Friday, 05 January 2018 11:52

Control Techniques for Noise Pollution in Textile Industry

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Abstract:

Textile manufacturing is one of the largest industrial process that uses water, many hazardous chemicals like formaldehyde, azo dyes chlorinated compounds and man power. However one of the major contributors to environmental pollution apart from air and water is noise.Noise is an unwanted sound that interfaces with the function in given time. Prolonged exposure to high noise causes psychological effects and physical damage includes loss in concentration which finally affects the job performance. Today the machinery manufactures are taking continuous efforts to reduce the noise level but the measures are not adequate to protect the textile workers from noise related diseases. This paper enlightens the facts about the noise pollution due to textile machines, its accessories in preventive measures and controlling the same.     

Keywords: Noise Pollution, Noise and Machine Behavior ,

Introduction to Textile Industry:

Textile industry is a significant contributor to many national economies, encompassing both small and large-scale operations worldwide. Though the textile industry is one of the largest industries,
its manufacturing process is characterized by high consumption of resources like water, fuel and a variety of chemicals in a long process sequence that generates a significant amount of waste. The system/procedure of low process efficiency results in substantial wastage of resources and a severe damage to the environment. The main environmental problems associated with textile industry are typically those associated with water body pollution caused by the discharge of untreated effluents. Other environmental issues of equal importance are air emission, notably Volatile Organic Compounds (VOC) and excessive noise as well as workspace safety[1]. In recent years, even developing country like India has taken positive steps against the noise pollution; Noise pollution has been accepted as major threat to human beings. Much discussion and legislation have been evolved in an attempt to recognize and combat the problem of noise pollution. It has been recognized that noise of sufficient intensity can damage hearing. The problem of noise pollution can be combated when there are means of measuring noise level and systems of classification.

 

Textile and pollution:

The textile process deals with production of fiber, yarn and fabric followed by pre and post chemical, mechanical process. Each process causes some environmental issues that can be listed as follows,

1)      Air pollution( Dust )

2)      Water pollution

3)      Solid waste pollution

4)      Noise pollution

 

1)      Air pollution:

Most processes performed in textile mills produce atmospheric emissions. Gaseous emissions have been identified as the second greatest pollution problem (after effluent quality) for the textile industry. Speculation concerning the amount and type of air pollutants emitted from textile operations has been widespread but, air emission data for textile manufacturing operations are not readily available. Air pollution is the most difficult type of pollution to sample test and quantify in an audit. 
Air emissions can be classified according to the nature of their sources.[2]

Textile mills usually generate nitrogen and sulphur oxides from boilers. Other significant sources of air emissions in textile operations include, fabricpreparation,dyeing,resin finishing, printing wastewater treatment plants. Apart from this in spinning mill, the process of removing trash from cotton fibers by opening and beating process results in liberation of fiber fluff in the surrounding environment. The amount of fiber fluff liberated varies from section to section, being highest in blow room and minimum at the cone winding section. The exposure of workersto such working environment conditions containing fiber particles and dust poses a severe health risk which is shown in the Fig.No 1. Generally, air suction system exists nearly in all departments to maintain certain humidity and remove air contaminants. At some places it works effectively but in certain areas air exchange is not proper resulting in suffocation and inconvenience to the workers. In weaving mill, fibrous particles present in the working environment are not much. The small fibrous particles generated during weaving activities disperse in occupational air [3] the fluff liberation in the departments with modern textile machines which is shown in the Table No.1, has drastically reduced with most of the machines having major sections fully enclosed.

 

 

 

 

 

Table 1: Concentration limits of dust in air stream

Process

Limit (mg/m3)

Blow room to Speed frame

0.50

Spinning (Ring Frame)

0.20

Twisting

0.20

Winding

0.20

Warping

0.20

Sizing

0.75

Weaving

0.75

Nonwoven

0.50

 

 


Fig.1: Problems of fluff liberation in spinning and weaving sheds

2)      Water pollution:

The textile industry uses high volumes of water throughout its operations, from washing of fibers to bleaching, dyeing and washing of finished products. On an average, approximately 200 liters of water is required to produce l kg of textiles.[4] from Fig No. 3 and it is seen that the large volume of wastewater generatedcontains a wide variety of chemicals used throughout processing. This polluted water can cause severe damage if it is not treated properly before being discharged into the environment. All the stages involved in textile manufacturing, wet processing creates the highest volume of wastewater.
          The aquatic toxicity of textile industry wastewater varies considerably among production facilities. The sources of aquatic toxicity can include salt, surfactants, ionic metals and their metal complexes, toxic organic chemicals, biocides and toxic anions. Most textile dyes have low aquatic toxicity; on the other hand surfactants and related compounds, such as detergents, emulsifiers and dispersants are used in most of each textile process and can be an important contributor to effluent aquatic toxicity, BOD and foaming.

 

 

Fig 2: Coloured Effluent from dyeing process            Fig 3:  Effluent Discharge

 

3)      Solid waste pollution:

The primary residual wastes generated from the textile industry are non-hazardous. These include scraps of fabric and yarn, off-specification yarn and fabric and packaging waste. There are also wastes associated with the storage and production of yarns and textiles, such as chemical storage drums, cardboard reels for storing fabric and cones used to hold yarns for dyeing and knitting. Cutting room waste generates a high volume of fabric scraps, which can often be reduced by increasing fabric utilization efficiency in cutting and sewing.

4)      Noise pollution and machine:

Noise is the environmental pollutant generated by any industry and spinning and weaving industries has no exception to this. The workers exposed to industrial noise of potentially damaging quality and intensity, suffer from impairment of hearing capacity of several degrees and other physiological disorders which is shown in the Fig No. 4 and 5 Prolonged exposure to a noise level of > 90 dB may cause hearing disorders since maximum permissible noise level for 8 hour exposure should be around 96.5 dB [5] As we know the term noise is the unpleasant sound with varying intensity. The machines are the main cause for this particular reason, and cannot be under direct control because we cannot keep machine as it is as it generate the noise and secondly lot of cost is involved on the machines is very high.

 

 

 

Impact of noise pollution on human beings

 

 

Fig 4: Psychological Disorders                                                Fig 5:  Hearing Problem

Machine behavior and noise generation: Any machine while in running is prone to develop the noise and textile machines have no exception for the same. When we talk about the noise with respect to machine it is the vibration generated due to two or more solid surface interface. The vibrating members alternately push and pull against air creating noise, off course there are many reasons for generation of noise and can be summarized as follow,

1)      Machine footing and its foundation.

2)      Type of mechanism adopted while designing the machine (no. of mechanical components presented and linkage mechanism)

3)      Working speed of machine.

4)      Maintenance of machine.

5)      Design of other machine parts like blowers, ducts and pipes etc. 

6)      Material handling system.

Overview of noise levels in Different departments:

1)      Spinning: Because of high spindle speeds reached on new machines (ring spindles up to 20000 rpm, rotor speed up to 11000 rpm) spinning mills can generally be assumed to generate a great noise. Noise levels of 70 to 100 dB are commonly recorded in workrooms.

2)      Weaving and knitting: Although considerable progress has been made in the weaving sector over the last 20 year, the whole area of noise nuisance and, closely associated with it, vibration coming from looms, cause major problems. Noise levels of 100 to 120 dB must be expected in weaving rooms, according to the design, type of loom.Fitting and erection and number looms used, fabric structure etc. The following table shows the noise levels in various departments.

Table 2: Noise level in textile industry (Texturing, spinning and Weaving)

Process

Noise level (dB)

Texturizing Plant

95-100

Spinning

 

1.Ring Frame

80

2.Rotor spinning

84

3.Two for one twister

100-110

4.Weaving

100-120

 

Today’s machine scenario against conventional one with respect to noise generation:

All modern machines are far differing than conventional one with respect to noise generation. The conventional practice of designing of machines was based on pure mechanical concepts rather than combination of mechanical and electronics, since the development in the electronics industries was not up to the level that today it is. Today we are talking about the automated machines purely based on mechatronics concept and it offers following advantage.

1)      Reduction in the mechanical parts and accessories with electronic base mechanisms.

2)      High and efficient accuracy

3)      Offers flexibility in the working.

4)      Ease of maintenance.

5)      Low mechanical complicity.

Also introduction of hydraulics, pneumatics with solenoid valves and PLC operating system on spinning on weaving machines offers efficient control on various parameters like yarn, fabric tension on spinning and weaving machines, speed control devices, Building mechanism on speed frame and ring frame as it was traditionally based on cam and linkage mechanism etc. Shows pronounced impact on noise reduction. The development in material handling system also offers positive contribution towards noise reduction this is especially while handling of plastic cops during doffing operation similarly beams handling system in weaving unit with monorail arrangement [6]. The handling of spare parts also shows some good correlation with noise level which involves proper storage of parts like boxes and bines etc. The following points show some features of modern machine.

         Sturdy design of machines

         Use of minimum number of linkages

         More focus on mechatronics which relates to minimum number of metallic parts

         Proper design of Jig& fixer shows reduction in vibration up to 20 dB

         Use of proper bearings and centralized lubrication system reduces friction

         Improved metallurgy  of metallic parts in other words use of light weight parts

         Provision of suction systems at various points results in dust reduction by 30-35%

         Enclosed machineparts minimizes accidental cases by 50%

         Machines are equipped with safety panels and sensors to sense the abnormalities

Design aspects to control the noise:

Behavior of sound: When designing engineering control to reduce the noise exposure it is important to have basic understanding of sound and its impact. Sound is always produced by change in the speed or force. Basic principle of sound includes,

1)      More noise is produced when great force is used for longer time than small force with shorter time.

2)      Airborne sound is caused by vibration of solid parts or turbulence in case of fluid.

3)      Vibration can produce sound after traveling a great distance.

4)      High frequency sound is more reflective.

5)      Low frequency noise is travels through object and through opening.

6)      Audible range of human ear is up to 80-90 dB.[7]

Design and planning: first step in effective noise control is design and purchase in noise control in mind. Take noise control in account when designing new facilities renovating existing buildings. Isolate noisy operations in designing rooms where fewer employees will be impacted. Use qualified engineers and architectures to design the work place and it becomes easier to control techniques before machine installation and other aspects. Before buying anything ask to the manufacture about the noise and other technical parameters related to noise generation.

Administrative control: It involves training to the workers staff about the noise and its consequences also job rotation technique to high level noise area and low level noise area in order to keep overall noise level constant, since this control technique is not efficient as there is lacuna in technological aspects to reduce the noise.

Simple engineering control: These controls should be evaluated before exploring more complex solution and this technique involves following aspects,

1)      Proper maintenance.

2)      Changing operating procedures

3)      Replacing operating procedures

4)      Applying room treatments

5)      Relocating equipment’s

6)      Simple machine treatments

7)      Using proper machine speed[8]

 

1)      Proper maintenance: It is observed that malfunctioning or improperly maintained parts produces more noise that well maintained one like,

a.       Loosely held bearings and belts.

b.      Torn belts

c.       Worn gears

d.      Imbalanced rotating masses

e.       Missing guards or shields

f.       Improperly adjusted cams and linkages

It is recommended that a good preventive maintenance practice should be adopted to reduce the noise level and also follow scheduled check list for lubrication to reduce the wear and tear of parts and maintain the same.

2)      Operating procedures and equipment replacement technique: This technique is totally in the hand of administration where provision of job rotation and purchasing of new equipment’s or tools is the main priority.

3)      Room treatments: One of the basic principles of noise control is to reduce the reflecting sound, for that use of absorbent materials in between the departments, modify the plant construction according to the acoustic principle and engineering approach.

4)      Relocation of equipment: Noise level drops off when the distance from the noise source is increase.

a.       Noisy equipment should be as far as possible from employees.

b.       Do not put noisy parts at corner to avoid noise reflection.

 

5)      Simple machine treatments: Many simple modifications in the machine show significant reduction in the noise level.

a.       Reduce the dropping height of parts from bins and storage tanks

b.      Enclose the bin and boxes with rubber base material to absorb the noise

c.       Keep optimum pressure when working with pneumatics and hydraulics

6)      Proper operating speed: As we know any increase in speed will prone to develop more noise so run the machines with manufacturer recommendation.

a)      Enclosures: These are like boxes covered with sound and heat absorbable coatings simple used to control the machines parts which are moveable especially in case of motor panels where both heat and noise generation are the key parameters to be performed.

b)      Shields and barriers: These are sound absorbable materials which are used to control high frequency noise they should be placed near to the high frequency source and they should be as thick as possible.

c)      Ducts and pipes: vibrating duct is the common cause of noise. The source of noise is the fan and is depend on

1)      Proper fan size and type

2)      Speed of the fan

Generally the backward curved fan produces low level of  noise than forward curve due to the low air turbulence also some other considerations are required to be taken like acoustic linings in the ducts to observe the sound, pressure balance in ducts to maintain the steady conditions during martial transportation.  

Conclusion:

 

Reduction in the noise is important and above all a demanding task. Today the machine manufactures have attempted serval techniques to keep the noise emission as low as possible but, what would have been achieved in lowering down the noise level has been canceled out by the continuous increase in the speed. We must practice sophisticated engineering and quantitative management techniques like Total Productive Maintenance to control noise and other pollutions with respect to machines and material handling practices.

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