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UNIVERSITY OF DAR ES SALAAM

COLLEGE OF ENGINEERING AND TECHNOLOGY

FACULTY OF CHEMICAL AND PROCESS ENGINEERING

DEPARTMENT OF CHEMICAL AND MINING ENGINEERING

PRACTICAL REPORT

PT 1

2013/2014

WELDING AND ALLIED PROCESSES

DEGREE PROGRAMME: BACHELOR OF SCIENCE IN CHEMICAL AND

PROCESS ENGINEERING

NAME OF STUDENT: MARO, ROLLAND D.

STUDENT’S REGISTRATION NUMBER: 2013-04-01965

NAME OF PT COMPANY: TANZANIA ZAMBIA RAILWAY AUTHORITY.

NAME OF INDUSTRIAL TRAINING OFFICER: Mr. MUSHI

NAME OF ACADEMIC TUTOR/SUPERVISOR: ABRAHAM TEMU

PT DURATION: EIGHT WEEKS

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AKNOWLEDGEMENT

I owe a great deal to the glorious almighty GOD who gave me health, strength and

capability to complete this program.

Many people have been extremely generous with their time and expertise while I have

been in my field work at Tanzania – Zambia Railway authority (TAZARA) Mbeya.

Particularly I should like to thanks the following people from TAZARA Mbeya for

their contribution all the time on during field work Work Shop manager ,Mr.

Joshua(Engineer at QUA department) , Mr. Banda(technician), Mr.

magemo(Laboratory artisan), Mr. Oswald Seme.

In very special way I extend my sincere and heartfelt gratitude to Mrs. Alice all

member of chemical and mining department at University of Dar es Salaam (UDSM). I

accept their full responsibility, patient, guidance, encouragement and useful antiques.

Lastly I would like to thanks all people who enhance their effort to work with me yet

their names do not appear in this report.

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GENERAL ABSTRACT

The objective of this field work training was to acquire training and experience in a

real life situation practicing the knowledge we acquired from course studies inside the

university.

The Tanzania – Zambia railway authority (TAZARA) deals with provision of

transportation through rail to people, goods and Manufacture parts and provide

maintenance and repairs services at any foundry, workshop or other factory owned or

operated by the Authority.

In Tanzania – Zambia Railway Authority (TAZARA) we make use of Diesel Electric

Locomotives with DC traction motors as major means of transportation. In TAZARA

workshop in Mbeya we dealt with maintenances and repair of parts and locomotives at

large using different sections of the workshop for example quality assurance

department dealt with maintenance of armatures and motors , production control

department dealt with welding, machinery and forging and maintenance department

which dealt with repairing of small repairs and major repairs that may be caused by

accident.

In PPC department (production planning and control) department we dealt with repair

by welding of different machine parts of locomotives. Welding was used for different

purposes for example reproducing/ filling worn out parts of different machine parts,

cutting and straightening metal parts, and joining different metal parts.

Also the heat given out by the welding torch was used for expanding rings and gears so

that they may fit into shafts or may easily be removed.

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Table of Contents AKNOWLEDGEMENT .............................................................................................................. i

GENERAL ABSTRACT ............................................................................................................ ii

PART A ........................................................................................................................................1

WEEKLY REPORT .....................................................................................................................1

PART B ........................................................................................................................................2

MAIN REPORT ...........................................................................................................................2

1.0 TANZANIA – ZAMBIA RAILWAY AUTHORITY ..........................................................2

(TAZARA) ...................................................................................................................................2

1.1 HISTORICAL BACKGROUND OF TAZARA. ...............................................................2

1.2 INSTITUTIONAL VISION AND MISSION ....................................................................3

1.2.1 VISION .......................................................................................................................3

1.2.2 MISSION ....................................................................................................................3

2.0 TAZARA MBEYA WORKSHOP .........................................................................................4

2.1 ORGANISATION STRUCTURE IN MBEYA WORKSHOP. ....................................4

2.2 SERVICES PROVIDED BY TAZARA MBEYA WORKSHOP. ................................4

3.0 PRODUCTION PLANNING AND CONTROL DEPARTMENT (PPC) ............................6

3.1 WELDING AND ALLIED PROCESSES. ........................................................................6

3.2.1 ARC WELDING .........................................................................................................6

3.1.2 GAS WELDING .......................................................................................................11

3.2.0 WELDING AND CUTTING TORCHES .....................................................................16

3.2.1 DESCRIPTION OF W ELDING AND CUTTING TORCHES. .............................16

3.2.2 FUNCTION OF A WELDING AND CUTTING TORCHES. .................................16

3.2.3.2 REPAIR AND PLACEMENT OF WELDING TORCHES ..............................19

CONCLUSION ..........................................................................................................................20

RECOMMENDATION .............................................................................................................20

REFERENCE .............................................................................................................................21

1

PART A

WEEKLY REPORT

2

PART B

MAIN REPORT

1.0 TANZANIA – ZAMBIA RAILWAY AUTHORITY

(TAZARA)

Tanzania-Zambia Railway Authority also known as TAZARA, is a two national

railway, jointly owned by the Government of the United Republic of Tanzania and the

Government of the Republic of Zambia on the basisi of equal share holding. The

1,860km-rail runs from Tanzania and East Africa’s major seaport of Dar es Salaam

into the parts of Zambia’s Central Province and ending at New Kapiri - Mposhi, where

it is further linked by road and rail to Zambia’s capital city, Lusaka (about 200km),

Zambia’s mining nerve centre, the Copper belt province (about 100km) and the

Democratic Republic of Congo (DRC).

1.1 HISTORICAL BACKGROUND OF TAZARA.

TAZARA raised from the need to develop vast areas of northern Rhodesia (Zambia )

and Tanganyika(Tanzania ) which was greatly motivated by the need to develop

agriculture in these regions. In northern Rhodesia these plans started to gain

momentum in the year 1963 while in Tanzania the plans were discussed for many

years.

The Tanzania-Zambia Railway Authority was established in March 1968 and the

survey and design work started in October 1968 and finished in May 1970. The

surveys that were done by the Chinese produced favourable recommendations, which

completely disregarded all conclusions of earlier surveys. By now it had been decided

that the line would start from Dar es Salaam and end at Kapiri Mposhi.

The leaders of Tanzania (the late Mwalimu Julius Nyerere) and Zambia (Dr. Kenneth

Kaunda) who were aware of Zambia’s dependence on the southern route and its

implications visualized that the North East Rail Link was the only other way for

Zambia to maintain economic and political independence. In a significant way,

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therefore, Ian Smith’s UDI spurred the proponents and even quickened the pace at

which the TAZARA project was implemented.

Construction of the line started in October 1970. The then Presidents Dr. Kenneth

Kaunda of Zambia and late Mwalimu Julius Nyerere of Tanzania officially inaugurated

the commencement at Dar es Salaam in Tanzania and Kapiri Mposhi in Zambia,

respectively. After two years construction reached a most complicated geographical

profile 158-kilometre Mlimba/Makambako section, The track crossed the Tanzanian

border at Tunduma into Zambia at Nakonde in August 1973. The track crossed the

Tanzanian border at Tunduma into Zambia at Nakonde in August 1973.

1.2 INSTITUTIONAL VISION AND MISSION

1.2.1 VISION

The vision of TAZARA is to provide a safe, reliable and quality means of

transportation to the traders, agriculturalists and all citizens of the two countries.

1.2.2 MISSION

The mission of TAZARA organization since the establishment of its foundation is to

be the most preferred means of transport to the countries involved.

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2.0 TAZARA MBEYA WORKSHOP

2.1 ORGANISATION STRUCTURE IN MBEYA WORKSHOP.

The production organization structure is as follows:

2.2 SERVICES PROVIDED BY TAZARA MBEYA WORKSHOP.

In Mbeya workshop we dealt with maintenance of General Electric/Krupp (Diesel

Electric) Locomotives and all scopes of repair, including the rehabilitation of

locomotives from serious train accidents also we dealt with some engineering services

like Steel casting, General purpose and light metal casting, Forging services, all basic

machining processes, including planning, grinding, turning, shaping and more,

laboratory services, equipment maintenance, repair and overhaul.

2.2.1 DIESEL ELECTRIC LOCOMOTIVES

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All the repairs and services done under Mbeya Tazara workshop was for diesel electric

locomotives. A summarized description of these locomotives is done in the following

diagram

Workshop Manager

The workshop manager manages all activities and finances inside the

workshop and coordinates with the higher administration for feedback and

requests of funds, tools and machine parts for repairs.

Locomotive maintenance department (LMR)

Dealt with casual light and overhaul mechanical and electrical repairs like oil

change , checking and changing of motor and combo(combination of traction

motor and wheel set)

Production planning and control (PPC)

PPC is incharge of planning the repairs of locomotives which are totally

damaged from accidents they build a locomotive from scratch, also it is

incharge of all welding activities in the workshop; this activity is the area of

concentration in this general field report.

Quality assurance department (QUA) dealt with assurance of quality of every

repaired and manufactured tools tools and machinery so that they can be safely

used again for example testing of motor, repaired locomotives, also laboratory

artisan under this section is incharge of checking fuel and oil samples for

safety.

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3.0 PRODUCTION PLANNING AND CONTROL

DEPARTMENT (PPC)

3.1 WELDING AND ALLIED PROCESSES.

In TAZARA workshop under production control department the main activity

engaged are welding processes to join material. A large bulk of materials that are

welded are metals of different or the same alloy. The allied processes besides welding

done are straightening of machine parts, expansionof rings and gears.

During the welding practical, 2 type of basic welding were called Arc and Gas

welding. At the practical, we learn different kind of tools that use in Arc and Gas

Welding. This kind of tools that use in each basic of welding is one of the most

different of Arc and Gas welding. At the same time, safety is no 1 to prevent an

accident while working at workshop.

3.2.1 ARC WELDING

The purpose of this practical is :

To learn the basic techniques of arc welding.

To learn a real life experience of metal arc.

3.1.1.1 PROCESS DESCRIPTION

In Arc welding a welding power supplies used to create an electric arc between an

electrode and the base material to melt the metals at the welding point. The welding

power supply used was either direct (DC) or alternating (AC) current, and consumable

or non-consumable electrodes, but consumable electrodes ware preferred. The welding

region is protected by some type of shielding gas, vapor, or slag that resulted from the

filler material. The method used is physical welding.

3.1.1.2 EQUIPMENTS

The description of equipments used in arc welding is as follows:

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WELDING MACHINE

Generaly there are two types of welding machines that are used during the welding

process.

I. Alternating current AC welding machine.

This type of machine was very useful in workshop as it was usually used compared to

DC machine. It worked with small voltage for example 37.5 amps. It was essential

for welding work in all conditions without considering whether the voltage is small or

large. Its distinctive advantages are:

It is cheap and the cost of running was low since it consumed less energy per

unit weight of deposited metal.

Maintanance of this machine was easy and it does not result in a lot of noise

during welding operations.

It produced a stable arc that was important when precision was considered.

It occupied less space.

Produced less noise.

It was suitable for most of the work pieces since most of them are thick

Although this type of machine was mobile, it can only used limited amount of

electrode ie. It was used for ferrous materials. Apart from that, it does not have

movable components and cannot be used on aluminum electrode. It uses only one level

of electricity.

II. Direct current DC welding machine

Direct current machine was built in capacities up to 1000A, having an open circuit

voltage 40 to 95 V. This machine is very expensive and it uses three level of

electricity and it requires a generator to provide the current. The advantages of using

the machine was:

there is no confinement on the type of electrode being used

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It was a good method to do welding operations when there was no electricity or

voltage level has dropped.

Arc produced by this DC machine was more stable.

It was used for welding non- ferrous metals and alloys.

It has less open ciruit voltage of 45 – 95V thus makes it safer.

This type of machine was used only few times. The disadvantages of this machine was

difficulty to maintain and it also produces a lot of noise while functioning. This DC

machines use air as cooling agent and thus it was always kept in a dry place to avoid

transformer and generator damage.

Cables

Generally, there are two cables that carry the electricity from welding machine to work

metal and back to welding machine and earth cable. These cables are made from small

copper wire coated with strong rubber so that we can hold it without feeling the intense

heat. Besides that, every cable has it own size. For instance, size No. 2 means that the

cable will be able to withstand welding electricity up to 200 amps. Therefore the

choice of these cables depend on the current used during the welding process. These

cables are connected to the welding machine through its copper end.

Electrode holder

The electrode holder had the following functions. Firstly, it was used to provide the

electricity from welding machine to metal work, also used to hold the electrode during

the welding operations. One of its constituent parts was the spring where it hold the

electrode firmly and withdrawn the electrode easily after finish welding, also it was

light weighted and has enough size conductor to carry electrons.

Earth electrode

The earth holder was always connected to the earth cable and clamped to the work

metal or to the work table. It has a spring so that is can be easily clipped and unclipped.

Without this equipment, welding operation definitely cannot be done.

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Shield

It is made from inflammable material. In the middle of the shield there is a bright

rectangular glass coated with dark colored glass. It is used to protect from flying hot

pieces of metal and harmful rays during welding work. The type of shield used is the

hand held type.

Chipping hammer

It is made from an old spring metal. Shape like a chisel at one end and has a sharpened

end at the other one. Its holder is made from welded soft metal. It is used commonly to

remove the slag excess stringer from the surface of the work metal.

Wire brush

It was used to clean the surface of the weld after the slag is chipped away and to

remove dirt from the surface of metal work before welding can be done.

Glove.

It is made from high quality leather. Used to protect your hand from fire-bolt and hot

metal welding.

Leather jacket

Leather jacket is used to protect the user from the intense heat produced during

welding operations. It is made of high quality leather to provide greater comfort for the

user.

Tongs

It is use to hold hot work metal after welding process.

3.1.1.3 PROCEDURES OF ARC WELDING.

Electrode cable and the earth cable was connected to the Alternating Current AC

Welding Machine.

i. The earth cable is connected, using its holder to the work piece .

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ii. The electrode is clipped with the holder. The flux is not in contact with the

holder so as to allow current to flow. Undesired spark would occur if the flux is

in contact with any metal.

iii. The welding machine is turned on and set the dial to 90 amps.

iv. Before beginning welding, gloves and shield are put on.

v. The electrode is held about 90o above the metal to be welded. The electrode is

tilted 20o-25

o degrees to the right or left depending on which hand do you use

from the work metal.

vi. The front end of the electrode is scratched onto the work metal to start the

burning. After the electrode has started burning, hold it at 10mm above the

work metal. If the electrode is in contact with the surface of work because the

electrode might be stucked onto the work, therefore this is avoided..

vii. The welding process is repeated for several times until you get a straight and

firm stringer bead line when welding. .

viii. When the welding line is done, the chipping hammer is used to chipp off the

slag and brush it off using a wire brush.

Welding process.

3.1.1.4 SAFETY PRECAUTIONS.

Before and during the welding process the following precautions were emphasized;

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a. All the personal protective equipment are worn.

b. Eyes protection is made sure; to protect from arc rays.

c. Face and body is protected from heat radiation and molten metal.

d. All the flammable material are moved off the working place or covered it using

fireproof material.

e. The welding machine is earthen.

f. Assurance that all line holder, earth clip and connection placed on good place.

g. Make sure that all electric connection is tight, clean and dry.

h. the cable is not to be pulled on top or near sharp things.

i. The welding machine is turned off when not in use.

j. Welding cable is to not contact hot metal, water, oil and grease.

k. All safety clothing are worn when welding.

l. All equipment such as hammer, chisel, brush and others are well maintained.

3.1.2 GAS WELDING

The common gas welding used was oxy-acetylene welding.

The purpose of this practical is :

To learn basic technics of gas welding.

To learn and exercise the safety precautions during gas welding.

To acquire real life experience of gas welding.

3.1.2.1 PROCESS DESCRIPTION

The heat in gas welding comes from the reaction as follows:

Stages of Chemical reaction and temperature distribution in a neutral oxy-acetylene

flame

• Oxy-acetylene Welding:

CaC2 + 2H

2O = Ca (OH)

2 + C

2H

2

C2H

2+2.5O

2= 2CO

2+H

2O

(vapour)+ 306.800 cal /mol

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.

When the inner core flame is passed over the metal fusion is obtained and the metal melts.

The later can simply be explained in the following block diagram.

3.1.2.2 EQUIPMENTS

1. Gas Cylinders; pressures are :oxygen-125kg/cm2 and acetylene-16 kg/cm2.

2. Regulators

The regulator was used to regulate the pressure from the tank to the working pressure

in the horse; Working pressure of oxygen 1 kg/cm2 and acetylene is 0.15 kg/cm2 .

3. Pressure Gauges

The pressure gauges are used to show the cylinder pressure and the working pressures

of the horse.

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4. Hoses

Gas horses were used to deliver the gases to the welding torch, horses has color coding

according to the gases they carry; the one that carries oxygen is green and the one that

carries acetylene gas is red.

5. Welding torch

The welding torch is the tool that was held when welding.

6. Check valve

7. Non return valve

The non- return valves prevented the back flow preventing fire to explode the

cylinders.

Types of flames used in gas welding.

Three types of flames were used in oxyacetylene welding:

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a. Neutral flame - Acetylene (C2H2) and O2 are mixed in equal amounts and burn

at the tip of the welding torch. The inner cone generates is the one that

generates a lot of heat. Used for welding steels, aluminium, copper and cast

iron.

b. Reducing flame - The excess amount of acetylene is used this produces a three

layer flame with the inner core, a white-hot second layer which is also called

acetylene feather and a blue colored outer core this flame was mostly used to

weld aluminium and high carbon content steel.

c. Oxidizing flame - The excess amount of O2 is used, the envelope becomes

darker and more pointed, while the envelope becomes shorter and fiercer

giving an oxidizing flame. This type produced highest temperature. It was

useful in welding brass and brazing operation.

3.1.2.3 PROCEDURES USED TO CONDUCT GAS WELDING.

I. Lighting the flame.

The main valve of the acetylene tank is opened at least 1/2 of its full turn which

charges the pressure regulator at the top of the tank. The pressure is regulated to

5 psi. The main oxygen pressure valve is opened and the pressure is regulated

to 10 psi. The acetylene valve is opened 1of 8th

turn and a striker is used to

ignite the flame.

II. Adjusting the flame.

The acetylene valve is opened further until the flame is about to detach from

the tip of the welding torch, the oxygen valve is slowly opened and flame turns

bluish in color the quantity of oxygen added determines the type of flame i.e.

neutral, oxidizing or reducing flame.

III. Welding

All protective gears are worn i.e. dark face shield, leather jacket, and

long sleeves.

The flame is applied to the parts to begin heating until the metal begins

to glow and forms a pool of molten metal near the edge of each parts of

the metals to welded.

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After the pool is formed the flame is used to gently stir the pool to form

a weld.

After the pool is mixed the torch is moved along the line of welding

while gently circulating the pool to help mixing the metal in a circular

swilling motion.

The process is continued until the weld is done.

DURING GAS WELDING.

• Simple equipment

• Portable

• Inexpensive

• Easy for maintenance and repair

The bed and viscosity of the weld was easily controlled since the welding filler

material is added separately of the welding heat source.

SETBACKS DURING GAS WELDING.

• Very low welding speed

• High total heat input per unit length

• Large heat affected zone

• Severe distortion

• Not recommended for welding reactive metals such as titanium and zirconium.

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3.2.0 WELDING AND CUTTING TORCHES

3.2.1 DESCRIPTION OF W ELDING AND CUTTING TORCHES.

A welding torch is been referred to as a complete unit , to which a tip and mixer are

added and gas is supplied. A Cutting attachment and tip can replace the tip (and nut) to

transform it into a Cutting Torch.

3.2.2 FUNCTION OF A WELDING AND CUTTING TORCHES.

Welding and cutting torches has the following functions:

1. Flame adjustment.

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The flame needed is selected by adjusting the proportions of oxygen to acetylene gas .The

flame is neutral, reducing or oxidizing flame.

2. Welding.

The main job for the welding torch is welding; it has the tip where flame forms, mixing

chamber and provide handling for the welder.

3. Cutting.

A specified cutting torch was used in this process ,it has an extra oxygen hose pipe for cutting.

3.2.3 SEQUENCE FOR TROUBLE SHOOTING AND REPAIR.

3.2.3.1 TROUBLE SHOOTING

When adjusting a malfunctioned or leaking torch, accessory or tool the following table was

useful

TROUBLE SHOOTING CHART

SYMPTOM POSSIBLE CAUSE REMEDY

1. Backfire,

flashback, or

erratic flame.

a. Damaged tip or

mixer.

a. Replace with

new tip or

mixer

b. Insufficient flow. b. Readjust

pressures.

Reduce

number of

fittings.

Increase hose

size.

c. Improper gas

pressures or

flows.

c. Readjust

pressures or

torch valves

d. Loose tip or

mixer.

d. Allow to cool,

then tighten,

or replace

seals.

e. Dirty or deformed

tip.

e. Allow tip to

cool, then

clean and

replace.

f. Tip too close to

work, or

f. Increase

distance.

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overheated.

g. Tip or torch head

does not seat

(cutting torch).

g Discard tip or

send torch to

service facility

for new head.

h. Failure to purge or

use check valves.

h. Purge lines.

Install check

valves.

2. Gas leakage. a. Loose torch or tip

nut

a. Tighten tip nut.

b. Dirty or damaged

seating surfaces

between torch

and tip.

b. Clean or send

torch to

service facility.

3. Oxygen or

fuel leak

through

valve stem.

a. Loose packing

nut.

a. Tighten nut

(packing type

only.

b. Worn packing or

O-ring.

b. Send torch to

service facility.

c. Improper gas

pressures or

flows.

c. Send torch to

service facility.

4. Oxygen or

fuel leak

through

valve seat.

a. Dirty or damaged

valve seat or bent

valve stem.

a. Clean or send

torch to service

facility.

b. Damaged body. b. Send torch to

service facility.

5. Cutting

oxygen valve

leaks.

a. Dirt in cutting

oxygen valve.

a. Send torch to

service facility.

b. Damaged cutting

oxygen valve

b. Send torch to

service facility.

c. Worn or damaged

valve seat.

c. Send torch to

service facility.

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d. Broken valve

spring.

d. Send torch to

service facility.

6. Oxygen leak

at cutting

oxygen valve

stem.

a. Damaged cutting

oxygen valve Oring

or packing.

a. Send torch to

a service

facility.

b.Packing loose b. Tighten

packing nut.

7. O-ring type

valve stem

binds.

a. Drag sleeve over

tightened.

a. Loosen

sleeve.

b.Damaged body. b. Send torch to

service facility.

8. Hose/Torch

connection

leak.

a. Damaged seat. a. Send torch to

service facility.

3.2.3.2 REPAIR AND PLACEMENT OF WELDING TORCHES

Firstly the gas supplies are shutoff at the source before attempting inspection, or

maintenance except for leak checks.

A defective or leaking torch or cutting attachment is not repaired but returned to the

authorized service facility, as special tools, tests and techniques may be required. Only

replacements of readily removable tips nuts, mixers, and cutting attachments are made.

For example the repairs of

Cleaning of welding tip

The flame is first switched off and the tip is allowed to cool first then the tip is cleaned.

Welding Tip and Mixer replacement

Welding tip and mixer chamber are removed by opening the head nut from the torch

head fitting ;while protecting the seat so as not to damage it. The defective part can be

changed by buying a new part from local dealers who engage in selling these kind of

equipments.

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Cutting oxygen valve leak

The packing nut is tightened over a wench ;but if the leak continues the torch is

discarded.

REORDERING OF PARTS

Reordering of small parts in smaller quantity is done using local dealers found in the

area/town, But ordering of large quantities of spare parts is done from international

dealers in China, this is where most of the parts are obtained.

CONCLUSION

During my practical training I learnt a lot of thing concerning my course of study. I

learnt also how to work with different people in an organization by cooperation. Apart

from that I enjoyed a lot both practical works assigned to me because they made me

become confident and familiar mostly to welding operations.

Welding operations were basic and common to all departments in the workshop;

therefore it’s a primary operation to any industrial practice because it resides and goes

hand in hand with other operation, for example in TAZARA welding was used in

smaller operations like filling worn out parts, straightening of metal parts to major

operations like rebuilding structures torn apart in accidents for example a structure

called cowcatcher.

RECOMMENDATION

The implementation of safety regulations for the organization is not strictly followed

which is due to lack of safety tools and equipment. This lack of safety tools and

equipment is due to lack of funds ,therefore since it is a governmental organization ;the

government should look into ways to revive the organization to be able to compete

again by providing it with funds, intellectuals and promotion.

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REFERENCE

Controls Corporation of America, 2009, Hand welding and cutting attachments(ADI 1647J),

1501 Harpers Road.Virginia beach, VA23454

American torch tip, Cutting, heating, welding and brazing instruction manual, 6212 29TH Street

East, Bradenton, FL 34203, United states

http://www.weldguru.com/welding-electrode.html

http://www.tazarasite.com/

http://www.acastronovo.com/ClassHtms/Weld01.htm

http://www.slideshare.net/RakeshSingh125/f-gas-welding

http://en.wikipedia.org/w/index.php?title=Oxy-fuel_welding_and_cutting&redirect=no

http://www.concoa.com/docs/ADIS/ADI1647J.pdf