Efficient Plant October 2021 - 18

feature | leak detection
Continued from p.15
with similar frequencies
coming from multiple
areas in the scene. Th e
acoustic data is transposed
in real-time on
top of a digital camera
image, which provides
pinpoint accuracy
of the sound source.
Some tools now include
the ability to automatically
save images to an
on-board microSD card or
they are Wi-Fi enabled to send
images directly to a cloud storage
system for post-inspection processing,
analysis, and severity evaluation.
With the ability to analyze the data, operators
A United States Offi ce
of Energy Effi ciency
& Renewable Energy
study demonstrated
that fi xing the 10
largest leaks in a
system can achieve
70% of the overall
available cost savings.
can easily separate sound sources and classify them
manually or with the assistance of artifi cial intelligence
developed from machine learning. Some
handheld devices only require one hand to operate.
Handhelds also off er the ability to quickly scan large
areas from a safe distance (more than 100 meters)
for safer detection and analysis, without the need to
physically touch machinery or shut down production
lines.
Single-microphone ultrasonic (acoustic) method:
Ultrasonic (acoustic) leak detectors can detect leaks
using a single microphone system operating around
40 kHz. Th is method relies on a process called heterodyning,
which enables the operator to distinguish
between leak noise and noise from the background.
Heterodyning converts high-frequency noise to lower,
audible frequencies, usually provided to the operator
through headphones. Th is method, however, requires
signifi cant training to enable the operator to recognize
issues based on specifi c sound characteristics.
A disadvantage of single-microphone ultrasonic
leak detection is the operator must scan the tool back
and forth over the equipment in question to locate
a suspected leak. In comparison to HD acoustic
imaging, this method oſt en leads to false alarms and
detection of nonexistent leaks. Most crucially, inex18
| EFFICIENTPLANTMAG.COM
perienced inspectors oſt en miss actual leaks. Finally,
manually moving the microphone around equipment
to locate leaks can be time-consuming and physically
demanding while potentially placing the operator in
danger.
Soap-bubble test method: Th e traditional, least
expensive, and most low-tech method for leak detection
is using a specialty soap solution. Th is requires
an individual to saturate a suspected leak area with
an approved soap solution. Th e solution will begin
to bubble if a leak is present, assuming the system in
question is well pressurized.
In many cases the exact leak site is unknown,
potentially leading to hours of work applying the
solution wherever a leak might be present-from
fl ange connectors to packing joints or any number
of common leak points. In short, soap-bubble tests
can become time consuming and messy without
providing any real data to confi rm a given leak's size,
let alone its fl ow rate. Th e method can also place the
operator in potentially precarious positions around
equipment.
Of the three tools outlined, HD acoustic imaging
provides the best balance of ease of use, eff ectiveness,
and accuracy for compressed-air leak detection. It
also comes with the highest upfront cost, which must
be factored into whatever method, or methods, an
organization chooses to invest in as part of a leakdetection
and mitigation program.
Regardless of the method, preventive leak-detection
measures represent a relatively fast and simple
way for organizations to reduce energy consumption
and enjoy the requisite cost and safety improvements
without the need to completely overhaul processes
and equipment. With compressed air representing
one of the largest energy operating expenses for organizations,
the ability to detect and eliminate leaks is
crucial for creating effi cient plant environments. EP
Rob Milner, PE, is the Global Business Development
Manager-Condition Monitoring for Teledyne FLIR,
Th ousand Oaks, CA (teledynefl ir.com). He has held this
role for more than 20 years, developing experience in
most of the company's market verticals.
OCTOBEER 2021
http://www.teledyneflir.com http://www.EFFICIENTPLANTMAG.COM
Efficient Plant October 2021

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