MECH 513: Smart Materials and Intelligent Structural Systems
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Condition Monitoring (CM)Condition monitoring is the use of advanced technologies to determine the
condition of equipment and predict its failure. This in turn should inform predictive maintenance (PM)
or reliability-centred
maintenance (RCM). Taylor [1] has suggested that "just as your physician
uses a variety of tests and evaluations to assess your state of health, we
should do the same for our machinery" and that there are six steps to a healthy
machine:
- First ask, what are the possible failures?
- Next ask, which of these failures are significant?
- Next ask, how can we avoid these failures?
- Then ask, when we can’t avoid failure, how can we get an early warning?
- Then, tailor a suite of tests to detect those early warning signs.
- Finally, collect the results of the tests at one decision point.
Techniques that can be used include:
- the Human Senses (look, listen, feel, smell etc.)
- Motor Current Analysis
- Oil Analysis and Tribology
- Non-destructive testing
(NDT) technologies
- Vibration Measurement and Analysis
- Acoustic Emission
- Ultrasonics
- Infrared Thermography
Lloyd’s Register’s integrated condition monitoring service (ICMS) [2] proposes
that "integrated condition monitoring helps optimise maintenance by judging the
health of machinery using non-invasive sensing technology". The consequent
benefits of the ICMS approach are:
- early detection of impending machinery failure to help lower the
risk of unscheduled downtime
- scheduling and utilisation of maintenance resources is more efficient
- reductions in time spent in dry dock, if a pre-dry-docking fault locating
survey is performed
- reduced likelihood of ‘maintenance induced’ failures
- availability of global condition monitoring data.
Risk-based inspection (RBI) is a method for deciding which
components to inspect. Instead of a fixed inspection interval, RBI
considers the risk of an item of plant or of a component failing and
decides the inspection interval on that basis. A description of the Risk
Assessment methodology (in the context of composites manufacture) can be found
on the appropriate
MATS324 page. The basic approach is to consider the Probability and
the Consequence (severity) of failure separately either as a range or simply as
low/medium/high and endeavour to move to the calculated risk from top right to
lower left or increase the inspection interval as the risk moves towards the top
right in the diagram below:
| |
Consequence
of failure |
| Low |
Medium |
High |
| Probability of
Failure |
High |
|
|
HIGH RISK |
| Medium |
|
|
|
| Low |
LOW RISK |
|
|
For more information on Risk Based Inspection, see references 3-5. For more information on Condition Monitoring, see
the review by Heyns [6], the international standards [7-13] and the other resources
below.
References
- James W. Taylor, Six Steps to A Healthy Machine,
http://www.reliabilityweb.com/art05/6_steps_machine_health.htm, accessed
06 February 2006.
-
Integrated condition monitoring – helping to reduce maintenance costs and
enhance machinery reliability,
http://www.lr.org/Industries/Marine/Services/Consultancy/Integrated+condition+monitoring+service.htm, accessed
28 October
2006.
- JB Wintle, BW Kenzie, GJ Amphlett and S Smalley (TWI and Royal & SunAlliance Engineering),
Best
practice for risk based inspection as a part of plant integrity management,
Health and Safety Executive Contract Research Report 363/2001, 2001.
ISBN 0 7176 2090 5 [3 MB PDF].
- W Geary,
Risk Based
Inspection - A Case Study Evaluation of Onshore Process Plant, Health and
Safety Laboratory HSL/2002/20, Sheffield, 2002.
- Best
practice for risk based inspection as a part of plant integrity management,
Health and Safety Laboratory CRR 363/2001, Sheffield, 27 September 2005.
- PS Heyns [21 references],
Tool condition
monitoring using vibration measurements - a review, Insight (BJNDT),
August, 2008, 49(8), 447-450.
- ANSI/IEC/ISO 17024:2003 Conformity
assessment - General requirements for bodies operating certification of
persons.
- ISO 18436-1:2004 Condition monitoring and diagnostics of machines -
Requirements for training and certification of personnel - Part 1:
Requirements for certifying bodies and the certification process
- ISO 18436-2:2003 Condition monitoring and diagnostics of machines -
Requirements for training and certification of personnel - Part 2: Vibration
condition monitoring and diagnostics
- ISO/DIS 18436-3 Condition monitoring and diagnostics of machines -
Requirements for training and certification of personnel - Part 3:
Requirements for training bodies and the training process
- ISO/DIS 18436-4 Condition monitoring and diagnostics of machines -
Requirements for training and certification of personnel - Part 4: Field
lubricant analysis
- ISO/DIS 18436-6 Condition monitoring and diagnostics of machines -
Requirements for training and certification of personnel - Part 6: Acoustic
emission
- ISO/DIS 18436-8 Condition monitoring and diagnostics of machines -
Requirements for training and certification of personnel - Part 8:
Thermography
Other resources
- Sandy Dunn, Condition Monitoring in the 21st Century,
http://www.plant-maintenance.com/articles/ConMon21stCentury.shtml,
accessed 06 February 2006.
- RK Mobley, Predictive maintenance, Chapter 50 of
Plant Engineers' Handbook ISBN 0-7506-7328-1.
- Richard Overman and Roger Collard, The complimentary roles of reliability
centred maintenance and condition monitoring, IMC-2003: 18th International
Maintenance Conference, 8-9 December 2003.
http://www.reliabilityweb.com/art04/collard.pdf, accessed 06 February
2006.
- Steve Reilly, Integrating Inspection-Based and Reliability-Based
Information,
http://www.reliabilityweb.com/excerpts/excerpts/integrating.htm, accessed
06 February 2006.
- JK Paik and R E Melchers (editors),
Condition assessment of aged structures, Woodhead Publishing, Cambridge, October 2008. ISBN-13: 978-1-84569-334-3.
Structural Health Monitoring (SHM)
Structural Health Monitoring (SHM) is a damage detection
process used for aerospace, civil and mechanical engineering infrastructure
which monitors the system over time. Typically, an array of sensors
collects dynamic response measurements either continuously or at regular
intervals. The basis for SHM is that a normal response can be determined
soon after installation. This response may be a statistical database: e.g.
a highway bridge probably has most activity during rush-hour Changes in
this response, or unusual features in the signal, will then suggest there has
been a departure from the normal loading situation and/or the possibility of
damage. Over time the output of the monitoring process may change due to
the inevitable aging and degradation of the structure resulting from the
operational environment, and/or from ageing of the sensors and instrumentation.
SHM can be particularly useful after catastrophic events (flooding, earthquakes
or explosions) for rapid assessment of the integrity of the structure.
A number of review articles exist:
- Los Alamos National Laboratory have published reviews of structural health monitoring covering the literature prior to 1996 [1, 2] and from 1996–2001 [3].
- Elsevier have published a 10-volume reference work Comprehensive Structural Integrity [4].
-
QinetiQ have just released a report on the subject [5].
- Pawar and Ganguli have reviewed SHM for helicopter rotors [6]
- Zou et al on vibration-based model-dependent delamination damage
identification [7]
De Leeuw and Brennan [8] identified a need for the development of objective measures to quantitatively assess the performance characteristics of monitoring technologies. They present
the background and development of such a measure of performance based on fatigue and fracture mechanics failure models of the host structure. The structural integrity monitoring index
(SIMdex)
can use any failure model and criterion and means that structural integrity monitoring technologies can be objectively judged solely on their suitability for specific applications.
There exist several targetted initiatives where SHM may
be applied:
An associated technology for cost reduction in the context of Structural
Health Monitoring is Virtual Testing Risk Management Methodology [9].
References
- SW Doebling, CR Farrar, MB Prime and DW Shevitz, Damage Identification and
Health Monitoring of Structural and Mechanical Systems from Changes in their
Vibration Characteristics: A Literature Review, Los Alamos National Laboratory
report LA-13070-MS, 1996.
http://www.lanl.gov/projects/damage_id/reports/lit_review.pdf, accessed 06
February 2006.
- SW Doebling, CR Farrar, MB Prime and DW Shevitz, A review of damage
identification methods that examine changes in dynamic properties, Shock and
Vibration Digest, 1998, 30(2), 91–105: a condensed version of reference 1.
- Hoon Sohn, CR Farrar, FM Hemez, DD Shunk, DW Stinemates and BR Nadler, A
Review of Structural Health Monitoring Literature: 1996–2001, Los Alamos
National Laboratory Report, LA-13976-MS, 2003.
http://www.lanl.gov/projects/damage_id/reports/LA_13976_MS_Final.pdf,
accessed 06 February 2006.
- I Milne, R Ritchie and B Karihaloo,
Comprehensive Structural Integrity (10-volume reference work), Elsevier,
2003. ISBN13: 9780-08-043749-1.
- Lisa Fixter and Caroline Williamson,
State of the Art
Review: Structural Health Monitoring, QinetiQ/S&DU/T&P/E&M/TR0601122,
2006.
- P M Pawar and R Ganguli,
Helicopter rotor health monitoring- a review, Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, 2007, 221(5), 631-647.
- Y Zou, L Tong and GP Steven,
Vibration-based
model-dependent damage (delamination) identification and health monitoring
for composite stuctures - a review, Journal of Sound and Vibration,
2000, 230(2), 357-378.
- B de Leeuw and FP Brennan, Structural integrity
monitoring index (SIMdex): a methodology for assessing structural health
monitoring technologies, Proceedings of the Institution of Mechanical
Engineers, Part G: Journal of Aerospace Engineering, 2009, 223(5), 515-524.
- F Abdi, T Castillo and E Shroyer,
Risk Management of Composite Structure, in Efstratios Nikolaidis, DM
Ghiocel and Suren Singhal,
Engineering Design Reliability Handbook, CRC Bress, Boca Raton, December
2004. ISBN-13: 9780849311802. ISBN: 0-8493-1180-2.
Other resources
Software
|
Condition Monitoring |
Structural Health Monitoring |
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Created by John Summerscales on 06 February 2006 and updated on
07 August 2009 11:42. Terms and conditions. Errors and omissions. Corrections.
