Summer Internship Report (National Engineering Services Pakistan)-2014

SUMMER INTERNSHIP
REPORT - 2014
Mechanical Section
National Engineering Services Pakistan-NESPAK
6/27/2014
Prepared by:
 Danial Sohail ME-089
 Muhammad Bilal Javaid ME-120
 Syed Irfan Ali ME-076
 Sagar P. Jesrani ME-122
 Zohaib Azhar Mallick ME-178
NED University of Engineering &Technology
Batch 2011-12

ii
Acknowledgements
All praise to ALMIGHTY ALLAH, the creator of the universe and all
thing in this universe. He made us super creature, blessed us to
accomplish this work. We are very thankful to Allah Almighty, Who has
provided us such an opportunity to gain knowledge in National
Engineering Services Pakistan (NESPAK). It was a great experience of
getting trained here. We learnt many things practically which we have
learnt theoretically earlier. We also pay our gratitude to the Almighty for
enabling us to complete this Internship Report within due course of time.
We would like to thank all staff, especially Mr. Saeed Ahmed Soomro,
for helping us and for their kind behavior towards us throughout our
internship. We acknowledge that we were unable to learn this much on
our own.
Thank you!
With warm regards;
Danial Sohail
Muhammad Bilal Javaid
Syed Irfan Ali
Sagar P. Jesrani
Zohaib Azhar Mallick

iii
Table of Contents
Executive Summary....................................................................................................................................... I
Lifts / Elevators............................................................................................................................................. 1
Types of Lifts ................................................................................................................................... 2
Advantages and Disadvantages of Different Types of Elevator....................................................... 3
Components of Elevator System...................................................................................................... 4
Elements of Lift Design .................................................................................................................... 7
Famous Lift Manufacturers.............................................................................................................. 8
Visit to NICL Elevator System........................................................................................................... 9
Fuel Storage Tanks ..................................................................................................................................... 10
Orientation of Storage Tanks......................................................................................................... 11
Basic Components of Storage Tanks.............................................................................................. 13
Fuel Storage Tank Designing.......................................................................................................... 14
Designing of 10000 Liter Fuel Storage Tank................................................................................... 15
Fire Suppression System ............................................................................................................................ 16
Classes of Fire................................................................................................................................. 17
Fire Ingredients.............................................................................................................................. 17
Fire Suppression Techniques ......................................................................................................... 18
Fire Suppression Using Gases ........................................................................................................ 19
HVAC........................................................................................................................................................... 21
Goal of an HVAC System ................................................................................................................ 22
Components of an HVAC System................................................................................................... 23
Split Air Conditioner System .......................................................................................................... 24
Packaged Air Conditioner............................................................................................................... 25
Cooling Tower Technology............................................................................................................. 27
Chillers ........................................................................................................................................... 29
Air Handling Units .......................................................................................................................... 30
Pumps ............................................................................................................................................ 32
Positive Displacement Pumps........................................................................................... 32
Kinetic Pumps ................................................................................................................... 38

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Welding Techniques................................................................................................................................... 41
Gas Welding................................................................................................................................... 42
Arc Welding.................................................................................................................................... 42
Shielded Metal Arc Welding .......................................................................................................... 43
Gas Shielded Arc Welding.............................................................................................................. 43
Weld Joints..................................................................................................................................... 44

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Preface
Internship is one of the keys for understanding more deeply the concepts
learned from formal education by going through practical practices
adapted by industries. And this rationale brought us to National
Engineering Services Pakistan NESPAK.
During our internship we have learned a lot about building services and
HVAC systems. Every topic from crust to core was explained to us and
this report is an overview of what we learned. Information in this report
is gathered from different sources like instruction manual, project
proposals, online websites and notes provided by instructors.
This document gives reader an insight of design techniques for lifts,
storage tanks, and HVAC systems along with introduction to
international standards. Interactive visuals provide an ease to reader for
understanding cyclic process and don’t let reader to get bored as
traditional technical text does.
We have tried our best to eliminate all mistakes and misrepresentation of
facts but since its natural for humans to make mistakes, so we ask your
pardon in advance for any such mistake.
Thank you!

vi
Executive Summary
Introduction:
During our internship at Mechanical Section NESPAK, we have gone through a lot
of stuff related to Building Services and HVAC system. We have studied and
discovered functioning of lifts, designing of fuel storage tanks, fire suppression
systems, welding techniques, HVAC systems and components, pumps and
Window and Split air conditioning systems.
Following is a brief topic wise detail of subjects we have studied during our
internship.
Lifts / Elevators:
Starting from basic types of lifts, area of application, advantages, disadvantages of
each type, our study have been extended to techniques of lift selection for
residential buildings, offices and medical facilities. Also visit to N.I.C.L building
Elevator system gave us an insight of working procedure of elevators.
Fuel Storage Tanks:
Demand of fuel storage tank is increasing day by day because of installation of
high power output standby generators in residential buildings, therefore during our
study of fuel storage tanks we were taught about tank orientation, tank’s basic
components and their significance. Techniques for designing tank following
international standards were taught by our instructors and a task of designing
10000 liter tank was assigned to us, which was successfully completed.
Fire Suppression System:
One of our internship course outline topic was Fire Suppression System. Our
instructors taught about fire ingredients (factors necessary for fire initiation). We
also have studied about 4 common classes of fires, ways to tackle with them. Our
training included Fire suppressions through Clean Gas Technology and Fire
suppression using water.
HVAC:
NESPAK has its expertise in designing HVAC systems for residential buildings,
offices, medical facilities. During our posting in HVAC systems we have learned a
lot about HVAC system, from the main reason for employing HVAC to goals
HVAC should be accomplished, we have learned about components found in every
HVAC system along with types of air conditioning systems for better

vii
understanding of working of each component. Not just study of systems but also
the study of their governing refrigeration cycle gave us an insight of purpose of
each component. Special attention was given to study of pumps because it has its
application not only in HVAC but also in Waste Water Treatment, Fuel
transportation, Industrial purposes. Therefore we have studied all pump types and
area of their application.
Welding Techniques:
Welding is most used method for making parts in industry, from seamless pipes to
chases of cars, most structures are joined by weld. Welding techniques includes
preparation of work piece before welding, pre heating of work piece and
electrodes. Welding techniques also includes selection of appropriate welding
mechanism according to application and purpose of weld.
Conclusion:
Internship at NESPAK is one of most knowledgeable period in our professional
lives. We have learned a lot here, all staff specially engineers helped us throughout
our internship and we hope that this knowledge we are taking from here will help
us throughout our life.

SUMMER INTERNSHIP REPORT - 2014
1 | P a g e
LIFTS / ELEVATORS
Lift – British English
Elevator – American English

2 | P a g e
Nowadays buildings are becoming taller and taller to confine large population into
a small piece of land, but access to floors above ground is inconvenient if done by
staircase because they are both time consuming and tiring, therefore lifts and
escalators are employed for transporting people from one floor to another.
Types of Lifts
Lifts are of two types
 Traction Lifts
 Hydraulic Lifts
Traction lift:
Works on the principle of pulling whereas hydraulic powered lifts works by
lifting through pushing action. In traction lifts pulling is done by electric motors
which rotate the pulley over which wire controls the motion of lift
corresponding to motion of balancing weights.

3 | P a g e
Hydraulic Powered Lifts:
Hydraulic powered lifts have telescoping plunger/piston being pushed by
pressurized fluid.
Advantages and Disadvantages of Different
Types of Elevators
Hydraulic Lifts:
 Each lifting mechanism has its own advantages and drawbacks.
 Hydraulic powered lifts are less costly.
 They have a larger lifting capacity.
 They have limitation of height up to which they can push lift cabin
(maximum 3-4 floors).
 They have lesser speeds.

4 | P a g e
Traction Lifts:
 They can lift up to greater heights.
 They have greater speeds
 They are more costly than hydraulic elevators.
Components of Elevator System
Elevator systems have following components:
 Elevator Car:
Elevator Car is the vehicle that travels between the different elevators stops
carrying passengers and/or goods, it is usually a heavy steel frame surrounding
a cage of metal and wood panels.
 Shaft:
A vertical shaft in a building that gives passage to elevator to travel from floor
to floor
 Guides:
Guides provide ways for traveling of cabin and counterweight and avoid
unnecessary vibration, providing a fixed path.

5 | P a g e
 Counter weight:
Counterweight balances the elevator car and provides an ease in functioning of
lifts. Initially during no load condition counter weight is equal to weight of
elevator car and then 50% weight of total lifting capacity of lift is added in
counterweights.
 Machine Room:
Machine room consists of different components necessary for elevator system.
These include:
 PCB’s for controlling actions and reactions of lifts during a lift call.
 Motor drive which gives power to lift car.
 Governor and brake lever: as ELD (emergency landing device)

6 | P a g e
 Governor:
It is an independent device which in case of failures acts and applies brakes
on guides to stop lift immediately.
 Buffer:
Buffer is a device used to absorb kinetic energy. Buffers are places at the
bottom of shaft at certain depth below floor, in case if cables supporting lifts
cuts off and lift fall then elevator car falls onto buffer and it reduces much of
its speed before striking ground.

7 | P a g e
Elements of lift design:
NESPAK has its expertise in lift design, lift designing is not as simple as it
seems by just installing a lift, there are numerous factors which should be
considered before designing lift system, these factors include building type,
either residential or commercial, approximate numbers of occupants, available
space and factors which should be viewed while designing including lift speed,
lift size, secure operation provision, comfort ability of passengers etcetera.
Mr. Zaki of Building services section instructed us about designing lifts by
presenting their ongoing project of designing lift system for crescent bay emmar
tower. He provided us floor plan of crescent bay indicating shaft for lift and
MCR (machine control room) along with his calculations of specification of lift
based on following assumed factors:
 Each tower comprises of 30 occupiable floors.
 20% of total population of building is using lifts every time.
 Specific number of occupants for each flat.
 Peak usage hours will be 7 a.m. - 10 a.m. & 4 p.m. - 6 p.m.
Based on above assumptions there were number of choices of lifting system
like
System Car speed Car capacity Remarks
System 1 1.5 m/s 1250 kg Poor
System 2 2.5 m/s 1250 kg Good
System 3 1.5 m/s 1600 kg Good
System 4 2.5 m/s 1600 kg Recommended
These systems can be installed / employed having different specification of
speed, area, lifting capacity and waiting time with corresponding
grades/remarks so management will not face trouble while selecting one.

8 | P a g e
Famous Lifts Manufacturers:
Various companies manufactures lifts these includes brands from Korea,
China, Japan and from Western countries. Prices of lifts from eastern and
western brands vary significantly. While going through catalogues from
different brand we got an insight of sizes of traction elevators. Residential
elevators may be small enough to only accommodate one person while some
are large enough for more than a dozen. Wheelchair, or platform elevators, a
specialized type of elevator designed to move a wheelchair 12 feet (3.7 m) or
less, can often accommodate just one person in a wheelchair at a time with a
load of 750 pounds (340 kg). And freight elevators can lift up to 4500 kg
mass.
Some common lift manufacturer includes:
 Doppler Lift manufacturer
 Thyssen Krupp Aufzüge
 Schindler
 Hyundai Elevators

9 | P a g e
Not only speed, lifting capacity is important but elevator car appearance is
important if installed in corporate buildings and shopping malls, so
manufacturer pays special attention to its appearance and sometimes to
bring more fantasy capsule lifts are installed.
Visit to N.I.C.L Elevator System:
After studying all standard practices for installing lifts and all safety
provisions which are given, Mr. Saeed Soomro of BSS have organized a
visit to N.I.C.L building lift system. He took us to Machine room, there were
PCB’s, Governors, Motors, Pulleys and also learned that incase of power
breakup how one can bring lift to nearest stop using brake release panel and
manually through pulley. One noticeable thing was presence of air
conditioning room in machine room and this was clarified as that it is used
to keep cool all electrical and electronic components so they don’t get
damaged.

10 | P a g e
FUEL STORAGE
TANKS

11 | P a g e
Continuous supply of fuel is required in all equipment’s like generators, HVAC
plants, fabric industry machinery, boilers etc. Therefore instead of laying long
underground supply pipelines from large reservoirs which is complicated, costly
and dangerous in case of fuel. Storage tanks are employed for storage of these
fluids capacitive enough to provide nonstop supply according to requirement up to
certain number of days.
Tanks are manufactured having storage capacity from few hundred liters for small
residential building to thousands of gallons for storing fuel for generators and
HVAC chillers in skyscrapers.
Orientation of Storage Tanks:
There are two possible orientations of storage tanks:
 Horizontal storage tanks
 Vertical storage tanks
These orientations are employed according to applications and space
availability of site where it is going to be placed.
Horizontal Storage Tanks:
Horizontal storage tanks are used when;
 Liquid stored is not required to be heated before extraction, because a larger
bottom fluid area takes more time to reach to a certain temperature before
extraction.
 When there is enough ground space but have limitation of height.

12 | P a g e
Vertical Storage Tanks:
Vertical storage tanks are employed when;
 Liquid stored in storage tank is required to be heated before extraction,
because of lesser cross section are, heat is more concentrated on bottom than
rest of tank therefore resulting in higher bottom temperature and thus hot
liquid is extracted from bottom.
 When there is limitation of available are but not any restriction on height.

13 | P a g e
Basic Components of Storage Tanks:
Basic components of fuel storage tank include:
Shell:
It covers majority of storage capacity of tank. It is simply a cylindrical shell
with dished ends to store any kind of liquid.
Dished Ends:
Dished ends closes shell opening so fuel can be confined in it, it is made dished
shape so forces developing on its surface will be distributed on a larger area
thus reducing its effect.
Air Vent:
Air vent is placed at top of tank on higher side of slope to prevent air trap.
Operating Valves:
Operation valves present in fuel storage tanks include:
 Inlet/input valve
 Outlet/output valve
 Drainage valve
Lifting Lug:
It helps lifting tank during installation and other maintenance operations.
Manhole:
It is a provision/space for workers to enter tank for cleaning and maintenance
purposes.
Level Indicator:
It is a glass tube whose one end is linked to tanks bottom and other end to tank
tops, it indicates fuel level in tank.

14 | P a g e
Saddles and Supports:
Tanks are placed on saddles; these saddles are designed and placed according to
tank size. Saddles themselves stands on supporting plates.
Fuel Storage Tank Designing:
To ensure proper and safe functioning of storage tanks they should be designed
and manufactured following international standards. These standards are
available in form of codes and norms published by different engineering
societies. These codes guide designer from setting up basic parameters to the
thickness and number of coats of paintjob. Societies which publish such codes
includes;
 ASME (American Society of Mechanical Engineers)
 UL (Underwriters Laboratories)
 DIN (DeutschesInstitutfürNormung)
 EN (European Standards)
 BSI (British Standards Institution)

15 | P a g e
Designing of 10000 Liter Fuel Storage Tank:
After spending enough time studying international standards for tank designing
and tank drawing, we were able to design our own tank. So Mr. Saeed Ahmed
Soomro gave us a task for designing a fuel storage tank with 10000 liter storage
capacity following European standards EN-12286-1 and EN-12285-2 entitled
“WORKSHOP FABRICATED STEEL TANKS”. After finding all design
parameter we designed that tank on CAD. Following is the 3D design of tank
on Pro-Engineer wildfire 4.0.

16 | P a g e
FIRE SUPPRESSION
SYSTEM

17 | P a g e
In 2012, National Fire Protection Association-United States responded to
1,375,000 fires, which caused 2,855 civilian fire fatalities, 16,500 civilian fire
injuries and a total estimated loss of $12,427,000,000. (source:
http://www.nfpa.org)
From above given statistics we can understand the necessity of firefighting. These
fires are caused when the temperature rises and crosses flash point of surrounding
material. In order to deal with fire effectively and to avoid any major loss Fire
Suppression Systems are adapted. These automated system fights with fire until
firefighting crew arrives to deal with it. It uses fire extinguishing material like
foams, water and gases depending upon surrounding area and cause of fire.
Classes of Fires:
Fires are divided into four basic classes depending on material which causes
initiation of fire and each fire class has its own coping strategy. Four classes
of fires are:
Class Causes / fuel type
Class A Household and office items: Wood, Paper, Plastics etc.
Class B Fuels: Petrol, Alcohol, Ethanol, Diesel
Class C Electrical Items: Short circuits, Over heated electric panels
Class D Exotic materials: Manganese, Potassium, Sulphur etc.
Fire Ingredients:
Fire Triangle also known as combustion triangle tells us about necessary
ingredients of fires. The triangle illustrates the three elements a fire needs to
ignite: heat, fuel, and oxygen. A fire naturally occurs when the elements are
present and combined in the right mixture. And a fire can be prevented and
extinguished by any of these elements. And this is what a fire extinguisher /
fire suppression system do. Different types of system attacks on different
ingredient like water attacks heat whereas gas based suppression system
attacks on oxidizing agent.

18 | P a g e
Fire Suppression Techniques:
Following are the techniques used for fire suppression nowadays.
 Fire suppression using water
 Fire suppression using gases
Fire Suppression Using Water:
Fire suppression through water is one of the oldest ways of extinguishing fire;
it eliminates heat from effected area. It is used for Class A fires and is the
cheapest way of extinguishing fire. These extinguishers are heat activated and
are mostly used in homes, hotels, smoking lounges and kitchens. It uses a
glass bulb type sprinkler head which sprays water into the room if sufficient
heat reaches the bulb and causes it to shatter and water continues to sprinkle
until someone closes valve from water source. Bulb is initially filled with
colored alcohol which represents its design temperature and upon reaching
that temperature it shatters.

19 | P a g e
.
Fire Suppression Using Gases:
In case of fires in offices and control rooms having important documents and
costly electronic appliances, water is not used for extinguishing fire because it
damages all appliances and ruins all documents. Therefore for such fires
Halon and inert gases are used and cleanly extinguishes fire;
 Halon Based Fire Suppression System:
Systems based on halons are smoke activated, as smoke enters smoke detector
and crosses a predetermined level, it activates and gives an alarm beep for
occupants to leave and after a fixed time period it releases halon gas into
environment which attacks heat and reduces room temperature thus
suppressing fire.
FM-200, Ecaro-25, Novec and Saphirecomes under the category of halon.
FM-200 is commercially most commonly used halon gas for firefighting and
is chemically hepta-fluoro-propane.
A separated pressurized piping system is required for halon based system and
is more costly than water sprinkler system.
Many organizations with such firefighting systems conduct fire drill regularly
to keep their staff prepared for any future happening.

20 | P a g e
 Inert Gas Based Fire Suppression System:
Another way of firefighting is to reduce amount of oxygen from surroundings
of fire, so fire extinguished because of lack of one of its ingredient i.e.
oxygen. Inert gases are preferred for this purpose because they don’t react
easily with materials around it and all materials tend to be more reactive at
high temperatures therefore other gases fails. Likewise halon based system
this system is also smoke activated and uses Imergen-55 (carbon-dioxide,
nitrogen, argon) Imergen-101 (nitrogen, argon) and pro-inert gasses. Since
inert gas don’t liquefy at high temperatures therefore cylinders with higher
schedule is required for their storage at high pressure. Inert gas based system
are more costly than water and halon based systems. Special vents are
provided in coverage area so pressure doesn’t buildup when nozzle releases
high pressure gas.

21 | P a g e
HVAC

22 | P a g e
Air quality is an essential consideration in maintaining productivity, comfort and
health of occupants of a building and should not be trivialized. If air quality and
temperature are not maintained occupants comfort in the workplace can suffer,
directly effecting productivity and morale.
Therefore modern commercial building along with other sophisticated systems
includes HVAC system. HVAC stands for
H- Heating
V- Ventilation
AC- Air-conditioning.
GOAL of an HVAC System:
Following are the goals of an HVAC system:
 HVAC system keeps occupants comfortable by controlling room
temperature.
 HVAC system keeps occupants comfortable by supplying fresh air to zones.
If HVAC introduces significant proportion of fresh exterior air and alleviate
carbon dioxide buildup occupants experience better health and performance
grows. Study shows direct relation between CO2 levels and short term sick
leaves in office work forces.
 HVAC systems job includes removal of contaminants and dust from air
using filters because in heavily air-conditioned energy efficient
environments re-circulated conditioned air can carry contaminants which
contribute to occupant’s respiratory illness. Compared to average office
building this feature is critical in facilities like clean rooms, medical
facilities and laboratory with hazardous material.
 HVAC system must also be efficient and economical because of increasing
cost of fuel. Energy efficient HVAC system might incorporate;
 Variable air volume design
 Components operating at low pressure
 Digital control systems
 Mechanisms for reclaiming heating and cooling benefits from
recirculate air

23 | P a g e
 High efficiency ECM (Electrical control module) motors.
Components of an HVAC System:
Following are basic components found in every HVAC system.
 Furnace:
The furnace pushes the cold or hot air outward into the ducts that run through
every room in the building. Throughout the ducts, there are vents that allow the
warm or cool air to pass into rooms and change their interior temperature. The
furnace unit is typically fairly large, requiring its own space within a building.
 Heat Exchangers:
When the furnace is activated by the thermostat, the heat exchanger begins to
function as well. Air is sucked into the heat exchanger, either from the outside
or from a separate duct that pulls cool air out of the building’s rooms then heats
it before pushing it back out into the ductwork.
 Evaporator Coil:
Evaporator coils performs the opposite function of the heat exchanger. It
supplies chilled air which is forced through ducts when required.
 Condensing Unit:
In this unit, refrigerant liquid exchanges heat with air outside and cools. It is
then transmitted to the evaporator coil where it can be distributed throughout
the home.
 Refrigerant Lines:
Refrigerant lines are series of tubes that contains refrigerant and transmits it
from the condensing unit to the evaporator coil and back.
 Thermostat:
The thermostat controls the function of the furnace. A thermostat is usually
positioned somewhere within the building where it can easily discern
temperature and remain accessible to users. If the air in the room or building is
too cold, the heat exchanger kicks in and blows heat through the vents. If the
room is too warm, the condensing unit and evaporator coil start to function, and
the air conditioning system sends cool air throughout the building or to one
particular section of the building.

24 | P a g e
 Ducts:
Heating ducts are put in during the construction of a home or a building. They
are often run through the ceiling. In each room, at least one rectangular opening
is cut into the duct so that a vent or vents can be installed.
 Vents
Vents are usually rectangular in shape. They are placed in the ceiling, with their
edges corresponding to the opening in the duct above. As warm or cool air
pours through the ducts, vents allow it to disperse into the rooms below.
Split Air Conditioner System:
Split air conditioners are used for small rooms and halls, usually in places
where window air conditioners cannot be installed.
There are two main parts of the split air conditioner;
 Outdoor unit:
This unit houses important components of the air conditioner like the
compressor, condenser coil and also the expansion coil or capillary tubing. This
unit is installed outside the room or office space which is to be cooled.
 Indoor unit:
It is the indoor unit that produces the cooling effect inside the room or the
office. This is a beautiful looking tall unit usually white in color, though these
days a number of stylish models of the indoor unit are being launched.

25 | P a g e
Air Conditioning and Refrigeration Cycle:
Following are the basis of air conditioning and refrigeration;
 Liquids absorb heat when changed from liquid to gas
 Gases give off heat when changed from gas to liquid.
For an air conditioning system to operate with economy, the refrigerant must be
used repeatedly. For this reason, all air conditioners use the same cycle of
compression, condensation, expansion, and evaporation in a closed circuit. The
same refrigerant is used to move the heat from one area, to cool this area, and to
expel this heat in another area.
 The refrigerant comes into the compressor as a low-pressure gas, it is
compressed and then moves out of the compressor as a high-pressure gas.
 The gas then flows to the condenser. Here the gas condenses to a liquid,
and gives off its heat to the outside air.
 The liquid then moves to the expansion valve under high pressure. This
valve restricts the flow of the fluid, and lowers its pressure as it leaves the
expansion valve.
 The low-pressure liquid then moves to the evaporator, where heat from
the inside air is absorbed and changes it from a liquid to a gas.
 As a hot low-pressure gas, the refrigerant moves to the compressor where
the entire cycle is repeated.

26 | P a g e
Packaged Air Conditioner:
Packaged Air Conditioner is one kind of the split air-conditioning, commonly
used in home and small office; usually it is applied to a larger area of the room,
whether as hanging air conditioning or cabinet air conditioning to be
determined according to the actual needs of the user.
The packaged air conditioners are available in the fixed rated capacities of 3, 5,
7, 10 and 15 tons.
As the name implies, in the Packaged Air Conditioners all the important
components of the air conditioners are enclosed in a single casing like Window
Air Conditioner. Thus the compressor, cooling coil, air handling unit and the air
filter are all housed in a single casing and assembled at the factory location.
Depending on the type of the cooling system used in these systems, the
packaged air conditioners are divided into two types;
 Packaged Air Conditioner with water cooled condenser
 Packaged Air Conditioner with air cooled condensers

27 | P a g e
Packaged Air Conditioners with Water Cooled Condenser:
In Water cooled condenser Packaged air conditions the condenser is cooled by
the water. The condenser is of shell and tube type, with refrigerant flowing
along the tube side and the cooling water flowing along the shell side. The
water has to be supplied continuously in these systems to maintain functioning
of the air conditioning system.
Packaged Air Conditioners with Air Cooled Condensers:
In Air cooled condenser packaged air conditioners the condenser of the
refrigeration system is cooled by the atmospheric air. There is an outdoor unit
that comprises of the important components like the compressor, condenser and
in some cases the expansion valve (refer the figure below). The outdoor unit
can be kept on the terrace or any other open place where the free flow of the
atmospheric air is available. The fan located inside this unit sucks the outside
air and blows it over the condenser coil cooling it in the process.
Cooling Tower Technology:
In all of the air conditioning systems we've described so far, air is used to
dissipate heat from the compressor coils. In some large systems, a cooling
tower is used instead. The tower creates a stream of cold water that runs
through a heat exchanger, cooling the hot condenser coils. The tower blows air
through a stream of water causing some of it to evaporate, and the evaporation
cools the water stream. One of the disadvantages of this type of system is that
water has to be added regularly to make up for liquid lost through evaporation.
The actual amount of cooling that an air conditioning system gets from a
cooling tower depends on the relative humidity of the air and the barometric
pressure.
Common application includes;
 Cooling the circulating water used in oil refineries
 Petro-chemical plants
 Thermal power stations
 HVAC systems for buildings.

28 | P a g e
Cooling towers can be classified on the basis of the type of air induction into
the tower. The main types of cooling towers are;
 Induced draft cooling towers
 Natural draft cooling towers
Induced Draft:
An induced draft cooling tower is provided with a top mounted fan that
induces atmospheric air to flow up through the tower, as warm water falls
downward. An induced draft tower may have only spray nozzles for water
break up or it may be filled with various slat and deck arrangements.
Natural Draft:
The natural draft cooling tower is designed to cool water by means of air
moving through the tower at the low velocities prevalent in open spaces
during the summer. Natural draft towers are constructed of cypress or red
wood and have numerous wooden decks of splash bars installed at regular
intervals from bottom to the top. Warm water from the condenser is flooded
or sprayed over the distributing deck and flows by gravity to the water
collecting basin.

29 | P a g e
Chillers:
A chiller is a machine that removes heat from a liquid via a vapor-compression
or absorption refrigeration cycle. This liquid can then be circulated through a
heat exchanger to cool air or equipment as required. As a necessary byproduct,
refrigeration creates waste heat that must be exhausted to ambient or for greater
efficiency, recovered for heating purposes. Concerns in design and selection of
chillers include performance, efficiency, maintenance, and product life cycle
environmental impact.
Vapor Compression Chillers:
Vapor compression chillers operate on the reverse-Rankine cycle, using
mechanical energy to compress the refrigerant, and may include:
 Reciprocating action – uses pistons for compression
 Screw – uses two counter rotating screws for compression
 Scroll – uses two interlocking spirals or scrolls to perform the compression
 Centrifugal – uses rotating impeller blades to compress the air
Following is the working cycle of Centrifugal type chiller.

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Absorption Chillers:
Absorption chillers uses heat to vaporize a working fluid (usually either
ammonia or lithium bromide)
 Single Effect Absorption – use a single generator & condenser.
 Double Effect Absorption – use two generators/concentrators and
condensers, one at a lower temperature and the other at a higher temperature.
It is more efficient than the single effect, but it must use a higher
temperature heat source.
Following is the working cycle of Absorption chiller;
Air Handling Units:
An air handler, or air handling unit (often abbreviated to AHU), is a device used
to condition and circulate air as part of a heating, ventilating, and air-
conditioning (HVAC) system. An air handler is usually a large metal box
containing a blower, heating or cooling elements filter racks or chambers, sound
attenuators, and dampers. Air handlers usually connect to ductwork
ventilation that distributes the conditioned air through the building and returns it

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to the AHU. Sometimes AHUs discharge (supply) and admit (return) air
directly to and from the space served without ductwork.
Small air handlers, for local use, are called terminal units, and may only include
an air filter, coil, and blower; these simple terminal units are called blower
coils or fan coil units. A larger air handler that conditions 100% outside air, and
don’t re-circulate air, is known as a makeup air unit (MAU). An air handler
designed for outdoor use, typically on roofs, is known as a packaged unit (PU)
or rooftop unit (RTU).
An air handling unit; air flow is from the right to left in this case. Some
AHU components shown are
1 – Supply duct
2 – Fan compartment
3 – Vibration isolator ('flex joint')
4 – Heating and/or cooling coil
5 – Filter compartment
6 – Mixed (re circulated + outside) air duct

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Pumps:
The storage of liquids is necessary for their usage. It is also necessary that the
liquids from the storage tanks may easily approach the places where they are to
be used. To make sure that the liquid approach its target easily with the required
flow rate, pumps are used. The basic purpose of pumps is to maintain the flow
by keep on injecting kinetic energy in it, because the liquid loses its flow with
the passage of time because of the friction in the pipes and viscous forces.
Different type of pumps has different usage but there are only 2 basic type of
pumps which are:
 Positive Displacement Pumps
 Kinetic Pumps
Positive Displacement Pumps:
The working principle of positive displacement pump is that it traps a fixed
amount of fluid and then forces it to the discharge pipe. The main advantage of
positive displacement pumps is that they can give same discharge as their
ability is no matter what the discharge pressure is and can also suck the air.
These pumps should be provided a bypass line by which if the pressure
increases the liquid may come back without causing any damage because if by
mistake they are operated against a closed valve than the pump will keep on
supplying the liquid at the discharge resulting in increase of pressure causing
the pump are the line or both to damage.

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The positive displacement pumps mainly work either on reciprocating action or
on rotary action therefore the 2 branches of positive displacement pumps are:
 Reciprocating positive displacement pumps
 Rotary positive displacement pumps
 Reciprocating Positive Displacement Pumps:
Reciprocating positive displacement pumps traps a known amount of liquid
either by using a diaphragm or a piston/plunger. Therefore there are two
types of reciprocating pumps i.e.
 Piston/Plunger pumps
 Diaphragm pumps
 Piston/Plunger Pumps:
A piston/plunger pump consists of a piston or plunger reciprocating in a
cylinder.In the cylinder there are 2 or more than 2 ports which may allow
uni directional flow.One port is the inlet and the other is discharge. When
the pump compresses the liquid then only discharge port opens while the
inlet remains closed because of the presence of uni directional valve.
While the piston moves backwards the inlet port experiences a negative
pressure and opens while discharge remains closed. If the pump is double
acting than there will be 4 ports 2 at either ends of the piston.

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 Diaphragm Pumps:
The diaphragm pumps or pneumatic diaphragm pumps use a flexible
diaphragm to trap and discharge the liquid rather using piston/plunger. It
also works on reciprocating action but the discharge and suction is with
the help of a diaphragm. The diaphragm may be of rubber, thermoplastic
or Teflon.
 Rotary Positive Displacement Pumps:
Rotary pumps is another type of positive displacement pumps which also
works on the principle of trapping liquid and supplying but in it there is no
piston/plunger but there is a rotor which while rotating traps and discharges
the liquid. The discharge is not on the centrifugal phenomenon because of
the critical design of rotor and its surrounding.
 Single Rotor:
If the rotary pump uses a single rotor than it is single rotor rotary pump.
 Vane Pump:
It is positive displacement pump in which there is a vane that is mounted on
a rotor. The rotor and the stator are not concentric so the liquid is pressurized
near the outlet where the area decreases. It consists of following
components;

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 Stator
 Rotor
 Vanes
 Spring
 Piston Pumps:
In case of rotary piston pumps there are several piston connected with
the rotor instead of diaphragms. The rotor shaft is eccentric with stator
center line as a result of which the piston moves in axial direction and
pushes the liquid out of the pump.
 Flexible Member Rotary Pumps:
The pump uses an elastomer rotating member with enlarged vane tips that
form a pumping chamber in conjunction with a casing when the rotor is
placed with the shaft centered in the substantially circular casing that
incorporates an eccentric section. Discharge forcing action is accomplished

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as the vane bends in the eccentric section, effectively squeezing liquid from
the discharge chamber.
 Screw Rotary Pump:
Screw rotary pump consists of a screw. In each revolution of the screw it
traps the liquid in its threading and pushes it forward. Its threading is in the
form of worm which pulls, traps and pushes the liquid.
 Multiple Rotor Positive Displacement Pumps:
The working principle is similar to single rotor pump, but the difference is that
in these pumps two or more than two pumps mesh together and pushes the
liquid.

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 Gear Pumps:
Gear pumps are also widely used in chemical installations to pump high
viscosity fluids. They work on the principle that as the gears rotate they
separate on the intake side of the pump, creating a void and suction which is
filled by fluid. The fluid is carried by the gears to the discharge side of the
pump, where the meshing of the gears displaces the fluid.
 Lobe Pumps:
Lobe pumps are used in a variety of industries including pulp and paper,
chemical, food, beverage, pharmaceutical, and biotechnology. They are
popular in these diverse industries because they offer superb sanitary
qualities, high efficiency, reliability, corrosion resistance and good clean-in-
place and steam-in-place (CIP/SIP) characteristics. There are lobes present
inside the goosing of the pump which while rotating traps the liquid and
discharges the pressurized liquid.

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 Circumferential Piston Pumps
In these pumps inside the housing there is a flexible member present. The
piston is in contact with the member during compression stroke delivers the
pressurized liquid while during the other strike it creates suction and pulls
the liquid.
 Multiple Rotor Screw Pumps
It is similar to screw pump except in it liquid is raped by the use of multiple
rotors. Two rotors trap it together and then discharge the pressurized liquid.
Kinetic Pumps:
Kinetic pumps can be divided into two classes, centrifugal and peripheral.
In kinetic pumps a velocity is imparted to the fluid. Most of this velocity head is
then converted to pressure head. The disadvantage of these pumps is that, if
head increases at the outlet than it can’t give the desired flow.
Kinetic pumps are classified into two main branches namely:
 Centrifugal pumps.
 Peripheral pumps.
 Centrifugal Pumps:
Centrifugal pumps are those pumps which work on the centrifugal action of
the rotor. As the rotor rotates the impeller applies centrifugal forces on the
liquid in contact with it. The housing is made in such a way that inner area is
not constant throughout.as the area decreases pressure increases near the

39 | P a g e
discharge this area increases and the pressure head of the liquid converts into
the velocity head.
 Radial Flow:
These pumps totally on the centrifugal action and discharges the liquid in the
radial.
 Mixed Flow:
These pumps are normally used in multistage where one impeller discharges
the pressurized liquid to the other and so on.The final discharge is obtained in
the radial direction. As the flow is both in the radial and axial direction
therefore it is known as mixed flow.

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 Axial Flow Pump:
An axial-flow pump, or AFP, is a common type of pump that essentially
consists of a propeller (an axial impeller) in a pipe. The propeller can be driven
directly by a sealed motor in the pipe or by electric motor or petrol/diesel
engines mounted to the pipe from the outside or by a right-angle drive shaft
that pierces the pipe.
 Single Suction/Double Suction Pumps:
The peripheral pumps are only present in single suction i.e.They can only
suck from one point whereas centrifugal pumps are present in single suction
as well as in double suction.
 Single Stage/Multi Stage Pumps:
Centrifugal and peripheral pumps both are present in single stage and multi
stage. Multi stage pumps are used where we have to pull liquid from the
great depth while single stage pumps are used to just energize the liquid.
 Peripheral Pumps:
The Peripheral pump is a niche product between the Displacement and the
Centrifugal pump, in which the medium is pumped in a Peripheral channel.
Following are the types of peripheral pumps;

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WELDING
TECHNIQUES

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Welding is a fabrication or sculptural process that joins materials,
usually metals or thermoplastics, by causing coalescence. This is often done
by melting the work pieces and adding a filler material to form a pool of molten
material (the weld pool) that cools to become a strong joint,
with pressure sometimes used in conjunction with heat, or by itself, to produce the
weld. This is in contrast with soldering and brazing, which involve melting a
lower-melting-point material between the work pieces to form a bond between
them, without melting the work pieces.
The most common types of welding are oxyfuel gas welding (OFW), arc welding
(AW), and resistance welding (RW). As a Steelworker, your primary concern
is gas and arc welding. The primary difference between these two processes is the
method used to generate the heat.
.
Gas Welding
One of the most popular welding methods uses a gas flame as a source of heat. In
the oxy-fuel gas welding process, heat is produced by burning a combustible gas,
such as MAPP (methylacetylene-propadiene)or acetylene, mixed with oxygen.
Arc Welding
Arc welding is a process that uses an electric arc to join the metals being welded. A
distinct advantage of arc welding over gas welding is the concentration of heat.
In gas welding the flame spreads over a large area, sometimes causing heat
distortion. The concentration of heat, characteristic of arc welding, is an advantage
because less heat spread reduces buckling and warping.
Shielded Metal Arc Welding
Shielded metal arc welding is performed by striking an arc between a coated-metal
electrode and the base metal.

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Gas Shielded Arc Welding
The primary difference between shielded metal arc welding and gas shielded arc
welding is the type of shielding used. In gas shielded arc welding, both the arc
and the molten puddle are covered by a shield of inert gas. The shield of inert gas
prevents atmospheric contamination, thereby producing a better weld.
Weld Joints
The weld joint is where two or more metal parts are joined by welding. The five
basic types of weld joints are;
Butt joint- used to join two members aligned in the same plane.
 Corner joint- used to join two members located at right angles to each other.
 Tee joint- used to join two members located at right angles to each other.
 Lap joint- made by lapping one piece of metal over another.
 Edge joint- used to join the edges of two or more members lying in the same
plane.
 Corner and tee joints are used to join two members located at right angles to
each other.

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Summer Internship Report (National Engineering Services Pakistan)-2014

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Summer Internship Report (National Engineering Services Pakistan)-2014