10 Point Guide to Humidity Control in Textile Manufacturing

10-POINT GUIDE TO HUMIDITY CONTROL IN TEXTILE MANUFACTURING

Humidification and Evaporative Cooling MANAGE HUMIDITY, INCREASE PROFITABILITY

Every textile product is affected by the resulting in a lower quality yarn. Drier As a global leader in humidification relative humidity of the environment in fibres during spinning causes a higher technology, Condair has developed which it is produced, particularly hairiness of the yarn, lower strength successful humidification strategies for natural fibres. and a low pilling resistance of the end textile manufacturers around the product. This all contributes to a world. This document present an Low air humidity can dry a fibre causing reduced market value for the textile. introductory 10-point guide for its internal moisture content to fall. If production managers looking to this moisture content drops below the As well as impairing quality, low enhance their factory’s profitability optimum level during processing, a humidity during production will also with improved humidity. manufacturer can experience a drop in directly reduce yield. A 4% evaporation productivity for a number of reasons. of a textile’s internal moisture content requires 4% more product to be As fibres dry their tensile strength is manufactured to meet a required impaired, they become less flexible, production weight. As dry fibres are thinner and more brittle. If a fibre or more prone to shedding, this again thread breaks while being processed, reduces yield, as more fibres are lost to textile machinery needs to be manually the atmosphere. product yield rethreaded, leading to downtime and reduced efficiency. Both these factors contribute to a textile manufacturer requiring more is optimised During weaving, every time a machine raw materials, energy and labour to needs to be rethreaded and tied-off, satisfy an order, thus increasing and quality loom stop marks are produced, overheads and reducing profits. By correctly humidifying a textile improved production facility, product yield is optimised and quality improved.

© Copyright Condair plc No part of this document may be reproduced, published or distributed in any material form, including inclusion on social media or distribution via the internet, without prior consent of Condair plc. 1 WHY HUMIDIFY?

LOW AIR HUMIDITY EQUILIBRIUM RELATIVE HUMIDITY HIGH AIR HUMIDITY

AIR AIR AIR

FIBRE FIBRE FIBRE

Moisture loss from the Moisture gain by No moisture movement fibre and shrinkage the fibre (regain)

Textile fibres have an internal equilibrium relative humidity and is the moisture content and will gain or lose ideal processing environment for water to the air depending on whether textile manufacturing. there is equilibrium between the air’s maintain relative humidity and the textile’s However, if the air’s relative humidity is moisture content. lower than this ideal level, moisture will be drawn from the textile’s exposed equilibrium If a fibre’s surface is exposed to the air surface and evaporate into the air. and there is balance between these between the two factors, no moisture movement Moisture loss from a textile can happen will occur. This is referred to as quickly during processing (see fig. 1). Cotton and wool can lose up to 4% in air’s relative under 10 minutes when exposed. 18% Wool Carding, spinning, winding and humidity and 16% weaving expose a huge amount of the 14% fibre’s surface area to rapidly moving 13% Cotton the textile’s air. This provides great potential for 11% evaporative losses from the fibre 9% should the ambient humidity be lower moisture 7% than the equilibrium relative humidity. Water content Water 5% Porous Acrylic content 4% The objective of humidifying a textile Polypropylene 2% factory is to maintain equilibrium 0% 0 10 20 30 40 50 60 70 80 90 between the air’s relative humidity and the textile’s moisture content. Time (min)

Fig. 1 - Speed of change for moisture loss from diﬀerent textiles when exposed to dry air 2 WHAT’S THE IDEAL MILL HUMIDITY LEVEL?

Wool

20 Jute

Viscose 15 Cotton

10 Acetate (secondary) Moisture content % content Moisture

Nylon 66

5 Acrylic The ideal humidity level for any textile To achieve the required internal production area will depend on the moisture content for any textile Polyester moisture content of the textile being product, a sorption isotherm graph is 0 processed and the production used to calculate the correct air 0 20 40 60 80 100 process itself. humidity (see fig. 2). The curved line Relative humdity % shows for any given moisture Fig. 2 - Moisture sorption data (median values Natural fibres are far more content of the material what the between wetting and drying) in atmospheres susceptible to moisture changes than corresponding air humidity ought to of various relative humidities manmade fibres, in terms of be for perfect equilibrium. performance. At the correct internal moisture content there is less yarn The table below shows a general breakage in spinning and twisting, and guide to the ideal humidity levels higher eﬃciencies in weaving. for processing diﬀerent textiles at various stages of production.

Optimal humidity levels use a sorption

Spinning Twisting Winding Weaving isotherm Wool 50-85%RH 60-65%RH 55-60%RH 50-60%RH Cotton 35-65%RH 50-65%RH 55-65%RH 70-85%RH graph to Man-made fibres 45-65%RH 45-65%RH 60-65%RH 60-70%RH Silk 60-65%RH 60-65%RH 60-65%RH 60-65%RH calculate the Jute 75%RH 75%RH 75%RH 75%RH Linen 80%RH 80%RH 80%RH 80%RH required air humidity 3 HOW CAN HUMIDITY BE CONSISTENTLY MANAGED ACROSS A LARGE FACTORY?

The characteristics of the atmosphere To achieve a consistent level of across a single production area can vary humidity, across areas that can be greatly. Any change in temperature will hundreds of metres long, it is important impact on the relative humidity (RH). to have a humidification system with Hot spots on machinery will cause a many points of moisture injection. localised drop in RH that can rapidly Single “spot” humidifiers that introduce many points decrease product weight and quality. a large amount of humidity from one or just a few units, cannot maintain room of moisture humidity as evenly as a system with many lower capacity outlets. injection Varying the quantity of moisture introduced at diﬀerent points of injection, given the room’s specific characteristics, can also help produce a more even moisture distribution. For example, it is important to introduce more moisture close to where the dry air enters the room and avoid over humidifying areas near to the points from where air is extracted.

Condair oﬀer free expert advice on humidity levels and system design 4 WHAT TYPE OF HUMIDIFIER IS BEST FOR A TEXTILE FACTORY?

Spray humidifiers that combine Compressed air and water systems, compressed air and water to create a such as the JetSpray from Condair, series of fine aerosols are a popular also have the benefit of self-cleaning choice for large textile production nozzles. A tiny pin is regularly combine areas. This type of humidifier has many forced through the spray orifice, advantages over high pressure or greatly reducing the possibility of spinning disc systems for a nozzle blockages. This reduces compressed textile factory. necessary maintenance and the associated downtime. air and water The compressed air creates highly directional sprays that evaporate Textile laboratories that need to without needing fans, which can precisely control humidity in smaller to create a frequently block and require areas, often use electric steam maintenance in very dusty production humidifiers. They can deliver humidity series of ﬁne environments. The droplet size of a either directly to a room with a fan unit compressed air and water humidifier is or to a ducted air conditioning system. aerosols very small at between 5-7 microns, so evaporates rapidly without drips or wetting onto machinery, walls or the floor of the room. 5 HOW MUCH WATER NEEDS TO BE INTRODUCED TO THE AIR?

Once the ideal level of air humidity has The desired humidity level kilogram of dry air can be determined been understood (see point 2), the (see point 2) along with the specific volume in m³/kg. volume of moisture required to maintain The air volume of the room this humidity will need to be calculated, (room height x width x length) The following equation is then used to given the production area’s specific The temperature of the room calculate the required humidity load for characteristics. This volume of moisture is The temperature of the outside air the room. typically expressed in kilograms per hour The humidity of the outside air and is referred to as the “humidity load”. Moisture x air vol x The number of air exchanges the no. of air changes room experiences per hour = Humidity load In order to calculate an area’s humidity Specific volume load, and therefore what capacity By plotting the internal and external air humidifier is required, the following conditions on a psychrometric chart, parameters need to be noted: To ensure the humidification system is the volume of moisture needed per capable of meeting the needs of the factory throughout the year, the %RH internal and external air conditions 80 +40%RH 40 should be based on the hottest and driest times. Desired room 80%RH

condition 30˚C 0.022

+0.0035 Moisture content Specific volume kg water/kg dry air (m³/kg) 0.0185 Outside air 40%RH condition 38˚C calculate the required humidity load

30 38-8°C Dry bulb temperature (°C)

Example psychrometric calculation

Condair oﬀer free expert advice on product selection and sizing 6 HOW DOES HUMIDITY AFFECT STATIC ELECTRICITY?

The occurrence of static can be a major uncomfortable but it can cause a problem when processing textiles and person to jump and fall, which presents it is directly related to levels of relative extreme risks when working with humidity. The electrical sensitivity that textile machinery. Static discharge is at around determines whether static also a risk to people with weak hearts electrification will occur is dependent or pace-makers fitted. on the moisture content of the air and 50%RH static fibres. As fibres lose moisture, they As well as the danger to staff, static increase their electrical resistance. They electrical build-up will cause materials build-up is no longer readily dissipate electrical to stick together and be less charge that is generated by frictional manageable. This in turn will slow contact on machinery. machinery, directly affecting naturally production schedules. Also, as most In a textile production facility with low machines are now microprocessor dissipated humidity, static discharges can jump up controlled, an uncontrolled electrical to 4-5 inches. Although they have a low discharge in the wrong place can current, discharges can be several damage the electronics of the unit hundred thousand volts. resulting in expensive repair bills and significant downtime. This presents a danger to staff working with the machines, as it is not only By maintaining humidity at around 50%RH static build-up is naturally dissipated and these associated problems are alleviated. 7 WILL HUMIDIFICATION AFFECT FACTORY WORKERS?

A cold water humidifier will provide fibres shed during processing, therefore the additional benefit of 680W of fewer particles are introduced to the evaporative cooling for every 1kg of air. These benefits combine to make water absorbed by the air. Across a the air much less polluted, more cooler textile production area, this cooling pleasant to breathe and healthier to effect can reduce the ambient work in. temperature by between 5-12°C. temperatures This is a welcome improvement to the Cooler temperatures and reduced working conditions for staff in the area. airborne pollution has a positive and reduced impact on productivity, as staff are An increased air humidity will healthier and happier. encourage airborne lint, dust and fly to airborne fall out of the atmosphere and settle faster. Maintaining the correct air pollution humidity also reduces the amount of

Condair oﬀers free expert advice on static control and evaporative cooling 8 WHAT HYGIENE MEASURES ARE REQUIRED?

As workers come into close proximity system or in the building’s pipework to the sprays released from a textile feeding the system. humidification system, and can potentially inhale the aerosols, it is vital Alongside these necessary the system is designed with hygiene as requirements, water treatment a primary concern. systems can also be used that either ALIT filter the water to remove bacteria and QU Y Systems should always be fed by a viruses or sterilise the water through water supply that is of drinking water dosing or exposure to ultra violet light. quality and correctly filtered to remove H O particulate matter.

2 The humidifier’s water pipelines should

A not incorporate any runs where water

D P

P could potentially rest for an extended V R O period of time without draining away. exceptionally Stagnant water is a potential breeding ground for microbes that can be high hygiene dangerous to health if inhaled. The humidifier should therefore have automatic flush and drain cycles to standards ensure water does not remain in the

I HAVE AN AIR WASHER IN MY 9 AIR HANDLING UNIT. DO I STILL NEED A HUMIDIFIER?

Many textile production facilities will load being required than the room’s air incorporate a spray system or air handling unit was originally designed washer inside the air handling unit that for. feeds conditioned air into the building. systems can However, these older air treatment In-room systems, such as the JetSpray systems are ineﬃcient and rarely able from Condair, accurately maintain to control humidity to the ideal level humidity levels across an area, be added to evenly across a production area. eﬃciently and economically. As a factory’s capacity increases, additional precisely Frequently, machinery upgrades within humidification systems can be added a factory will also change the to precisely meet the needs of the meet the characteristics of the air profile across a production machinery. room and result in a greater humidity needs of the production machinery 10 WHAT’S THE PAYBACK OF A HUMIDIFICATION SYSTEM?

There are many benefits in maintaining Fibre shedding will reduce yield but to the optimum humidity in a textile mill, quantify this reduction and humidity’s including increases in yield, machine impact upon it, will depend on the uptime and product market value. It is textile in question and its susceptibility therefore difficult to precisely quantify to damage from drying and shedding. increases the financial implications of them all in advance but an informed estimate Production efficiency based upon in yield, can be made. machine uptime is a factor that ought to be considered when looking at a machine The most obvious financial benefit is payback period for maintaining the reduction in evaporative weight optimum humidity levels. How much loss from the raw material during time is spent rethreading machines uptime and processing. If a 4% loss is experienced, due to fibre breakage and what is the the cost could be calculated on the estimated cost of this inefficiency? product market value of 4% of end product but is most typically calculated on 4% Lastly, an assessment of the potential additional raw material cost. As well as increase in market value of the end market value the raw material cost, the production product should be made. This can cost to process the fibres should also take into account improvements in be considered. yarn hairiness, tensile strength, pilling resistance and a reduction in loom stop marks.

Condair oﬀers free expert ROI projections for humidifier installations ASK FOR A FREE ON-SITE CONSULTATION

WORLD LEADING HUMIDIFICATION SPECIALIST

Condair is a world leader in available, clients are supported by local return on the investment in their humidification and evaporative cooling. specialist humidification engineering humidification systems through It has manufacturing facilities in Asia, teams, which can oﬀer installation, improved productivity. Europe and North America, sales commissioning, maintenance and operations in 20 countries and spares support. Contact us today for a free expert distributors in over 50 more. assessment of your manufacturing The company has been serving the environment and discover how As well as benefiting from the most global textile industry for many years improved humidity can enhance your advanced humidifier technology and helps manufacturers achieve rapid profitability.

USA 2700 90th Street, Sturtevant, WI 53177 Canada 2740 Fenton Road, Ottawa, Ontario K1T 3T7 Tel 1.866.667.8321 Fax 613.822.7964 Email [email protected]

02/2019