Humidification and ventilation management
in textile industry
About the Author
B. Purushothama completed his B.Sc (Textiles) in 1969 and then M.Sc
(Textiles) in 1974 from Bangalore University. He is a postgraduate in Business
Administration from St Joseph’s College of Business Administration,
Bangalore. He associated with The Textile Association (India) in 1973 and
got Fellowship of The Textile Association (India) in 1985, and Fellowship of
Institute of Engineers in 2009. He is a Lead Auditor in ISO 9000 since 1994
and a Certified Quality Analyst from Tata Quality Management Services. He
took extensive training in Total Quality Management from M/s Win Research
and Consultants, Mumbai. He got trained by Tata Quality Management Services
for the JRD QV (The Quality System named after late JRD Tata and now
called as TBEM, i.e. Tata Business Excellency Model) and Malcolm Baldrige
National Quality Awards. He worked as an examiner for TBEM for 5 years
and has trained thousands in Total Quality Management, Malcolm Baldrige
Quality Awards and in various technical aspects of textiles.
B. Purushothama, in his service of 40 years in the textile and garment
industry, has worked in various capacities in Spinning, Maintenance, Projects,
Quality Assurance, and in Research. He has published over 50 papers in various
technical and management areas, and has presented papers in various
conferences and seminars. Some of his publications include Fundamentals of
Textile Mill Management, Guidelines to Process management in Textiles,
Quality management in Garment Industry, Winning Strategies, In the
Wonderland of Problems, etc. He has guided hundreds of students from
different universities and colleges in their project works.
He is an active member of The Textile Association (India) and has served
as Joint Secretary, Secretary, Management Committee Member, and Chairman
of Ichalkaranji Miraj Unit. He is also a member of Spinning Advisory sub-
committee of BTRA (Bombay Textile Research Association, Mumbai). He

was a member of TX-30 sub-committee of Bureau of Indian standards, dealing
with Industrial textiles and Geo textiles. He has also served as a member of
syllabus committee for Shivaji University for B.Text. He is a member of
various associations like Quality Council of India, Gokak Management
Association and Asian technology group, which work for the spread of
knowledge.
He is also active in Kannada Literature and has written novels, poems, and
devotional songs in Kannada, and several books on Management, Hilarious
talks, etc. Huchchuraamana Muktakagalu and Kareyutide Yasha Shikhara are
books on Management written in Kannada. Huchchana vichaaradhaare, a
hilarious book of philosophy; Tumula, Kaalada hakki, Ayyo Huchchumundede,
Miss Maala and Jagadodharana are social novels; Gaardhabha Maartanda
and Banni Makkale Kathe Heltini are short stories for children; Sumamaale,
light poems; and Gana stuti and Devaranaamagalu are devotional songs.
Humidification and ventilation
management in textile
industry
B. Purushothama
WOODHEAD PUBLISHING INDIA (P) LTD
New Delhi ● Cambridge ● Oxford
Published by Woodhead Publishing India (P) Ltd.
Woodhead Publishing India (P) Ltd., G-2, Vardaan House, 7/28, Ansari Road
Daryaganj, New Delhi – 110 002, India
www.woodheadpublishingindia.com
Woodhead Publishing Limited, Abington Hall, Granta Park, Great Abington
Cambridge CB21 6AH, UK
www.woodheadpublishing.com
First published 2009, Woodhead Publishing India (P) Ltd.
© Woodhead Publishing India (P) Ltd., 2009
This book contains information obtained from authentic and highly regarded

sources. Reprinted material is quoted with permission. Reasonable efforts have
been made to publish reliable data and information, but the authors and the
publishers cannot assume responsibility for the validity of all materials. Neither
the authors nor the publishers, nor anyone else associated with this publication,
shall be liable for any loss, damage or liability directly or indirectly caused or
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ing India (P) Ltd. for such copying.
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Woodhead Publishing India (P) Ltd. ISBN 13: 978-81-908001-2-9
Woodhead Publishing India (P) Ltd. EAN: 9788190800129
Typeset by Sunshine Graphics, New Delhi
Printed and bound by Raj Press, New Delhi
Contents
Preface ix
1 Need for maintaining humidity 1
1.1 Introduction 1
1.2 Relation of humidity to working in the textile mills 2
1.3 Dust control 5
1.4 Control of air pollution 8
1.5 Air changes 8
1.6 Humidity and the health 9

1.7 Protection of electronics and equipments 10
2 A glance at the developments 12
2.1 General 12
2.2 Unit humidifiers 14
2.3 Central station-type plant 14
2.4 Supplementary humidification 18
2.5 All-air system 18
2.6 Energy management 18
3 Different types of humidification 22
3.1 Steam humidification 22
3.2 Evaporative pan 29
3.3 Water spray humidifiers 36
4 Air handling units in textile industry 41
4.1 Introduction 41
4.2 Supplying air to air washer plants 45
4.3 Air filter construction and cleaning system 49
4.4 Type of fans used 57
4.5 Gravity louver damper 62
4.6 Eliminators 62
4.7 Water spray 65
4.8 Water supply 71
4.9 Supply air distribution 73
4.10 Roto-spray units 76
4.11 Chilling plants or cooling towers 76
4.12 Temperature and humidity monitoring 85
5 Humidification requirements in manmade-
fibre plants 87
5.1 Introduction 87
5.2 Quench box 87
5.3 Take-up area 89

5.4 Draw twist area 91
5.5 Textile area 91
5.6 Other areas 92
6 Humidification requirements in nonwoven plants 95
6.1 Processes in nonwoven plant 95
6.2 Air distribution needs in nonwoven industry 96
6.3 Material air-conditioning and spot air-conditioning 98
6.4 Cleaning of the air 98
6.5 Recycling and disposal of wastes 99
6.6 Compact Filter Unit (CFU) 100
7 Concept of total air control 101
7.1 Introduction 101
7.2 Different individual solutions 102
7.3 Cleaning and disposal of air 105
7.4 Controls 108
7.5 After-sales service: trouble-free operation 109
8 Localised humidification control 110
8.1 Need for localised humidification control 110
8.2 Use of heating lamps 111
8.3 Subsystem humidification 112
vi Contents
vii
8.4 AirBell air outlet 114
8.5 Exhausting air 115
8.6 Machine air-conditioning 117
8.7 Super soft terry towels weaving 118
8.8 Yarn-conditioning plants 118
8.9 Static elimination 120
9 Maintenance of humidity 121
9.1 Understanding the calculations 121

9.2 Operation and problems associated with air washer systems 130
9.3 Efficient use of humidification plants 136
9.4 Keeping AHUs clean 139
9.5 Monitoring humidity 149
9.6 Problems of not getting required conditions 153
9.7 Basic humidity control preparation 155
9.8 Guidelines to select supply outlets and return grilles 156
9.9 Guidelines to size the duct runs 157
9.10 Power consumption 157
9.11 Ionisation of air using chemicals 160
10 Auxiliary units to make humidification
units effective 162
10.1 Building design to have effective control of humidity 162
11 Air-conditioning units 174
11.1 History of air conditioning 174
11.2 Application of air conditioning 177
11.3 Different types of air conditioners 179
11.4 Design for air conditioning system 185
11.5 Central air conditioning 192
11.6 Health implications 193
12 Air pollution control in textile industry 194
12.1 Introduction 194
12.2 Source of air pollution 195
12.3 Air pollution control 196
12.4 Use of UV disinfestations 203
12.5 An integrated approach for the textile industry 204
Contents
13 Dehumidification 206
13.1 Introduction 206
13.2 Reducing the humidity 206

13.3 Types of dehumidification 207
14 Designing heating, ventilating and air-
conditioning (HVAC) 212
14.1 What is HVAC? 212
14.2 Fundamental of energy and resource-efficient HVAC design 213
15 Definitions of terms used in humidification
engineering 227
Appendix 1 Some of the commercial humidification plants 253
Appendix 2 Cooling and heating systems 308
Appendix 3 Fogging fans and Jets 317
Appendix 4 Spray nozzles and mist eliminators 346
Appendix 5 Fans and blowers 356
Appendix 6 Dampers and diffusers 373
Appendix 7 Sensors and data loggers 387
Appendix 8 Dehumidifiers 418
Appendix 9 Fume and dust control, air ventilation 424
hose and ducts
Appendix 10 Filters and dust collectors 431
References 443
viii Contents
ix
Preface
The importance of maintaining and managing humidity and temperature
in a textile mill is not a new concept, but understanding the requirements,
the equipment capabilities and utilizing them to get the best results is a
challenge the technicians face all the time. Now the systems have changed
from manually operated to fully automatic; however, unless one knows
how to monitor, he shall still have the problem. Some guidelines are needed
for the shop floor technicians relating to maintenance of humidity and
monitoring the air.

The idea of writing a book on Managing of Humidity came from my
friend Ananth Harnahalli. I hesitated first, as I was only a Textile
Technologist and not a Humidification Engineer. Ananth reminded me that
I had faced lot of problems due to improper maintenance of humidity while
working on the shop floor and had struggled a lot to get required conditions.
The problems faced were always unique as the systems were getting
changed, materials were getting changed and also the working conditions.
Ananth told that the purpose of this book should be to guide the shop floor
technicians and engineers in maintaining required conditions and to act in
advance. They need the basic concepts and the choice available in the
market to update their humidification plants; hence this book.
An attempt is made to collect and provide information starting from the
basic concepts, developments, varying needs of the industry, the problems
associated with maintenance of plants to get the required conditions,
designing of plant capacity, modification or designing of building to get
the best results, various issues of health and hygiene, the pollution control
issues, various models available in the market, etc. However, it should be
noted that it is practically impossible to explain all the equipments and
give details of all manufacturers. Hence, efforts are made to explain at
least one unit in each type.
I am thankful for all the information providers, without which this book
would not have come out. Also I am thankful to all my friends who
Preface
encouraged me to write this book, and the family members for their
complete cooperation. My special thanks are to Ravindra Saxena and Sumit
Aggarwal for the initiations taken to publish this book so that it could
reach masses.
B. Purushothama
x Preface
1

Need for maintaining humidity
1.1 Introduction
Spinning of yarn from cotton and then weaving or knitting cloth from the
yarn is known to mankind for millenniums. It is probably one of the first
crafts developed as men’s thought of civilisation. As this primitive craft
flourished in tune with civilisation, the ancients learnt that if water is
sprayed on the floor on the hot days or if wet cloth is kept over the warp,
the working is easier because of less yarn breakage. This was the state of
affairs till 200 years back, but as the industrial revolution took place and
mass production was aimed, different methods were developed to provide
moisture to the material in process. As more people were concentrated
under one roof along with number of machines working at a pace, the
generation of temperature also added to the problem. Though frequent
use of water cans for humidity, and wide windows for fresh air were
provided, it did not help in improving the working conditions. The increase
in speed of machinery also liberated fibrous dust.
Air is an important element for every human being. Man’s capacity for
work and his general health may seriously be impaired by defective
ventilation. The purity of air, the temperature and the movement of air are
few of the many factors to be considered. The comfort of an occupied
space depends as much on its condition as on its freshness. Although
humidity is invisible to our eyes, we can easily observe its effects. In human
terms, we are more comfortable and more efficient with proper
humidification. In business and industrial environments, the performance
of equipment and materials is enhanced by effectively applying humidity
control. Maintaining indoor air quality through humidity management can
lower the energy costs, increase productivity, save labour and maintenance
costs, and ensure product quality. Controlled humidification helps to protect
humidity-sensitive materials, personnel, delicate machinery and equipment.
Beyond the important issues of comfort and process control, humidity

1
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2 Humidification and ventilation management in textile industry
control can help safeguard against explosive atmospheres. In short,
humidification can provide a better environment and improve the quality
of life and work.
Air free from dirt, debris and fibres that is closely maintained within
fixed limits of temperature and humidity is a vital necessity to the textile
industry. It is not only because of the changes in dielectric properties and
tensile properties of fibres due to varying humidity and temperature, but
also for maintaining a clean working environment. The generation of static
electricity while processing in spinning and weaving creates dust and fibre
fly (fluff). Higher moisture content lowers the insulation resistance and
helps to carry off the electrostatic charge. Hence, relative humidity needs
to be maintained above the lower limit, specified for various textile
processes so as to avoid the problems of yarn breakage in dry and brittle
condition and also minimise the build up of static charge so as to reduce
dust and fibre fly (fluff).
1.2 Relation of humidity to working in the textile
mills
Correct ambient conditions are essential to prevent degradation of textile
materials during a series of operations right from beating in blow room to
weaving fabric at loom shed or knitting the fabric or producing non-woven
sheets. Fibres should have requisite properties so that the final product
retains its basic shape, size and strength. Above certain moisture limit, i.e.
above the upper limit of relative humidity for the fibre and the process,

fibres tend to stick and lead to formation of laps on the rolls which disrupt
the production process. Removal of laps is not only a manual and time-
consuming process, but results in the damage of machine parts, especially
the rubber coatings. Fibres become brittle and store electric charges
generated because of friction between the fibres during their
individualisation process when atmospheric relative humidity is very low.
In case of weaving, as the warp yarns are coated with size film, the
environment should be suitable for the size film on the yarn. Too low
humidity makes size film brittle resulting in cracking of the film, where as
too high humidity makes the beam soft.
Modern spinning equipments are designed to operate at high spindle
speed; however, the increase in ambient temper ature curtails the speed
limits of operation. Moreover, the sophisticated electronic controls in
modern textile machinery also require controlled temperature which should
not exceed 33°C or so. It is also necessary to limit the range of temperature
to which the textile machinery is exposed, since the steel and aluminium
parts of machinery which expand at different rates with temperature rise
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Need for maintaining humidity 3
(due to difference in co-efficient of thermal expansion) will be subjected
to mechanical stress. Hence, along with the maintenance of stable relative
humidity conditions, recommended for different textile processes, it is also
desirable to maintain the temperature level within a range, without
fluctuation.
Mechanical properties of fibres and yarns also depend on the
surrounding temperature conditions to which these are exposed during

the textile process. Apart from the dust levels, the stickiness in some of
the cottons also demands controlled weather. When cotton is sticky, higher
humidity creates sticking of fibres to rollers and other parts of the machine.
The general reasons for controlling temperature and humidity in a textile
mill are as follows:
● Dry air causes lower regain and this contributes to poor quality and
lower productivity.
● Yarns with low moisture content are weaker, thinner, more brittle
and less elastic, create more friction and are more prone to static
electrification.
● Materials at optimum regain are less prone to breakage, heating and
friction effects; they handle better, have fewer imperfections, are more
uniform and feel better.
● Higher humidity reduces static problems. Reduced static makes
materials more manageable and increases machine speed.
● Textile weights are standardised at 60% RH and 20°C. Low humidity
causes lower material weight and lowered profits.
● Low humidity causes fabric shrinkage. Maintained humidity permits
greater reliability in cutting and fitting during garment creation and
contributes to the maintenance of specification where dimensions
are important, such as in the carpet industry.
● Humidification reduces fly and micro-dust, giving a healthier and
more comfortable working environment.
Adequate yarn humidity (moisture in yarn) is needed to enhance the
strength and the elasticity and to have smooth yarn surface. Both tensile
strength and elasticity depend on fibre and spinning characteristics, on
warp pre-treatment (slashing) and increase with moisture content of the
yarn being fed into the weaving process. Hairiness depends on the spinning
system, speed, humidity and the fibre quality. Higher spindle speed, lower
humidity and abrasion while spinning are the major reasons for increased

hairiness. It is reduced by slashing, as fibres protruding from the yarn are
glued to it. Moisture content smoothens the hairs and lubricates the yarn
surface. Abrasion between yarns, mainly in the shed area, removes short
fibres (lint) and size dust from the warp yarn. Adequate yarn moisture
reduces the fall out.
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4 Humidification and ventilation management in textile industry
While weaving, the yarn adsorbs water from the air. Lint and dust falling
out from the yarn are incorporated into the room air. Power consumed by
the loom and other devices in the room is converted into heat and
incorporated into the room air. This heat evaporates the moisture from
yarn. Previous results show that yarns perform best in weaving machines
when their moisture content is 7–9% (parts of water in 100 parts of dry
yarn). Less moisture reduces strength, elasticity and smoothness. Higher
moisture may make the size glue the warp yarns together. Therefore, there
is a need to humidify the area with suitable controls.
Maintaining adequate high RH levels provides the most effective and
economical means of preventing the build-up of static charges. With high
RH, an invisible film of moisture forms on surfaces in the room. The
presence of normal impurities makes this film a conductor that carries
static electricity harmlessly to the ground before it can harm. A relative
humidity of at least 45% is needed to reduce or prevent the accumulation
of static charges, although some materials such as wool and certain
synthetic fabrics may require higher RH levels. Similarly, heat-generating
machines may require higher RH to provide sufficient moisture in proximity
to the machine to dissipate static charges.

Due to high heat dissipation from spinning as well as weaving and
knitting equipment, there is a significant increase in temperature conditions
particularly in the vicinity of the machinery and their driving motors. The
natural wax covering cotton fibres softens at these raised temperature
conditions, thereby adversely affecting the lubricating property of wax
for controlling static and dynamic friction.
Increase in temperature beyond the design limit also reduces the relative
humidity condition near the processing elements of the machinery. Hence
textile air-engineering design has to take care of controlled air flow within
the textile machinery for dissipating heat generated at the source and it is
customary to carry the waste heat along with the return air to the return air
trench. The quantity of return air going to exhaust or re-circulation is
regulated for controlling the inside design conditions.
The requirement of humidity is lower at blow room at around 45–50%,
moderate at spinning processes from carding to ring spinning at around
55%, around 65% in winding and warping, where as weaving rooms need
high relative humidity of 80–85% at the warp sheet level, i.e. at ‘loom
sphere’, whereas it would suffice to maintain general humidity condition
in the room at around 65% RH. Knitting operation also requires a stable
relative humidity condition at 55±5% for precise control of yarn tension.
Hence it is important to maintain stable relative humidity conditions within
the prescribed tolerance limits at all steps of textile processing.
Workers are a part of manufacturing process. Therefore, the conditions
maintained in the shed should not only be comfortable for the process and
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Need for maintaining humidity 5

the product but they should also be comfortable to the people. Following
table gives generally recommended humidity levels in a textile mill:
Table 1.1 General recommendations of RH% in a textile mill
Department Cotton Man-made Department Wool (%)
(%) fibres (%)
Opening and picking 45–60 50–55 Raw wool storage 50–55
Carding 50–55 50–60 Mixing and blending 65–70
Silver lapping 55–60 55–65 Carding – worsted 60–70
Ribbon lapping 55–60 55–65 Carding – woolen 60–75
Combing 55–65 55–65 Combing – worsted 65–75
Drawing 50–60 50–60 Drawing – worsted –
Roving 50–60 50–60 Bradford system 50–60
Spinning 45–60 50–65 French system 65–70
Winding and spooling 60–65 60–65 Spinning – Bradford Worsted 50–55
Twisting 60–65 50–65 French (mule) 75–85
Warping 55–70 50–65 Woolen (mule) 65–75
Knitting 60–65 50–60 Winding and spooling 55–60
Weaving 70–85 60–70 Warping – worsted 50–55
Similar to the requirement of humidity, the temperature also plays a
very important role in the textile processes. Following are the normal
temperature levels followed in textile mills.
Table 1.2 Normal temperature levels followed in textile mills
Department Minimum temperature Maximum temperature
°C °F °C °F
Cotton mixing 27 80 33 92
Blow room 27 80 35 95
Cards and draw frames 27 80 35 95
Comber 27 80 33 92
Ring frame 30 85 35 95
Winding 27 80 33 92

Warping 27 80 33 92
Weaving 21 70 31 88
1.3 Dust control
Normally, the term ‘textile mill’ reminds of cotton dust laden environment.
Major problem of cotton dust exists in the blow room and carding section
of spinning mill, whereas exposure level in other areas is comparatively
not much. In spinning mill, the extent of cotton dust contamination varies
from section to section; it is worst in the blow room and minimum at the
cone winding section.
Cotton dust is defined as dust present in the air during the handling or
processing of cotton, which may contain a mixture of many substances
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6 Humidification and ventilation management in textile industry
including ground up plant matter, fibre, bacteria, fungi, soil, pesticides,
non-cotton plant matter and other contaminants which may have
accumulated with the cotton during the growing, harvesting and subsequent
processing or storage periods. Any dust present during the handling and
processing of cotton through the weaving or knitting of fabrics, and dust
present in other operations or manufacturing processes using raw or waste
cotton fibres and cotton fibre by-products from textile mills are considered
cotton dust within this definition. The workers are exposed to such working
environment and inhale fibrous particles and dust whole day. Generally
air suction system exists in all departments to maintain certain humidity
and to remove air contaminants; however, at some places it works
effectively, but at certain areas improper air exchange results into
suffocation and inconvenience for the workers. In a weaving mill, fibrous

particles in small quantity are present in the working environment, which
are inhaled by most of the workers. These small fibrous particles are
generated during weaving activities and disperse in occupational air. It is
therefore essential to have sufficient circulation of filtered air. Air washers
and ventilation systems are very essential for this.
All textile manufacturing processes, except garment making, generate
environmental pollution. During cotton spinning and weaving, dust and
fly are released into the air streams of the production departments. Most
of the modern textile mills are equipped with automatic waste removal,
dust filtration and humidification plants. The dust and fly released by the
machines are sucked away by suction nozzles and ducts. The dust laden
air is filtered, humidified and re-circulated. The number of air changes
per hour is optimised in each department to keep the air streams clean and
hygienic to prevent any risk to the health of the workers. The normal air
changes are as follows:
Table 1.3 Normal air changes per hour
Department Number of air changes
per hour
Blow room, drawing, combing and roving 15
Carding 20
Spinning 45
Winding 30
Twisting, warping, sizing and weaving 20
To minimize risk of industrial diseases such as byssinosis (lung
disease) among the workers, the US Occupational Safety and Health
Authority (OSHA) has specified concentration limits of dust in the air
streams of production rooms for compliance by the concerned industries
as follows:
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Need for maintaining humidity 7
● 0.5 mgm per cubic metre, from blowing to roving preparation and
for manufacture of nonwovens.
● 0.2 mgm per cubic meter, for spinning, twisting, winding and warping.
● 0.75 mgm per cubic metre, for sizing and weaving.
With the industrial growth, the quality of air has been considerably
deteriorated. Atmospheric air contains lot of aerosol. This has created the
need for air-conditioning, which implies fresh air supply, removal of
aerosols and heat, and air motion for cooling and refreshing. Compliance
with the above listed limits for air cleanliness brings in economic benefits
for the textile mills in the form of improved worker attendance, product
quality, process efficiency, reduced end-breakage rate in spinning and
weaving mills and improved yield of yarn.
Because of this need, the textile industry is one of the largest industrial
users of air-washing equipment. Similar equipment is used in other
industries such as automotive industry spray paint booths, tobacco industry,
hospital surgery and nursery rooms, photographic film manufacturing
plants and aircraft industry’s clean rooms. Each of these industries normally
uses water in a gas scrubbing device to clean and process air so that it
meets their particular clean air standards. The use of air-washing equipment
in the textile industry is more difficult to understand than in other industries
as there are many different processes and different combinations of
processes in one plant. Air washers are utilised throughout the various
processes in cotton mills where raw cotton is processed into woven cotton
fabric. They are also used in blending plants where raw cotton is processed
and blended with synthetic staple into yarn and then woven into blended
fabric. Man-made fibre plants producing nylon or polyester yarn also use

air washers. Fibreglass plants producing fibreglass yarn for tyre cord and
other industrial uses also utilise air washers extensively. Some of these
plants have gas-scrubber systems which double as plant air washers and
which present some of the most difficult water-treatment problems. Air
washers are found extensively in knitting plants including ladies’ hosiery
plants, and in carpet mills where carpet yarn is processed and dyed, as
well as in the carpet weaving plants. Dyeing, finishing, and bleaching
processes generally do not require air washer systems; but these processes
are often located in the same plant as one or more of the previously
described processes. For example, a plant blending cotton with synthetic
staple to produce drapery material may have another section of the plant
where they dye this material, finish it, and possibly run it through a printing
process. Although dyeing and finishing operations do not require air
washers, they have started using various types of smoke-abatement
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8 Humidification and ventilation management in textile industry
equipments to control vapours emanating from the plant from some of
these finishing processes.
1.4 Control of air pollution
The textile industry is plagued by air pollution problems which must be
resolved. In particular, smoke and odour arising in the process require
abatement. The major air pollution problem in the textile industry occurs
during the finishing stages, where various processes are employed for
coating the fabrics. After the coatings are applied, the coated fabrics are
cured by heating in ovens, dryers, tenter frames, etc. A frequent result is
the vapourisation of the organic compounds into high molecular weight

volatile organic (usually hydrocarbon) compounds (VOCs). In terms of
actual emissions, the industry must also deal with larger particles,
principally lint. The other problem is the creation of VOCs, which take
the form of visible and invisible smoke, and objectionable odour. Smoke
is basically made up of tiny solid or liquid particles of VOCs less than one
micron in size that are suspended in the gaseous discharge. When the
smoke/gas mix goes up the stack, the Environmental Protection Agency
(EPA) measures the density or opacity of the emission using an official
transparent template, and labels the opacity as ranging from 0 to 100%.
The more opaque the smoke, the more visible it is. Opacity of smoke is
actually related to the quantity, rather than the weight, of particles present
in the gas.
The problem with odour is that it is not practically measurable. It is a
sensation originated by interaction between molecules of hydrocarbons
and ten million nerve fibres in the human olfactory membranes. The human
nose can differentiate between 4000 different odours. The odours
associated with textile plant emissions are usually caused by hydrocarbons
with molecular weight less than 200, and fewer than 15 carbon molecules
(C1 to C14). These odorous molecules attach themselves to the particles
of smoke and can be carried at great distances from their point of origin,
causing complaints. Proper system for collecting the polluted air and
directing it for suitable treatment is an important aspect of air controlling
in textile industry.
1.5 Air changes
The number of air change is an important factor to ensure that air is clean
and safe. The number of air changes required depends on the type of activity
being taking place. Following table gives the specified air changes for
different levels of air controls:
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Need for maintaining humidity 9
Table 1.4 Specified air changes at different levels of air control
ISO Controls Air velocity Air changes HEPA coverage
class at table level rate per hour as % of ceiling
in FPM
1 Stringent 70–130 >750 100
2 Stringent 70–130 >750 100
3 Stringent 70–130 >750 100
4 Stringent 70–110 500–600 100
5 Stringent 70–90 150–400 100
6 Intermediate 25–40 60–100 33–40
7 Intermediate 10–15 25–40 10–15
8 Less stringent 3–5 10–15 05–10
The method used to calculate CFM requirements for a given fan or fans
is based on complete number of changes of air in a structure or room in a
given period. To determine the CFM required, the room volume (in cubic
ft.) is divided by the appropriate ‘minutes per air change’. In textile industry
the minutes per air change ranges from 5 to 15. Additional considerations
are local code requirements on air changes, specific use of the space and
the type of climate in the area. Air changes are required more when the
people working in a section, the generation of heat, or the generation of
dust is more and the maximum dust level is allowed in the air.
When considering air purification systems, it is typical to evaluate the
filter media, product efficiency claims, and the size and portability of the
unit. The most important factor in the success of any system is the frequency
of air changes per hour (ACH) that the system can create. The rate of
ACH determines the rate at which the total volume of air in the room is

cleaned by an air purification system, which is a major factor in the degree
of air cleaning that can be achieved.
1.6 Humidity and the health
Providing ideal indoor air quality includes air purity, temperature and
moisture level. A low humidity level can be as unhealthy and uncomfortable
as excessive humidity. Dry air causes dry, rough and flaky skin because
the skin’s outer layers lose moisture to the surrounding air. Respiratory
passages such as the nose and throat also lose moisture from their
membranes causing dryness and irritation. Low levels of humidity can
also contribute to respiratory infections, allergic and asthmatic symptoms
and an increase in airborne dust and allergens. If the humidity level is too
low, bacteria, viruses, respiratory infections and allergic asthma will
increase. If the humidity level is too high, dust mites and fungi/mold will
proliferate and allergic asthma will also increase.
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10 Humidification and ventilation management in textile industry
Numerous studies done by ASHRAE and other indoor air quality experts,
suggest an optimum RH range of 40–60%. Dryer or wetter causes different
kinds of problems, at each extreme. See the chart below, based on ASHRAE
sponsored research. The shaded portions indicate problems. For example,
bacterial problems shall be less at 26–60% RH and viral problems from
43 to 70%. Most of the problems are not there between 45% and 55%, as
can be seen from the table.
10 20 30 40 50 60 70 80 90
Bacteria
Viruses

Fungi
Mites
Respiratory infections
Allergic rhinitis and
asthma
Chemical interactions
Ozone production
RH

1.1 Comfortable levels of humidification. (ASHRAE findings)
1.7 Protection of electronics and equipments
The last 2 decades have seen a major shift in the technology adopted in
textile industry. The manual operations are being replaced by automations
controlled by programmed electronic logic systems. It is not only the case
with testing laboratories; but monitoring of speeds, settings, temperature,
humidity and various other factors are also controlled by electronic gadgets.
Central to all electronic circuits today is the IC (integrated circuit) or ‘chip’.
The heart of the IC is a wafer-thin miniature circuit engraved in
semiconductor material. Electronic components and chips in particular
can be overstressed by electrical transients (voltage spikes). This may cause
cratering and melting of minute areas of the semiconductor, leading to
operational upsets, loss of memory or permanent failure. The damage may
be immediate or the component may fail sooner than an identical part not
exposed to an electrical transient. A major cause of voltage spikes is
electrostatic discharge (ESD). Although of extremely short duration,
transients can be lethal to the wafer-thin surfaces of semiconductors.
Electrostatic discharge may deliver voltage as high as lightning, and it
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Need for maintaining humidity 11
strikes faster. In addition to the risk of damage to electronic devices from
static electricity charges, there are grave risks associated with sparks from
static charges in many process applications. Static electricity is extremely
dangerous in the presence of gases, volatile liquids, or explosive dusts
such as is found in munitions plants, paint spray booths, printing plants,
pharmaceutical plants, and other places. Many static control products
(special mats, carpeting, sprays, straps, etc.) are available, but they cannot
replace the work done by humidification, which is a passive static control,
which means working to control static all the time. However, care should
be taken to ensure that there are no condensations on electronic parts. The
RH preferred is from 40 to 70%.
Conclusions
The need for providing conditioned and controlled air, monitoring the air
movement in textile industry is very essential not only from the point of
view of product quality and productivity, but also for the consideration of
the health of employees and the community around. Extensive works have
been done to design the best possible combination considering the
effectiveness and the cost implications. It is not possible to discuss all the
available systems, but some of the widely used systems are discussed in
the further chapters.
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12 Humidification and ventilation management in textile industry
2

A glance at the developments
2.1 General
While moving heat via machinery to provide air conditioning is a relatively
modern invention, the cooling of buildings is not. The concept of air
conditioning is known to have been applied in ancient Rome, where
aqueduct water was circulated through the walls of certain houses to cool
them. Medieval Persia had buildings that used cisterns and wind towers to
cool buildings during the hot season: cisterns (large open pools in a central
courtyards, not underground tanks) collected rain water; wind towers had
windows that could catch wind and internal vanes to direct the airflow
down into the building, usually over the cistern and out through a downwind
cooling tower. The evaporation of cistern water made the air cool in the
building.
The concept of modern air conditioning was first established by an
American Mr. Stuart W. Cramer in the beginning of 20th century. The
term ‘air conditioning’ was coined by him and defined it as a process of
treating the air so that its temperature, humidity, cleanliness and distribution
with in the room are controlled simultaneously. He was exploring ways to
add moisture to the air in his textile mill. Cramer coined the term air
conditioning as an analogue to ‘water conditioning’, then a well-known
process for making textiles easier to process. He combined moisture with
ventilation to ‘condition’ and changed the air in the factories, controlling
the humidity so necessary in textile plants. Willis Carrier further developed
the system, and in 1906 the first Buffalo humidifier and air washer plant
was designed. He adopted the term and incorporated it into the name of
his company. This evaporation of water in air, to provide a cooling effect,
is now known as evaporative cooling.
Early commercial applications of air conditioning were manufactured
to cool air for industrial processing rather than personal comfort. Modern
air conditioning emerged from advances in chemistry during the 19th

12
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A glance at the developments 13
century, and the first large-scale electrical air conditioning was invented
and used in 1902 by Willis Haviland Carrier. Designed to improve
manufacturing process control in a printing plant, his invention controlled
not only temperature but also humidity. The low heat and humidity were
to help maintain consistent paper dimensions and ink alignment. Later,
Carrier’s technology was applied to increase productivity at the workplace,
and the Carrier Air Conditioning Company of America was formed to meet
rising demand. Over a time air conditioning came to be used to improve
comfort in homes and automobiles. Residential sales expanded dramatically
in the 1950s.
Early textile mills had north light roofing to get a uniform sunlight.
Further there used to be windows and number of openings so that the air
could move freely. However, these buildings were not able to protect the
temperature and humidity inside the working area. Any change in outside
temperature or humidity was affecting the work. Normally there used to
be problems in the evenings when temperature was changing, and also in
the afternoons when out side temperature was high. The supervisors had
the main task of getting water sprinkled on the floor in the afternoons, and
getting all windows closed in the nights. There used to be closed steam
pipes to heat the section when the temperature was low. Heating lamps on
draw frames, speed frames and combers was a common feature. The
experience of the technician and the speed at which he could monitor the
facilities was very important for smooth working. After the false ceilings

were introduced, the effect of outside humidity and temperature got
reduced, and also the amount of air to be controlled became less. The
windows were permanently closed, which helped further to control the
temperature and humidity.
As the speed of machinery increased, the precision in controlling
temperature and humidity became prime necessity. The central air washer
plants with automatic controls became an inseparable part of textile mills.
Just a few years ago, textile air washers were designed primarily as
low-air-velocity, non-chilled water systems. They were so large that air-
washer rooms were an integral part of the building housing the textile
operation. Lint and fibre screens ahead of the washers were non-existent
in many cases, and the washer rooms were typically filled with cotton lint.
The warm water in the washer was a perfect environment for bacteria.
Lint, dirt, and other suspended matter in the water continually plugged air
washer spray nozzles, reducing the efficiency. As the industry began to
install air conditioning equipment, these units were upgraded and modified
to perform properly with chilled water.
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14 Humidification and ventilation management in textile industry
2.2 Unit humidifiers
Unit humidifiers came into picture in the middle of last century, which
almost became an integral part of textile mills. Unit humidifier or Semi-
Central Duct Unit is a combination of axial flow fan, one or more
centrifugal atomisers, air mixing chamber with interconnected fresh air
and return air dampers to take fresh air as well as to re-circulate
departmental air, a set of large area V-shaped air filters and fabricated

distribution duct with eliminator-type grills. If required, steam heating coils
can also be mounted on return air damper of the mixing chambers.

Return water
turf
Man hole
Duct
Humidifier
Fan
Fresh air
dampers
Return air dam
p
ers
Heater
Production department

Eliminator -
cum-diffuser
Roof
2.1 Unit-type plant.
Different models with various fan capacities from 12000 to 25000 cfm are
available in the market. Unit humidifiers are normally fitted at the top
near the ceiling. The ducts normally shall be extended up to 50 ft (15.2 m).
2.3 Central station-type plant
Early system of air cooling consisted of a cooling coil arrangement in
which supply air was cooled and dehumidified by indirect heat exchange
with cold water pumped through tubing. Willies Carrier, the developer of
air washers, surmised that an alternative design using direct contact
between the air and chilled water might improve performance. In his early

air-conditioning systems, he observed that although the air came in contact
with water on the cooling coil surface, dehumidification occurred. In a
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