High Specific Speed in Circulating Water Pump Can Cause Cavitation, Noise and Vibration
Excessive vibration means increased wear, increased
repair efforts, bad product selection & quality and high energy
consumption. This may be sometimes experienced by cavitation or
suction/discharge recirculation which could occur only when net
positive suction head available NPSHA drops below the net positive
suction head required NPSHR. Cavitation can cause axial surging, if it
is excessive, will damage mechanical seals, bearings, possibly other
pump components frequently, and shorten the life of the impeller.
Efforts have been made to explain Suction Energy (SE), Specific
Speed (Ns), Suction Specific Speed (Nss), NPSHA, NPSHR & their
significance, possible reasons of cavitation /internal recirculation, its
diagnostics and remedial measures to arrest and prevent cavitation in
this paper. A case study is presented by the author highlighting that
the root cause of unwanted noise and vibration is due to cavitation,
caused by high specific speeds or inadequate net- positive suction
head available which results in damages to material surfaces of
impeller & suction bells and degradation of machine performance, its
capacity and efficiency too. Author strongly recommends revisiting
the technical specifications of CW pumps to provide sufficient NPSH
margin ratios >1.5, for future projects and Nss be limited to 8500 -
9000 for cavitation free operation.
[1] “Investigation of Recirculation Effects on the Formation of Vapour
Bubbles in Centrifugal Pump Blades” by Mohammad Taghi Shervani
Tabar, Seyyed Hojjat Majidi, Zahra Poursharifi, -World Academy of
Science, Engineering & Technology- 49 2011.
[2] “Pump Cavitation-Various NPSHR Criteria, NPSHA Margins And
Impeller Life Expectancy” by Bruno Schiavello, Director Fluid
Dynamics, Applied Technology Department Philipsburg, New Jersey
and Frank C. Visser, Principal Design & Fluid Dynamics Engineer,
Flowserve Pump Division, Technical Services, Central Engineering
Etten-Leur,The, The Netherlands. Proceeding of the Twenty-Fifth
International Pump Users Symposium-2009.
[3] “Detecting Cavitation in Centrifugal Pumps” by Jeremy Jensen, Project
Engineer and Kenwood Dayton, Sr. Research Engineer, Bently Rotor
Dynamics & Research Corporation, Orbit journal 2nd Quarter 2000, page
no 26-27.
[4] “Hydraulic Institute standards”: Pump Operations, Efficiency, Testing &
Systems and NPSH margin; www.pump.org/
[5] “Pump Cavitation and High Pressure Liquid Health Essay” by
UKEssays.com..
[6] “A review of Nss Limitations-New Opportunities” by Michael
Hirschberger, Head of Hydrodynamic Department and Ian James
Engineering Manager, Ruhrpumpen Inc. of Ruhrpumpen Group, Tulsa,
Oklahoma. Proceeding of The Twenty-Fifth International Pump Users
Symposium-2009.
[7] “How to Avoid Expensive Pump Failures and Repairs from Cavitation
by Determining the ‘Suction Energy’ of a pump”, WaterWorldCE.com.
[8] “Specific Speed v Suction Specific Speed” Newsletter on pumps and
reliability, Nov 2007 by Dale B. Andrews- Lawrence pumps
http:/www.lawrencepumps.com
[9] “Specific Speed” by Steve Wilson by Grundfos (White Paper)
https://www.grundfos.com/
[10] “All About Specific Speed 7-3” http://www.mcnallyinstitute.com
[11] “Does Impeller Affect NPSHR?” by Daisude Konno, Senior Engineer
and Project Team Leader and Yoshiyuki Yamada, Design Engineer,
Hydraulic Machinery Department Ebara Corporation Tokyo, Japan,
Proceedings of The First International Pump Symposium.
[12] “Understanding Pump and Suction Specific Speed” by PDH online
Course M136 (2PDH) Randall W. Whitesides, PE 2012,
PDHonline.com.
[13] “Sufficient NPSH Margin Important to Pump Reliability” by Allan R.
Budris, www.waterworld.com/
[14] “What is Best Efficiency Point?” Frequently asked questions
http://epumpdoctor.com/
[15] “Avoid Repeat Pump Failure” By Heinz P. Bloch, P.E., Process
Machinery Consulting, www.plantservices.com/
[16] “Article #3: Suction Specific Speed” http://www.pump-magazine.com/
[17] “Centrifugal Pump: Which Suction Specific Speeds are Acceptable?” by
J. L Hallam, Amoco Oil Co. Texas City, Texas. Hydrocarbon
Processing, April 1982, page 195.
[18] “Pump Vibrations” by W.E(Ed) Nelson, Consultant Dickinson, Texas &
J. W. Dufour, Chief Engineer, Mechanical Equipment Services, Amoco,
Oil Company, Chicago, Illinois -Proceedings of The Ninth International
Pump Users Symposium,
[19] “Can Pump Design Upgrades Allow Lower Flow Operation without
NPSHR Recirculation Damage?” by Lev Nelik, Ph.D., June 2014 in
Pumps & Systems. www.pumpsandsystems.com/
[20] “Cavitation Prediction” www.pumpfundamentals.com/ [21] “Why NPSHR Changes With Impeller Diameter?” by Petroskills by John
M Campbell, www.jmcampbell.com/
[22] “Which is Which Cavitation or Recirculation?” by John C. Robertson
PE/CPE, AMSCO Inc. 105 Goldenrain Way, Simpsonville, S.C.
29680, www.maintenanceresources.com/
[23] “What is Pump Cavitation?” Crane Engineering, Optimizing Fluid
System Performance. Posted by Brad Parkhurst. (July 10. 2014).
[24] “Influence of Impeller Suction Specific Speed on Vibration
Performance” by David Cowan, Hydraulic Engineer, ITT Goulds Pumps
Basingstoke, Hampshire, UK, Simon Bradshaw, Director of API Product
Development & Technology And Thomas Liebner, Hydraulics Engineer,
ITT Goulds Pumps, Seneca Falls, NY, USA. Proceedings of Twenty-
Ninth Turbomachinery International Pump Users Symposium, October
1-3, 2013, Houston, Texas.
[25] “Understanding Pump Curves #6 Minimum Flow” Part Two: Suction
Specific Speed by Ron Astall, United Pumps Australia. Courtesy PIA
Australian Pump Technical Handbook.
[26] “Pump Guy Mailbag: Minimum Acceptable Flow for Effective Pump
Operation” by Larry Bachus http://www.flowcontrolnetwork.com/pumpguy-
mailbag-minimum-acceptable-flow-for-effective-pump-operation/
[27] WPIL Limited India, Data sheet of CW Pumps (3x500 MW )
[1] “Investigation of Recirculation Effects on the Formation of Vapour
Bubbles in Centrifugal Pump Blades” by Mohammad Taghi Shervani
Tabar, Seyyed Hojjat Majidi, Zahra Poursharifi, -World Academy of
Science, Engineering & Technology- 49 2011.
[2] “Pump Cavitation-Various NPSHR Criteria, NPSHA Margins And
Impeller Life Expectancy” by Bruno Schiavello, Director Fluid
Dynamics, Applied Technology Department Philipsburg, New Jersey
and Frank C. Visser, Principal Design & Fluid Dynamics Engineer,
Flowserve Pump Division, Technical Services, Central Engineering
Etten-Leur,The, The Netherlands. Proceeding of the Twenty-Fifth
International Pump Users Symposium-2009.
[3] “Detecting Cavitation in Centrifugal Pumps” by Jeremy Jensen, Project
Engineer and Kenwood Dayton, Sr. Research Engineer, Bently Rotor
Dynamics & Research Corporation, Orbit journal 2nd Quarter 2000, page
no 26-27.
[4] “Hydraulic Institute standards”: Pump Operations, Efficiency, Testing &
Systems and NPSH margin; www.pump.org/
[5] “Pump Cavitation and High Pressure Liquid Health Essay” by
UKEssays.com..
[6] “A review of Nss Limitations-New Opportunities” by Michael
Hirschberger, Head of Hydrodynamic Department and Ian James
Engineering Manager, Ruhrpumpen Inc. of Ruhrpumpen Group, Tulsa,
Oklahoma. Proceeding of The Twenty-Fifth International Pump Users
Symposium-2009.
[7] “How to Avoid Expensive Pump Failures and Repairs from Cavitation
by Determining the ‘Suction Energy’ of a pump”, WaterWorldCE.com.
[8] “Specific Speed v Suction Specific Speed” Newsletter on pumps and
reliability, Nov 2007 by Dale B. Andrews- Lawrence pumps
http:/www.lawrencepumps.com
[9] “Specific Speed” by Steve Wilson by Grundfos (White Paper)
https://www.grundfos.com/
[10] “All About Specific Speed 7-3” http://www.mcnallyinstitute.com
[11] “Does Impeller Affect NPSHR?” by Daisude Konno, Senior Engineer
and Project Team Leader and Yoshiyuki Yamada, Design Engineer,
Hydraulic Machinery Department Ebara Corporation Tokyo, Japan,
Proceedings of The First International Pump Symposium.
[12] “Understanding Pump and Suction Specific Speed” by PDH online
Course M136 (2PDH) Randall W. Whitesides, PE 2012,
PDHonline.com.
[13] “Sufficient NPSH Margin Important to Pump Reliability” by Allan R.
Budris, www.waterworld.com/
[14] “What is Best Efficiency Point?” Frequently asked questions
http://epumpdoctor.com/
[15] “Avoid Repeat Pump Failure” By Heinz P. Bloch, P.E., Process
Machinery Consulting, www.plantservices.com/
[16] “Article #3: Suction Specific Speed” http://www.pump-magazine.com/
[17] “Centrifugal Pump: Which Suction Specific Speeds are Acceptable?” by
J. L Hallam, Amoco Oil Co. Texas City, Texas. Hydrocarbon
Processing, April 1982, page 195.
[18] “Pump Vibrations” by W.E(Ed) Nelson, Consultant Dickinson, Texas &
J. W. Dufour, Chief Engineer, Mechanical Equipment Services, Amoco,
Oil Company, Chicago, Illinois -Proceedings of The Ninth International
Pump Users Symposium,
[19] “Can Pump Design Upgrades Allow Lower Flow Operation without
NPSHR Recirculation Damage?” by Lev Nelik, Ph.D., June 2014 in
Pumps & Systems. www.pumpsandsystems.com/
[20] “Cavitation Prediction” www.pumpfundamentals.com/ [21] “Why NPSHR Changes With Impeller Diameter?” by Petroskills by John
M Campbell, www.jmcampbell.com/
[22] “Which is Which Cavitation or Recirculation?” by John C. Robertson
PE/CPE, AMSCO Inc. 105 Goldenrain Way, Simpsonville, S.C.
29680, www.maintenanceresources.com/
[23] “What is Pump Cavitation?” Crane Engineering, Optimizing Fluid
System Performance. Posted by Brad Parkhurst. (July 10. 2014).
[24] “Influence of Impeller Suction Specific Speed on Vibration
Performance” by David Cowan, Hydraulic Engineer, ITT Goulds Pumps
Basingstoke, Hampshire, UK, Simon Bradshaw, Director of API Product
Development & Technology And Thomas Liebner, Hydraulics Engineer,
ITT Goulds Pumps, Seneca Falls, NY, USA. Proceedings of Twenty-
Ninth Turbomachinery International Pump Users Symposium, October
1-3, 2013, Houston, Texas.
[25] “Understanding Pump Curves #6 Minimum Flow” Part Two: Suction
Specific Speed by Ron Astall, United Pumps Australia. Courtesy PIA
Australian Pump Technical Handbook.
[26] “Pump Guy Mailbag: Minimum Acceptable Flow for Effective Pump
Operation” by Larry Bachus http://www.flowcontrolnetwork.com/pumpguy-
mailbag-minimum-acceptable-flow-for-effective-pump-operation/
[27] WPIL Limited India, Data sheet of CW Pumps (3x500 MW )
@article{"International Journal of Mechanical, Industrial and Aerospace Sciences:71813", author = "Chandra Gupt Porwal", title = "High Specific Speed in Circulating Water Pump Can Cause Cavitation, Noise and Vibration", abstract = "Excessive vibration means increased wear, increased
repair efforts, bad product selection & quality and high energy
consumption. This may be sometimes experienced by cavitation or
suction/discharge recirculation which could occur only when net
positive suction head available NPSHA drops below the net positive
suction head required NPSHR. Cavitation can cause axial surging, if it
is excessive, will damage mechanical seals, bearings, possibly other
pump components frequently, and shorten the life of the impeller.
Efforts have been made to explain Suction Energy (SE), Specific
Speed (Ns), Suction Specific Speed (Nss), NPSHA, NPSHR & their
significance, possible reasons of cavitation /internal recirculation, its
diagnostics and remedial measures to arrest and prevent cavitation in
this paper. A case study is presented by the author highlighting that
the root cause of unwanted noise and vibration is due to cavitation,
caused by high specific speeds or inadequate net- positive suction
head available which results in damages to material surfaces of
impeller & suction bells and degradation of machine performance, its
capacity and efficiency too. Author strongly recommends revisiting
the technical specifications of CW pumps to provide sufficient NPSH
margin ratios >1.5, for future projects and Nss be limited to 8500 -
9000 for cavitation free operation.
", keywords = "Best efficiency point (BEP), Net positive suction
head NPSHA, NPSHR, Specific Speed NS, Suction Specific Speed Nss.", volume = "9", number = "12", pages = "2147-13", }
