Hydrocarbon Processing - May 2021 - 59

Valves, Pumps and Turbomachinery

FIG. 8. Casing anomaly with high-resolution
palette.

The subject-produced water injection
pumps were critical to plant operations
and, therefore, were tested annually to
monitor and trend performance. Part of
this testing included thermal imaging
checks compared to baseline thermal
signatures to identify any anomalies for
early detection of failures.
A baseline thermal signature under
normal conditions (FIG. 6) shows a uniform casing temperature across the pump
with no more than 1°F (0.8°F) difference.
During subsequent tests, operations
began to complain about a decrease in
injection flowrate for this particular
pump. This was confirmed during the
performance testing, which indicated
a significant amount of total dynamic
head (TDH) deterioration (~6%).
When the thermal imaging was conducted on the pump casing and compared to the baseline image, a significant
temperature gradient was noticed across
the center-stage bushing. The pump casing was now showing a temperature difference of ~4°F across the center-stage
bushing (FIG. 7).
FIG. 8 shows the same casing thermal
image with a high-resolution temperature palette applied, which clearly shows
the temperature difference on both sides
of the center-stage bushing.
FIG. 9 shows the results of the inspection of center-stage bushing, showing
the significant erosion damage. This was
confirmation of the identified anomaly
detected with the thermal imaging.
Takeaway. Based on the casing thermal

signature anomaly and the measured
head deterioration, it was suspected that
the center-stage bushing running clearance may have increased, resulting in excessive leakage across the bushing. With
this condition, a temperature rise will
occur due to the Joule-Thomson Effect.

FIG. 9. Center-stage bushing and case split-line damage.

The temperature increase of the fluid
leaking from 12th-stage discharge back
to 6th-stage crossover resulted in the observed casing temperature profile. Based
on these findings, it was recommended
to inspect and overhaul this pump at the
next opportunity.
Upon internal inspection, the center-stage distress was confirmed. The
loss of center-stage bushing clearance,
and subsequent excessive leakage rate,
resulted in significant casing split-line
damage from high-velocity cutting. Internal inspection also confirmed the
presence of an abnormal amount of
abrasive material, which was determined to be the root cause of the loss of
running clearances.
The cost of thermal imaging equipment has become more economically
attractive for maintenance and reliability professionals. Using thermal imaging
for condition monitoring of pumps and
other rotating equipment can identify
thermal anomalies and provide early detection of pending failures.
The aforementioned case studies are
good examples of how these techniques
can be applied to pump condition monitoring. The case studies resulted in not
only early detection of failures, but also
can be used to identify energy savings
potential, as with the case of passing
pump recycle valves.

Many of the common pitfalls of using
infrared devices, such as emissivity and
other issues, were not addressed here. A
slight learning curve exists for effective
measurement and analysis.
Training and certification courses
are readily available to maximize any return on investment of this technology.
As with all field related activities, safety
should come first. Thermal imaging in
the field can inhibit the ability to keep
" eyes on path, " which can result in potential slips, trips and falls.
KEITH BRASHLER is a
Pump Specialist with Saudi
Aramco and has 31 yr of
rotating equipment experience
in refining, pipeline, power
generation, pulp and paper,
and nuclear facilities with
emphasis on pump and system troubleshooting.
He earned a BS degree in mechanical engineering
from Washington State University, and is a
Certified Vibration Analyst: ISO Category IV,
and a Certified Maintenance and Reliability
Professional (CMRP).
YASSER ALSHAHRANI is a
Pump Engineer at Saudi
Aramco. He has 6 yr of rotating
equipment experience and is
a Certified Vibration Analyst:
ISO Category II. Mr. Alshahrani
earned a BS degree in
mechanical engineering and an MS degree in
engineering management from King Fahad
University of Petroleum and Minerals.
Hydrocarbon Processing | MAY 2021 59

Hydrocarbon Processing - May 2021

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