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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

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27

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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

Department of Mechanical Engineering

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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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1

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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

Department of Mechanical Engineering

34

Table of Contents

Introduction .................................................................................................................... 37

Origin of the report..................................................................................................... 38 2.1

Aims and Objectives ................................................................................................... 38 2.2

2.2.1 Board Objectives ............................................................................................................................ 38

2.2.2 Specific Objectives ......................................................................................................................... 38

Scope ......................................................................................................................... 38 2.3

Methodology .............................................................................................................. 39 2.4

Sources of Data .......................................................................................................... 39 2.5

Limitations ................................................................................................................. 40 2.6

3 Company Overview .................................................................................................. 41

About Milnars Pumps Limited ..................................................................................... 42 3.1

Company Location (Office & Factory) .......................................................................... 45 3.2

Message from Executive Chairman .............................................................................. 46 3.3

Mission ...................................................................................................................... 47 3.4

Vision ......................................................................................................................... 47 3.5

Social commitment ..................................................................................................... 47 3.6

MPL Management Chart ............................................................................................. 48 3.7

MPL Product Application and Specifications ................................................................ 49 3.8

Production Capacity of Milnars Pumps Ltd. ................................................................. 53 3.9

Certificate and Award of MPL ..................................................................................... 53 3.10

Product ...................................................................................................................... 53 3.11

Analysis of products of MPL ........................................................................................ 54 3.12

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 ................................................................................................................... 56 4.1

Pump Setup & Installation .......................................................................................... 57 4.2

4.2.1 Foundation .................................................................................................................................... 57

Mounting ................................................................................................................... 58 4.3

Common Base Plate .................................................................................................... 58 4.4

Definition of Centrifugal Pump .................................................................................... 59 4.5

History of a Centrifugal Pump ..................................................................................... 59 4.6

Classification of Centrifugal Pump ............................................................................... 61 4.7

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: ........................................................................... 63 4.8

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 ................................................................. 70 4.9

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) ............................................................................... 73 4.10

Brake Horse Power (BHP) ............................................................................................ 75 4.11

........................................................................................................................................ 76 4.12

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5 Manufacturing Process of Centrifugal Pump ............................................................. 76

Foundry shop ............................................................................................................. 77 5.1

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 ...................................................................................................... 89 5.2

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........................................................................................................ 99 5.3

6 Pump Testing Section & QC .................................................................................... 101

Pump performance curve .......................................................................................... 102 6.1

Head and Capacity Relationship ................................................................................ 104 6.2

Efficiency .................................................................................................................. 105 6.3

7 Problem and Solution ............................................................................................. 107

LOCATION LOGIC ...................................................................................................... 108 7.1

8 Supplementary Part ............................................................................................... 111

Conclusion ................................................................................................................ 112 8.1

Recommendations .................................................................................................... 113 8.2

Abbreviations ........................................................................................................... 115 8.3

Bibliography ............................................................................................................. 116 8.4

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Chapter: One

Introduction

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Origin of the report 2.1

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 Objectives 2.2

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.

Scope 2.3

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

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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.

Methodology 2.4

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 Data 2.5

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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Limitations 2.6

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 Limited 3.1

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.

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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 Chairman 3.3

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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Mission 3.4

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.

Vision 3.5

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 commitment 3.6

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 Chart 3.7

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 Specifications 3.8

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

Agricultural undertakings, Irrigation & drainage. Drinking

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

Agricultural undertakings, Irrigation & drainage. Drinking

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 MPL 3.10

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.

Product 3.11

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 MPL 3.12

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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Definition 4.1

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 & Installation 4.2

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

Mounting 4.3

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 Plate 4.4

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 Pump 4.5

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 Pump 4.6

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 Pump 4.7

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 Pump 4.9

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 shop 5.1

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

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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 Section 5.2

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.

90

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.

92

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.

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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.

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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.

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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

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Assembly Section 5.3

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.

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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 curve 6.1

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 Relationship 6.2

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

Efficiency 6.3

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

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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 LOGIC 7.1

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

Conclusion 8.1

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.

Recommendations 8.2

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.

114

I had seen the best of one emasculation of MPL, that is insufficient safety equipment‘s and

rare of it uses. In the foundry shop, workers were dealing with the melted metal without safety

gloves and boots. So, I think they should take some step about safety all of the working

section to ensure the workers security.

Proper handling the maintenance schedule.

Positive work environment and helpful manpower.

Marketing of product to promote and enhance produce selling.

Product marketing is a very important process to promoting and selling a product to an

audience. Product marketing, as opposed to product management, deals with more

outbound marketing or customer-facing tasks. There is no commercial advertisement of MPL

to enhance face value of Milnars Pump, so I think they get focus on the product marking too

more.

The manufacture of Centrifugal pump based on many operations such as metal casting, metal

melting, machine operation those are very risky. All of the worker‘s and engineers must

maintain their personal safety and make sure they are using safety roles and proper working

processes.

115

Abbreviations 8.3

B

BWDB- Bangladesh Water Development Board

D

DIN- Deutsches Institutfür Normung

E

ETA-Engine Turnover Assembly

H

H-Head

I

I.H.P-Indicated Hours Power

ISO-International Organization for Standardization

M

MPL-Milnars Pump Limited

N

NPSH-Net positive suction head

P

P- Pressure

PPM-Predictive and Preventative Maintenance

Q

Q-Discharge

R

R.P.M-Revolutions Per Minute

S

SS-Stainless steel

SG- Sherardized Graphite

T

QA- Quality Assurance

TQM- Total Quality Management

116

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There are no sources in the current document.

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http://www.pumps.org/public/pump_resources/discussion/NPSH_Standard/pu

mp_NPSH_margin.htm

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117

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