Chemical Engineering October 2021 - 39

pipe areas for area change fittings,
standard of smooth flanged elbows,
long radius elbows and so on.
The more information that is specified,
the more accurate the results
will be. There are many ways that
things can be effectively simplified.
However, modeling the system as
close to reality as possible is best
practice. Even better when test or
measured data are available to calibrate
a model. A calibrated model
that matches data very closely will
provide more confidence when it
comes to using the model to predict
how system changes will impact results
and operation.
An example
Figure 3 demonstrates an example of
a piping system flow model for a raw
brine injection system. There were
five vertical pumps in parallel operation
and five other horizontal pumps
scattered elsewhere throughout the
system. The vertical pumps in parallel
competed with each other hydraulically
and each pump provided significantly
different flow than the others.
Ideally, the flow distribution should
be similar to help all pumps operate
close to BEP rather than some
pumps operating close to BEP and
some operating further away. Within a
five-year period, there were a total of
41 repairs, costing near $1.23 million.
The MTBF was roughly 15 months.
The consultants on this project
were tasked to improve reliability of
the system to mitigate the constant
repair issues. After the model was
built and calibrated, many scenarios
were reviewed. The major problem is
that the normal operation of the vertical
pumps in parallel were operating
between 23 and 58% of BEP. Each
pump delivered much less flow than
its designed capacity. Several scenarios
were run that included various
system changes such as only operating
two of the vertical pumps in
parallel instead of three in parallel or
more. Other mitigation attempts included
closing off a crossover valve
as well as increasing the discharge
pressure of the cavern.
After all the test scenarios were
evaluated, the consultants determined
that the combination of only
operating two of the vertical pumps
in parallel at a time, as well as closing
the crossover valve and increasing
the cavern pressure, had a dramatic
improvement in each pumps' operating
proximity to BEP. After these
changes, the pumps would then
operate at about 75% of their BEP,
the flow demands were easily met
with only two out of the five vertical
pumps and this resolved the many
operational problems the facility had.
Final remarks
In conclusion, a system-wide approach
for design and analysis of
new and existing
piping systems
can help engineers and owner and
operators better understand system
interactions and what steps can be
made to improve reliability. This is
much more useful than a component-by-component
approach
of
constantly
repairing parts that wear
out or break. Flow-analysis software
greatly aids in treating the root cause
of the problem rather than the symptom.
The flow analysis sheds more
light on why pumps, control valves
and other pieces of equipment are
operating poorly and have problems.
The impact of this approach
is massive with improved reliability,
minimized maintenance and repair
costs, downtime, production losses,
and increased profits.
n
Edited by Gerald Ondrey
References
1. " Optimizing Pumping Systems: A Guide For Improved Energy Efficiency,
Reliability, & Profitability " , First Edition, Hydraulic Institute
& Pump Systems Matter, 2008.
2.
Jantunen, E. and Itaranta, H. Expert System for the Diagnosis
of the Condition and Pumping Efficiency of Centrifugal Pumps,
Proceedings of the 53rd meeting of the Society for Machinery
Failure Prevention Technology, April 19-22, Virginia, 1999.
Author
Ben Keiser is a technical sales
consultant for Applied Flow Technology
(AFT;
2955 Professional
Place, Suite 301 Colorado Springs,
CO 80904; Phone: 719-6861000;
Email: info@aft.com; Website:
www.aft.com), a leading dynamic
fluid flow analysis and
waterhammer mitigation software
company. Keiser helps engineers
understand how to design safe and efficient piping and
ducting systems. His passion and expertise can be accessed
around the world as he trains engineering teams
how to efficiently preform flow analysis simulations to
find optimized solutions. Prior to joining AFT, he worked
for Eaton Corp. and WellbornYX Corp. Keiser holds a
B.S.Ch.E. degree from the Colorado School of Mines.
For details visit adlinks.chemengonline.com/80074-19
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