Chemical Engineering March 2022 - 41

projects that are not justified and always
listen to your managers' concerns
if they question your calculations
or assumptions. Don't let your
enthusiasm get in the way of your
company's best interests.
Pump replacement
Typically, the costliest way to improve
a pump's reliability performance
is by completely replacing
it with one that is better suited for
the application. Initially, site personnel
tend to seek improvement with
mechanical seal, metallurgy, bearing
upgrades or modifications to operating
procedures in their attempts to
gain better reliability. Yet, after years
of frustration, site management may
eventually have to concede that the
existing pump or pumps were completely
misapplied.
When considering a centrifugal
pump replacement, the project
group must first find a pump that fits
the current hydraulic requirements.
If several pump designs are being
considered, the pump that requires
the least piping modifications is usually
favored above the other options.
If the selected pump will not fit on the
existing foundation, then the cost of
the new foundation, or modifying/
adapting foundations and/or base
plates must be included in the total
project cost. Other miscellaneous
project costs, such as replacing
warehouse spares, training of maintenance
and operations personnel,
required control modifications, and
so on, must also be included in the
total cost of the project.
As an example, consider having
two 150-hp pumps that are oversized
and operate at 25% of the
BEP flow. The repair history shows
that the pumps have been repaired,
on average, once yearly at a cost of
$20,000 per repair for the past five
years. A review of the pump curve
shows that the current hydraulic efficiency
is about 27%. The most attractive
replacement pump option
being considered can provide an efficiency
of 67%. The energy savings
from the more efficient pump have
been calculated to be $46,990/yr
(based on an energy cost of $0.097/
hp-h). We will assume that a new,
more reliable pump pair will, on average,
have a MTBF of 10 years, which
equates to a maintenance cost savings
of $20,000 - $20,000/10 or
$18,000/yr. These findings mean
that the project will attain a total annual
Authors
Robert
Perez is a mechanical engineer
and semi-retired consultant
based in San Antonio, Tex. (Email:
rxperez1665@msn.com),
with
revenue stream of $46,990/
yr plus $18,000/yr (or $64,990/yr).
(Note that this total does not include
any process losses or additional operational
labor costs.)
After researching pump and piping
options, the project group has
determined that replacing these
pumps will cost $500,000, which includes
the cost of two new pumps
(assuming there is a main and an
installed spare) all design costs, recommended
spare parts, and all field
modifications and installation costs.
If we enter these data into an Excel
spreadsheet and solve for the internal
rate of return and the net present
value (NPV), we get the output
data shown in Table 2. There we can
see that the IRR (14.41%) and NPV
($617,276) for this project are factorable,
which is the first hurdle the
project will face.
Next, management will compare
these economic projections with
the other competing projects being
considered at the time. Since capital
budgets are finite, only the most attractive
projects will be funded. The
possible outcomes are that the project
will either be fully funded, deferred
until the next capital budget review,
or canceled. Reliability professionals
must realize that many reliabilityimprovement
projects never see the
light of day for reasons outside of
their control. At the end of the day,
remember that only well-conceived
reliability improvement projects are
ever fully approved and eventually
realized. To have a realistic chance of
approval, reliability projects need to
have excellent economics numbers
and key sponsors who will support
the project every step of the way.
Sponsors can be reliability managers,
operations superintendents,
plant managers, and executives. n
Edited by Gerald Ondrey
Reference
1. Perez, R. X. and Bloch, Heinz P., " Pump Wisdom - Problem
Solving for Operators and Specialists, " 2nd Edition, John Wiley
& Sons, Hoboken, N.J., 2022.
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
MARCH 2022
41
over 40 years of rotating equipment
experience in the petrochemical
industry. He earned a
BSME degree from Texas A&M
University at College Station, an
MSME degree from the University
of Texas at Austin and holds a Texas PE license. Perez
has authored numerous articles for magazines and conference
proceedings, five books, and coauthored five
books covering machinery reliability.
Heinz P. Bloch is a consulting
engineer at Process Machinery
Consulting, and resides in Montgomery,
Tex. (heinzpbloch@gmail.
com).
His
professional
career
commenced in 1962 and included
long-term assignments as
Exxon Chemical's Regional Machinery
Specialist for the U.S. He
has authored or co-written over
790 publications, among them 24 comprehensive
books on practical machinery management, failure
analysis, failure avoidance, compressors, steam turbines,
pumps, oil mist lubrication and optimized lubrication
for industry. Bloch holds B.S. and M.S. degrees
(cum laude) in mechanical engineering from the New
Jersey Institute of Technology. He is an ASME Life Fellow
and was awarded life-time registration as a Professional
Engineer in New Jersey.
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