Chemical Engineering June 2016 - 62

Engineering Practice
Field Troubleshooting 101 and
How to Get the Job Done
A major part of field work lies in troubleshooting problems: finding out why a system
is not operating the way it is intended. This article provides guidelines for effective
troubleshooting and contains many practical examples of their successful use
Thomas F. McGowan and
Dennis J. Coughlin
TMTS Associates
E
ffective troubleshooting in the
field requires not only skillful
engineering but also an equal
dose of the right behavior.
Together, these qualities represent
a combination of " art and science "
that will get the troubleshooting job
done well and done quickly.
Field troubleshooting is not for everyone,
but if you like a challenge, it
may be for you. Troubleshooters are
always in demand when equipment
goes down or is not making product
the way it should. They are brought
in to solve problems that have defeated
on-site personnel.
It is much like crime scene investigation
on television. It's the engineering
equivalent of detective work, tracking
down the felons that are causing
problems. When it is done effectively,
everyone walks away satisfied.
A blend of science and art
A wise mentor once said that troubleshooting
involved breaking the
problem in half and breaking it in half
again. His trade involved test trains
for combustion gas analysis. Each
train contained perhaps 20 ground
glass joints, which were prone
to leaks. Our mentor could have
checked each one, with an average
of 10 steps to find the leak. But
using his heuristic, the math says we
can find it in, at most, five steps (the
leak is in joints 1-10 → 1-5 → 3-5 →
3 or 4 → 4, bingo!). The bigger the
system, the greater the reduction in
the number of steps needed to find
a leak, or a break in a series wiring
system (think Christmas lights),
compared to a linear search.
62
Figure 1. Troubleshooting may require a variety of test equipment - some typical items are shown here
Having the right tools is important,
too. They need not be expensive,
but it helps if you have them in
your gear bag ready to use. Figure 1
shows (left to right) a Pitot tube for
flow measurement, a measuring
tape, pipe-thread-to-barbed tubing
adapters and connectors, a digital
manometer, thermocouples and a
field readout, a hand-held infrared
temperature probe, a clamp-on ammeter
and multimeter, a combination
pressure/vacuum gage, a roll of electrical
tape, and of course a flashlight.
They will help you get the hard data
you need to back up your hunches.
One can also use bigger and more
expensive tools, like the combustion
test system shown in Figure 2,
to provide fast feedback on what
is going on inside the process. For
those who want to learn about the
wide variety of tools used by many
trades, government training manuals
and other source materials are available
online [1, 2].
The " art " side of troubleshooting
includes being a good listener, being
observant, taking time to think over
information, taking action, opening
things up to look at them, and
being willing to get dirty to get the
job done. The science side includes
doing calculations, testing the system,
and comparing the results to
what was expected in the design.
The following is a litany of field
problems encountered and solved
in the experience of the authors by
employing the guidelines suggested
in this article.
Those pesky valves
Each type of valve has its own set
of quirks, and many an engineer has
learned to distrust all types. Here are
two examples of ball valves that did
not operate as expected.
Valve failure makes scrubber prequench
inoperative. A brand-new
solid-waste incinerator was failing
particulate-matter stack tests, deChemiCal
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