maintenance planning yields
  substantial benefits
• understand the inherent reliability of parts
• forecast maintenance events
• anticipate maintenance activities
• determine maintenance workload and material
  requirements during a specific period of time
• strategic assessment of maintenance needs
• identify support resources
• optimize inventory requirements
• repairable parts
• expendable parts
• design optimal maintenance program

9
Motivations

• Reliability-based maintenance planning reduces
  the unit cost of production and delivery

Unit Cost
Overage
Shortage
Resource Level

• Needed resources can be scientifically justified
  and decisions can be analytically supported

10
Project reliability-based maintenance planning
Scoping
Framing
Structuring input
Beta version
Production version
Implementation
6 months