Hydrocarbon Processing - January 2021 - 67

Process Controls, Instrumentation and Automation
steam traps that fail open or closed, and
determine if they are leaking or working
improperly.
These transmitters listen in ultrasonic
ranges and can recognize sounds made
by units in various states by using an algorithm to identify failure modes and conditions (such as " good, " " blow through, "
" cold " or " inactive " ), and can also send
warnings of malfunctioning units.
Corrosion monitoring. Understanding
the effects of corrosion requires monitoring
pipe and vessel wall thickness to determine
how much metal has been lost and when
containment will be lost. The traditional
monitoring approach involves technicians
taking manual thickness measurements by
using a handheld ultrasonic device.
A large plant may have several thousand locations scheduled for inspection
at periodic intervals that can range from
every few weeks in high-risk locations to
once every 5 yr in other less-critical areas.
Manual inspections incur costs for the
technicians to gain access to the desired
measurement location, which may involve erecting scaffolding and removing
insulation, among other requirements.
Even if the inspections are performed
fastidiously, manual methods are notoriously inconsistent, and no data is available
between inspections. Variability of ±1
mm (.04 in.) is typical, but if a pipe wall
is 5-mm (0.2-in.) thick, the engineer may
lack confidence when trying to determine
when that pipe will reach its retirement
thickness. Achieving consistent, reliable
readings requires a different method.
Permanently installed, ultrasonic sensors monitoring wall thickness (FIG. 3), and
which are designed specifically to work in
harsh environments, can send data on a
WirelessHART network. The installation
cost of ultrasonic sensors is low because
they are non-intrusive and can be mounted
nearly anywhere without any cabling.
These corrosion monitoring systems
allow even small levels of corrosion or
erosion to be detected. Advanced signal
processing software, along with its data
visualization and analysis features, makes
data interpretation significantly easier
and quicker. Data from multiple sensors
can be visualized on a single screen as a
corrosion heatmap (FIG. 4).
Safety showers and eyewash stations. Companies often call people their

most valuable asset, so monitoring the condition of human beings is critical. Safety
showers and eyewash stations are scattered
throughout process units, but are typically
unmonitored. A distressed worker reaching a station may have to call for help on
the plant radio or hope to be spotted by
a colleague. With a simple WirelessHART
valve monitoring device (FIG. 5), however,
any activation of a safety shower or eyewash station can immediately be reported,
along with its location, to the control room
and first responders. This monitoring also
helps protect equipment, as a leak or spill
might be in progress.
The water supply must be monitored
for temperature and pressure. If piping
feeding the shower systems is exposed
to the sun, it can get hot. These systems
should use lines with enough flow to

avoid solar heating or should automatically dump water when necessary. Similarly, monitoring pressure confirms that
an operator has not inadvertently closed
a valve and rendered a station inoperative.
This can be done with a WirelessHART
DP transmitter or pressure gauge.
Location awareness. If plant manag-

ers want a mechanism to indicate who is
in the plant and where each individual is
at any given moment, using Wi-Fi for this
application is expensive. WirelessHART
networks can support location monitoring at a lower cost, using a different technology than what is used when adding
new process instruments to the network.
Location triangulation functions operate with a device that is called an " anchor "
(FIG. 6). These devices communicate with

FIG. 5. Simple valve position indicators combined with a WirelessHART transmitter can warn the
control room and first responders when a safety shower or eyewash station has been activated.

FIG. 6. Location anchors communicate with individual workers' tags, with each other and
with the WirelessHART gateway.
Hydrocarbon Processing | JANUARY 2021 67

Hydrocarbon Processing - January 2021

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