Ksb internship report

NATIONAL UNIVERSITY OF SCIENCES & TECHNOLOGY
SCHOOL OF MECHANICAL & MANUFACTURING ENGINEERING (SMME)
INTERNSHIP REPORT
Submission Date: ____________
Internship Duration: 7 June – 15 July , 2016
BY
ALI FAIZAN WATTOO
SUBMITTED TO
DANISH KHAN
This report and its content is copyright of author- © [2016]. All rights reserved.
Any redistribution or reproduction of part or all of the contents in any form is prohibited
15-07-2016

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PREFACE
Currently, I’m pursuing Bachelors in Mechanical Engineering at School of Mechanical & Manufacturing
Engineering (SMME), National University of Sciences & Technology (NUST), Pakistan.
After completing 3 years of the degree I’ve opted KSB Pumps Company Pvt. ltd. for its internship program to
gain practical experience in the field, as it is the only company leading in the pump & valves market throughout
the country.
Furthermore, my interests tend towards learning & discovering more about turbomachines. There is no better
option other than to start with the pumps and then to proceed next to more complex and complicated
turbomachines like gas turbines.
This report contains an overview of my learning & experiences during the internship period. Furthermore it
describes the tasks, projects and hands-on experience I’ve got here throughout my stay.

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ACKNOWLEDGEMENTS
Special thanks to:
Danish Khan
I want to acknowledge
Khurram
M.Asif Sohail
Waqas
Ehtisham Siddiqui
for their invaluable guidance and support for writing this report.
I’m also also thankful to the technicians, staff, workers of the company who helped me on the field,
providing the relevant information

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Table of Contents
1. About KSB..............................................................................................................................................................7
1.1 KSB Global ........................................................................................................................................................7
1.2 KSB in Pakistan.............................................................................................................................................................. 7
1.3 Departments ................................................................................................................................................................. 8
2. Products made in KSB Pakistan.............................................................................................................................11
2.1 DWT B-Pumps.................................................................................................................................................11
2.2 Etanorm....................................................................................................................................................................... 11
2.3 SEWATECH/SEWABLOC............................................................................................................................................... 12
2.4MOVITECH/MOVIBOOST...................................................................................................................................13
2.5 KRT .............................................................................................................................................................................. 14
2.6 RPH.............................................................................................................................................................................. 15
2.7 KWP ...............................................................................................................................................................15
2.8 PNW, SNW- Vertical Tubular Casing ........................................................................................................................... 16
2.9 ZORO Submersible motor Pump................................................................................................................................. 17
3. Tasks & Assignments............................................................................................................................................18
4. Pump Basics ........................................................................................................................................................22
4.1 Types of Pump............................................................................................................................................................. 22
5. Selecting between Centrifugal or Positive Displacement Pumps ............................................................................23
6. Classification of Centrifugal Pumps based on Several Design Features ...................................................................25
7. Some topics related to centrifugal pump ..............................................................................................................26
7.1 Air entrainment in the centrifugal pumps .........................................................................................................26
7.2 Energy and head in pump systems ............................................................................................................................. 26
7.3 Impeller eye ................................................................................................................................................................ 27
7.4 Cavitation ......................................................................................................................................................27
7.5 Net Positive Suction Head (NPSH)............................................................................................................................... 28
7.6 Pump Curve, System Curve & Duty/Operating Point ................................................................................................. 29
7.7 Best Efficiency Point (B.E.P.) ............................................................................................................................29
7.8 Suction-specific speed ................................................................................................................................................ 30
7.9 Specific speed ............................................................................................................................................................. 30
7.10 Trimming of an impeller ................................................................................................................................31

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7.11 Volute Casing and addition of diffuser vanes .......................................................................................................... 32
7.12 Velocity triangles -- Impeller .................................................................................................................................... 32
7.13 Priming ........................................................................................................................................................33
7.14 Losses in a pump ...................................................................................................................................................... 34
8.Some Useful Pump Formulas ................................................................................................................................34
8.1 Pressure to Head ............................................................................................................................................34
8.2 Mass Flow to Volumetric Flow ................................................................................................................................... 34
8.3 Net Positive Suction Head .......................................................................................................................................... 35
8.4 Pump Head ....................................................................................................................................................35
8.5 Pump Power ............................................................................................................................................................... 36
8.6 Pump Torque .............................................................................................................................................................. 36
8.7 Temperature Rise ...........................................................................................................................................36
8.8 Fluid Velocity .............................................................................................................................................................. 36
8.9 Velocity Head ............................................................................................................................................................. 35
8.10 Specific Speed at BEP ....................................................................................................................................35
8.11 Suction Specific Speed at BEP .................................................................................................................................. 35
8.12 Affinity Laws ............................................................................................................................................................. 36
8.13 Bernoulli’s Equation ......................................................................................................................................36
9.Parts of a typical Centrifugal Pump .......................................................................................................................39
9.1 Impeller .........................................................................................................................................................40
9.2 Casing ......................................................................................................................................................................... 41
9.3 Delivery pipe and Suction pipe with foot valve and a strainer .................................................................................. 42
9.4 Shaft ..............................................................................................................................................................43
9.5 Bearings ...................................................................................................................................................................... 44
9.6 Lubrication .................................................................................................................................................................. 47
9.7 Seal ................................................................................................................................................................48
9.8 Coupling ...................................................................................................................................................................... 49
9.9 Casing Wear Rings ...................................................................................................................................................... 55
ANNEXURE ..............................................................................................................................................................56

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[Klein, Schanzlin, Becker]
Year Founded: 1887
Founders: Johannes Klein , Friedrich Schanzlin , Jakob Becker
Headquarters: Frankenthal (Pfalz), Germany
Product: Pumps, Valves & related services
Company Designation: Aktiengesellschaft (public limited company)
Global Footprint: KSB manufactures products and components in a total of 16 countries; they are sold
through the Group’s own companies or agencies in more than 100 countries
Employees: Around 16,000
Targeted Industries:
 Chemical industries
 Petrochemical industries
 Energy sector
 Construction/building services
 Transport equipment manufacturers and
operators
 Water and waste water utilities,
 Mining companies
1.2 KSB in Pakistan
The company's first Asian-Pacific subsidiary was set up in Pakistan in 1959. Since its inception KSB Pumps
Company Limited has attained a leadership status in the market and become the leading supplier and
manufacturer of pumps, valves and related systems in the country
Head Office : Lahore - 16/2 Sir Aga Khan Road 54000 Lahore, Pakistan
Factory : KSB Works, Hazara Road Hassanabdal, Pakistan
Website: https://www.ksb.com/ksb-pk/
Phone: +92 42 111 572 786
Fax: +92 42 36366192
E-Mail: info@ksb.com.pk

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1.3 Departments
1.3.1 Projects
Projects department is responsible for acquiring special orders and carrying out their execution
independently. Main focus is on developing innovative solutions that are beneficial for society and mass
population of the country.
In 2015, KSB acquired a project from PHED Mirpur, Azad Jammu Kashmir “Mirpur New City” . The
objective of this project is to provide clean drinking water to cater around 40,000 homes. safe water
initiative for the communities. KSB designed and developed a complete solution: Solar Water Filtration
and purification plant.
In the same year, KSB Pakistan secured an order under Punjab Saaf Pani Project. Under this order ,
KSB developed turnkey Solar Powered Water Filtration Plants in 4 Tehsils ( Hasilpur,Minchinabad,
Khanpur & Lodhran) in the Districts Bhahawalpur, Bhawalnagar, Rahim Yar Khan and Lodhran. This
included Designing, Supply, Installation Commissioning of total of 86 Solar Powered Ultrafiltration &
Reverse Osmosis Plants.
1.3.2 Sales
Sales department is responsible for
 Handling customer purchase of a product
 Engage with the clients
 Take orders and enquire the needs of the customer related to the required product
 Provide consulting to the customers to match the best product for their requirement
 create product orders and forward them to the design.
1.3.3 Design
Responsibilities of design department include:
 Designing of different products a company offers
 Perform modifications as required to match the clients customized needs
 Creation & Handling of drawings and technical data related to different products
 Creating Bill off Materials (BOMs) for each product order
 Standardization and Material designation
 Managing Materials and standards on SAP MM module
 Co-ordinate with other departments with all matters related to design & material
1.3.4 Planning
Responsibilities of planning department include:
 Provide a whole plan, how and when to execute the order, step by step, from its production
to delivery
 Create a timeline and sub-timelines specifying the durations of processes and operations a
product will go through from raw material up to the delivery to the customer
 Inform each department about its timelines and roles
 Co-ordinate with other departments where ever there are delays or obstacles in keeping up
to the timelines
 Follow-up the plan execution
1.3.5 Procurement
Responsibilities of procurement department include:
 To carry out and handle tenders, contracts and mange outsourcing

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 To reach vendors and contractors to buy the materials, components which are on in the Bill
off Materials (BOMs) but not available in the store
 Shipment and provision of the required materials from the vendor to the store
 Following the timelines
 Co-ordinate with other departments for all matters relating to the procurement of required
equipment and services
1.3.6 Production
Responsibilities of production department include:
 To set SOPs for each process and operation to be carried out
 To carry out all the production activities, machining, casting, assembling, testing etc. to
produce a full product
 To make sure all the components are without any defects & short-comings
 All manufactured parts are well according to the drawings provided by the design
department
 To manage and make sure all the manufacturing machinery and equipment is working
properly, well according to the set standards
1.3.7 Customer Service (Repair & Service)
Responsibilities of Customer Service (Repair & Service) department include:
 To perform after sales services
 Repairing and servicing of the sold components when required
 To assist customer in the proper functioning and installation of the product
 Guiding and training customers for installing and operating the product
 At field servicing
 Assisting in trouble-shooting of the product
1.3.8 Maintenance
Responsibilities of Maintenance department include:
 To maintain and repair the manufacturing equipment
 Request for the defected parts and components of the broken machinery
 To handle the scrap
 To assure each equipment is delivering to its optimal point

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 To keep the equipment upto the set standards
1.3.9 Quality
Quality management ensures that an organization, product or service is consistent. It has four main
components: quality planning, quality assurance, quality control and quality improvement. Quality
management is focused not only on product and service quality, but also on the means to achieve it
Responsibilities of Quality department include:
 To assure the quality of the products and services meet the set standards consistently
 To assure each product is according to the design and the set standards
 To point out the defects and shortcomings in the manufactured parts and products
 To assure that each product is meeting the requirements of the client
1.3.10 HSE (Health, Safety & Environment)
Responsibilities of HSE department include:
 To Suggest proactive measurements that prevent incidents before they manifest as accidents
 Coordinate all health and safety aspects of the company
 Draft health and safety plans
 Comply with all relevant HSE regulations and requirements
 Ensure the health and safety of workers, decrease accident risks and improve onsite productivity
 To conduct Safety training courses

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2.Products Made in Pakistan by KSB
KSB is one of the market leaders in manufacturing quality pumps, in its state-of-the-art manufacturing facilities,
that are reliable as well as suitable for a particular application in an industry. KSB expert
Although there are 71 types of pumps that KSB manufactures & distribute around the globe which include
reciprocating & centrifugal pumps. But KSB Pakistan is producing 17 different models of centrifugal pumps
only, each customized for a particular application. The most widely demanded models being produced are
discussed here:
2.1 DWT B-Pumps
Application
Deep Well Turbine (DWT) B Pumps are suitable for water supply
schemes, irrigation
schemes, lowering of ground water level and dewatering of mines,
quarries, construction
sites and sea water applications. These are particularly suitable for
narrow bore holes.
Minimum bore hole sizes required ranges from 150mm to 600mm.
Operating data
Capacity up to 2600 m3/hr
Total head up to 160 m
Speed up to 3500 RPM
Temperature up to 105°C
Suspended Depth up to 120 m
Design
Main pump parts are the
Pump Bowl Assembly, Column Pipe Assembly, and Discharge
Head Assembly. Bowl Assembly consists of single or multistage radially
split, interchangeable intermediate bowls. Column Pipe Assembly
consists of interchangeable lengths of the column pipes and variable
setting depth. Discharge head assembly consists of discharge head with
packed stuffing zone/mechanical seal and thrust bearing arrangement
(in case of solid shaft drive only).
2.2 Etanorm
Main applications
Pump for handling clean or aggressive fluids which are neither chemically nor mechanically aggressive to the
pump materials.
▪ Water supply systems
▪ Cooling circuits
▪ Swimming pools
▪ Fire-fighting systems
▪ General irrigation systems
▪ Drainage systems
▪ Heating systems
▪ Air-conditioning systems
▪ Spray irrigation systems

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Operating Data
Design
▪ Volute casing pump
▪ Horizontal installation
▪ Back pull-out design
▪ Single-stage
▪ Dimensions and ratings to EN 733
Pump casing
▪ Radially split volute casing
▪ Volute casing with integrally cast pump feet2)
▪ Replaceable casing wear rings
Impeller type
▪ Closed radial impeller with multiply curved vanes
2.3 SEWATECH / SEWABLOC
2.3.1 Main applications
▪ Waste water transport
▪ Waste water disposal
▪ Waste water management
▪ Transport of contaminated surface water
▪ Sludge processing
2.3.2 Fluids handled
▪ Grey water
▪ Solids-laden river water
▪ Contaminated surface water
▪ Waste water with faeces
▪ Industrial waste water
▪ Gas-containing fluids
▪ Activated sludge
▪ Digested sludge
▪ Raw sludge

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2.3.3 Operating Data
2.3.4 Design
Sewatec:
▪ Single-stage
▪ Various, application-oriented installation types
Sewabloc:
▪ Close-coupled pump with shaft seal
▪ Various, application-oriented installation types
2.4 MOVITECH/MOVIBOOST
2.4.1 Main application
▪ Fire-fighting systems
– Sprinkler systems to NFPA20, EN 12845, CEA 4001
– Watermist systems to CEN TS 14972
– Foam systems to EN 13565
2.4.2 Operating data
2.4.3 Design
▪ High-pressure in-line pump
▪ Maximum pressure class PN 40

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▪ Centrifugal pump
▪ Single-stage or multi-stage
2.4.4 Installation types
Standard:
Vertical installation
Optional:
Horizontal installation
2.5 KRT
▪ Waste water management
▪ Service water supply systems
▪ Disposal
▪ Sewage treatment plants
▪ Sludge disposal
2.5.2 Fluids handled
▪ Waste water with faeces
▪ Activated sludge
▪ Digested sludge
▪ Raw sludge
▪ Gas-containing fluids
▪ Industrial waste water
2.5.4 Design
▪ Fully floodable submersible motor pump
▪ Not self-priming
▪ Close-coupled design

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2.6 RPH
Pump for handling the large variety of crude oil products in
refineries as well as in the chemical and petrochemical
industry.
▪ Refineries
▪ Chemical industry
▪ Petrochemical industry
2.6.3 Design
▪ Single-stage
▪ Meets technical requirements to API 610, 11th edition /
ISO 13709
Pump casing
▪ Volute casing
with integrally cast pump feet
▪ Centerline pump feet
▪ Single or double volute, depending on the pump size
▪ Axial inlet nozzle, tangential discharge nozzle pointing
vertically upwards.
▪ Volute casing with casing wear ring
▪ Casing cover (with casing wear ring)
2.7 KWP
Pump for handling pre-treated sewage, waste water,
all types
of slurries without stringy material and pulps up to 5
% bone
dry with a maximum density of 2000 kg/m³.
▪ Paper and cellulose industry
▪ Sugar industry
▪ Food and beverages industry
▪ Fossil-fuelled power stations
▪ Chemical industry

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▪ Petrochemical industry
▪ Flue gas desulphurisation
▪ Coal upgrading plants
▪ Industrial effluent treatment systems
▪ Seawater desalination/reverse osmosis
2.7.3 Design
▪ Single-stage
▪ Single-entry
2.7.3.1 Pump casing
▪ Volute casing with
integrally cast pump feet
▪ Pump casing fitted with a
wear plate
2.7.3.2 Impeller type
▪ Back vanes reduce axial
thrust.
▪ Various, application-based
impeller types
2.8 PNW, SNW – Vertical tubular casing pumps
2.8.1 Applications:
■ Irrigation and drainage
■ Storm water handling in storm water
pumping stations
■ Raw and clean water transport in waterworks
■ Cooling water handling in power stations and
industrial plants
■ Industrial water supply
■ Docks, locks and sluices

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2.9 ZORO Submersible Motor Pump

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3.0 Tasks & Assignments
As the company shifted its ERP system to SAP in 2011, there was a large number of materials and
components which remain unregistered in the SAP Materials Database of the company. There is still around
3000 of those materials.
I was given the task to provide the documentation for as many materials as possible. Those components
whose standards are established already, were to be searched and get them registered in the SAP materials
module. Those components which were not standardized must be issued from the company’s store. If there is
some kind of technical data available for them from anywhere it must be searched for and attached, otherwise,
I was required to measure dimensions with the help of Vernier caliper and create drawings to get them
registered on SAP against the material.
I documented around 120 materials and get the, registered on the SAP database. Following is the list of the
materials which were documented:
S#
MATERIAL
NO.
DESCRIPTION STANDARD/DRAWING
1 1394667 CABLE LUGS 120 MM DIN 46329
2 1394643 CABLE LUGS 12-95 MM DIN 46329
3 1394668 CABLE LUGS 150 MM DIN 46329
4 1394645 CABLE LUGS 16MM TAIWAN DIN 46329
5 1394670 CABLE LUGS 185 MM DIN 46329
6 1394653 CABLE LUGS 25 MM 60 AMP DIN 46329

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7 1394649 CABLE LUGS 35 MM DIN 46329
8 1394651 CABLE LUGS 50MM DIN 46329
9 1394647 CABLE LUGS 6 MM 30 AMP DIN 46329
10 1394655 CABLE LUGS 70 MM DIN 46329
11 1394672 CABLE LUGS 95 MM DIN 46329
12 1391637 CARBIDE TIPS A-20-P30 ISO 242
13 1391632 CARBIDE TIPS A25 P30 - P40 ISO 242
14 1391633 CARBIDE TIPS B20 P30 - P40 ISO 242
15 1391636 CARBIDE TIPS B-20-P30 ISO 242
16 1391631 CARBIDE TIPS C 25 K20-K30 ISO 242
17 1391641 CARBIDE TIPS C16 -P30 ISO 242
18 1391640 CARBIDE TIPS C20 -P30 ISO 242
19 1391634 CARBIDE TIPS D 5 P30 - P40 ISO 242
20 1391639 CARBIDE TIPS D5-P30 ISO 242
21 1391568 CARBIDE TIPS D6 K10 ISO 242
22 1391630 CARBIDE TIPS D6-P30 ISO 242
23 1391638 CARBIDE TIPS E10 -P30 ISO 242
24 1391635 CARBIDE TIPS E10 P30 - P40 ISO 242
25 1394745 COPPER ENAMEL WIRE 16 SWG DIN 60317
35 1391231 COPPER ENEMALLED WIRE 18 SWG DIN 60317
41 1391982 COUNTER SINK HSS DIA 20MM 60DEG DIN 334-ISO 3294
42 1391984 COUNTER SINK HSS(A) DIA 30 MM DEG 90 DIN 335
43 1391980 COUNTER SINK(A) DIA 25 MM 90 DIGREE DIN 335
44 1530088 CROSS SLOTTED WOOD SCREWS 6 X 40MM DIN 7997 / DIN 97
54 1394298 DRILL COLLET ER 25 FOR SIZE 10.5 MM ISO 10897

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56 1662561 DRILL COLLET ER 25 FOR SIZE 13-14 MM ISO 10897
59 1394290 DRILL COLLET ER 40 FOR SIZE 17 MM ISO 10897
62 1395966 ELBOW 1/2" DWG.
63 1395978 ELBOW 1" DWG.
64 1407730 ELBOW 1";90 DWG.
65 1395980 ELBOW 1"X 1/2" DWG.
66 1407732 ELBOW 1.5";90 DWG.
67 1407863 ELBOW 1/2" DWG.
68 1407865 ELBOW 2" DWG.
69 1407734 ELBOW 2";uPVC DWG.
70 1395957 ELBOW G.I 1" DWG.
71 1395951 ELBOW G.I 1/2" DWG.
72 1395955 ELBOW G.I 3/4" DWG.
73 1395962 ELBOW GI 1x 1/2" DWG.
74 1395960 ELBOW GI 2"X1-1/2" DWG.
75 1394378 END MILL HOLDER BT50 SLA14-105 Attached
82 1394161 IMPACT HEX BIT 10 MM A/F-1/2" DIN 3126
96 1394337 TAPPING COLLET ER 25 WITH DIA 10 MM DIN 6499
102 1394340 TAPPING COLLET ER 40 WITH DIA 11.2 DIN 6499

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103 1394339 TAPPING COLLET ER 40 WITH DIA 11MM DIN 6499
106 1394346 TAPPING COLLET ER 40 WITH DIA 14MM DIN 6499
111 1396092 TEE 1" DWG.
112 1395164 TEE 1" SIZE 1" DWG.
113 1407723 TEE 1"X1"X1" DWG.
114 1407721 TEE 1.5"X1.5"X1.5" DWG.
115 1396076 TEE G.I 1" DWG.
116 1396070 TEE G.I 1/2" DWG.
117 1396088 TEE G.I 2" DWG.
118 1396074 TEE G.I 3/4" DWG.
119 1396072 TEE REDUCING G.I 3/4"X 1/2" DWG.
120 1396090 TEE REDUCING G.I 2"X 1" DWG.
121 1396093 TEE SS 3/4" DWG.
122 1391539 TWIST DRILL 2.5MM DIA DIN 340
131 1407683 UNION 1" DWG.
132 1396104 UNION 1" DWG.
133 1407685 UNION 1.5" DWG.
134 1396099 UNION G.I 1" DWG.
135 1396097 UNION G.I 1/2" DWG.
136 1396101 UNION G.I 2" DWG.
137 1396106 UNION S.S AISI 316L G 1/2" DWG.
138 1396102 UNION SS 1/2" DWG.
139 1407567 UNION-Y 1/4"X1/4"X1/4" DWG.
140 1390417 WELDING ELECTRODE 3.2 X 350 MM ISO 544
150 1390421 WELDING ELECTRODE 4 X 350 MM ISO 544

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153 1407725 REDUCING TEE 1.5"X1.5"X0.5" DWG.
154 1407859 REDUCING TEE 2"X1" DWG.
155 1407861 REDUCING TEE 2"X1/2" DWG.
4.0 Pump Basics
“A pump is a device that moves fluids (mostly liquids), or sometimes slurries, by mechanical action”
OR
“Hydraulic machines which move fluid from one place to another by converting the mechanical energy
into hydraulic energy ( Pressure energy) of the fluid”
Pumps operate by some mechanism (typically reciprocating or rotary), and consume energy to perform
mechanical work by moving the fluid.
Pumps operate via many energy sources, including manual operation, electric motors, engines, turbines.
4.1 Types of Pumps
Pumps are in general classified as:
I. Positive Displacement Pumps
II. Centrifugal Pumps (Roto-dynamic pumps)
4.1.1 Positive Displacement Pumps
A positive displacement pump operates by alternating filling a cavity and then displacing a given volume of
liquid.
 A positive displacement pump delivers a constant volume of liquid for each cycle independent of
discharge pressure or head.
The positive displacement pump can be classified as:
a. Reciprocating pumps - piston, plunger, radial and diaphragm
b. Power pumps
c. Steam pumps
d. Rotary pumps - gear, lobe, screw, vane, regenerative (peripheral) and progressive cavity
4.1.2 Centrifugal Pumps
The centrifugal or roto-dynamic pump produce a head and a flow by increasing the velocity of the liquid
through the machine with the help of the rotating vane impeller.

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 This increased kinetic energy of the fluid is converted into pressure energy by implementing a volute
casing or diffuser to deliver higher heads.
 The Centrifugal Pump has varying flow depending on the system pressure or head
5.0 Selecting between Centrifugal or Positive Displacement Pumps
Selecting between a Centrifugal Pump or a Positive Displacement Pump is not always straight forward.
 Flow Rate and Pressure Head
The two types of pumps behave very differently regarding pressure head and flow rate:
 The Centrifugal Pump has varying flow depending on the system pressure or head
 The Positive Displacement Pump has more or less a constant flow regardless of the system pressure
or head. Positive Displacement pumps generally make more pressure than Centrifugal Pumps
 Capacity and Viscosity
Another major difference between the pump types is the effect of viscosity on capacity:
 In a Centrifugal Pump the flow is reduced when the viscosity is increased
 In a Positive Displacement Pump the flow is increased when viscosity is increased
Liquids with high viscosity fills the clearances of Positive Displacement Pumps causing higher volumetric
efficiencies and Positive Displacement Pumps are better suited for higher viscosity applications. A Centrifugal
Pump becomes very inefficient at even modest viscosity.
 Mechanical Efficiency
The pumps behaves different considering mechanical efficiency as well.Changing the system pressure or head
has little or no effect on the flow rate in a Positive Displacement Pump
 Changing the system pressure or head may have a dramatic effect on the flow rate in a Centrifugal
Pump
 Net Positive Suction Head - NPSH
Another consideration is the Net Positive Suction Head NPSH.
 In a Centrifugal Pump, NPSH varies as a function of flow determined by pressure
 In a Positive Displacement Pump, NPSH varies as a function of flow determined by speed.
Reducing the speed of the Positive Displacement Pump, reduces the NPSH

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COMPARISON
CENTRIFUGAL PUMP RECIPROCATING PUMP
1. Operating
Principles
a. Fast Rotating
b. Converts kinetic energy to pressure
head
c. Direct coupled driver
a. Linear Movement
b. Exerts force to overcome
system resistance (pressure)
c. Speed reduction needed
2. Capacity & Head
(Pressure)
a. High Volume, Low Pressure
b. High Pressure, more stages
c. Capacity is proportional to impeller
speed and diameter
d. Head is proportional to the square
of the diameter or speed
a. High pressure (up to
40,000psi) ,low volume
b. Smaller plunger, higher
pressure
c. Capacity is proportional to
speed and plunger diameter
d. Pressure is as high as the
design limit
e. Rated pressure is for full
speed range
3. Efficiency
a. Efficiency loss: hydraulic, volumetric
and mechanical
b. Normal efficiency 30-60%, Best
efficiency point usually less than
80%
c. Efficiency changes as flow rate &
head changes
a. Efficiency Loss: Hydraulic &
mechanical
b. Normal efficiency 90%
c. Efficiency keeps constant
4. Effect of
Viscosity
a. High viscosity drops head & flow
rate
b. High viscosity reduces efficiency
and increases power requirement
a. High viscosity has usually little
effect on pressure and flow
rate
b. High viscosity has little effect
on efficiency
5. Energy
Consumption
 Centrifugal pump has 1.40-1.90
times the energy consumption of
reciprocating pump, upto 2-3 times
if operated below 40% efficiency
6. Performance at
constant speed
a. Head drops as flow rate increases
b. Loss of flow rate if system head
requirements are higher than
design point
c. Needs a regulator valve and
consumes more energy than
needed if system head is lower than
design point
d. Needs a regulator valve consumes
more energy than needed if design
point has a safety margin on head
and flow rate
a. Constant flow rate even if the
pressure changes
b. Constant flow rate if system
head is higher than design
point
c. Constant flow rate and lower
energy consumption if system
head is lower than design
point
d. Needs a bypass valve
consumes less energy than
needed if design point has a
safety margin on head and
flow rate
7. Pump
Characteristics
a. Steady smooth flow a. Flow variation
b. Pulsation suppression device
needed to avoid excessive
vibrations
8. Maintenance
 Shop repair usually need if pump
fails
 Field repairable

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6.0 Classification of Centrifugal Pumps based on Several Design Features
Centrifugal Pumps can be Classified on the basis of several characteristics:
1. Suction Design
a. Single-Suction
b. Double ended suction
2. Number of Impeller stages
a. Single stage
b. Double Stage
c. Multistage (more than two)
3. Guide Vanes
a. Volute
b. Diffuser vanes
4. Casing
a. Radially Split casing
b. Axially Split casing
c. Double Casing
d. Single casing
e. Back-Pullout casing
5. Construction
a. Submersible
b. Inline
c. Axial
6. Impeller Type
a. Open
b. Semi-closed
c. Closed
7. Shaft Orientation
a. Vertical
b. Horizontal
c. Inclined
8. Fluid Flow
a. Radial
b. Axial
c. Mixed
9. Volute casing
a. Single Volute
b. Double Volute
10. Multi units
a. Series
b. Parallel
11. Impeller Installment
a. Overhung
b. Impeller B/w bearings

26
7.0 Some Topics related to centrifugal pump
7.1 Air entrainment in the centrifugal pumps
Centrifugal pumps are designed as
hydraulic machines to move liquids. Any
amount of entrained air or gas present will
cause deterioration in pump performance
as well as it will be a cause of
 Turbulence,
 Cavitation,
 Vibrations,
 Noise
 Pitting, wearing of pump
components
Therefore we can say that presence of
air/gas is highly undesirable. Air can be
entrained in the pump due to many
reasons:
 Improper suction conditions
 Vortex Formation
 Recirculation
 Cavitation
 Leakage
 Improper Piping
Vent Holes: It is a common practice by the manufacturers to introduce holes in the pump body called the vent
holes, to release any kind of entrapped air/vapour which may accumulate in the pump during the operation due
to re-circulation, eddies, vortex, turbulence, cavitaton etc.
7.2 Energy and head in pump systems
Energy and head are two terms that are often used in pump systems.
There are four forms of energy in pump systems:
 Pressure
Pressure is produced at the bottom of the reservoir because the liquid fills up the container completely
and its weight produces a force that is distributed over a surface which is pressure. This type of
pressure is called static pressure.
 Elevation
Elevation energy is the energy that is available to a liquid when it is at a certain height.
 Friction
Friction energy is the energy that is lost to the environment due to the movement of the liquid through
pipes and fittings in the system.
 Velocity
Velocity energy is the energy possess by the fluid moving in the pump system due to its velocity.
When talking about pumps, we have to deal with raising the fluids to some heights at specific flowrates. It is
therefore much convenient to express energy of the fluid in terms of height (m,ft,in) i.e Head

27
7.2.1 Head is expressed in units of height such as meters or feet. The static head of a pump is the maximum
height (pressure) it can deliver the fluid. Also known as specific energy or energy per unit weight of fluid,
expressed in feet or meters.
7.2.2 Different Types of Pump Heads
Total Static Head -- Total head when the pump is not running, TSH is the pressure energy the fluid already
possess before entering into the pump
Total Dynamic Head (Total System Head) – Total head when the pump is running
Static Suction Head – Head on the suction side, with pump off, if the head is higher than the pump impeller
Static Suction Lift – Head on the suction side, when pump is off, if the head is lower than the pump impeller
Static Discharge Head – Head on discharge side of pump with the pump off
Dynamic Suction Head/Lift – Head on suction side of pump with pump on
Dynamic Discharge Head – Head on discharge side of pump with pump on
7.3 Impeller eye
The area of the centrifugal pump that channels fluid into the vane area of the impeller is impeller eye. The diameter
of the eye will control how much fluid can get
into the pump at a given flow rate without
causing excessive pressure drop and
cavitation.
7.4 Cavitation
The collapse of bubbles that are formed in the eye of the impeller due
to low pressure leads to cavitation. The implosion of the bubbles on
the inside of the vanes creates pitting and erosion that damages the
impeller. The design of the pump, the pressure and temperature of
the liquid that enters the pump suction determines whether the fluid
will cavitate or not.
as the liquid travels through the pump the pressure drops, if it is
sufficiently low the liquid will vaporize and produce small bubbles.
These bubbles will be rapidly compressed by the pressure created by
the fast moving impeller vane. The compression creates the
characteristic noise of cavitaion. Along with the noise, the shock of the
imploding bubbles on the surface of the vane produces gradual
erosion and pitting which damages the impeller.

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7.5 Net Positive Suction Head (NPSH)
NPSH can be defined as two parts:
7.5.1 NPSH Available (NPSHA):
The absolute pressure at the suction port of the pump is NPSHA
AND
7.5.2 NPSH Required (NPSHR):
The minimum pressure required at the suction port of the pump to keep the pump from cavitating.
7.5.2.1 Why NPSHR prediction is important?
Liquid will vaporize if its pressure reduces below the its vapour pressure in the prevailing conditions. As liquid
travels from suction nozzle to the the impeller eye, it will experience pressure losses caused by friction,
acceleration and shock at the blade entry. If the summation of these losses permits vaporization of the liquid,
vapor bubbles will form in the impeller eye and travel through the impeller and upon reaching a high pressure
region will collapse causing many problems like pitting, wearing of impeller, vibrations, noise etc. Hence
prediction NPSHR is highly important for safe, reliable and persistent operation of the pump.
NPSHR depends upon following characteristcs
 Design of the pump casing
 Impeller Design and material
 Impeller eye area
 The velocity of fluid within the impeller eye
 The peripheral velocity of the fluid at impeller tip
 Speed of rotation of the impeller
Therefore, for safe, reliable and persistent operation of the pump it is therefore necessary that the pressure of
the fluid entering into the pump (NPSHA) be greater than the required minimum pressure (NPSHR) to prevent
the pump from cavitating.

29
NPSHA > NPSHR
7.6 Pump Curve, System Curve & Duty/Operating Point
7.6.1 Pump Curve: The Flow vs. Head curve of the pump at a constant RPM, also called the performance curve of the
pump
7.6.2 System Curve: The flow vs. total head curve generated according to the calculations done for the required
pump system under the customer’s given inlet & piping conditions. Calculations are done for the total head at
different flow rates, these points are linked and form a curve called the system curve.
It can be used to predict how the pump will perform at different flow rates.
The Total head includes the
 static head which is constant
 the friction head loss
 velocity head difference which
depends on the flow rate
7.6.3 Duty / Operating Point: The
intersection of the system curve with
the pump characteristic curve defines
the operating point of the pump.
 It should lie around the BEP of
the pump for long-life operation
of the pump.
7.7 Best Efficiency Point (B.E.P.)
The point on a pump's performance curve that corresponds to the highest efficiency. At this point, the impeller is
subjected to minimum radial force promoting a smooth operation with low vibration and noise.
 At B.E.P a pump have the maximum life expectancy and least chances of failure during a
prolonged operation. It corresponds to the maximum performance a pump can deliver.
 BEP is the function of the pump design.

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7.8 Suction-specific speed
A number that indicates whether the suction conditions are sufficient to prevent cavitation. It also predicts the
stable operation range of a pump.
According to the Hydraulic Institute the suction specific speed should be less than 8500 for a stable operation.
Other experiments have shown that the suction specific speed could be as high as 11000.
When a pump has a high suction specific speed value, it will also mean that the impeller inlet area has to be
large to reduce the inlet velocity which is needed to enable a low NPSHR. However, if you continue to increase
the impeller inlet area (to reduce NPSHR), you will reach a point where the inlet area is too large resulting in
suction recirculation (hydraulically unstable causing vibration, cavitation, erosion etc..). The recommended
maximum suction specific speed value is to avoid reaching that point.
Suction Specific speed can be calculated as:
N: RPM
Q: Flowrate @ BEP
NPSH: NPSH Required (NPSHR) @ BEP
7.9 Specific speed
Specific speed is defined as "the speed of an ideal pump geometrically similar to the actual pump,
which when running at this speed will raise a unit of volume, in a unit of time through a unit of
head "
 Specific speed predicts the geometry (shape) of a pump impeller
Specific speed is calculated from the following formula, using data from these curves at the pump's
best efficiency point (bep.):
N = The speed of the pump (rpm.)
Q = The flow rate
H = The total dynamic head

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7.10 Trimming of an impeller
7.10.1 Why trim an impeller?
 Usually, a company manufacturing pumps have a line of pump series, each pump having its specific
performance curve. When selecting pump, in order to meet the desired performance it is sometimes
needed to match the pump curve to the duty/operating point. To do so, there are several ways. One
way is to trim the impeller to reduce its diameter until its performance curve meets the duty point.
 As a trimmed impeller requires lesser power, sometimes it is often necessary to trim the impeller to
reduce its operating power in order to adjust it according to the available motor’s rating. But it should be
done within narrow ranges in order to avoid affecting the pump performance.

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7.10.2 Consequences of trimming:
 Decreases the overall efficiency of the pump
 If the diameter is reduced more than 5-10% of the original diameter, the NPSHR will increase
abruptly. Therefore, trimming should be avoided if the difference between the NPSHR and NPSHA
is small
 A trimmed impeller requires lesser power to rotate at the same speed
7.11 Volute Casing and addition of diffuser vanes
Centrifugal pumps are suitable to applications
where large heads are required with large flow
rates. Impellers impart kinetic energy to the fluid.
But in order to reach high heads, pressure must be
increased. In order to increase pressure, the
imparted kinetic energy is converted into pressure
energy by volute casing. In addition to volute casing
diffuser vanes can also be used for more efficient
operation
7.11.1 Volute Casing: Volute is a curved funnel
that increases in area as it approaches the
discharge port and acts like a diffuser increasing
the pressure of the fluid.
The addition of diffuser vanes depend upon the
application.
Pump with Volute Casing Only Pump with Diffuser Vanes in the Volute
Spacious, requires a bigger casing
Compact, occupies lesser space leading to
reduced casing size
Cheaper Extra machining required, costlier
Less efficient, large radial thrust leads to
non-uniform pressure distribution which
can cause deterioration of the pump
casing
Most efficient
7.12 Velocity triangles -- Impeller
In pump, a velocity triangle or a velocity diagram is a triangle representing the various components of velocities
of the working fluid while passing through an impeller. Velocity triangles may be drawn for both the inlet and outlet
sections of the impeller. The vector nature of velocity is utilized in the triangles, and the most basic form of a velocity
triangle consists of the tangential velocity, the absolute velocity and the relative velocity of the fluid making up three
sides of the triangle.

33
7.13 Priming
Before starting a centrifugal pump which has to lift the fluid from some depth, it will be initially fully filled with
air. As centrifugal pumps are not capable of pumping air or vapors, the pump will not suck liquid and will keep
on running without extracting water out from its reservoir i.e it will not operate.
Priming is the process in which the impeller of a centrifugal pump will get fully sub merged in liquid without any
air trap inside. This is especially required when there is a first start up. Priming can be done either manually by
use of some external auxiliary pump or by introducing the self-priming mechanism in the pump.
7.13.1 Self-Priming:
A pump will be self-priming if its casing is always filled with some fluid either when it is running or is turned off.
So that the next time when its turned ON the casing is still filled with some water and there is a column of
entrapped air in between. The pump will release the entrapped air by creating a vaccum while retaining the
fluid inside the casing.

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7.14 Losses in a pump
7.14.1 Hydraulic losses
 Friction losses in the impeller.
 Shock or eddy losses at inlet to outlet of impeller.
 Friction and eddy losses in the diffuser or guide vanes and casing.
 Friction losses in suction and delivery pipes.
7.14.2 Mechanical losses
 Losses due to friction between liquid and impeller in space between impeller and casing
 Losses due to friction between different parts like bearing, glands packing etc.
7.14.3 Leakage losses
 Loss of energy due to pressure difference between liquid inside the pump and atmosphere.
8.0 Some Useful Pump Formulas
8.1 Pressure to Head
8.2 Mass Flow to Volumetric Flow

35
8.3 Net Positive Suction Head
8.4 Pump Head

36
8.5 Pump Power
8.6 Pump Torque
8.7 Temperature Rise
8.8 Fluid Velocity

37
8.9 Velocity Head
8.10 Specific Speed at BEP
8.11 Suction Specific Speed at BEP

38
8.12 Affinity Laws
8.13 Bernoulli’s Equation

39
9.0 Parts of a typical Centrifugal Pump

40
9.1 Impeller
It is rotating element of centrifugal pump that imparts kinetic energy to the fluid. It consists of finite number of
curved vanes. The number of vanes vary, normally 6 to 12 in the impeller. Impeller is mounted on shaft which
is coupled with the shaft of electric motor.
Following types of vanes can be used, depending upon the application
9.1 Closed or shrouded impeller:
 The vanes are covered with metal side plate (shrouds) on both sides.
 Wear is reduces.
 Long life performance with full capacity.
 High efficiency.
 This type of pump is used when liquid to be pumped is pure and free from debris.
9.2 Semi-open impeller:
 In this single plate (shroud) on the back side.
 This pump handle liquids containing fibrous materials like paper pulp, sugar molasses and sewage
water etc.
9.3.Open impeller:
 Impeller vanes are not containing shrouds (side plate) on either side.
 Vanes are open on both side.
 Handle abrasive liquids like a mixture of water-sand, pebbles and clay etc.

41
9.2 Casing
It is an air tight passage surrounding the impeller and its designed in such a way that the kinetic energy of
liquid coming from impeller is converted
into pressure energy before the delivery
pipe
Centrifugal pumps are suitable to
applications where large heads are required
with large flow rates. Impellers impart kinetic
energy to the fluid. But in order to reach high
heads, pressure must be increased. In order
to increase pressure, the imparted kinetic
energy is converted into pressure energy by
ther casing of the pump.
9.2.1 Volute or spiral casing type pump:
 Impeller is surrounded by the spiral
casing known as volute chamber
provides a gradual increasing area to
the discharge pipe.
 Simple in construction.
 Greater eddy losses which decreases
overall efficiency.

42
9.2.2 Vortex (whirlpool) casing type pump:
 Modified type of volute casing pump.
 Circular chamber is inserted between the impeller and volute chamber this chamber is known as vortex
or whirlpool chamber.
 Improvement in performance due to reduces of eddies.
9.2.3 Diffuser type (turbine) pump:
 The impeller is surrounded by a series of stationary guide blades mounted on a ring which is known as
diffuser.
 More pressure head is developed compared to vortex & volute type pump.
 Higher efficiency.
9.3 Delivery pipe and Suction pipe with foot valve and a strainer
• 9.3.1 Suction pipe: It is pipe whose one end is
connected to the inlet of the pump and other end dips in
to water in a liquid sump.
• 9.3.2 Delivery Pipe: A pipe whose one end is
connected to the pump and other end delivers at a
required height is called delivery pipe.
• 9.3.3 Foot valve: It is a non-return valve essentially for
all types of roto-dynamic pumps. It helps in allowing the
liquid to enter into pump at the suction but does not
allow it to flow back. The purpose of a foot valve is to
maintain pump prime between pumping cycles.
• 9.3.4 Strainer: The strainer is essential for all type of
pumps. It protects pump against foreign material passes through the pump, without strainer pump may be
chocked.

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9.4 Shaft
9.4.1 Shaft:
A shaft is a rotating machine element, usually circular in cross section, which is used to transmit power from one
part to another, or from a machine which produces power to a machine which absorbs power
In pumps the shaft transmits power from the power source to the fluid through the impeller. Shaft diameter depends
upon the type and design of the pump.
Shaft also holds other components of the pump like seal, bearings etc.
9.4.2 Stresses induced in shaft:
As the pump shaft rotates there are several stresses induced in the shaft, which must be addressed otherwise,
pump may fail. Following are the stresses induced:
1. Shear stresses due to the transmission of torque (due to torsional load).
2. Bending stresses (tensile or compressive) due to the forces acting upon the shaft due to other machine
elements like gears and pulleys, as well as the weight of the shaft itself.
3. Stresses due to combined torsional and bending loads.

44
9.5 Bearings
Machine elements which are used to guide the moving (turning, sliding, rolling) parts of the machines and
to”bear” any kind of loads/stresses (Axial,radial,torsional) induced in them, offering minimal frictional resistance
and energy losses are Bearings
9.5.1 Bearings in Pumps:
Bearings are used to counter the stresses produced in a pump shaft during operation. Stresses are induced in
the shaft due to:
 Hydraulic loads imposed on the impeller (radial, axial)
 Mass of impeller and shaft
 Loads due to the shaft coupling or belt drive.
Bearings are used in pumps as they keep the shaft axial end movement and lateral deflection within
acceptable limits for the impeller and shaft seal.
9.5.2 Hydraulic Loads:
The hydraulic loads comprise of hydrostatic and momentum forces from the fluid.
The forces on the impeller are simplified into two components: axial load and radial load.
9.5.2.1 Axial Load The axial hydraulic pressures consists of:
1. The hydrostatic force acting on the impeller’s front shroud and
hub (back) shroud due to the hydraulic pressures acting on the
surface areas of the shrouds
2. The momentum force due to the change in direction of the
fluid flow through the impeller.
3. The hydrostatic force due to the hydraulic pressure acting on
the impeller (suction) opening. The hydrostatic forces dominate

45
the impeller loading
9.5.2.2 Radial Load:
Radial Load The hydraulic radial load is due to the unequal velocity of the
fluid flowing through the casing. The unequal fluid velocity results in a non-
uniform distribution of pressure acting on the circumference of the impeller.
The radial load is most influenced by the design of the pump casing. The
casing is designed to direct the fluid flow from the impeller into the
discharge piping. In a theoretical situation at BEP, the volute casing has a
uniform distribution of velocity and pressure around the impeller periphery.
In a real volute at the BEP, the flow is most like that in the theoretical
volute except at the cutwater (or tongue) which is needed for the volute
construction. The disturbance of flow at the cutwater causes a non-uniform
pressure distribution on the circumference of the impeller resulting in a net
radial load on the impeller.
 The radial load is minimum when the pump is operating at the BEP
and is directed towards the cutwater. The radial load increases in
magnitude and changes direction at flows greater than and less
than the BEP
9.5.3 Calculating Bearing Reactions/loads:
Use following formulas to calculate bearing reactions in order to select
bearings. Bearing loads should be evaluated at the BEP condition and at the maximum and minimum pump
rated conditions

46
9.5.4 Bearing types for
centrifugal pumps
Figure illustrates that the rolling
bearings are most suitable and
common to centrifugal pumps.
 Cylindrical roller bearing
 Spherical roller bearing
 Taper roller bearing set
 Spherical Roller thrust
bearing
The three most used ball bearing
types are
 Single row deep groove ball
bearing
 Double row angular contact
ball bearing
 Universally matchable
single row angular contact
ball bearing
Ball bearings are most commonly
used in small and medium sized
pumps because of their high speed
capability and low friction.
For pump applications, Conrad (i.e.
without filling slots) bearings are
preferred over the filling slot type
bearing.
9.5.5 Bearings used in KSB:
At KSB angular contact ball
bearings are preferred in all types of
pumps due to their ability to bear
axial as well as radial loads while
offering minimum frictional
resistance du to the point contact of
the ball bearings. In case of roller
bearings, rollers make a line contact
with the bearing case due to which
there is larger frictional losses.
Angular contact ball bearings can
be arranged in different pairs to
offer more useful application
depending upon the requirements.
Following figure shows different
arrangements.

47
9.6 Lubrication
The primary functions of the lubricant in rotating equipment are:
 Minimize or eliminate friction – Separate moving parts
 Wear control – Reduce abrasive wear
 Corrosion control – Protects surfaces from corrosive substances
 Temperature control – Absorbs and transforms heat
 Contamination control – Prevention of dirt and wear debris damage
Lubrication is necessary wherever rotating elements come in contact with each other to avoid any material
damage which may ultimately lead to the pump failure.
The most common types of methods for lubricating rolling element bearings in horizontal process pumps are:
 Grease
 Oil Splash
 Pure oil mist

48
9.7 Seal
During the pumping operation, the pressure builds up inside the pump casing. The fluid can leak from holes
and uncovered openings in the casing other than the suction and the discharge ports. Therefore, the suction
side of the pump where the shaft enters into the casing and the backside of the pump where the shaft leaves
the casing for coupling to the power source, must be sealed to avoid leakage. There are usually two types of
seals used in pumps.
9.7.1 Mechanical Seals:
A mechanical seal is a sealing device which forms a running seal between rotating and stationary parts. They
were developed to overcome the disadvantages of compression packing.
9.7.1.1 Construction:
All mechanical seals are constructed of three basic sets of parts:
 A set of primary seal faces: one that rotates and one that
remains stationary.
 A set of secondary seals known as shaft packings and
insert mountings, such as
 O-rings
 Rubber boots
 PTFE
 Grafoil wedges
 V-Rings
 Mechanical Seals have hardware including
 Gland rings
 Collars
 Compression rings,
 Pins
 Springs
 Retaining rings
 Bellows
9.7.1.2 How it works:
A mechanical seal works through the use of two very flat lapped faces which make it difficult for leakage to
occur. As mentioned above one face is stationary and one rotates with the shaft. One of the two faces is
usually a non-galling material such as carbon-graphite. The other will be a harder material providing dissimilar
materials making contact and allowing one to be a sacrificial. The softer mechanical seal face usually has the
smaller mating surface and is commonly called the "wear nose" of the mechanical Seal.
9.7.1.3 Types:
 Single spring mechanical seals:
Utilize a single spring coiled in a right of left hand design to accommodate left and right hand turning
pumps. They have the flexibility to accommodate misalignment, shaft deflection, and break away shock
loading. It resists clogging in extremely viscous fluids.
 cartridge type mechanical seal:
The Easiest seal to install is a cartridge type mechanical seal, which is slid onto the shaft and bolted to the
pump gland, fitted in the stuffing box
The benefit of cartridge seals is that they are self-contained. Holding all the elements of a mechanical seal
set:
 Rotating Face Seal
 Stationary Seal face or faces
 Shaft sleeve
 Gland

49
9.7.2 Gland packing:
This type of seal consists of a typical stuffing box with gland packing. The function of packing is to control
leakage and not to eliminate it completely. The packing must be lubricated, and a flow from 40 to 60 drops per
minute out of the stuffing box must be maintained for proper lubrication. This makes this type of seal unfit for
situations where leakage is unacceptable but they are very common in large primary sector industries such a
mining and pulp and paper industry.
9.8 Coupling
A coupling is a device used to connect two shafts together at their ends for the purpose of transmitting power.
The primary purpose of couplings is to join two pieces of rotating equipment while permitting some degree of
misalignment or end movement or both.
In pumps coupling connects the pump to the power source.By careful selection, installation and maintenance
of couplings, substantial savings can be made in reduced maintenance costs and downtime.

50
9.8.1 Function:
 To provide for misalignment of the shafts or to introduce mechanical flexibility.
 To reduce the transmission of shock loads from one shaft to another.
 To introduce protection against overloads.
 To alter the vibration characteristics of rotating units.
 To connect driving and the driven part
 To transfer power one end to another end
9.8.2 Selection Criteria:
The following technical information is normally required when selecting a coupling:
 Horsepower/torque to be transmitted
 Operating speed
 Angular Misalignment
 Torsional Flexibility to accommodate torsional forces
 Offset misalignment
 Axial travel of the shaft due to axial loads
 Limitation on coupling generated forces
 Ambient temperature
 Space limitations
Radial and/or axial loads that are transmitted to the pump and/or motor bearings (through the coupling) will
reduce the life of the bearings thus adding to the cost of the pump. Further, any transmitted vibration will also
short the life of the pump components, thus leading it to the failure.

51
9.8.3 Types of couplings used in pumps:
Depending upon the application and requirements, following couplings can be used in the pumps
9.8.3.1 Sleeve couplings
 Cheapest
 Easy to manufacture
 Easy to replace
 Misalignment not permitted
 Transmits Vibrations
 Cant absorb shocks
9.8.3.2 Flanged Coupling
Consist of two separate flanges coupled together by bolts and nuts.
 can be disassembled
 doesn’t allow misalignment
9.8.3.3 Gear Coupling
Gear couplings are probably the most frequently used mechanically flexible coupling configuration. They are
"power-dense", meaning that they are capable of transmitting high torque at high speeds in a compact size.
Axial force and moment transmission can be quite significant with gear couplings. The axial force must be
absorbed by the thrust bearings in the driver and driven machines. Also, these couplings must be periodically
lubricated with coupling specific grease, which adds to the maintenance cost. Further, the gear teeth are prone
to wear over time.

52
9.8.3.4 Flexible couplings
Flexible couplings, which are used for most horizontal pump applications, may be separated into two basic
types, mechanically flexible, material-flexible.
ADVANTAGES:
 No downtime for lubrication
 Transmit low, known, thrust forces
 Can be designed for infinite life
 Better balance can be maintained
 Torsionally Stiff
 Good high temperature capability
 High torque
 High speed
 Zero backlash
 Mechanically flexible couplings compensate for misalignment between two connected shafts by means
of clearances incorporated in the design of the coupling.
 Material-flexible couplings rely on flexing of the coupling element to compensate for shaft misalignment,
by using flexible materials such as elastomers.

53
9.8.3.5 Pin Coupling
 Suitable for shock load conditions
 Rubber buffers provide robust flexibility
 Torsional flexibility - shock absorbing
 Maintenance free - minimum number of wearing parts
 Misalignment capabilities - flexibility in installation
9.8.3.6 Magnetic Coupling
Magnetic couplings are the most modern coupling devices which have proved their usefulness in the pump
industry due to its advantages. Biggest advantage of this type of coupling is that they are non-contact
couplings. Hence, there is no longer need of the stuffing box or seals as the pump shaft and the power source
can still transmit power with no physical connection in between.
Magnetic couplings rely on rare earth permanent magnets which induce current flow in the mating electro
magnets. They are separated by an air gap.
Advantages of magnetic couplings:
 Low maintenance, does not require periodic lubrication
 Tolerates gross parallel and angular misalignment.
 Eliminates vibration transfer between motor and pump
 Increases seal life
 Permits shock loading
 Overload torque protection, self-resetting
 Cushioned starts and stops

54
Limitations of magnetic couplings:
 High initial cost
 Couplings will experience a 1% - 3% slip (slight speed reduction)
 Heat sensitive:
– Induction current adds heat to driven portion of coupling
– Excessive heat can weaken permanent magnet strength.
9.8.4 Arrangement:
Long-Coupling:
The motor shaft is connected to the impeller with an intermediate shaft with two couplings
Close Coupling:
The motor shaft is connected to the impeller without an intermediate coupling providing a compact
arrangement. The flow range is typically less than 300 gpm.

55
9.9 Casing Wear Rings
Due to vibrations and moments generated in the shaft, it may show some irregular movements causing the
rotating impeller to come in contact with the pump casing. The casing will wear off leading to the pump failure.
In order to avoid it, casing wear rings are installed at both the suction side and the discharge side in order to
prevent the casing from wearing off. Wear rings are made up of soft-metal which acts as a sacrificial element.
It can be replaced when it wears off.

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