Manufacturing Processes of Centrifugal pumps at Milnars Pumps Ltd.

21
A Study on Manufacturing Process of Centrifugal Pumps at Milnars Pumps Ltd.
Md. Amir Hossain
ID # 12207034
Department of Mechanical Engineering
IUBAT—International University of Business Agriculture & Technology
Submission Date:

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In the name of Allah, The Most
Beneficent, the Most Merciful
and the Most Gracious

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A Practicum Report Submitted to the Department of Mechanical
Engineering at IUBAT – International University of Business
Agriculture and Technology in Partial Fulfillment of the
Requirements for the Degree of Bachelor of Science in Mechanical
Engineering

29
Student’s Declaration
This to inform that the Practicum Report ―A Study on Manufacturing Process of
Centrifugal Pumps at Milanars Pumps Ltd.‖ has been prepared only for academic
purpose. I also confirm that it has not been submitted elsewhere for any reward or
presentation or any other purpose.
Md. Amir Hossain
ID # 12207034

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Abstract
Milnars Pumps Limited is one of the leading centrifugal pump manufacture company in
Bangladesh, which is come out holding the hand of KSB. It was originally founded in 1961 in
the name of KSB Pumps Company Limited as an affiliate of KSB Germany at time when the
country was just on the verge of making a breakthrough in agricultural production of food
through small localized mechanical Irrigation system. Milnars pumps ltd. based on metal
casting manufacture of centrifugal pump. MPL have foundry shop, grinding shop, machine
shop, assembly shop, painting shop and test bench. They are used induction furnace for metal
melting; there are two furnaces which have 200 kg and 270 kg meting capacity respectively.
In foundry shop they cast volute casing, B.B Stole, Impeller of the centrifugal pump. In a
foundry, molten metal is poured into molds. Pouring can be accomplished with gravity, or it
may be assisted with a vacuum or pressurized gas. After degating and heat treating, sand or
other molding media may adhere to the casting. To remove this surface is cleaned using a
blasting process. The final step in the process usually involves grinding, sanding, or
machining the component in order to achieve the desired dimensional accuracies, physical
shape and surface finish. Removing the remaining gate material, called a gate stub, is usually
done using a grinder or sanding. These processes are used because their material removal
rates are slow enough to control the amount of material. These steps are done prior to any
final machining. There are several machine in MPL machine shop. Operators use these
machines for different purposes. Casting the product need machine operation to remove
runner and riser, surface finishing, turning, facing, drilling, boring, knurling, slot cutting etc.
When the machining is done and all the parts are completed as fit to assemble. After that the
pump is move through the testing bench for performance testing of the pump. The basis of
centrifugal pump testing is a direct function of its criticality to its application. If everything is
all right and pump performance is meet the customer requirement than it select for delivery, if
not than again this back to the assembly shop or machining shop for further operation.

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Acknowledgement
Professor M Alimullah Miyan, PhD
Vice Chancellor and Founder of IUBAT.
Prof Dr Engr A Z A Saifullah
Professor & Chair, Department of Mechanical Engineering.
Md. Abdul Wadud
Professor & Coordinator, Department of Mechanical Engineering
Md Sharifuzzaman
Internal Supervisor, Department of Mechanical Engineering
Engr. Morshed Cho. Miraz
Inspection and Quality Control Engineer, Milnars Pumps Ltd.
Engr. Md Badrul Alam
Sr. Dicetor, Milnars Pumps Ltd.

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2 A Study on Manufacturing Process of Centrifugal Pumps at Milnars Pumps Ltd.
Md. Amir Hossain Md Sharifuzzaman
ID # 12207034 Internal Supervisor

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Table of Contents
Introduction ....................................................................................................................37
Origin of the report..................................................................................................... 382.1
Aims and Objectives ................................................................................................... 382.2
2.2.1 Board Objectives............................................................................................................................ 38
2.2.2 Specific Objectives......................................................................................................................... 38
Scope ......................................................................................................................... 382.3
Methodology.............................................................................................................. 392.4
Sources of Data .......................................................................................................... 392.5
Limitations ................................................................................................................. 402.6
3 Company Overview..................................................................................................41
About Milnars Pumps Limited..................................................................................... 423.1
Company Location (Office & Factory) .......................................................................... 453.2
Message from Executive Chairman.............................................................................. 463.3
Mission ...................................................................................................................... 473.4
Vision......................................................................................................................... 473.5
Social commitment..................................................................................................... 473.6
MPL Management Chart............................................................................................. 483.7
MPL Product Application and Specifications................................................................ 493.8
Production Capacity of Milnars Pumps Ltd. ................................................................. 533.9
Certificate and Award of MPL ..................................................................................... 533.10
Product ...................................................................................................................... 533.11
Analysis of products of MPL........................................................................................ 543.12
3.12.1 Opportunities............................................................................................................................ 54
3.12.2 Strength .................................................................................................................................... 54
3.12.3 Weaknesses .............................................................................................................................. 54

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4 Theory of Centrifugal Pump......................................................................................55
Definition................................................................................................................... 564.1
Pump Setup & Installation .......................................................................................... 574.2
4.2.1 Foundation .................................................................................................................................... 57
Mounting ................................................................................................................... 584.3
Common Base Plate.................................................................................................... 584.4
Definition of Centrifugal Pump.................................................................................... 594.5
History of a Centrifugal Pump ..................................................................................... 594.6
Classification of Centrifugal Pump............................................................................... 614.7
4.7.1 Mechanically Actuated .................................................................................................................. 61
4.7.2 Hydraulically Actuated................................................................................................................... 62
4.7.3 Solenoid......................................................................................................................................... 62
4.7.4 Air Operated Double Diaphragm Pumps ....................................................................................... 62
Different Parts of Centrifugal Pump: ........................................................................... 634.8
4.8.1 Impellers........................................................................................................................................ 64
4.8.2 Volute Casing................................................................................................................................. 65
4.8.3 Suction cover ................................................................................................................................. 66
4.8.4 B.B Stool ........................................................................................................................................ 66
4.8.5 Shaft............................................................................................................................................... 67
4.8.6 Wear rings ..................................................................................................................................... 67
4.8.7 Ball Bearing.................................................................................................................................... 68
4.8.8 Gasket............................................................................................................................................ 68
4.8.9 Couplings ....................................................................................................................................... 69
Working Mechanism of a Centrifugal Pump................................................................. 704.9
4.9.1 Generation of Centrifugal Force.................................................................................................... 70
4.9.2 Conversion of Kinetic Energy to Pressure Energy.......................................................................... 71
4.9.3 Power............................................................................................................................................. 71
4.9.4 Efficiency........................................................................................................................................ 72
NPSH (Net Positive Suction Head) ............................................................................... 734.10
Brake Horse Power (BHP)............................................................................................ 754.11
........................................................................................................................................ 764.12

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5 Manufacturing Process of Centrifugal Pump.............................................................76
Foundry shop ............................................................................................................. 775.1
5.1.1 STEP-01: Core & Pattern Making................................................................................................... 78
5.1.2 STEP-02: Preparation of Sand & Mold Making .............................................................................. 82
5.1.3 Step-3 Melting and Pouring........................................................................................................... 84
5.1.4 Cast Iron Grade and Standard ....................................................................................................... 87
Machining Section ...................................................................................................... 895.2
5.2.1 Lathe Machine & its Operation ..................................................................................................... 89
5.2.2 Milling Machine & its Operations.................................................................................................. 93
5.2.3 Shaper Machine & its Operations.................................................................................................. 95
5.2.4 Grinding Machine & its Operations ............................................................................................... 96
5.2.5 Drill Machine & its Operations ...................................................................................................... 97
Assembly Section........................................................................................................ 995.3
6 Pump Testing Section & QC ....................................................................................101
Pump performance curve.......................................................................................... 1026.1
Head and Capacity Relationship................................................................................ 1046.2
Efficiency.................................................................................................................. 1056.3
7 Problem and Solution.............................................................................................107
LOCATION LOGIC ...................................................................................................... 1087.1
8 Supplementary Part ...............................................................................................111
Conclusion................................................................................................................ 1128.1
Recommendations.................................................................................................... 1138.2
Abbreviations........................................................................................................... 1158.3
Bibliography............................................................................................................. 1168.4

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Origin of the report2.1
Internship is the process of on-the-job training, which particularly beneficial for students with
major in technical courses. International University of Business Agriculture and Technology
(IUBAT) provide that glorious opportunity to their students of having an internship within
their bachelor program. For these purpose industry people are invited to IUBAT to talk about
their companies and experiences, often some technical courses are entirely conducted by
them. The four month internship program is another, possibly most effective, way of
achieving industry orientation. Internship helps the students to link-up their academic
experience with industry practices. I have tried my best to combine the both together. The
company I was sent for internship is Milnars Pumps Ltd. It is one of the leading pump
Manufacture companies in Bangladesh.
Aims and Objectives2.2
2.2.1 Board Objectives
The board objective of the report is to introducing with the Milnars Pump Ltd. and also their
production procedure, mainly the manufacturing proccess and the related other aspects of the
Milnars Pumps Ltd.
2.2.2 Specific Objectives
 To study about manufacturing process of centrifugal pumps.
 To study metal casting process, pattern making, core making and heat treatment
process of centrifugal Pumps.
 To study about the Induction furnace for metal casting.
 To study different type of machine operations.
 To study about the assemblies of centrifugal Pumps and
 To study about the testing process of centrifugal pump.
Scope2.3
Milnars Pump Limited has many types of product, such as Centrifugal Pumps, Multi-stage
Submersible Pumps, Jaw Plate, Sluice Valves etc. In this report I have only focused on the
manufacturing process of centrifugal pumps of the company, not on the overall product of the
industry. The internship report is concentrating on to instate and to shine the feasibility into

39
the existing industry and the sources are referred text and internet. All of their workers,
technician, and engineers are very helpful to gather information what I need ever.
Methodology2.4
The method of manufacturing process is started from foundry section by the raw metal
casting, mold making, pattern making etc. After that it will come to the machining section,
turning, facing, knurling, and boring all kinds machining work done by separate machine and
processes. Rest of the work done by the assembly shop and painting shop. After that a pump
go throw the test bench for final checking and quality control. I have collected information
verbally from engineer and technicians and some are collected from there data sheet, work
log, client work order, and testing data.
Sources of Data2.5
I have collected two types of data for prepare this report purpose. These are Primary data
which I collected from the factory, and Secondary data which I collected from out of the
factory.
 Primary Data: I have collected primary data verbally from engineer and technicians
and some are collected from there operators Log Sheet, Machine catalog, Client Work
order the User Manual etc.

 Secondary data: Secondary data has been collected from the Books, Journals,
Searchers papers, article, internet etc.

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Limitations2.6
During Practicum in Milnars Pumps Ltd, I have got a lots of information and they are very
much cooperative and they help us a lot. This report has been prepared for only the
Centrifugal Pump & Submersible Pump. Nothing is described about the other pumps like
turbine pump, reciprocating pump, rotary pump. i focused on the manufacturing process only.
 Project time was insufficient.
 There was some safety problem.
 Updated tools are not sufficient.
 Technical term is not sufficient.
 Special tools are not sufficient & some spares parts have no available.
 Few experienced engineer so that I can‘t get various information to a subject.

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Chapter: Two
3 Company Overview

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About Milnars Pumps Limited3.1
Milnars Pumps Limited (MPL) has a history of over four decades. It was originally founded
in 1961 in the name of KSB Pumps Company Limited as an affiliate of KSB Germany at time
when the country was just on the verge of making a breakthrough in agricultural production of
food (HYV) through small localized mechanical Irrigation system. Its factory was established
at Tongi, 20 Km north of Dhaka City on an area covering about 3.50 acres.
After 1972 independence of Bangladesh, the parent company KSB Ag of Germany took
direct control of the management and renamed it as KSB Pumps Company (Bangladesh)
Limited. Later in 1980, After obtaining majority of share from KSB, its operation started
under the name MILNARS PUMPS LTD. Under the new management presently, MPL is
wholly owned by AFTAB GROUP.
Aftab Group is one of the leading multidisciplinary Industrial and business house of
Bangladesh. It is involved in Banking, Engineering/manufacturing, agro-industrial
productions, garments, textile and multifarious trading activities in Bangladesh and real-estate
business in USA.
MPL is involved in the assembly and manufacturing of pumps which are essentially devices
for lifting and movement or transfer of water or any other fluid. The company‘s present yearly
production capacity is 12,000 Centrifugal pumps, 1,500 Deep Well Turbine Pumps,
Submersible Pumps, High Pressure Industrial Pumps and Domestic pumps of various design
and capacities, MPL also manufactures Sluice and Non-Return ( Reflex ) valves from
diameter 37 mm to 200 mm sizes.
The company has it's own foundry in its premises at Tongi Works. Backed-up with an on-job
solid experience of more than four decades, the MPL products are the result of forward
looking techniques, modern machining and accurate & precision tooling under the inspiring
and dedicated professionalism of its 12 highly qualified engineers and 175 skilled work
personnel. Very recently, the company underwent extensive and exhaustive BMRE program.
Under the program, Induction Furnace has been installed with well-equipped laboratory for
casting of quality stainless steel (SS),other alloy steel and spherodized graphite iron (SG)
products. This modern plant is the only and first of its kind in Bangladesh and can meet the
demand of casting of different type of products of different qualitative specification required
in pump valve and other machine part/component manufacturing.

43
MPL Pumps and its other products are manufactured according to DIN Standard and to
highest design meeting international quality. Every product has to undergo comprehensive
inspection and tests in company‘s most modern Test Bed.
In 2002. MPL obtained ISO9001:2000 certification for Quality Management System, as the
first and only Pump and casting industry in Bangladesh.
MPL’scurrent product lines what we believe to be among the best and finest available in this
part of the world. Hundreds and thousands of MPL pumps can be seen at work all over
Bangladesh in surface and ground water irrigation projects,BWDB Hydro projects, Municipal
water supplies as wel as in various INUSTRIAL enterprises.
If you have any water handling or pump related problem or interest please contact us. We are
here to help you to solve any of your problems and com-up with the perfect answer and select
the pump to suit your requirement.
Figure 1: Back View of Milnars Pumps Ltd. Factory

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Foundry Shop Machine Shop
Grinding Shop Assembly Shop
Painting Shop Test Bench
Figure 2: Deferent shops in MPL

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Company Location (Office & Factory)3.2
Head Office
Uttara Bank Bhaban(5th
Floor)
90, Motijheel Commercial Area, Dhaka-1000
Bnagladesh, G.P.O Box No. 428
E-mail
sales@milnarspumps.com,
milnars@bdmail.com
Fax 880-2-9559431, 9563319
Web www.milnarspumps.com
Phone 9563526,9563436,9567203
Factory Location
Aftab Complex, Cherag Ali 89-90,Tongi
I/A.
Gazipur-1704
Fax 9815549
Phone 9802385

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Message from Executive Chairman3.3
Welcome to Milnars Pumps Limited We are thankful to Al-mighty Allah for his kindness to
us all.
Milnars Pumps Ltd, is the oldest pump manufacturing company of Bangladesh. Our aim is to
continue our effort to get highest confidence and satisfaction of our valued customer by
continuous improvement of our service and quality. Support from the valued customers of
Milnars Pumps Ltd. have enabled us to meet the demands of development and have made it
possible to strengthen our commitment to growth and set higher quality standards of
management, technology, operations system and human resources.
We always appreciate suggestions and comments from our customers for developing our
service and quality.
Regards for all our well-wishers.
Azharul Islam

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Mission3.4
They want to market valves, complete system solutions and foundry products including
patterns for captive, automotive and other industries. I will develop a world class human
resource with highly motivated and empowered employees. They manufacture and market a
selected range of standard and engineered pumps and castings of world class quality. Their
efforts are directed to have delighted customers in the water, sewage, oil, energy, and industry
and building services sectors. In line with the Group strategy, they are committed to develop
into a center of excellence in water application pumps and be a strong regional player.
Vision3.5
The management of MPL strongly appreciates the diversity in the vast amount of knowledge
and experience their people bring with them to the company. The company‘s vision is to
make progress possible through excellence in technology, integrity and unsurpassed customer
services. They also acknowledge the professional specialization of each company personnel
and believe that there is always something one can teach and learn from others; hence they
actively encourage everyone to work collaboratively together. The company principles evolve
around the idea of providing high quality customer services with reliability and innovative
practices through persistent teamwork of responsible employees.
Social commitment3.6
MPL commitment towards our Country shines through the efforts we put in our business and
our corporate social responsibility. Milnars Pumps Limited places particular value on social
welfare and environmental protection. Working under the name of MPL Care, their Corporate
Social Responsibility program is focused to provide a sustainable infrastructure.

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MPL Management Chart3.7
General
Manager
Asistant
Manager Project
Asistant
Manager
Foundry
Supervisor
Manager
Palaning
Sr.
Foremen(Qualit
y Control)
Inspector
(Quality
Control)
Draft man
Store officer Store clerk
Sub Asst.
Engineer
Planing
Assistant
Jr. Store officer Store clerk
Asistant
Manager
Production
Production
Codinator
Foremen
Production
Foremen
Maintains
Asistant
Manager
Personal
Time Keeper
Production
Engineer

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MPL Product Application and Specifications3.8
ETA
Centrifugal pump
Applications
Agricultural undertakings, Irrigation & drainages, General
water supply duties for Municipal, Community, Industry &
pressure booting. Semi open Impeller Pumps available for
paper industries.
Materials of construction
Volute casing, Impeller, Suction cover, Bearing stool etc. are
made of Cast Iron(Bronze or SS for special requirement)Shaft
made from cold drawn carbon steel(SS for special
requirement)
Specifications
Size NW 40 to 250 mm
Capacity Q up to 550 m³/hr
Total Head H up to 100 meter
Discharge Pressure P up to 8.50 bar
Temperature T -10 to 130° C
Speed N up to 2900 rpm
SLUICE VALVES
Sluice valve of DIN 3216 standard for water
Materials
The selection of the correct material of construction for
valves body from the wide choice available is government by
the pressure, the temperature and the nature of the fluid
flowing through the valves.

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Standard execution
:: Body, dome, wedge gate, Stuffing box and hand wheel
are of Cast Iron.
:: Face ring in body and on the gate are of Bronze, an alloy
of high wearing qualities material naturally developed for
use in valves and fittings.
:: Spindle of forged bronze upto valve size NW 100 and
stainless steel for NW 125, 150 & 200.
:: Spindlenut, gland bush and gland nuts are of bronze.
MOVI
High pressure multistage pump
Applications
Irrigation, water, General water supply, Fountains, Pressure
Boosting, Pumping of Boiler Feed water, Cooling water and
Hot water Circulation, Pumping of Condensates, fire fighting
etc.
Specifications
Size NW 32 40
Capacity Q upto 42 m³/hr (0.41 cusec)
Tatal Head H upto 400 M (1300 ft)
Discharge Pressure P upto 40 bar (570 psi)
Temperature T -10° to +140 °C
Speed N upto 2900 rpm

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Deepwell Turbine Pump
Water Lubricated, vertical, Single stage or Multi stage
Turbine Pump
Applications
Agricultural undertakings, Irrigation & drainage. Drinking
Water supplies for Town and country. Industrial Water
Supply for Trade and industry. Lowering of ground water
water table on construction site
Specifications
Well Diameter D 8″ to 20″
Delivery size NW 3″ to 8″
Bowl size A 5.5″ to 11.5″
Capacity Q upto 300 m³/hr
Total Head H upto 100 meter
Speed N upto 2900 rpm
Motor rating HP upto 125
Submersible Pump
Submersible Motor Pump
Applications
Water supplies for Town and country. Pressure Boosting.
Industrial water Supply for Trade and Industry.
Specifications
Well Diameter D 6″ to 14″
Delivery size NW 50 to 250 mm
Capacity Q up to 360 m³/hr
otal Head H up to 450 meter
Speed N up to 2900 rpm

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Voltage V 360 to 440 v
Motor rating HP up to 250
Reflux(Non Return) Valves
Cast Iron reflux Valves DIN 3232 for water
Applications
Water supplies for Town and country. Pressure Boosting.
Industrial water Supply for Trade and Industry.
Specifications
Reflux Valve is a one way shut-off device. Flap opens in one
direction automatically permitting the flow, while reversal of
flow is prevented as flap door closes under the action of
gravity and back pressure.
Demestic Pumps
mono-block Domestic pumps
Applications
Used for Domestic water lifting purpose
Any of the above products can be made from any special material as per customer‘s
requirement.
Also manufacture Parts and products of special alloy steel and S.G. Iron as required by
customer as :
Crushing Jaw plates of Stone crushing machines from Hadfield Manganese steel, Excavator
teeth, Cement mill liners Manhole covers of S.G Iron and other spare parts for construction
machines, Cement mills etc.

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Production Capacity of Milnars Pumps Ltd.3.9
The company‘s present yearly production capacity is 20,000 Centrifugal pumps, 1,500 Deep
Well Turbine Pumps, Submersible Pumps, High Pressure Industrial Pumps and Domestic
pumps of various design and capacities, MPL also manufactures Sluice and Non-Return
valves from diameter 37 mm to 200 mm sizes.
Certificate and Award of MPL3.10
In 2002, MPL obtained ISO9001:2000 certification for Quality Management System, as the
first and only Pump and casting industry in Bangladesh. MPL’s current product lines what we
believe to be among the best and finest available in this part of the world. Hundreds and
thousands of MPL pumps can be seen at work all over Bangladesh in surface and ground
water irrigation project, BWDB Hydro projects, And Municipal Water Supplies as well as in
various industrial enterprises.
Product3.11
Centrifugal Pumps, Sluice Valves, MOVI, Deep well, Turbine pump, Submersible pump,
Reflux valve, Domestic pumps.
1. Place: Country wide.
2. Price: Competitive.
3. Promotion: Competitive.
Internal and external factors:
The aim of any SWOT analysis is to identify the internal and external factors that are
important to achieving the objective. These come from within the company‘s unique valve
chain. SWOT analysis groups key pieces of information into two main categories.
 Internal factors-The strengths and weaknesses internal to the organization.
 External factors-The opportunities and threats presented by the external environmental
to the organization.

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Analysis of products of MPL3.12
3.12.1 Opportunities
The external environmental analysis may reveal certain new opportunities for profit and
growth.
 An unfulfilled customer need
 Arrival of new technologies
 Removal of international trade barriers
 A developing market such as the internet
 Market vacated by an ineffective competitor
 Shifts in consumer tastes away from the firm‘s products
 Emergence of substitute products
 Price wars with competitors
 Competitor has new, innovative product or service.
3.12.2 Strength
A firm‘s strengths are its resources and capabilities that can be used as a basis for developing
a competitive advantage.
 Patents
 Strong brand names.
 Cost advantages.
 Specialist marketing expertise.
 A new, innovative product or service and location of business.
3.12.3 Weaknesses
The absence of certain strengths may be viewed as a weakness. For example, each of the
following may be considered weaknesses.
 Poor reputation among customers
 Lack of access to the best natural resources
 Lack of access to key distribution channels
 Undifferentiated products or services

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Chapter: Three
4 Theory of Centrifugal Pump

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Definition4.1
Head – A measure of pressure, expressed in meters for centrifugal pumps. Indicates the
height of a column of water being moved by the pump (without friction losses).
Static Head – The hydraulic pressure at a point in a fluid when the liquid is at rest.
Friction Head – The loss in pressure or energy due to frictional losses in flow.
Discharge Head – The outlet pressure of a pump in operation.
Total Head – The total pressure difference between the inlet and outlet of a pump in
operation.
Suction Head – The inlet pressure of a pump when above atmospheric pressure.
Suction Lift – The inlet pressure of a pump when below atmospheric pressure.
Pressure – The force exerted on the walls of a tank, pipe, etc. by a liquid. Normally measured
in pounds per square inch (psi) or kilopascals (kpa).
Prime – Charge of liquid required to begin pumping action when liquid source is lower than
pump. Held in pump by a foot valve on the intake line or by a valve or chamber within the
pump.
Self/Dry Priming – Pumps that draw liquid up from below pump inlet (suction lift), as
opposed to pumps requiring flooded suction.
Specific Gravity – The ratio of the weight of a given volume of liquid to pure water.
Pumping heavy liquids (specific gravity greater than 1.0) will require more drive kilowatts.
Static Discharge Head – Maximum vertical distance (in metres) from pump to point of
discharge with no flow.
NPSH – Net positive suction head – total head at pump suction branch over and above the
vapour pressure of the liquid being pumped.
NPSHr– NPSH required – is a function of the pump design and is the lowest value of NPSH
at which the pump can be guaranteed to operate without significant cavitation. There is no
absolute criterion for determining what this minimum allowable NPSH should be, but pump
manufacturers normally select an arbitrary drop in total dynamic head (differential head) of
3% as the normal value for determining NPSHr.
NPSHa— NPSH available – is a function of the system in which the pump operates and is
equal to the absolute pressure head on the liquid surface plus the static liquid level above the
pump centreline (negative for a suction lift) minus the absolute liquid vapour pressure head at
pumping temperature minus the suction friction head losses.

57
Cavitation – Process in which small bubbles are formed and implode violently; occurs when
NPSHa<NPSHr.
Density (specific weight of a fluid) – Weight per unit volume, often expressed as pounds per
cubic foot or grams per cubic centimeter.
Flooded Suction – Liquid flows to pump inlet from an elevated source by means of gravity.
Flow – A measure of the liquid volume capacity of a pump. Given in gallons per minute
(GPM), litres per second and cubic meters per hour.
Strainer – A device installed in the inlet of a pump to prevent foreign particles from
damaging the internal parts.
Sump – A well or pit in which liquids collect below floor level; sometimes refers to an oil or
water reservoir.
Total Head – Sum of discharge head, suction lift, and friction loss.
Viscosity – The ―thickness‖ of a liquid or its ability to flow. Most liquids decrease in
viscosity and flow more easily as they get warmer.
Bypass Valve – Internal many pump heads that allow fluid to be r circulated if a given
pressure limit is exceeded.
Check Valve – Allows liquid to flow in one direction only. Generally used in discharge line
to prevent reverse flow.
Foot Valve – A type of check valve with a built-in strainer. Used at point of liquid intake to
retain liquid in system, preventing loss of prime when liquid source is lower than pump.
Relief Valve – Used at the discharge of a positive displacement pump. An adjustable, spring
loaded valve opens when a preset pressure is reached. Used to prevent excessive pressure
buildup that could damage the pump or motor.
Pump Setup & Installation4.2
4.2.1 Foundation
The pump foundation should be suffi ciently substantial to form a level, rigid support for the
combined weight of the pump and driver and maintain alignment of the installed unit.
Foundation bolts, of the proper size, should be imbedded in the concrete. A pipe sleeve, about
2½‖ diameters larger than the bolt, should be used to allow for final positioning of the bolts.

58
Mounting4.3
Position the unit on the foundation and level the pump base, using metal shims, so that the
pump shaft is in vertical alignment and the pump suction and discharge flanges are level in
both vertical and horizontal plane. Base may be grouted following alignment. Use a plumb
line from floor above to establish centerline of pump and flexible drive shaft and bearings.
Common Base Plate4.4
Pumps and drivers that are received from the factory with both machines mounted on a
common base plate, were accurately aligned before shipment. All baseplates are flexible to
some extent and, therefore, must not be relied upon to maintain the factory alignment.
Preliminary alignment is necessary after the complete unit has been leveled on the foundation,
and again, after the unit is piped, and rechecked periodically as outlined in the following
paragraphs. Position unit on foundation and level the base plate, using rectangular metal
blocks and shims, or wedges having a small taper as shown in Figure 2. A gap of 3/4‖ to 1½‖
should be allowed between the base plate and foundation for grouting.
Figure 3: Foundation Bolt Location and Anchorage
Figure 4: Adjusting Wedges for Mounting

59
Definition of Centrifugal Pump4.5
A centrifugal pump converts the input power to kinetic energy in the liquid by accelerating
the liquid by a revolving device - an impeller. The most common type is the volute pump.
Fluid enters the pump through the eye of the impeller which rotates at high speed. The fluid is
accelerated radically outward from the pump chasing. A vacuum is created at the impellers
eye that continuously draws more fluid into the pump. The energy created by the pump is
kinetic energy according the Bernoulli Equation. The energy transferred to the liquid
corresponds to the velocity at the edge or vane tip of the impeller. The faster the impeller
revolves or the bigger the impeller is the higher will the velocity of the liquid energy
transferred to the liquid be. This is described by the Affinity Laws.
Figure 5: A centrifugal pump
History of a Centrifugal Pump4.6
According to Reti, the first machine that could be characterized as a centrifugal pump was a
mud lifting machine which appeared as early as 1475 in a treatise by the Italian Renaissance
engineer Francesco di Giorgio Martini. True centrifugal pumps were not developed until the

60
late 17th century, when Denis Papin built one using straight vanes. The curved vane was
introduced by British inventor John Appold in 1851.
4.3 Working Mechanism of a Centrifugal Pump
A centrifugal pump is one of the simplest pieces of equipment in any process plant. Its
purpose is to convert energy of a prime mover (an electric motor or turbine) first into velocity
or kinetic energy and then into pressure energy of a fluid that is being pumped. The energy
changes occur by virtue of two main parts of the pump, the impeller and the volute or diffuser.
The impeller is the rotating part that converts driver energy into the kinetic energy. The volute
or diffuser is the stationary part that converts the kinetic energy into pressure energy. The
process liquid enters the suction nozzle and then into eye (center) of a revolving device
known as an impeller. When the impeller rotates, it spins the liquid sitting in the cavities
between the vanes outward and provides centrifugal acceleration. As liquid leaves the eye of
the impeller a low-pressure area is created causing more liquid to flow toward the inlet.
Because the impeller blades are curved, the fluid is pushed in a tangential and radial direction
by the centrifugal force. This force acting inside the pump is the same one that keeps water
inside a bucket that is rotating at the end of a string.
A centrifugal pump works by the pump directing liquid in the system into the suction port of
the pump and from there into the inlet of the impeller. The rotating impeller then moves the
liquid along the spinning vanes, at the same time increasing the velocity energy of the liquid.
The liquid then exits the impeller vanes and moves into the pump volute or diffuser casing,
where the high velocity of the fluid is converted into high pressure through a diffusion
process. The fluid is then guided into the discharge port of the pump and from there out into
the system, or on to the next stage in the case of a multi-stage pump.
Centrifugal pumps are usually the preferred choice for lower viscosity (thin) liquids and high
flow rates. They are typically used across many residential, commercial, industrial, and
municipal applications.

61
Figure 6: Cutaway view of centrifugal pump
Classification of Centrifugal Pump4.7
There are four main type classifications of centrifugal pump, with the chief distinction of each
being the mechanism that drives the reciprocating diaphragm.
4.7.1 Mechanically Actuated
This type of pump has a reciprocating mechanical linkage that is directly attached to the
diaphragm. The pump includes a gear set or other mechanical mechanism to convert the
rotation of the motor into a reciprocating motion of the linkage that is attached to the
diaphragm. Flow may be varied by varying the stroke length or pump speed.

62
4.7.2 Hydraulically Actuated
This type of operation employs an intermediate hydraulic fluid located on the non-product
side of the diaphragm to flex the diaphragm. The hydraulic fluid is pressurized by a
reciprocating plunger. Though it acts similar to a mechanically actuated diaphragm, the
plunger isn‘t attached to the diaphragm, but rather pressurizes the intermediate hydraulic
fluid, which flexes the diaphragm. Flow is varied with this type of diaphragm pump by
varying pump speed or by varying the amount of hydraulic fluid that is bypassed.
4.7.3 Solenoid
These pumps have an electric motor that alternately energizes and de-energizes a solenoid,
creating an electro-magnetic force that reacts with a metal part on the diaphragm. This causes
the diaphragm to flex. Flow is varied by varying the pump speed.
4.7.4 Air Operated Double Diaphragm Pumps
This is a type of double acting pump. They have two diaphragms and two sets of check
valves. The pump is driven by compressed air operating alternately on the non-product side of
one diaphragm, and then the other. The air is delivered to the alternate sides of the diaphragm
by means of a shuttle valve. Flow is varied by varying air pressure supplied to the pump.
Centrifugal
Pump
Overhung
Impeller
Close
Coupled
Single and
Two Stage
End Suction
Inline
Separately
Coupled
Single and
Two Stage
Inline
Frame
Mounted
Impeller
between
Bearings
Separately
Coupled
Single Stage
Axial Split
Case
(Horizontal)
Radial Split
Case
(Vertical)
Separately
Coupled
Multistage
Axial Split
Case
(Horizontal)
Radial Split
Case
(Vertical)
Turbine Type

63
Different Parts of Centrifugal Pump:4.8
1. Volute Casing. 2. Suction Cover.
3. B.B Stool. 4. Shaft.
5. Impeller. 6. Wearing Ring.
7. Ball Bearing. 8. Gasket
9. Gland. 10. Key.
11. Coupling. 12. Buffer.
Figure 7: Different parts of a centrifugal pump

64
4.8.1 Impellers
Figure 8: Impeller After Casting
The impeller of the centrifugal pump converts the mechanical rotation to the velocity of the
liquid. The impeller acts as the spinning wheel in the pump.
It has an inlet eye through which the liquid suction occurs. The liquid is then guided from the
inlet to the outlet of the impeller by vanes. The angle and shape of the vanes are designed
based on flow rate. The guide vanes are usually cast with a back plate, termed shroud or back
cover, and a front plate, termed front cover.
Impellers are generally made in castings and very rarely do come across fabricated and
welded impellers.
Impellers can have many features on them like balancing holes and back vanes. These help in
reducing the axial thrust generated by the hydraulic pressure
In order to reduce recirculation losses and to enhance the volumetric efficiency of the
impellers, they are provided with wearing rings. These ring maybe either on the front side or
both on the front and backsides of the impeller. It is also possible to have an impeller without
any wearing rings.

65
The casting process, as mentioned above, is the primary method of impeller manufacture.
Smaller size impellers for clean water maybe cast in brass or bronze due to small section
thickness of shrouds and blades. Recently, plastic has also been introduced as casting
material.
Figure 9: Impeller on Machining
4.8.2 Volute Casing
Figure 10: Volute Casing After Casting
Volute Casing is made cast iron some time for special requirement it made by Bronze or
stainless steel. A volute casing is a main and essential part of a centrifugal pump. This part
contains other parts such as suction cover, Pump shaft, Impeller, Ball bearing, Gasket etc.

66
Volute casing is a root of liquids flow direction it can help for kinetic energy with less
friction. It also helps to increase flow head. Its size depends on impellers diameter.
4.8.3 Suction cover
Suction cover is made by cast iron some time for special requirement it made by stainless
steel or Bronze. It mainly use for attesting suction pipe with coupling easily. Inside of its
create vacuum by impeller for this reason liquids are suck. Its size depends on volute casing.
4.8.4 B.B Stool
Break bearing Stool is made by cast iron. B.B Stool mainly uses for contains ball bearings, oil
seal, Lubricating oil and pump shaft. The electric motors rotating motion is past form B.B
stool by pump shaft. B.B stool fixed with base with buffer for avoid vibration. Its size
depends on volute casing.
Figure 11: Break bearing stool

67
4.8.5 Shaft
Figure 12: Pump Shaft
Pump shaft contain mainly impeller which fixed by key and slot. Electrical motors rotating
motion is transform by this shaft to impeller. Pump shaft is a moving part so It is necessary to
observe pump shafts designed and metal selection that it not twist or shear by any sudden
load. Pump shaft made from cold drawn carbon steel some time for special requirement pump
shaft made from stainless steel.
4.8.6 Wear rings
Figure 13: Wear Ring

68
Wear ring provides an easily and economically renewable leakage joint between the impeller
and the casing. clearance becomes too large the pump efficiency will be lowered causing heat
and vibration problems. Most manufacturers require that you disassemble the pump to check
the wear ring clearance and replace the rings when this clearance doubles.
4.8.7 Ball Bearing
The purpose of a ball bearing is to reduce rotational friction and support radial and axial
loads. A ball bearing is a type of rolling-element bearing that uses balls to maintain the
separation between the bearing races. It achieves this by using at least two races to contain the
balls and transmit the loads through the balls. In most applications, one race is stationary and
the other is attached to the rotating assembly (e.g., a hub or shaft). As one of the bearing races
rotates it causes the balls to rotate as well. Because the balls are rolling they have a much
lower coefficient of friction than if two flat surfaces were sliding against each other.
Ball bearings tend to have lower load capacity for their size than other kinds of rolling-
element bearings due to the smaller contact area between the balls and races.
Figure 14: A ball bearing
4.8.8 Gasket
Gaskets allow "less-than-perfect" mating surfaces on machine parts where they can fill
irregularities. Gaskets are commonly produced by cutting from sheet materials. Gaskets for
specific applications, such as high pressure steam systems, may contain asbestos. However,
due to health hazards associated with asbestos exposure, non-asbestos gasket materials are
used when practical. A gasket is a mechanical seal which fills the space between two or more
mating surfaces, generally to prevent leakage from or into the joined objects while under
compression.

69
.
Figure 15: Gaskets
4.8.9 Couplings
Figure 16: Coupling of Centrifugal Pump
Couplings for pumps usually fall in the category of general-purpose couplings. General-
purpose couplings are standardized and are less sophisticated in design. The cost of such
coupling is also on the lower side. In these couplings, the flexible element can be easily
inspected and replaced. The alignment demands are not very stringent.

70
Working Mechanism of a Centrifugal Pump4.9
A centrifugal pump is one of the simplest pieces of equipment in any process
plant. Its purpose is to convert energy of a prime mover (a electric motor or turbine) first
into velocity or kinetic energy and then into pressure energy of a fluid that is being
pumped. The energy changes occur by virtue of two main parts of the pump, the impeller
and the volute or diffuser. The impeller is the rotating part that converts driver energy into
the kinetic energy. The volute or diffuser is the stationary part that converts the kinetic
energy into pressure energy.
Note: All of the forms of energy involved in a liquid flow system are expressed in
terms of feet of liquid i.e. head.
4.9.1 Generation of Centrifugal Force
The process liquid enters the suction nozzle and then into eye (center) of a revolving device
known as an impeller. When the impeller rotates, it spins the liquid sitting in the cavities
between the vanes outward and provides centrifugal acceleration. As liquid leaves the eye of
the impeller a low-pressure area is created causing more liquid to flow toward the inlet.
Because the impeller blades are curved, the fluid is pushed in a tangential and radial direction
by the centrifugal force. This force acting inside the pump is the same one that keeps water
inside a bucket that is rotating at the end of a string. Figure below depicts a side cross-section
of a centrifugal pump indicating the movement of the liquid.
Figure 17: Liquid flow path inside a centrifugal pump

71
4.9.2 Conversion of Kinetic Energy to Pressure Energy
The key idea is that the energy created by the centrifugal force is kinetic energy.
The amount of energy given to the liquid is proportional to the velocity at the edge or
vane tip of the impeller. The faster the impeller revolves or the bigger the impeller is,
then the higher will be the velocity of the liquid at the vane tip and the greater the energy
imparted to the liquid.
This kinetic energy of a liquid coming out of an impeller is harnessed by creating
a resistance to the flow. The first resistance is created by the pump volute (casing) that
catches the liquid and slows it down. In the discharge nozzle, the liquid further
decelerates and its velocity is converted to pressure according to Bernoulli‘s principle.
Therefore, the head (pressure in terms of height of liquid) developed is
approximately equal to the velocity energy at the periphery of the impeller expressed by
the following well-known formula:
H
Where, H=Total head developed in feet
v=Velocity at periphery of impeller in ft/sec
g=Acceleration due to gravity – 32.2 ft/
4.9.3 Power
The energy usage in a pumping installation is determined by the flow required, the height
lifted and the length and friction characteristics of the pipeline. The power required to drive a
pump ( ), is defined simply using SI units by:
where:
is the input power required (W)
is the fluid density (kg/m3
)

72
is the standard acceleration of gravity (9.80665 m/s2
)
is the energy Head added to the flow (m)
is the flow rate (m3
/s)
is the efficiency of the pump plant as a decimal
The head added by the pump ( ) is a sum of the static lift, the head loss due to friction and
any losses due to valves or pipe bends all expressed in metres of fluid. Power is more
commonly expressed as kilowatts (103
W) or horsepower (multiply kilowatts by 0.746). The
value for the pump efficiency may be stated for the pump itself or as a combined efficiency
of the pump and motor system.
The energy usage is determined by multiplying the power requirement by the length of time
the pump is operating.
4.9.4 Efficiency
,
where:
is the mechanics input power required (W)
is the fluid density (kg/m3
)
is the standard acceleration of gravity (9.80665 m/s2
)
is the energy Head added to the flow (m)
is the flow rate (m3
/s)
is the efficiency of the pump plant as a decimal
The head added by the pump ( ) is a sum of the static lift, the head loss due to friction and
any losses due to valves or pipe bends all expressed in metres of fluid. Power is more
commonly expressed as kilowatts (103
W, kW) or horsepower (hp = kW*0.746). The value
for the pump efficiency, , may be stated for the pump itself or as a combined efficiency
of the pump and motor system.

73
NPSH (Net Positive Suction Head)4.10
When discussing centrifugal pumps, the two most important head terms are NPSHr and
NPSHa. Net Positive Suction Head Required, NPSHr, NPSH is one of the most widely used
and least understood terms associated with pumps. Understanding the significance of NPSH is
very much essential during installation as well as operation of the pumps. Pumps can pump
only liquids, not vapors. The satisfactory operation of a pump requires that vaporization of
the liquid being pumped does not occur at any condition of operation. This is so desired
because when a liquid vaporizes its volume increases very much. For example, 1 ft3 of water
at room temperature becomes 1700 ft3 of vapor at the same temperature. This makes it clear
that if we are to pump a fluid effectively, it must be kept always in the liquid form.
Rise in temperature and fall in pressure induces vaporization
The vaporization begins when the vapor pressure of the liquid at the operating temperature
equals the external system pressure, which, in an open system is always equal to atmospheric
pressure. Any decrease in external pressure or rise in operating temperature can induce
vaporization and the pump stops pumping. Thus, the pump always needs to have a sufficient
amount of suction head present to prevent this vaporization at the lowest pressure point in the
pump.
NPSH as a measure to prevent liquid vaporization
The manufacturer usually tests the pump with water at different capacities, created by
throttling the suction side. When the first signs of vaporization induced cavitation occur, the
suction pressure is noted (the term cavitation is discussed in detail later). This pressure is
converted into the head. This head number is published on the pump curve and is referred as
the "net positive suction head required (NPSHr) or sometimes in short as the NPSH. Thus the
Net Positive Suction Head (NPSH) is the total head at the suction flange of the pump less
the vapor pressure converted to fluid column height of the liquid.
NPSHr is a function of pump design
NPSH required is a function of the pump design and is determined based on actual pump test
by the vendor. As the liquid passes from the pump suction to the eye of the impeller, the
velocity increases and the pressure decreases. There are also pressure losses due to shock and
turbulence as the liquid strikes the impeller. The centrifugal force of the impeller vanes
further increases the velocity and decreases the pressure of the liquid. The NPSH required is

74
the positive head in feet absolute required at the pump suction to overcome these pressure
drops in the pump and maintain the majority of the liquid above its vapor pressure. The NPSH
is always positive since it is expressed in terms of absolute fluid column height. The term
"Net" refers to the actual pressure head at the pump suction flange and not the static suction
head.
NPSHr increases as capacity increases
The NPSH required varies with speed and capacity within any particular pump. The NPSH
required increase as the capacity is increasing because the velocity of the liquid is increasing,
and as anytime the velocity of a liquid goes up, the pressure or head comes down. Pump
manufacturer's curves normally provide this information. The NPSH is independent of the
fluid density as are all head terms. Note: It is to be noted that the net positive suction head
required (NPSHr) number shown on the pump curves is for fresh water at 20°C and not for
the fluid or combinations of fluids being pumped. Net Positive Suction Head available,
NPSHa
NPSHa is a function of system design
Net Positive Suction Head Available is a function of the system in which the pump operates.
It is the excess pressure of the liquid in feet absolute over its vapor pressure as it arrives at the
pump suction, to be sure that the pump selected does not cavitate. It is calculated based on
system or process conditions.
NPSHa calculation
The formula for calculating the NPSHa is stated below:
= Pressure Head i.e Barometric Pressure of the suction vessel converted to Head
= Static suction Head i.e the vertical distance between the eye of the first stage impeller
centerline and the suction liquid level.
= Vapor pressure Head i.e. vapor pressure of liquid at its max. pumping temperature
converted to Head.
= Friction Head i.e. friction and entrance pressure losses on the suction side converted to
Head.

75
Brake Horse Power (BHP)4.11
The work performed by a pump is a function of the total head and the weight of the liquid
pumped in a given time period. Pump input or brake horsepower (BHP) is the actual
horsepower delivered to the pump shaft. Pump output or hydraulic or water horsepower
(WHP) is the liquid horsepower delivered by the pump. These two terms are defined by the
following formulas.
Where,
Q = Capacity in gallons per minute (GPM)
= Total differential head, ft
Sp.Gr = Specific Gravity of the liquid
Eff. = Pump efficiency,
Where,
Q = Capacity in gallons per minute (GPM)
= Total differential head, ft
Sp.Gr = Specific Gravity of the liquid
The constant 3960 is obtained by dividing the number or foot-pounds for one horsepower
(33,000) by the weight of one gallon of water (8.33 pounds).

76
4.12
Chapter Four
5 Manufacturing Process of Centrifugal
Pump

77
Milnars Pumps Limited has different shop for different type of work. Manufacturing process
of a centrifugal pump is a combination of Casting, Machining, Assembly, and Testing. From
casting to Testing there are many working procedure to produce a ready pump. I have
classified there shop by 4 parts-
1. Foundry Section.
2. Machine Section.
3. Assembly & Painting Section.
4. Testing & QC.
Figure 18: Machine shop
Foundry shop5.1
A foundry is a factory that produces metal castings. Metals are cast into shapes by melting
them into a liquid, pouring the metal in a mold, and removing the mold material or casting
after the metal has solidified as it cools. The most common metals processed are aluminum
and cast iron. However, other metals, such as bronze, brass, steel, magnesium, and zinc, are
also used to produce castings in foundries. In this process, parts of desired shapes and sizes
can be formed.

78
Figure 19: Foundry Shop: Melted iron in ladle
Foundry section can have the following processes:
Figure 20: Casting process chart of Foundry shop
5.1.1 STEP-01: Core & Pattern Making
Master Pattern from Design Engineer: Milnars Pumps Limited used Wood Pattern, Cast
Iron Pattern and Plastic Pattern for making mold. Many of the parts are like- Impeller, Volute
casing, BB Stool is made by cast iron pattern. This patterns are made by a Master pattern,
which is a form of plastic object.

79
The master pattern is made by the experienced engineer and pattern designer of Milnars
Pumps Ltd. Some the time, the master pattern is changed according to the requirement of the
production.
Figure 21: Master Pattern: Made by Plastic
Master Pattern to Cast Iron Pattern by worker: After released a master pattern from
designed section, the pattern send to foundry shop for making 10-20 pieces (depend upon the
production) by experienced workers.
Pattern allowance
To get approved casting there gives some allowance some are positive some are negative
those are:
 Shrinkage allowance – Metals shrink when it cools. Cast iron—1/8 in/ft, Brass-3/16
in/ft, and Steel-1/4in/ft. It is positive allowance.
 Distortion allowance: - Distortion allowance is applied only of cooling because of
metal shrinkage.
 Draft allowance: When the pattern is drawn from a mold, the tendency to tear away
the edges of the mold in contact with the pattern is greatly decreased if the surfaces of

80
the pattern are slightly tapered known as draft. 1/8 to ¼ in/ft (external), 3/4 in/ft
(interior).
 Finish allowance: - Positive allowance is provided for machining.
Core making from copper master pattern & plastic pattern:
Core is mainly used for making hole or space in the mold, like as space between impeller
propellers, hole on the B.B stool, and empty space on the Casing etc. Cores are utilized for
castings with internal cavities or passages. A core is a body usually made of sand used to
produce a cavity in or on a casting cores are placed in the mould cavity before casting to from
the interior surfaces of the casting. Milnars Pumps Ltd. used Sand, Molasses, Tar, and Wire
for making core.
Figure 22: Core for Volute Casing

81
Figure 23: Core making by worker

82
5.1.2 STEP-02: Preparation of Sand & Mold Making
The Milnars Pumps Ltd use geen sand for making mold, there are some step to mking sand.
Firstly sand is breezier by the Roller Dryer. This roller makes the sand dry and breezy.
Figure 24: Sand Roller Dryer
Green Sand is making by the mixture of sand, bentonite clay, saw-dust, and a bit of water.
Milnars Pumps Limited has a mixture machine for making the proper mixture of green sand.
30 kg River sand, 5 kg bentonite clay, 5kg saw-dust, and 10 litter water in a mixture into the
mixture machine.
Figure 25: Sand Mixture

83
Mold making is done by the very experienced workers who are working in Milnars Pumps
Limited science 10-12 years almost.
Some Tools those are used in foundry shop:
1. Shovel
2. Riddle or sieve
3. Rammer
4. Trowel
5. Spurge Cutter
6. Riser Pin
7. Vent wire
8. Slick
9. Lifter
10. Gate cutter
11. Swab brush
12. Runner Pin
13. Draw Spike
14. Clamp
15. Strike-of Bar
16. Spirit Level
17. Bucket
They are use sand bad as a drag part of the mold and use a mold box as a cope part of the
mold. The whole process of mold making I discuss step by step-
1st.Place iron pattern in flask with enough room for gating. They use a wood/iron pattern for
"runner" and "gate".
2nd. Dust pattern with parting dust to keep it from sticking. Parting dust is a hydrophobic
material, it repels moisture.
3rd.Use a fine riddle to cover just the pattern, and then fill up the flask with sand, level (flush)
with the top. There is no need to riddle all the sand, just make sure there are no lumps. The
riddle fluffs the sand up so it can be packed properly, the same way a flour sifter works.
4th.Use paddle side of rammer to tuck edges first. Hold the flask with your other hand.
5th.Use the butt side of rammer east to west (lightly to protect pattern), then north and south
(harder to pack mold tight). Ramming strokes should be 1 inch apart, like you are planting
corn. Do not ram twice in the same spot, do not ram close together. You can ram too soft,
you can't ram too hard.
Ram really hard the second pass!
6th.Fill it up with sand to about 2 inches above flask.
7th.Use rammer again North to South, then East to West pattern. Planting corn. Hard, to pack
the sand very tight. Hold the flask with your hand.
8th.Strike off drag section with rammer, then spread small amount of sand (handful) out to
cushion bottom board.
9th.Place bottom board on top of your mold.
10th. Holding bottom board and flask together, flip it over.
11th. Remove the cope and pattern board.
12th. Use your spoon and smooth the edges of the pattern and any rough areas.

84
13th. Strike off cope level with the rammer/striker. Use your trowel to smooth.
14th. Tap runner pattern to loosen, then remove.
15th. Remove wood gate pattern.
16th. Tap pattern lightly to loosen.
5.1.3 Step-3 Melting and Pouring
Melting by Induction Furnace: Milnars Pumps Limited use 2 Induction furnace for raw
materials melting purpose. One has capacity 300 kg and another one id 50 kg. The channel
induction furnace consists of a refractory lined steel shell which contains the molten metal.
Attached to the steel shell and connected by a throat is an induction unit which forms the
melting component of the furnace. The induction unit consists of an iron core in the form of a
ring around which a primary induction coil is wound. This assembly forms a simple
transformer in which the molten metal loops comprise the secondary component. The heat
generated within the loop causes the metal to circulate into the main well of the furnace. The
circulation of the molten metal effects a useful stirring action in the melt. Channel induction
furnaces are commonly used for melting low melting point alloys and or as a holding and
superheating unit for higher melting point alloys such as cast iron. Channel induction furnaces
can be used as holders for metal melted off peak in coreless induction units thereby reducing
total melting costs by avoiding peak demand charges.
Figure 26: Raw metal melting in Induction Furnace

85
Coil repairing of induction furnace:
Sometimes leakage is occurred in the iron core or coil. It is the cause of extreme heat or lack
of cooling water. This leakage is maintenance by technician Harun of the factoey. He used gas
welding and to maintain this leakage.
Figure 27: Coil repairing of induction furnace
Figure 28:
Pouring: Milnars Pumps Ltd. has a crane for being the big ladles from the furnace. In a
foundry, molten metal is poured into molds. Pouring can be accomplished with gravity, or it
may be assisted with a vacuum or pressurized gas. Many modern foundries use robots or
automatic pouring machines for pouring molten metal. Traditionally, molds were poured by
hand using ladles.

86
Degassing: In the case of aluminum alloys, a degassing step is usually necessary to reduce the
amount of hydrogen dissolved in the liquid metal. If the hydrogen concentration in the melt is
too high, the resulting casting will be porous as the hydrogen comes out of solution as the
aluminum cools and solidifies. Porosity often seriously deteriorates the mechanical properties
of the metal. In cases where porosity still remains present after the degassing process, porosity
sealing can be accomplished through a process called metal.
Figure 29: Big ladle moving by the crane
Shakeout: The solidified metal component is then removed from its mold. Where the mold is
sand based, this can be done by shaking or tumbling. This frees the casting from the sand,
which is still attached to the metal runners and gates - which are the channels through which
the molten metal traveled to reach the component itself.
Finishing Surface by Grinding: They are used hand grinding marching to primary finishing
surface of the casted materials.

87
Figure 30: Finishing Surface by Grinding
5.1.4 Cast Iron Grade and Standard
Materials Option:
Cast Iron (GG25/ ISO 185 - Class 250)
Cast iron refers to a group of iron alloys that have a high percentage of carbon (> 2 %) and
silicon (> 1.5 %) as well as e.g. manganese, chrome or nickel. Grey iron contains carbon in
the form of graphite.
Chromium martensitic stainless steel (X20Cr13/ANSI 420)
EN 1.4021 is used in the quenched and tempered condition in a host of constructional and
fastener applications where moderate corrosion resistance is required. The knife blade variant
of 1.4021 can be polished to high gloss finishes. Optimal corrosion resistance is also attained
when the surface is finely ground or polished. corrosion resistance average, mechanical
properties very good, ferromagnetic grade suitable for use up to 550 °C, density (kg/dm3)
7.70, electrical resistivity at 20 °C (½ mm2/m) 0.60.

88
Table of Iron Properties According to Standard:
Material code (as
per DIN EN)
EN-GJL-250 EN-GJS-400-15 EN-GJS-600-3
Material number (as
per DIN EN)
EN-JL1040 EN-JS1030 EN-JS1060
Material code (as
per old DIN)
GGC 25 GGG 40 GGG 60
Material number (as
per old DIN)
0.6025 0.7040 0.7060
Other names
Grey iron, cast
iron with flake
graphite
Cast iron with graphite
cast iron, spheroidal
graphite iron
Cast iron with graphite
cast iron, spheroidal
graphite iron
Versions from stock
Properties
Good sliding
properties,
pressure-tight,
heat resistant, high
wear resistance
and excellent
machinability
Good machinability
Good machinability
and wear resistant
Use
Maintenance,
repair, general
mechanical
engineering
Maintenance, repair,
general vehicle
construction and
mechanical engineering
Maintenance, repair,
general vehicle
construction and
mechanical
engineering
Density(g/cm³)
approx.
7,20 7,20 7,20

89
Machining Section5.2
Machining is the process to achieve desire shape of the material by different type machining
work. Milnars Pump Limited has such kind of machine to do this task. Like as, Lathe
Machine, Milling Machine, Shaper Machine, Grinding Machine, and Drill Machine. These
machines are used for specific purpose, and their working process is also different. I try to
discuss their operation as possible I can.
5.2.1 Lathe Machine & its Operation
Lathe is one of the most important machine tools in the machining section of Milnar Pump
Limited. A lathe operates on the principle of a rotating work piece and a fixed cutting tool.
The cutting tool is feed into the work piece, which rotates about its own axis, causing the
work piece to be formed to the desired shape. Lathe machine is also known as ―the
mother/father of the entire tool family‖.
Figure 31: Engr. Morshed Cho. Miraz observing lathe operations
(i) Facing: This operation is almost essential for all works. In this operation, as shown in fig.,
the work piece is held in the chuck and the facing tool is fed from the center of the work piece
towards the outer surface or from the outer surface to the center, with the help of a cross-slide.

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Figure 32: Schematic diagram of lathe operations 1
(ii) Plane Turning: It is an operation of removing excess amount of material from the surface
the surface of the cylinder work piece. In this operation, shown in fig., the work is held either
in the chuck or between centers & the longitudinal feed is given to the tool either by hand or
power.
(iii) Step Turning: It is an operation of producing various steps of different diameters of in
the work piece as shown in fig. This operation is carried out in the similar way as plain
turning.

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Figure 33: Schematic diagram of lathe operations 2
(iv) Drilling : It is an operation of making a hole in a work piece with the help of a drill. In
this case as shown in fig., the work piece, by rotating the tail stock hand wheel. The drill is
fed normally, into the rotating work piece, by rotating the tail stock hand wheel.
(v) Reaming : It is an operation of finishing the previously drilled hole. In the operation as
shown in fig., a reamer is held in the tailstock and it is fed into the hole in the similar way as
for drilling.
Milnars Pump Ltd. mainly sued two types of lathe machine.
1. Centre Lathe, and
2. Turret Lathe
Center Lathe Machine: The Centre Lathe is used to manufacture cylindrical shapes from a
range of materials including; steels and plastics. Many of the components that go together to
make an engine work have been manufactured using lathes.
Turret Lathe Machine: The turret lathe is a form of metalworking lathe that is used for
repetitive production of duplicate parts, which by the nature of their cutting process are
usually interchangeable.

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Figure 34: Centre Lathe & Turret Lathe of MPL
Some Main Components of Lathe:
The Headstock Component
The upper end of the spindle is held in place and anchored by the headstock on the lathe
machine. It also houses the motor that rotates the wood. The way in which you adjust the
speed of the spindle is to use a number of pulleys you can find in the back of the headstock.
The wood piece stays in place even while the spindle spins due to a chuck or high-tension
spring that steadies it.
The Tailstock unit
A lathe machine is a centered mechanism that is attached to the piece of wood, and that is
held in place by a tailstock. The center can turn with the wood or stay in one place. Within the
rotating device or live center are bearings that permit movement.
Cutting tools (gauge and chisel), finishing tools and spear
Depending on your project and the cutting tool needed, you can choose from different
attachments to your lathe machine. For removing the extra wood we use gauge tool. A skew
chisel is utilized to create more intricate carved features. Finer details are made using round
chisels and narrower spears. The wood finishing tools have round edges in order to protect
wood from slicing.
Carriage Component
The lathe's cutting tool is steadied by the carriage, giving the craftsmen the freedom to do his
work. The carriage consists of five different components, which include the compound rest,
cross-slide, apron, tool rest and saddle. These components function in conjunction to allow
the cutting tool to be used to slide into place.

93
Spindle mechanism
There is a trio of configurations for lathe spindles. The threaded, tapered and cam-lock
configurations are the three that mainly concern us here. Attaching the chuck to a threaded
model is complex, as the threaded model's configuration is old and the model doesn't have
taper Cam-lock spindles slides into a ring of similar holes and contain cam studs on one end.
When you turn the chuck key, the studs will be locked into place. The third configuration, the
tapered spindle, narrows at the tip and has a threaded collar with a built-in chuck key.
5.2.2 Milling Machine & its Operations
Milling is the process of machining flat, curved, or irregular surfaces by feeding the
workpiece against a rotating cutter containing a number of cutting edges. The milling machine
consists basically of a motor driven spindle, which mounts and revolves the milling cutter,
and a reciprocating adjustable worktable, which mounts and feeds the workpiece.
Milling machines are basically classified as vertical or horizontal. These machines are also
classified as knee-type, ram-type, manufacturing or bed type, and planer-type. Most milling
machines have self-contained electric drive motors, coolant systems, variable spindle speeds,
and power-operated table feeds and supports the worktable.
Milnars Pump Ltd. basically used knee-type milling machine:
Knee-type milling machines are characterized by a vertically adjustable worktable resting on
a saddle which is supported by a knee. The knee is a massive casting that rides vertically on
the milling machine column and can be clamped rigidly to the column in a position where the
milling head and milling machine spindle are properly adjusted vertically for operation.
Operation:
The success of any milling operation depends, Before setting up a job, be sure that the to a
great extent, upon judgment in setting up the job, workpiece, the table, the taper in the
spindle, selecting the proper milling cutter, and holding the cutter by the best means under the
circumstances Some fundamental practices have been proved by experience to be necessary
for and the arbor or cutter shank are all clean and good results on all jobs. Some of these
practices are mentioned be low.

94
 Before setting up a job, be sure that the workpiece, table, the taper in the spindle, and
the arbor or cutter shank are free from chips, nicks, or burrs. Do not select a milling
cutter of larger diameter than is necessary.
 Check the machine to see if it is in good running order and properly lubricated, and
that it moves freely, but not too freely in all directions.
 Consider direction of rotation. Many cutters can be reversed on the arbor, so be sure
you know whether the spindle is to rotate clockwise or counterclockwise.
 Feed the workpiece in a direction opposite the rotation of the milling cutter
(conventional milling).
 Do not change feeds or speeds while the milling machine is in operation.
 When using clamps to secure a workpiece, be sure that they are tight and that the piece
is held so it will not spring or vibrate under cut.
 Use a recommended cutting oil liberally.
 Use good judgment and common sense in planning every job, and profit from previous
mistakes.
 Set up every job as close to the milling machine spindle as circumstances will permit.
Speed Computation
The formula for calculating spindle speed in revolutions
per minute is as follows:
RPM = CSx4D
Where RPM = Spindle speed (in revolutions per minute).
CS = cutting speed of milling cutter (in SFPM)
D = diameter of milling cutter (in inches)
Figure 35: Milling Machine of MPL

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5.2.3 Shaper Machine & its Operations
Shaper Machine is rarely used in Milanrs Pump Ltd. machine shop. It is used for some special
purpose. A shaper is a type of machine tool that uses linear relative motion between the
workpiece and a single-point cutting tool to machine a linear tool path. Its cut is analogous to
that of a lathe, except that it is (archetypally) linear instead of helical.
Operations:
The workpiece mounts on a rigid, box-shaped table in front of the machine. The height of the
table can be adjusted to suit this workpiece, and the table can traverse sideways underneath
the reciprocating tool, which is mounted on the ram. Table motion may be controlled
manually, but is usually advanced by an automatic feed mechanism acting on the feeds crew.
The ram slides back and forth above the work. At the front end of the ram is a vertical tool
slide that may be adjusted to either side of the vertical plane along the stroke axis. This tool-
slide holds the clapper box and toolpost, from which the tool can be positioned to cut a
straight, flat surface on the top of the workpiece. The tool-slide permits feeding the tool
downwards to deepen a cut. This adjustability, coupled with the use of specialized cutters and
toolholders, enable the operator to cut internal and external gear tooth profiles, splines,
dovetails, and keyways.
The ram is adjustable for stroke and, due to the geometry of the linkage, it moves faster on the
return (non-cutting) stroke than on the forward, cutting stroke. This action is via a slotted link.

96
5.2.4 Grinding Machine & its Operations
Grinding machine is mostly used in Milnars Pump Ltd. machine shop for make cutting tool
edge, surface finishing and maintain accuracy of shaft. The grinding machine consists of a
bed with a fixture to guide and hold the work piece, and a power-driven grinding wheel
spinning at the required speed. The speed is determined by the wheel‘s diameter and
manufacturer‘s rating. The grinding head can travel across a fixed work piece, or the work
piece can be moved while the grind head stays in a fixed position.
1. Accuracy (+-0.02mm). 2. Surface finish (0.1mmr).
Figure 36: Grinding Machine is MPL Machine Shop
The grinding machine consists of a bed with a fixture to guide and hold the work piece, and a
power-driven grinding wheel spinning at the required speed. The speed is determined by the
wheel‘s diameter and manufacturer‘s rating. The grinding head can travel across a fixed work
piece, or the work piece can be moved while the grind head stays in a fixed position.


97
5.2.5 Drill Machine & its Operations
A drilling machine comes in many shapes and sizes, from small hand-held power drills to
bench mounted and finally floor-mounted models. They can perform operations other than
drilling, such as countersinking, counterboring, reaming, and tapping large or small holes.
Because the drilling machines can perform all of these operations, this chapter will also cover
the types of drill bits, took, and shop formulas for setting up each operation.
A drilling machine comes in many shapes and sizes, from small hand-held power drills to
bench mounted and finally floor-mounted models. They can perform operations other than
drilling, such as countersinking, counterboring, reaming, and tapping large or small holes.
Because the drilling machines can perform all of these operations, this chapter will also cover
he types of drill bits, took, and shop formulas for setting up each operation.
Drill press operators must know how to set up the work, set speed and feed, and provide for
coolant to get an acceptable finished product. The size or capacity of the drilling machine is
usually determined by the largest piece of stock that can be center-drilled (Figure 4-3). For
nstance, a 15-inch drilling machine can center-drill a 30-inch-diameter piece of stock.

98
Operations:
The column of most drill presses is circular and built rugged and solid. The column supports
the head and the sleeve or quill assembly. The head of the drill press is composed of the
sleeve, spindle, electric motor, and feed mechanism. The head is bolted to the column.
The worktable is supported on an arm mounted to the column. The worktable can be adjusted
vertically to accommodate different heights of work. or it may be swung completely out of the
way. It may be tilted up to 90° in either direction, to allow for long pieces to be end or angled
drilled. The base of the drilling machine supports the entire machine and when bolted to the
floor, provides for vibration-free operation and best machining accuracy. The top of the base
is similar to a worktable and maybe equipped with T-slots for mounting work too large for the
table.
Figure 37: Drill Operation in MPL Machine Shop

99
Assembly Section5.3
Assembly and Painting is the last part of the manufacturing of Milnars pumps. After
assembly, a pump go throw the testing section, if its ok, then ready for sell, if it is not than the
pump is feedback to assembly section again. Sometimes maintenance work is also occur in
assembly section of Milnars Pump Ltd.
The main steps of pump assembly are:
1. Install bearings and oil seals on the shaft.
2. Install the shaft on the housing.
3. Put front and back covers and tighten the bolts.
4. Install mechanical seal on correct distance from the other end of the shaft.
5. Install flange coupling on the other end.
6. Install the impeller then put and tighten impeller lock-nut.
7. Install the suction volute housing, then put and tighten the bolts.
Figure 38: Pump assembly working in assembly shop
MPL Assembly procedure:
1. Clean and inspect all pump parts (O-ring, seal seats, motor shaft, etc.).
2. Apply sealant in bracket bore hole and possibly around seal case according to sealant
instructions. For SS seal, chamfer the edge of the bracket bore hole.

100
Figure 39: Schematic diagram of pump assembly
3.
4. Press carbon graphite seal into bracket while taking care not to damage carbon
graphite face.
5. Place slinger (rubber washer) over motor shaft and mount bracket to motor.
6. Carefully lubricate boot or O-ring around ceramic piece and press into impeller (if
ceramic has O-ring, the marked side goes in). Use glycerine for EPDM.
7. Sparingly lubricate carbon graphite and ceramic sealing surfaces. Water, glycerine or
lightweight machine oil may be used, depending on the elastomers used in the pump.
Do not use silicon lubricants or grease!
8. Thread impeller onto shaft and tighten. If required, remove motor end cap and use a
screwdriver on the back of motor shaft to prevent shaft rotation while tightening.
Replace motor end cap.
9. Electrically, connect the motor so that the impeller will rotate CCW when facing the
pump with the motor toward the rear. Incorrect rotation will damage the pump and
void the warranty! For 3-phase power, electrically check rotation of impeller with
volute disassembled from bracket. If pump end is assembled and rotation is incorrect,
serious damage to pump end assembly will occur even if the switch is "quickly
bumped." If rotation is incorrect, simply exchange any two leads.
10. Seat O-ring in volute slot and assembly volute to bracket.
11. Install drain plug with its O-ring in volute drain hole.

101
Chapter Five
6 Pump Testing Section & QC

102
Figure 40: Pump Testing Work on Test Bench
Milnars Pump Ltd. used manual pump testing method by take reading from pressure gauge,
flow meter, water level scale and digital kw reading meter. They are taking reading 10 times
on a data sheet, and used some equation and curves to determine the desired pump
performance which I‘m describe below. Centrifugal pumps are among the important
equipment‘s in any process plant. In any refinery they are considered to be equivalent to heart
of a refinery, as they keep the flow running with a certain pressure and quantity from one
place to another, each pump has its own pump performance curve.
Pump performance curve6.1
A performance curve is plotted to indicate the variation of pump differential head against
volumetric flow (gpm) of a liquid at an indicated rotational speed or velocity, while
consuming a specific quantity of horsepower (BHP). The performance curve is actually four
curves relating with each other on a common graph. These four curves are:
The Head-Flow Curve. It is called the H-Q Curve.
The Efficiency Curve.
The Energy Curve. It records Brake Horsepower, BHP.
The Pump‘s Minimum Requirement Curve. It‘s called Net Positive Suction Head required,
NPSHr.

103
Pump performance curve image with all the important curves
Typical Procedure of Pump Performance Test
The purpose of pump performance test is to ensure that the actual performance of a pump is
typical to that set by supplier. Typical steps to be followed to conduct a pump performance
test are outlined below.
Prepare the original pump curve sent by supplier.
Make sure that the suction strainer is clean and the suction valve is fully open.
Ensure that discharge valve is fully closed.
Start the centrifugal pump take the reading of the discharge pressure, flow rate, suction
pressure and pump Ampere. (Finish this procedure in less than 1 min. As not to damage the
internal parts of the pump)
Open the discharge valve slightly till the flow rate reaches the first value indicated in pump
performance curve provided by pump supplier.
Write down the discharge pressure, flow rate, suction pressure and pump Ampere.
Increase the opening of the discharge valve till you reach the next value indicated in pump
performance curve provided by pump supplier.

104
Open the discharge valve in small increments until it is fully open and take the readings of the
discharge pressure, flow rate, suction pressure and pump Ampere at each of the steps.
Equation:
Head H=Suction gauge reading×0.346+Delivery gauge reading ×10.21+0.34 (m) Discharge
Q={372-V notch high/304.8}2.47×2.52 (m3/hr) W.H.P= (Head ×Discharge×2.727/746) (kw)
I.H.P= (Watt meter reading/.746) (kg) Efficiency ηc=W.H.P/I.H.P
Figure 41: Pump efficiency curve
Head and Capacity Relationship6.2
Not only Milnars Pump but also every pump will be capable of developing a specific pressure
(PSI or BAR measurement translated into feet or meters head) at a specific flow (normally
represented in gallons per minute or liters per minute). The pump will pump any liquid to a
given height or head depending upon the diameter and speed of the impeller. The amount of
pressure we get depends upon the weight (specific gravity) of the liquid. Head (feet) is a
convenient term because when combined with capacity (gallons or pounds per minute) you
come up with the conversion for horsepower (foot pounds per minute).

105
Efficiency6.3
Pump efficiency is the ratio of the liquid horsepower delivered by the pump and the brake
horsepower delivered to the pump shaft. When selecting a pump, a key concern is optimizing
pumping efficiency. It is good practice to examine several performance charts at different
speeds to see if one model satisfies the requirements more efficiently than another. Whenever
possible the lowest pump speed should be selected, as this will save wear and tear
on the rotating parts. The pump performance curve also gives information on pump
efficiency. The efficiency curves intersect with the head-capacity curve and are labeled with
percentages. The pump‘s efficiency varies throughout its operating range. Each pump will
have its own maximum efficiency point. The best efficiency point (BEP) is the point of
highest efficiency of the pump. All points to the right or left of the BEP have a lower
efficiency. The impeller is subject to axial and radial forces, which get greater the further
away the operating point is from the BEP. These forces manifest themselves as vibration
depending on the speed and construction of the pump. The point where the forces and
vibration levels are minimal is at the BEP. Pumps should be sized as close as possible to its
best efficiency point or flow rate. This not only makes the pump more efficient but also
improves the reliability of the pump. Note that total efficiency is never realized because of
mechanical and hydraulic losses incurred in the pump.
Figure 42: Best Efficiency Points Curve

106
Milnars Pump Selection chart depending upon the Flow rate and Head:
Where, 32/160 means by 32 mm discharge flange size, and 160mm impeller nominal diameter
Figure 43: Performance Area Curve of Milnars Pump Ltd.

107
Chapter Six
7 Problem and Solution

108
LOCATION LOGIC7.1
One of the first decisions faced by pump users is where to locate the pump. This may seem
like a very simple matter, but all too often it‘s where many pump problems begin. An ill-
considered placement, where the pump is exposed to extreme temperature conditions, or too
far from the supply vessel, can be the source of considerable trouble down the road.
 Clogged or blocked suction strainer
 System discharge pressure greater than pump internal relief valve setting
 Starved suction
Pumps properly installed with piping fully supported prevent stress on component
connections. The installation of unions will help simplify pump servicing to the supply vessel
as practical, to help minimize friction loss in the suction piping.
Always take into account the environment in which your pump will be located, since extreme
temperature fluctuations, particularly on pumps installed outdoors, can have a pronounced
effect on metering pump performance. For example, pumps installed where temperatures fall
below freezing should be equipped with a heat source to prevent chemical freezing.
It‘s also important to change hydraulic oil in pump to reflect changing temperature conditions.
In addition, you‘ll want to sufficiently protect all components from rain, snow and ice. Failure
to do so could result in a situation similar to the following:
 Clean or replace (suction line was not flushed prior to making connection to pump,
permitting solids or debris such as pipe sealant, tape, etc. to enter and block check
valves)
 Check and reset relief valve (within pump rating)
 Insufficient NPSH. Shorten suction piping, increase suction piping size or suction
head.
Probable Cause
 Insufficient hydraulic oil
 Clogged or blocked check valves, or check valves held open by solids
Remedies
Fill the pump to proper level.

109
Problem: A leading Gulf Coast chemical manufacturer experienced total operating failure
shortly after start-up of several new metering pumps equipped with electronic capacity control
actuators.
Solution: The service technician discovered that the installation contractor had removed the
pumps! actuators from factory-supplied baseplates, resulting in serious misalignment
problems.
Although installed outdoors, the contractor had wired the pumps and actuators using indoor-
type non- watertight electrical connectors. This allowed rain to thoroughly penetrate wiring
and enter the pumps and actuators, shorting-out critical electronic components.
Alter realigning pumps and actuators, rewiring them with watertight electrical connectors, and
replacing the damaged electronic parts, the pumps operated properly.
8.2 SUCTION PIPING
Nearly 85% of all metering pump operating problems can be directly attributed to suction
difficulties, either because of undersized suction piping or due to blockage and/or restrictions
in the suction line.
Unlike the steady flow characteristics of a centrifugal pump, a reciprocating metering pump
with its pulsating flow requires piping large enough to handle the peak instantaneous flow,
which is three times greater than the rated pump capacity. Thus, a metering pump rated at 60
gph produces a 188 gph peak instantaneous flow rate. (60 gph x 3.14 = 188 gph)
Problems can be avoided by keeping suction lines as short and as straight as possible. Piping
should be sloped, if necessary, to eliminate vapor pockets. Although suction pipe size
requirements vary greatly with each application, a good ‗rule of thumb‖ is
Probable Cause
• Partially clogged/dirty suction strainer
• Insufficient hydraulic oil
• Leak in suction piping
• Internal or external relief valve is relieving
• Insufficient suction pressure
• Worn or dirty check valves.
• Liquid close to boiling point
• Liquid viscosity too high

110
Remedies
• Clean strainer
• Fill to proper level
• Repair piping
• Reset valve
• Raise liquid tank level
8.3 PUMP MOTOR FAILS TO START
Probable Cause
• Blown fuse or tripped breaker
• Open thermal overload in motor starter
• Low line current
• Open circuit in limit switches, timers or other control devices in pump motor starter
circuit
• Motor damage
Remedies
• Replace fuse after correcting cause of overload
• Reset after correcting cause of overload. If malfunction recurs, check heater size
• Determine cause and correct
• Reset
• Check motor for physical damage that may hinder operation

111
Chapter Seven
8 Supplementary Part

112
Conclusion8.1
As completed my attachment programme at Milnars Pumps Limited. I believed that, it was
great practical learning session of my engineering life. I am very thankful to my honorable
faculty and supervisor Engr. Sarifuzzaman and also grateful to Eng. Morshed Cho. Miraz.
Milnars Pumps Ltd. is one of the leading centrifugal pump manufacture company in
Bangladesh, which is started with the hand of KSB. As I have done my attachment at MPL,
now I can say that I have a clear concept about manufacturing process and procedure of
centrifugal pumps, as well as working principle and testing of centrifugal pumps. MPL is a
leading metal casting company in our country. They can make centrifugal pump based on the
customer requirements. MPL try to make sure the quality of their product. I have learn a lot of
practical and theoretical information from there engineers and workers. MPL can maintain
highest quality by their high experienced engineers. Centrifugal Pump based on total head
(not discharge pressure) and flow rate. The flow rate will depend on maximum requirement.
Total head is the amount of energy that the pump needs to deliver to account for the elevation
difference and friction loss in system. Pump selection starts with acquiring detail knowledge
of the system. Just replacing an existing pump then of course there is no problem. Replacing
an existing pump with problems or looking for a pump for a new application then we will
need to know exactly how the systems is intended to work. We should make our own sketch
of the system that includes all the information on the MPL plus elevations (max., min., in, out,
equipment), path of highest total head, fluid properties, max. and min. flow rates and anything
pertinent to total head calculations. Depending on the industry or plant that we work in, it will
be forced to either select ascertain type of pump or manufacturer or both. Manufacturers are
normally a very good source of information for final pump selection and it should always
consult with them, do our own selection first and confirm it with the manufacturer. They can
help me to select the right type, model, and speed if I have all the operating conditions and if
not they will rarely be able to help me. This form will help gather all the information pertinent
to operation and selection of the pump. Aside from the normal end suction pump, vertical
turbine and submersible pumps, there is a wide variety of specialized pumps that should
consider for application if some have unusual conditions. I have passed a quality time with the
stuff of MPL when I was there. I observed that MPL will be in the leading of supplying
pumps in the field of agricultural undertakings, irrigation & drainage, general water supply

113
duties for municipal, community, industrial and pressure boosting, textile industries, organic
and inorganic corrosive liquids in chemical handling, pharmaceutical industries and
petrochemical plants etc. The practicum has been completed successfully by the grace of
Allah. Practicum sends to the expected destiny of practical life. The completion of the
practicum at ―Milnars Pumps Ltd‖ The impression that factory is of the most modern input
oriented machinery composite company in Bangladesh.
Recommendations8.2
The company is professionally managed by a team of experienced professionals and promoted
by highly qualified and experienced personnel. As it‘s a Quality Policy states, it is eager to
adopt new and advanced technologies to provide service to the customers with satisfaction of
its customer.
In workshop with this view the following recommendations can be made for Milnars Pumps
Limited out of the study:
To reduce metal waste by operation and maintenance to get more benefit.
They can use more experienced technician and worker in casting section. The reason is if the
cast materials make default it will produce the machining time and lots of metal waste by
removing extra metal on the materials. Even I think they badly need a Drafting and
―AutoCAD‖ experienced engineer for pattern designing but they have not.
Skilled and dedicated engineers need to monitor all the activities.
To ensure the customer requirements.
Their pump testing process is not digital or computerize now, so it can demotivate the
customer to choosing his/her required pump. They may update the test bench to ensure the
customer requirement and satisfaction.
To ensure first workers satisfy and work with joy.

Manufacturing Processes of Centrifugal pumps at Milnars Pumps Ltd.

Manufacturing Processes of Centrifugal pumps at Milnars Pumps Ltd.

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