Maintenance Technology May 2017 - 31

ELECTRICAL SYSTEMS

IR windows provide
a measure of
safety and reduce
labor by allowing
thermographers to
inspect switchgear
without opening
panel covers. (Photo
courtesy of Fluke
Corp.)

Use IR Switchgear
Windows Properly
Jim Seffrin, Director
Infraspection Institute

IN AN EFFORT to reduce the risk of injuries associated with arc flash,
many sites have installed infrared (IR) transmissive windows or ports that
permit IR inspections of switchgear without the need to open panel covers.
Although such devices can provide a measure of safety and help to reduce
labor associated with those inspections, they pose unique challenges not
associated with direct line-of-sight imaging.

Switchgear windows are typically constructed of
a rigid frame with a fixed IR transparent material
that enables an imager to view through them.
Switchgear ports consist of a rigid frame with
small openings through which an imager may
be sighted. Depending upon type, some feature
a single hole, others incorporate metal screens
containing multiple holes.
IR windows will always attenuate infrared
energy received by the imager. While this attenuation affects qualitative and quantitative data, the
greatest challenge involves temperature measurement. Accurate temperature measurements can't
be obtained through a screened port. Furthermore, the ability to accurately measure temperatures through an IR window is possible only if the
following conditions are met.
■ The window opening must be larger than the
imager's lens objective.
■ The target must be at or beyond the imager's
minimum focus distance.
■ Values for window transmittance and target
emittance must be known and properly
entered into the imager's computer.
■ The imager's lens must be kept perpendicular
to and in contact with the window.
When it is not possible to meet all of the above
conditions, imagery should be evaluated only for
its qualitative value. As always, any inexplicable
hot or cold exceptions should be investigated for
cause and appropriate corrective action taken. MT

Words to the Wise: Beware Hidden Electrical Danger
Getting ready for an infrared inspection
of electrical equipment often requires
manual preparation of switchgear
components, which could be a riskier
endeavor than many people might
think. Unwary thermographers and other
personnel can, in fact, be injured through
contact with cabinets or component
surfaces that have become accidentally
or unintentionally energized.
Switchgear enclosures and components are generally designed to prevent
their surfaces from becoming energized.
Under certain circumstances, however,
enclosures and other dielectric surfaces
can become unintentionally energized to
significant voltage levels. This potentially
lethal condition can be caused by

improper wiring, faulty equipment, or
contamination due to dirt or moisture.
When conducting infrared inspections
on or near electrical equipment, always
keep the following in mind:
■ Only qualified persons should be
allowed near energized equipment.
■ Treat all devices and enclosures as
though they are energized.
■ Never touch enclosures or devices
without proper PPE (personal protective equipment).
■ Do not lean on or use electrical
enclosures as work surfaces.
■ Always follow appropriate safety rules.
■ Know what to do in case of an
accident.
Working alone near exposed,

energized electrical equipment isn't
just dangerous, it's a violation of
federal law. Thermographers who
perform infrared inspections on any
electrical equipment should never
work alone. Since CPR can't be
self-administered, at least two people
trained in first aid and CPR must always
be present when working near most
exposed, energized equipment. Having
a second CPR-trained person along
not only satisfies OSHA requirements, it
may save your life.
To paraphrase a time-honored
electrician's admonishment, remember
that while there are old thermographers
and bold thermographers, there are no
old, bold ones.

Jim Seffrin, a practicing thermographer with more than 30 years of experience in the field, was appointed to the position of
Director of Infraspection Institute (Burlington, NJ), in 2000. This article is based on several of his "Tip of the Week" posts on
IRINFO.org. For more information on electrical systems, safety, and other infrared-related issues, as well as various upcoming
training and certification opportunities, email jim@infraspection.com or visit infraspection.com
MAY 2017

MAINTENANCETECHNOLOGY.COM | 31


http://www.IRINFO.org http://www.infraspection.com http://www.MAINTENANCETECHNOLOGY.COM

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