Transcript Title

Condition Monitoring (CM)
Structural Health Monitoring (SHM)
a joint lecture for MECH 512:
Design for Structural Integrity
MECH 513: Smart Materials and
Intelligent Structural Systems
John Summerscales
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).
Condition Monitoring (CM)
Taylor [2006] 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“.
There are six steps to a healthy machine:
• what are the possible failures?
• which of these failures are significant?
• how can we avoid these failures?
• if we can’t avoid failure, can we get an early warning?
• select a suite of tests to detect early warning signs.
• collect the results of the tests at one decision point.
Condition Monitoring (CM)
Techniques that can be used include:
• the Human Senses
o
look, listen, smell, taste, feel etc.
• Motor Current Analysis
• Oil Analysis and Tribology
• Non-destructive testing (NDT)
Condition Monitoring (CM)
• 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".
Condition Monitoring (CM)
The benefits of an 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-drydocking fault locating survey is performed
• reduced likelihood of ‘maintenance induced’ failures
• availability of global condition monitoring data.
Condition Monitoring (CM)
Risk-Based Inspection (RBI)
• 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.
Risk assessment
• Consider the Probability (likelihood) and the
Severity (consequence) of failure separately.
• classify them either as a range
or simply as low/medium/high
• the risk is the product of the two numbers
• a high number is a high risk
• endeavour to reduce the calculated risk
Risk assessment
Consequence of
failure
Low
High
Probability
of Failure
Medium
High
HIGH
RISK
Medium
Low
LOW
RISK
e.g. http://www.tech.plym.ac.uk/sme/MATS324/risk.htm
Condition Monitoring (CM)
So how might we monitor that:
• the mp3 player has enough power now,
and for five hours time
• the washing machine is consuming the
minimum power needed and , if not, where
the additional load is being taken
• that the car will continue to run smoothly
• that the car tyres are at the correct pressure
Condition Monitoring (CM)
•
•
•
•
•
The options might include:
voltage and current measurement
noise and vibration
the instrument panel
in-wheel pressure sensors
ISO/DIS 18436-4
Condition monitoring and diagnostics
of machines Requirements for training and
certification of personnel
1:
2:
3:
4:
6:
8:
certifying bodies and the certification process
vibration condition monitoring and diagnostics
training bodies and the training process
field lubricant analysis
acoustic emission
thermography
Structural Health Monitoring
(SHM)
• 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.
Structural Health Monitoring (SHM)
So how might we monitor:
• an earth filled masonry arch bridge carrying
a road or railway
• cracking at joints in an offshore oil
exploitation rig jacket
• corrosion of a liquid storage tank
while full of hazardous chemicals
• barely visible impact damage
(dropped tools on CFRP aircraft wings)
Structural Health Monitoring (SHM)
The options include:
• mechanical/dead-weight loading with
measurement of deflections
• modes and frequencies of vibration
• embedded sensors
• non-destructive testing technologies
(MATS324 lecture A12) ...