On-Demand Learning: Centrifugal Pump Fundamentals
Part 1 Recording
Part 2 Recording
Centrifugal Pump Fundamentals: Parts 1 & 2
With the exception perhaps of motors and valves, the component with the highest
population in a typical ship's engine room is the pump, which is required whenever liquid must be moved
from a location where the liquid is at a lower pressure or elevation to one at which the same liquid is at a
higher pressure or elevation. The majority of the pumps used today are of the centrifugal type, and their
design and operation is critical to successful shipboard operation.
The video below shares the 2.5-hour
Part 1 webinar on the key design and operational fundamentals associated with centrifugal pumps.
Please give us feedback using the 2-minute survey.
Follow up Q&A
Q: From Part 2 Chat: "Do you see
movement away from split mechanical seals toward seals that outlast their
A: Most pumps are expected to last for 20 years or more with
periodic overhauls, including the replacement of wearing parts, and proper operation.
API610, Centrifugal Pumps for Petroleum, Petrochemical and Natural Gas Industries, requires that pumps be
designed and constructed for a minimum service life of 20 years (excluding normal wear parts, such as
bearings, seals, sleeves, etc.). In addition, these pumps should be designed for at least 3 years of
uninterrupted continuous service.
Other specifications may require longer lives, such as some military
specifications that require each pump to have a service life of 30 years with operation during 40% of this
In addition, in some critical applications, pumps can be expected to have a service life of 40
years with proper operation and maintenance.
Each main feed pump on a steam-propelled LNG carrier is
typically overhauled every 5 years after approximately 2.5 yrs of operation (i.e., operating 50% of the
time). During the overhaul, mechanical seals are usually replaced (regardless of their condition). Bearings
and wearing rings are also replaced.
One issue that limits mechanical-seal life is the life of the
elastomers that are used. One seal manufacturer states that O-ring life is approximately 10 years, which can
include up to 5 years in proper storage prior to installation. Based on this, the expected operating life
could be 5 years.
However, seal life can also be shortened due to various factors, such as dry running,
inadequate or high-temperature flushing liquid, excessive vibration, misalignment, corrosion (sometimes when
the pumped liquid is changed), excessive seal-chamber pressure, improper installation, and contaminants in
the pumped fluid. In addition, seals that operate in lower-speed applications with lower-temperature clean
liquids will probably last longer than seals operating with more severe conditions.
Taking the above
into consideration, the average expected mechanical-seal life, provided that the seal is not damaged during
installation and it is not abused during operation, is probably approximately 3 to 5 years. Also, API682,
Pumps-Shaft Sealing Systems for Centrifugal and Rotary Pumps, specifies that all seals should operate
continuously for 25,000 h (approximately 3 years) without the need for replacement. Therefore, mechanical
seals would usually have to be replaced several times during the life of the typical pump.
split seals, they do have speed and pressure limitations. In addition, some of these split seals are
designed to fit into stuffing boxes that originally were fitted with packing. Also, one seal manufacturer
advises that their split seals may drip over a 24-hour period after the initial startup, so they typically
should not be used with fluids that have emission limits.
These expansive webinars covers these topics:
- Typical Pump Specifications
- Euler Head & Velocity Vector Diagrams
- Calculating Total Head & Performance Curves
- Losses, Efficiency, Power & Torque Requirements
- Effects of Throttling, Varying Speed & Impeller Diameter
- Types of Impellers & Wearing Rings
- Types of Pressure Recovery Devices & Collectors
- Single-Stage & Multi-Stage Pump Configurations
- Packing & Mechanical Seals
- Net Positive Suction Head & Suction Specific Speed
- Suction & Discharge Recirculation
- Priming & the Effects of Air Entrainment
- Effects of Droop & Saddles
- Parallel & Series Operation
- References & Suggested Readings
Dr. Bill Sembler
Dr. William J. Sembler is a former Principal Engineer (2019 to 2021) and Vice President
of Engineering (2014 to 2019) at Coffin Turbo Pump, Inc., a company that specializes in designing,
manufacturing, testing, and servicing boiler feed pumps. While serving as VP of Engineering, he was
responsible for all of the company’s engineering functions, including boiler operation and
testing. In addition, Dr. Sembler brought computerized design techniques to Coffin, including the use of
computational fluid dynamics. He joined Coffin in 2014 after retiring as Head of the Department of
Engineering at the United States Merchant Marine Academy (USMMA), where he had been a faculty member for
22 years developing and teaching various courses in marine and mechanical engineering. In addition, Dr.
Sembler sailed as an Engineering Officer during training cruises aboard SUNY Maritime College’s
T.S. Empire State from 1993 to 2000, and from 2002 to 2006, he served as Chief Engineer on the USMMA
training vessel, the T/V Kings Pointer. From 2000 until 2012, he was also an ABET Program Evaluator for
accredited college and university programs in marine engineering and naval architecture. Prior to being
appointed to the faculty at the USMMA, Dr. Sembler had over 15 years of pump-company experience with
Worthington Pump Corp. in various marine sales and engineering positions, including Manager of the
Marine and Navy Engineering Department. In this latter position, he was responsible for the satisfactory
design of all Worthington pumps supplied from the USA for commercial marine and naval
Dr. Sembler has a B.S. from the USMMA in Marine Engineering and Nautical Science, as
well as both a Master of Engineering and the Degree of Mechanical Engineer from Stevens Institute of
Technology. In addition, he has a Ph.D. in Mechanical Engineering from Polytechnic Institute of NYU. Dr.
Sembler is also a licensed Professional Engineer in the states of NY and NJ and has held USCG licenses
as Chief Engineer of Steam, Motor, or Gas Turbine Vessels of any Horsepower and Third Mate of Steam or
Motor Vessels of any Gross Tons upon Oceans, and he is a licensed stationary engineer (boiler operator)
in the state of NJ.
Dr. Sembler is a member of the American Society of Naval Engineers
(ASNE). He is also a Life Fellow in the Society of Naval Architects and Marine Engineers (SNAME) and is
a past Chairman of SNAME’s New York Metropolitan Section (2000 – 2001), as well as a past
Northeast Regional Vice President (2002 – 2004). He also served as the Faculty Advisor to the
USMMA SNAME Student Section from 1995 to 2005. Dr. Sembler received SNAME’s Distinguished Service
Award in 2000, and he received the Rear Admiral Lauren S. McCready Award for Outstanding Achievement in
Marine Engineering from the USMMA Alumni Foundation in 2003 and the Maritime Service Superior
Performance Medal in 2014. He was also awarded with the honorary title of Professor Emeritus after
retiring from the USMMA. Dr. Sembler is a published author of technical papers and textbook chapters on
marine pump design and operation, including the chapter on pumps, compressors, blowers, and ejectors in
the upcoming 4th edition of SNAME’s Marine Engineering, and on the analysis and use of fuel cells
in marine applications.
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