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Infrared Thermography (IR)
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What is IR ?
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Infrared
thermography is the technique of using a non-contact & non-destructive
Infrared Scanning Camera to detect invisible Infrared thermal radiation of
objects, and recording these pictures as thermal images called "Thermograms"
to assist in identifying potential equipment failures.
Infrared
radiated energy is emitted by all objects, animate or otherwise, having a
temperature above absolute zero.
Amount
of energy emitted depends upon how hot the object is and how well it can emit
energy.
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How is it Measured ?
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Since
Infrared energy is not visible to the human eye, detection requires a physical
device to convert the IR to a visible image.
The
Thermographic Camera utilizes a system to focus the IR energy onto an IR
sensitive detector which is sensitive to radiation within the Infrared
Wavelength between 2 - 14 um.
The
detector converts the IR energy to a voltage signal, which is in turn, imaged
into a TV-like display. These images would then be recorded onto Disk or memory
chips.
The Temperature range of a typical Infrared Camera is –15° C to 1500°
C in 0.1° C steps.
Analysis
of the Thermal Images would be carried out on Computer using specialised
software. As a general rule, the following temperature differentials for
electrical connections is recommended :
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| DIFFERENTIAL |
PRIORITY
RATING |
ACTION |
MAXIMUM
TIME TO REPAIR |
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1
to 9ºC |
LOW |
Monitor |
N.A. |
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10
to 15ºC |
MEDIUM |
As
soon as possible |
Next
scheduled shutdown (but < 12 mths.) |
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16
to 29ºC |
URGENT |
Urgent |
1
Month |
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>30ºC |
SEVERE |
Immediately |
Immediately |
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Why use IR ?
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Infrared Thermographic scanning is a very effective tool for predictive
maintenance.
Equipment
failure is usually preceded by an abnormal temperature pattern, and this
temperature rise is easily detected by an Infrared Thermographic inspection.
The
biggest advantage of this method is the ability to detect faults in time without
the necessity to shut down Plant.
Some
of the APPLICATIONS are :
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| ELECTRICAL |
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Overheated
connections owing to loose joints |
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Uneven
phase loading |
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Hot
motor bearings |
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Loose
Battery Connections |
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Eddy
Current heating |
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| AIRCONDITIONING
& REFRIGERATION |
Cooling
leaks |
| MECHANICAL
PLANT |
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Overheated
Bearings
- Misaligned couplings
- Slipping fan
belts |
| STEAM
LINES |
Leakage |
| KILNS
/ FURNACES |
-
Refractory
breakdown
- Furnace tube temperatures |
| CONCRETE
ROOFS / PANELS |
Cracks
& thermal insulation breakdown |
| ENERGY
MANAGEMENT |
Heating
& Cooling losses |
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| Advantages
of IR Inspection |
| REDUCES
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- Unplanned
down-time
- Maintenance costs
- Overtime |
| IMPROVES
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-
Equipment life
- Plant safety |
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From
the Insurance Point of View :-
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Statistics reveal that 20% to 30% of electrical failures are caused by
loose connections.
IR
Inspection reduces chances of FIRE due to electrical failures resulting in
reduced paid claims. This not only reduces property damage, but also the number
of work related injuries.
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When is IR Required ?
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is dependent upon
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- size and nature of the
Installation.
-
severe environment
-
high loading |
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| Generally,
for Plants operating 24Hrs a day, the schedule shall be categorized into the
importance of each equipment as follows : |
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Category |
Inspection
Interval |
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Critical |
1
to 3 months |
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Important |
6
months |
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Unimportant |
12
months |
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| For
newly commissioned Installations, inspection should commence : |
- When loaded to 60% of maximum demand or 2 to 3months after Practical
Completion.
- Just before expiry of equipment warranty.
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rectification of faulty equipment, to ensure that the work had been efficiently
and properly completed, it is essential to carry out a re-inspection. |
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