This report summarizes a study of the steam circuit across three departments - Soap Processing (SPD), Soap Finishing (SFD), and Personal Products (PP) - at Unilever Bangladesh Ltd. It analyzes the existing steam distribution system and future steam requirements given changes in operations. The report recommends redesigning parts of the steam distribution lines and insulation to improve efficiency and reduce thermal losses. It also proposes a condensate recovery system to reuse flash steam and reduce water and energy costs. Key aspects covered include analyzing pipe sizes, insulation thickness, steam flow rates, a bill of quantities, types of steam traps used, and calculations on flash steam generation.

1. 1
REPORT
INDUSTRIAL TRAINING
Course number: ME 370
Name of the Project:
Study Steam Circuit across SPD, SFD & PP Department Explore all options, including
assessing right pipe size, to optimize Energy Consumption
Organization: Unilever Bangladesh Ltd
Prepared by:
NASHIYAT FYZA
Student Number: 1110061
GAZI SHEHZAD SHAHWANI
Student number: 1110066
DEPARTMENT OF MECHANICAL ENGINEERING
BANGLADESH UNIVERSITY OG ENGINEERING AND TECHNOLOGY

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Table of Content:
Content Page
Introduction 03
Industrial Safety 03
Boiler Overview 04
Main Safety Devices of the Boiler 05
Efficiency of Boiler & Steam Distribution System 06
Boiler Steam Distribution Circuit 06
Recommended Velocity of Steam 12
Sample Calculation of Pipe Size 14
Calculated Pipe Size List 17
Thermal Insulation in Steam Line 19
Calculated Thickness of Insulation 21
Calculation of Steam Flow Rate 23
BOQ (Bill of Quantity) Calculation 24
Condensate Recovery 25
Calculation of % Flash Steam Generated 29
Calculation for Flash Gas 31
Types of Trap Used 32
Conclusion 39
Acknowledgement 39

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Introduction:
This report include an overview of the steam circuit of Unilever Bangladesh Kalurghat
Factory. The Steam Circuit and the Boilers operating in the factory were installed years
ago. The steam pipe size was up to the requirement at that time. But recently the steam
requirement has decreased due to installment of improved technology. There are some
changes in the steam requirement plants, too. Therefore, the present steam distribution
line needs to be redesigned to improve efficiency and reduce thermal loss. This report
includes existing steam circuit, analysis the future requirement, redesign the steam line
and insulation up to that requirement and propose an efficient steam recovery system.
Industrial Safety:
Industrial safety is defined as policies and protections put in place to ensure plant and
factory worker protection from hazards that could cause injury. Safety policies put in
place by the Occupational Safety & Health Administration (OSHA) are examples
of industrial safety policies.
There are some basis safety rule in the factory:
• Gather to the assembly point in case of sudden emergency
• Safety shoe, Hair cap & Apron is needed in the factory premise
• Use pedestrian walkways & Zebra Crossing
• Switch off Phone at NG Substation & Perfume Storage
• Never browse phone while using staircase & always hold the hand rail
• In case of Medical Emergency, ambulance service is provided right to the assembly
point

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• Never touch any chemical line, tank, steam pipe line etc.
• Smoking is prohibited inside the area
• PPE (Personal Protective Equipment) should be provided in the restricted area
• Loose Dress, watches & rings are not allowed
• Permission must be taken before taking any picture
• Proper use of dustbin/ Trash can
• Visitors’ card should always be displayed
• Put at least one leg on ground while sitting on a chair
• Never put bags/chairs in walkway
Boiler Overview:
There are three boilers working for the steam supply for the factory.
Cochran Thermax III & Thermax IV: Thermax III and Thermax IV use fuel the
produce necessary heat to produce steam. Both of them are Fire Tube Boiler. Wet back
system is introduced in both of the boilers to reduce thermal stress of the boiler main
body. The boilers can operate up to 12 bar pressure. But the operating pressure is
usually kept at 10 bar. The burner is rotary cap type which has a turndown ratio of
4:1.Turndown ratio is an important boiler parameter which is defined as the ratio of
maximum firing rate to the minimum controllable firing rate. Usually diesel is
preferred as fuel of the boiler burner, but gas can also be used as the burner fuel.
Thermax III has a capacity of 12 ton/hr and Thermax IV has a capacity of 11 ton/hr.
Exhaust Gas Boiler (EGB): The exhaust gas boiler uses the exhaust heat of the
generator to produce steam. This boiler works at a pressure of 8 bar and has a capacity
of producing 1.5 ton steam/hr

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Main Safety Devices of the Boiler (Steam Line):
1. Pressure Safety Valve:
Releases steam to atm when steam pressure exceeds the limit. Two PSV operates.
One at 12.6 bar & other at 12.7 bar. If first one fails, the other starts working.
2. Steam High Pressure Switch: (Electrical device)
This switch triggers when the steam pressure inside the vessel reaches too high a
point (180psig) and triggers the burner to stop firing
3. Steam Excess Pressure Switch:
Same kind of electrical device which works when steam high pressure switch fails
(182 psig)
4. Burner Hinge Proving Switch:
If the burner door opens accidentally, it shuts the boiler down
5. Flame Detector:
Detects the flame color of the pilot burner through photocell and thereby determines
whether the air fuel mixture is in correct proportion or not.

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6. First Low Water Cut Off:
When the water level in the boiler drops below the Permitted limit (-63mm), 1st
alarm
bells and stops firing
7. Second Water Cut Off:
If previous system fails and water level drops below the lower limit (-76mm), 1st &
2nd alarm bells simultaneously and stops firing automatically
8. Steam Pressure Regulator:
Keeps the steam Pressure at the Operating level (175psig)
Efficiency of Boiler & Steam Distribution System:
• Proper Boiler Design
(Material of Boiler, Type of Burner Used, Proper Boiler Insulation, Amount of scale & films
in the heat transfer surface, Type & quality of fuel, proper AF ratio, efficient steam
generation process)
• Heat Recovery devices used in the system ( i.e. Economizer, Air- preheater)
• Proper steam transmission process in the pipeline including proper insulation
(i.e. losses in the pipeline is low)
• 100% condensate recovery
• Type of condensation ( i.e. film condensation reduces the heat transfer rate, drop wise
condensation increases heat transfer)
Boiler Steam Distribution Circuit of the Factory:
The Steam from the main two boilers are distributed into three department of the factory: Soap
Processing Department (SPD), Soap Finishing Department (SFD) and PP ( Personal Product
Department). The steam is distributed into four header.

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Fig: Steam Circuit from the main boiler to the Main Headers
Soap Processing Department (SPD) Steam Distribution:
As SPD requires more steam than the two other departments , two steam headers are installed
for this department. This headers are known as SPD header and Still header.
From the SPD six steam line go to the Pan Room, DPU, Evaporator, Jet, Meltout & Bleacher
Plant.

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Fig: Existing Steam Line Distribution from the SPD header To the Processing Department
This steam lines are designed according to the past steam requirement. But, the future steam
requirement will change as there are some changes in the plant operation. The Pan Room plant
will require 2500 kg/hr of extra steam at 6 bar for Scrapping Operation (Manual Fitting- Prefit &
Fit Operation). 200 kg/hr extra flow at 4 bar for inline fitting will also be needed. The steam line
for inline fitting will also be drawn from the Pan Room line. As a huge amount of steam will be
needed in the pan room section, an individual pan room header is proposed in the project to
increase the dryness of the steam. The DPU and Jet steam requirement will also increase about
500 kg/hr and 200 kg/hr respectively. The bleacher plant will not be needing any steam. But the
Wheel Crutcher from SFD will be installed in the SPD. Which will need 200 kg/hr of steam of
about 4 bar. Therefore, the Wheel Crutcher steam line is drawn from the bleacher line. All the
changed pipe size are tabulated in following section.

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Fig: Proposed Steam Line Distribution from the SPD header To the Processing Department
according to the Future requirement
Fig: Present Steam Distribution Line in the Still header of SPD
The steam requirement of the Still plant will not be needing any change. Therefore, the steam
line will remain same.

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Soap Finishing Department (SFD):
The Wheel Crutcher plant from line 4 will be replace to the SPD bleacher department. Other
steam requirement will be the same.
Fig: Present Steam Distribution Line in SFD header

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Personal Product Department:
Steam from main boiler as well as EGB are supplied to the PP department. There are three
header in the PP department:
1. PP header
2. High pressure header
3. Low pressure header
Fig: Present Steam Distribution Line in the PP department
The chiller line will be needing 2000 kg/hr extra steam supply and a new 5 ton mixer CIP will be
installed in the line.

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Fig: Steam Distribution Line in the PP department according to the future requirement
Recommended velocity of steam in pipe:

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Sample Calculation for Pipe size: (Source: Spirax Secro: Pipe Size.pdf )

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Sample Calculation for Pipe Size:
Sample Calculation from Equation (For Prefit & Fit):
Input Parameter:
Pressure, P=6 bar g
Velocity, v=35 m/s (assuming)
Mass Flow Rate, m= 2500 kg/h
Calculated Parameter:
Specific Volume at 6 bar g=0.315 m3/kg
Volumetric Flow rate=0.21875 kg/s
Diameter= 89.21mm
Sample Calculation from Chart: (For Prefit & Fit Operation)
Input Parameter:
Pressure: 6 bar g
Velocity: 35 m/s (assuming)
Mass Flow Rate: 2500 kg/h
Output Result:
Calculated Pipe Size: 89 mm
Recommender Pipe Size: 100 mm

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Sample Calculation from Spirax Sarco’s app:
( for Pre-fit & Fit Operation)
Input Parameter:
Pressure: 6 bar g
Velocity: 35 m/s (assuming)
Mass Flow Rate: 2500 kg/h
Output Result:
Calculated Pipe Size: 82.8942 mm
Recommender Pipe Size: 100 mm

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Calculated Pipe Dia Chart:

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= Pipe dia for new installed plant
= Pipe dia which have to be changed from existing

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Thermal Insulation in a Steam Pipe:
1. Conserve energy by reducing heat loss
2. Control surface temperatures for personnel
protection and comfort
3. Facilitate temperature control of a process

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Sample Calculation for thickness:
T1=20 deg C
T2=184 deg C
r1=6”=6×0.0254m= 0.1524m
k= 0.033
N=length of the cylinder
Q/N= Heat loss per unit length of pipe=80 W/m (assumed)
So,
80= 2π×0,033× (184-20)/ ln ((0.1524+t)/0.1524)
t = 80.72 mm
Calculated Thickness of Insulation:
Taking Rock Wool as the insulating Material, Heat loss per length as 80 W/m and
Operating temperature as 184 degree:

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Insulation Calculation from Table:
To avoid heat loss and reduced efficiency pipe work in heating systems should always be
insulated. Very hot systems, like hot water and steam systems should also be insulated to avoid
potential personal injuries.
The table below indicates recommended insulation thickness.
based on insulation with thermal resistivity in the range 4 - 4.6 ft2
hr o
F/ Btu in
(typical for mineral wool at room temperature)
Source: http://www.engineeringtoolbox.com/pipes-insulation-thickness-d_16.html

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Calculation of Flow rate in Universal Mixture 1 ( Due to absence of Flow
meter):

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BOQ Calculation:
Requirement Size/Quantity
For Steam line:
Pipe 5m (65mm)
PRV 10 bar to 8 bar
Pressure Gauge Quantity: 2
Globe Valve Quantity: 2
Pipe 38m (80 mm)
Bend 5, L type
1, T type

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For Condensate line:
Float type Trap Quantity: 2
Pipe 30m (25mm)
15m (15mm)
Bend 10, L type
5. T type
Globe Valve Quantity: 4
What is Condensate Recovery?
If 1 t/h of steam is supplied to equipment for a heating process, then the same amount of
condensate (1 t/h) needs to be discharged from the equipment. Condensate recovery is a process
to reuse the water and sensible heat contained in the discharged condensate. Recovering
condensate instead of throwing it away can lead to significant savings of energy, chemical
treatment and make-up water.

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Condensate Recovery: Vented System
Steam trap inlet pressure or a condensate pump is used to return condensate to an open-to-
atmosphere.
The maximum recovery temperature of condensate is some value less than 100°C
Larger amount of energy is lost when condensate flashes to atmosphere
Formation of vapor clouds can also have a negative impact on a plant’s work environment
Configuration is much simpler, typically require a much lower initial investment
Piping can be sized like water piping once condensate and flash steam have been separated
Use: boiler make-up water, pre-heat, Water for cleaning or other hot water applications.

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Condensate Recovery: Pressurized System
Recovered condensate is maintained above atmospheric pressure throughout the recovery
process
Condensate can be recovered at much higher temperatures. For example 184°C with steam at 10
barg.
A specialized valve must be installed to regulate the release of flash steam to atmosphere
Since flash steam is not vented to atmosphere, a greater amount of water can be recovered and
reused
Condensate transport piping must be sized for two-phase flow of steam and condensate
The absence of vapor clouds can also considerably improve a plant’s work environment
Use: direct feed to boiler, and Flash Steam Recovery Applications

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Condensate can be reused in many different ways
As heated feedwater, by sending hot condensate back to the boiler’s deaerator
As pre-heat, for any applicable heating system
As steam, by reusing flash steam
As hot water, for cleaning equipment or other cleaning applications
The Benefits of Condensate Recovery
Reduced Fuel Costs
Lower Water-related Expenses
Positive Impact on Safety and the Environment

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Calculating the % Flash Steam Generated
The % of flash steam generated (flash steam ratio) can be calculated from:
where:
• hf1 = Specific Enthalpy of Saturated Water at Inlet*
• hf2 = Specific Enthalpy of Saturated Water at Outlet
• hfg2 = Latent Heat of Saturated Steam at Outlet
What to Do With Flash Steam?

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Method of using Flash Gas
A Flash steam vent condenser is incorporated in the system to recover the flash steam by using
an external heat exchanger.
The vent condenser (heat exchanger) will consume the flash steam by heating air, water or some
other process fluids.
Method of using Flash: Heating air is another application for a vent condenser:

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Calculation for use of Flash Gas:
Example: Use of Flash Gas:
NEW CHILLER operates at 8 bar pressure with a steam flow rate of 2000kg/hr.
Flash Gas produced from Condensate of New Chiller can partially meet the demand of 5 Ton
Mixture & Inline Fitting.
5 Ton Mixture requires 800 kg/hr at a pressure of 2bar. When the condensate from NEW
CHILLER flows through steam trap & expands through pressure drop to 2 bar, 10% flash steam
if produced. That means we get steam of 200 kg/hr at 2 bar, which will meet the at least 25%
demand of 5ton mixture.

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Inline Fitting requires 200kg/hr steam at a pressure of 4 bar. Flashing the NEW CHILLER
condensate at 4 bar would produce 130kg/hr ( 6% of 2200kg/hr) which will meet 65% demand of
Inline Fittings.
In the same way, demand of line 4 can be partially met by flash steam produced by line 1 & line
2.
Two Types of Thermodynamic Steam Trap
Operating Mechanism of Thermodynamic Disc Traps
Situation 1: From the Open to the Closed Position (Thermodynamic Explanation)
When in the open position, there are two main forces that act on the disc valve: steam in the
pressure chamber on top of the disc, and steam racing across the underside of the disc.
This steam acting to open and close the valve is known as Control Steam.

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When steam rapidly flows under the valve disc, the pressure under the disc decreases. The valve
disc is then "pushed" onto the valve seat because of the greater pressure within the chamber. This
closes the valve
Situation 1: From the Open to the Closed Position (Thermodynamic Explanation)
Situation 2: From the Closed to the Open Position (Thermodynamic Explanation)
Radiant and other heat losses cause a decrease in the pressure within the chamber, which
eventually causes the disc to lift off its seat, discharging condensate

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Balanced Pressure Thermostatic Steam Trap
The operating element is a capsule containing a
special liquid and water mixture with a boiling
point below that of water
In the cold conditions the capsule is relaxed, the
valve is off its seat and is wide open, allowing
unrestricted removal of air
As condensate passes through the balanced
pressure steam trap, heat is transferred to the liquid
in the capsule.
The liquid vaporizes before steam reaches the trap

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The vapor pressure within the capsule causes it to expand and the valve shuts
Heat loss from the trap then cools the water surrounding the capsule, the vapor condenses and
the capsule contracts, opening the valve and releasing condensate until steam approaches again
and the cycle repeats
Bimetallic Thermostatic Steam Traps:
On start-up, the bimetallic element is relaxed and the valve is open. Cooled condensate, plus air,
is immediately discharged.
Hot condensate flowing through the trap heats the bimetallic element causing it to pull the valve
towards the seat.
As the hot condensate is discharged and approaches steam saturation temperature the bimetallic
element closes the valve.

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Liquid expansion steam trap
It can be seen from Figure 11.2.2 that when the pressure is at pressure P1, condensate would
have to cool by only a small amount ( T1), and trapping would be acceptable
If pressure is increased to P2 then condensate has to cool more ( T2) to pass through the steam
trap

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Ball float steam trap
Condensate reaching the trap will cause the ball float to rise, lifting the valve off its seat and
releasing condensate the valve is always flooded and neither steam nor air will pass through it.
The automatic air vent uses the same balanced pressure capsule element as a thermostatic steam
trap.
The Float and Thermostatic Steam Trap

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Inverted bucket steam trap:
In (i) the bucket hangs down, pulling the valve off its seat. Condensate flows under the bottom of
the bucket filling the body and flowing away through the outlet
In (ii) the arrival of steam causes the bucket to become buoyant, it then rises and shuts the outlet
In (iii) the trap remains shut until the steam in the bucket has condensed or bubbled through the
vent hole to the top of the trap body.

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Conclusion:
It can be concluded that all modern equipment and hi-tech machineries are available in Unilever.
It has been keeping up its position among the renowned companies for years. So, it was a great
opportunity to learn about machineries, production processes and supply chain in this training.
All the steam flowing through the pipelines are saturated steam. So, the property of saturated
steam was considered in the calculation. Though theoretically it was considered that steam
delivers only sensible heat by changing its phase from saturated vapor to saturated liquid, but
practically some degree of cooling takes place below saturation temperature.
The pressure drop in the pipe was considered due to frictional loss. But there may be some
pressure loss due to radiation heat transfer from pipe and hence comes the need for proper
insulation.
Pipes available in the market are of certain specific diameter. So, we cannot use pipe of any
diameter. Hence, pipe diameter chosen for steam circuit, is the next available size of the
calculated value. Again, due to the limitation of the project period, exact measurement of the
required pipe length was not possible for the future requirement. The required pipe size,
insulation, type of steam trap, condensate return piping has been designed, from which we can
easily calculate the BOQ, Bill of Quantity.
Acknowledgement:
The project required a huge amount of data from different departments of the factory. We would
like to thanks the Engineering Department & all the operators of the factory. This training
certainly add a great value to our career. We would like to thanks Unilever Bangladesh Ltd. &
Department of Mechanical Engineering (BUET) for creating such opportunity.