Assessment of Noise Level of a Thermal Power Plant

Executed By

Amit Kumar

Master of Public Systems Management(Environment Management)Roll No-107/MPS/090006

Indian Institute of Social Welfare & Business Management

Management House College Square WestKolkata-700073

June, 2010

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Assessment of Noise Level of a Thermal Power Plant

Executed By

Amit KumarMaster of Public Systems Management

(Environment Management) Roll No-107/MPS/090006

Indian Institute of Social Welfare & Business Management

Management House College Square WestKolkata-700073

June, 2010

Contents

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1.0 Executive Summary

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2.0 IntroductionLife is powered by the coal-fired thermal power plant that contributes 2% (2000 MW) of the total power generation (40494 MW) in India. The share of hydel power is around 25- 30% (25000 MW) while the rest 3-5% is due to nuclear power and wind resources. Thermal power plant is one of the noisiest factories. Ambient air monitoring, stack emission monitoring, water and effluent testing are mandatory to compliance the needs of pollution control board to run the industry. Many industrial authorities as well as pollution control boards do not give due weight age to the problem of noise pollution because it does not jeopardize employee’s life immediately after exposure. However, prolong exposure to industrial noise can’t be neglected which may be the cause of neurobehavioral change, psychological stress and unhappiness in daily life without showing the symptoms of chronic / acute diseases. Since, the ears have no natural device to check or protect it from noise; it has no option but to receive all the sound that strikes the eardrum. In industry, excessive noise exposure can cause both auditory and extra-auditory effects. The most important of these is hearing damage

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resulting from prolonged exposure to excessive noise. Another undesirable effect is speech interference or interruption of communication. Annoyance is a third undesirable effect of noise.

The damaging effect on hearing due to noise pollution depends on following parameters --

(1) The level and spectrum of the noise,

(2) Duration of exposure,

(3)Frequency of occurrence,

(4)Susceptibility of individual,

(5) Age of Individual.

At first, excessive exposure to harmful noise causes auditory fatigue or a temporary threshold shift (TTS). However, repeated insults of excessive noise can transform this TTS into a permanent threshold shift. Auditory effects like noise-induced hearing loss can happen unnoticed over a period of years. The extra- auditory effects of noise result in physiologic changes other than hearing. Laboratory studies have shown that noise reduces efficiency on some tasks, can upset the sense of balance and can cause blood vessels to constrict, raising blood pressure and reducing the volume of blood flow. It causes the pupils of the eyes to dilate. Even when we are sleeping, noise can cause changes in electro-encephalograms and blood circulation without waking us. It can also cause fatigue, nervousness, irritability and hypertension and add to the overall stress of living.

3.0 Objectives of the StudyThe prime objectives of the present study are as follows:

To identify the major sources/noise producing machines of the thermal power plant,

To monitor and generate baseline data with regard to different machines,

To assess the possible health effect on the workers working in the high noise zone based on the threshold limit of American Conference of Governmental Industrial Hygienists.

To adopt some mitigative measures to attenuate the noise pollution.

4.0 General Description of Plant

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The Kolaghat Thermal Power Station Stage-1 consists of 3 Nos. 210 MW Units and Stage –II consists of 3 Nos. 210 MW Units designed on the concept of unit system a single boiler supplies steam to a single turbine, coupled to an AC, Generator connected to the 220KV Station bus for Stage – I and 100KV for Stage-II.

The ABL or BHEL make Boiler is of single, water tube natural circulation type super heaters and reheaters. The maximum continuous evaporation of the boiler is 700 T/hr, at 136 kg/cm2 and 5400

super heater outlet pressure and temperature with the final feed water temperature of 247 0C. The reheated steam conditions are 26.2kg./cm2 and 5400c, the maximum reheated flow being 605 T/hr. The water cooled furnace walls, super heaters, reheaters and economizers being self-contained construction and are suspended from a supporting structure.

The boiler enclosure is in two parts, the furnace or radiant zone and the rear pass of convection zone. The four sides of the furnace has membrane type water cooled wall. The Platen Super heater is suspended at the exit of the furnace followed by the final super heater and final reheater in the gas path.

The feed water enters the drum from the economizer outlet header and from the water flows to bottom headers of furnace water walls through the down corners. The water steam mixture reentering the drum from the water wall riser rubes is delivered inside baffles provided and presses down to the water space through the cyclone separators, while separated steam passes through the primary scrubbers at the cyclones and the main scrubbers before passing through the saturated steams outlet pipe.

The steam leading the drum passes through steam cooled roof tubes, cage-walls, primary super heater low Temperature super heater, Platen super heater and Final super heater and exits through two main steam lines.

For ABL make No. 4 boiler total six Nos. B&W type 8.SE pressurized, large ball, slow speed pulverizes with B&W drag link raw coal feeds for each have been provided. Twenty-four (24) Nos. Horizontal circular turbulent type burners with secondary air register are arranged in four tiers in the front wall of the furnace, mill feeding to four (4) burners symmetrically placed in each section of the divided furnace. Six (6) Nos Primary Air heater air provided one for each pulverizer. The hot air for P. Fans suction is tapped off from air heater air outlet and the tempering air from F. D. fan outlet before air heater. The twenty four (24) Nos Oil fired gas/electric igniter and 24 Nos. carbon igniters are provided, one set for each burner. They are suitably mounted on each circular burner to permit easy ignition of light up (LU)/Load carrying (LC) burners.

For BHEL make No. 5&6 Boilers total six Nos. slow speed Half HP Bowel Mills with eddy current drive colimetric Rotary type coal feeders for each Boiler have been provided. Twenty-four (24) Nos. Mill discharge piping. Coal nozzles with felting tangential firing system along with three (3) Nos. P. A. fans (50% capacity each), three nos. seal air fans (50% capacity each), supply the pulverized coal to be titled in the vertical plane by a burner tilting arrangement basically for controlling the stream temperature.

To ensure increase safety, reliability and care in operation, the fuel firing system is equipped with Burner management System (BMS) for No. 4 Boiler AND furnace safeguard supervisory system (FSSS) for unit No. 5 & 6 Boilers.

Two Nos. constant speed forced draft fans and two Nos. variable speed Induced draft fans are provided to supply the combustion air and no exhaust the flue gas chimney respectively.

Both the fans are electric motor driven. The F. D Fans taking suction from atmosphere through inlet regulating vanes discharge air into the Air Heaters. The heated air from the Air Heaters passes through two Nos. hot air ducts on the sides of the boiler to a common burner wind Box. The

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secondary air from the wind Box enters the furnace around the burner through air registers (for No.4 Boiler) and through Sec. Air Control Damper (for 5&6 Boilers).

The flue gas leaving the economizer enters the stationary rubular air heaters (for No. 4 Boiler)/rotary air heaters (for No. 5 & 6 Boilers). For No. 4 Boiler Air Heater air out let supplies required air for secondary air as well as primary air for P. A. Fans, whereas for No. 5 & 6 boilers’ rotary air heaters heated up air discharged by P. A. Fans. The gas leaving the air heater passes through the electrostatic precipitator before entering the ID Fans Inlet.

All the three turbines for unit Nos. 4, 5 & 6 are of BHEL make, C-210MW turbine which are condensing tandem compound, three cylinders, impulse type machine, with nozzle governing and regenerative feed heating. The double flow LP Turbine incorporates a muil0exhaust Baumen Stage in each flow. The Steam after expanding through twelve stages of HP Turbine is reheated in the reheater at Boiler and returned to the IP turbine through IP control valves. After expending through eleven stages of IP and four double flow stages of IP turbine, it is exhausted to the twin surface condensers welded directly to the exhaust part of LPT.

The rated output of the generator is 210 MW with main stream parameters before Emergency stop valve (ESV) being 130 at, and 5350C at inlet to the interceptor valves. The HP and IP rotors are connected by a rigid coupling and have a common bearing. The IP & LP rotors are connected by a semi flexible coupling.

The direction of rotation of the rotors is clockwise viewed from the front bearings. The common bearing of HP and IP rotor is combined journal-cum-thrust bearing. The turbine is anchored at the middle foundation frame of the front exhaust part of the LPT. The turbine expands barely by 32 mm to words the front bearing and by 3mm towards the generator is steady state operation at full load with rated parameters. The turbine is equipped with a barring gear which rotates the rotor at 3.4 r.p.m.

Figure 1 and 2 present process flow chart of circulating water and air & flue gas system at the Kolaghat Thermal power plant.

6RUPNARAYAN RIVER

ACW/CW SUMPACW PUMPCW PUMPCONDENSERPOST TREATMENT

PLANTRESERVIORCOOLING TOWER

MAKE UP PUMP

RESERVIORINTAKE PUMP

Figure 1: Process Flow Chart of Circulating Water at Kolaghat Thermal Power Plant

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COOLING TOWER

(1,2&3)

PRE-TREATMENT

PLANT

COOLING TOWER

(1,2&3)

COOLING TOWER

(4,5&6)

FOR COOLING

OTHER

A

T

M

O

S

P

H

E

R

E

AIR PRE HEATER

CHIMNEY

ATMOSPHERE

PRIMARY

AIR FAN

F.D. FAN

Figure 2: Process Flow Chart of Air & Flue Gas System at Kolaghat Thermal Power Plant

The regenerative feed water heating is effected by heating the condensate in ejectors, two Nos. gland steam coolers, 4 Nos. L.P heaters, deaerator and 3 Nos HP Heaters Extracted steam from various points of the turbine is utilized to heat the condensate in these heaters.

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RURANCE

FLUE

COAL MILLPLATEN SH

RE-HEATER

FINAL SH

I.D FAN

LOW TEMP SH

E.S.P AIR PRE HEATER ECONOMISER

The condenser cooling water system is a closed cycle. Three Nos. 331/3% capacities C. W. pumps of 9000m1hr. Capacity provided for each unit take suction from the common C.W. basin and supply water to the twin condenser of each unit. The hot return water is taken to the cooling Tower of the unit consisting of eight Nos. of cell. After being cooled in the induced draught type cooling tower, the water is returned to the C.W. basin through a concrete tunnel. To make up the draft and evaporation losses, soft water is supplied from the water reservoir after treatment at pre and Post treatment Plant.

Six Nos. of Intake pumps of 4000M1/hr capacity each are provided in the intake pump located on the banks of river Rupnarayan. The pumps take suction from the river and discharge into the Midnapur high level canal from where water reservoir. From the reservoir the water is taken to the pretreatment plant by running C. T. make-up pumps. From pretreatment plant water to the post treatment plant and to the D. M. Plant which supplying dematerialized water to the unit as heat cycle make up and to Unit DMCW System. Post treatment plant supplies make up water to the cooling tower cold-water basin.

A close D. M. cooling water system has been envisaged for supplying cooling water to the bearings, oil coolers, water coolers etc., of the various auxiliaries and the generator hydrogen, seal oil and stator water coolers. Five Nos DMCW Pumps have been provided for each unit. Make up for the system is from DMCW make up tank. Two Nos DMSW pumps are used to supply D. M water from surge Tank to D. M Cooling water makeup tank.

The deep bore well pumps have been provided around the plant to supply water to the two Nos. clear water tanks near DM Plant. Clear Water may also be supplied to these Tanks from pre-treatment Plant.

The service water for miscellaneous services and drinking water supplied by three Nos. service water Pumps which take water from clear water Tanks. Two Nos. seal water Pumps have been provided to supply seal water to ash water Pump gland sealing and clinker grinder gland sealing. Four Nos. clear water Pumps also take suction from the same tanks for supply to the Dematerializing Plant.

The demineralisting plant consists of four chains. Each chain consisting, pressure sand filter, activated carbon filter, weak and strong cation unit, Anion Unit and Mixed Bed Unit supply high quality water to the steam cycle make up and to the make up to the closed cycle D. M. cooling system.

The compressed air required for various instruments are met by two nos Instruments Air Compressors for each unit. Two Nos Plants Air compressors are also provided for each unit for supply of service air, air to ash handing system, BOBR unloading system etc. Both the system is provided with air drying equipments.

The fly ash in the boils is collected in Electrostatic Precipitator located in the flue gas path between air heater and ID Fans. The bottom ash is collected in a water impounded hopper located at the bottom of the furnace. The fly ash removal is done by hydro-pneumatic system with the help of an air separator, hydro exhauster and dry ash transport lines, dust extraction valves etc. and the system is automatic sequentially operated. The bottom ash is removed by hydro-ejecting system, which utilizes high velocity water to remove the ash after being crushed by clinker grinders located below the bottom ash hopper.

The coal requirement of the 3 Units, about 8000 T/day, is met by coal handling plant. The coal in Box wagons is unloaded by 2 Nos. wagon Tipplers and BORR wagon are unloaded at Track Hopper. Transfer points of coal to bunkers is achieved by double route of coal Conveyors along with crushers, transfer points etc. (8000T/hr. capacity). Picker0boys have been engaged to separate stones, foreign materials etc. present in the coal before crusher and finally after crusher.

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Each 210MW generator is connected to 400KV grid through 250 MVA delta-star step-up transformers for Stage –II. For supply of auxiliary power for each unit auxiliaries, 2 Nos UTAS each of 16MVA capacity are connected to the outgoing bus of wach generator. SF-G breakers with isolators are provided to connect HV side of Generator – Transformer to the 400KV grid. To supply auxiliary power during start up, shut down or in case of unit auxiliary power failure, two nos Station. Auxiliary Transformers (SAT) each of 31.5MVA capacity are included in the system. These STTS also system of two Nos Inter Bus Transformers (IBTs). The inter Bus Transferors (315MVA) each are used to interconnect 400KV Bus of Stage – II with 220KV Bus of Stage – I and also supply 44KV power to SATs. There are two Auto Transformers (150MVA each which receive power from 220KV Bus and supply 132KV to 132KV Bus. At Stage – I there are two bus. Reserve Transformers (31.5 MVA each) which receive power from 132 KV and supply 6.6 power to Station Auxiliary Bus like stage – II SATs.

The 6.6 KVLV Output from Auxiliary transformers and reserve transformers are further stepped down to 415V through suitable transformers for feeding low voltage auxiliaries. For supplying necessary D. C. power for emergency drives, protections and interlock circuits, a 220V station D. C. System with battery and battery charger has been installed. Moreover, 3 Nos Diesel Generating set (1 MVA each) have been provided to supply 415 power to all power to all the six survival power.

For evacuation of 400KV power, Single jeered Feeder (capacity 600MW), single Talcher Feeder (capacity 600MW) and single Durgapur Feeder (not completed) of capacity 600MW have been provided. Foe Evacuation of 220KV power, double Howrah Feeder (180 MW each) have been provided. Double Kolaghat Feeder (90 MW each) and double Haldia Feeder (90MW each) are connected with 132KV Bus for evocation of Power. To increase the capacity of these Kolaghat &Haldia 132KV feeders, one more 220KV/132KV Auto Transformer (150MVA) has been proposed to be installed.

5.0 Methodology of Noise Measurements

Survey Techniques

Cirrus sound level meter, model 236 A, UK make sensitive to sound pressures between 20 and 20000 Hz was used to measure the noise level. Calibrated instrument was transported in a brief case containing sponge groove that protect from vibration and shock. The range and sensitivity of the instrument is 32-140 dB (A) with accuracy ± 5% [12] the noise level was recorded at a distance of 5-10 feet on the basis where cumulative noise was expected from different sources or at operator. Monitoring was done at a height of 1.5 m and 1m away from the chest for 30 mm at an interval of ‘15 5.

Principles of Leq

The short Leq (equivalent continuous sound level) concept was proposed by Komorn and Luquet.”3 Leq is the level which, if maintained constant for the same period as the measurement, would contain the same amount of energy as the fluctuating noise level. It is measured directly by an integrating averaging sound level meter. It is a linear integration over time. The formula used for Leq calculation is given below in the form it appears in the international standard IEC 804.

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T is the total measurement time. PA is the A-weighted instantaneous acoustic pressure. Po is the reference acoustic pressure (20 p PA). Leq is used as the basis for calculating L0 (day-night average sound level) LNP (noise pollution level).

Among A-weighting (ears response to sounds near the 40 dB level), B-weighting (near 10 dB), C-weighting (near 100 dB) D-weighting (jet plane noise)

Measuring scales, the A-weighting is the commonly used scale to measure steady sound levels.

5.1 Monitoring location

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Alter primary walk through the survey, 13 locations of plant area had been identified based on the maximum sound pressure for noise measurements. These locations are shown in Table 1 along with short description of the noise sources and the specific function of the noise source/machines.

These are: -- Besides the above major sources which contribute —80 % noise, the remaining noise might be attributed to the background noise generated from incoming /outgoing vehicles, servicing and repairing, minor construction, office work etc.

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Coal unloading plant-2

Coal crusher plant- 3

Compressor - 5

Boiler feed pump-7

Operator sitting place for boiler feed pump-I

Control room-4

Operator sitting place-2

Turbine -8

Boiler operating room-I

Boiler operator sitting place-I

E D. fan-8

I. D. fan-a

Operator sitting place of I. D. fan-6

D. M. plant-I

Cooling tower-I

Table 1: Monitoring Locations, Noise Sources and Particular Function of the Machines

6.0 Results and Discussions

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The observed noise levels recorded during survey work for different machines and locations are presented in Tables 2 and 3 respectively. SLM recorded noise in the form of Event Leq and Ln cycle. Ln cycle represents that N% of the time, the noise level was below the given value of X viz. Compressor No. 4: b-I represents that 4% of the measured time the noise level was above 100.6 dB (A) and L-99 represents that 99% of the measured time the noise level was below 86.2 dB (A) [Table 2]

Coal Unloading Plant

Among the two coal unloading plants, minimum Leq, 87.8 dB(A) was recorded near unloading plant-I and while the maximum Leq, 90.1 dB (A) was recorded near unloading plant- 2 with an log average Leq 89.10± 1.63 dB(A) [Table 2].

Coal Crusher Plant

The minimum Leq [85.8 dB (A)] was found at crusher plant-2 while the maximum Leq, 93.1 dB (A) was found near crusher plant-I. The log average.beq of crusher plants was 90.28±4.30 dB (A) which is higher than the prescribed standard of 90 dB (A) [Tables 2 and 4].

Compressor Noise

The minimum event Leq, 81 dB (A) was recorded near Compressor-3 and while the maximum event Leq, 93.6 dB (A) was recorded near compressor-I with log average Leq 90.54 ± 2.41 dB (A). All the compressors were producing noise level which touches the maximum permissible limit of 90 dB (A) for 8h. Especially compressor-I showed levels beyond the maximum permissible limit of 90 dB (A) for 8h /day [Table 2]. Compressors generated second highest log, average Leq 89.98 dB (A) noise level after the ED. Fan with log average Leq 95.91±6.45 dB (A) [Table 2]. These data do not fall in the safe zone for occupational environment; out of 5 compressors; 2 were producing beyond the permissiblelimit of 90 dB(A) [Table 4].

Boiler feed pump (BFP)

The minimum event beq, 81.5 dB (A) was recorded near 13FF- 5A and while the maximum event beq, 92.4 dB (A) was recorded at I3FP-313 with log average beq 89±1.16 dB (A) [Table 2]. All the I3FPs were producing noise level which touched the maximum permissible limit of 90 dB (A), especially; I3FF-313 showed beyond the maximum permissible limit of 90 dB (A) for 8h/day.

Turbine

The noise level found between 14.9-86.0 dB (A) with log average beq 83.44±3.82 dB (A). The lowest was measured for turbine No. 6 while highest for turbine No. 2 and 8. Turbine sound pressure is

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lesser than ED. fan, boiler feed pump but higher than I. D. fan and cooling tower. It produced almost equivalent sound pressure of DM plant and aerial rope way [Table 2].

F.D fan

The minimum event beq, 83.8 dB (A) was recorded for ED. fan No. IA and while the maximum event beq, 103 dB (A) was recorded for E D. Fan No. 6A. With log average beq 95.94 ±6.45 dB (A). E D. Fans were the noisiest one among the power plants. F D. Fan Nos. 2A, 3A, 4A, 5A, IA and 9A produced noise level of about 85.1, 95.8, 94.9, 88.6, 92.1 and 90.5 dB (A) respectively [Table 2].

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Table 2: Noise Levels dB (A) at Different Locations of a Thermal Power Plant

Source:

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Table 3: Noise Levels dB (A) at Different Locations of a Thermal Power Plant

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Table 4: Threshold Limit, Values for Non-Impulsive Noise (Adopted in 1970 by the American Conference of Governmental Industrial Hygienists)

Source: The Noise Pollution (Regulation & Control) Rules, 2000, Gazette of India vide SO 123(E), dated 14.2.1998 and subsequent amendment vide SO 1013 (E) dated 22.11.1998

I.D. fan

The minimum event Leq11.1 dB (A) was recorded for ID. Fan No. IA while the maximum event Leq, 83.8 dB (A) was recorded for I. D. fan No. 5A with log average Leq 81.11±2.22 dB (A). ID. fan is comparatively better than E D. fans in terms of noise level [Table 2].

D. M. plant, cooling tower and aerial rope way (Mono cable)

The level of noise of D.M. plant was 83.6 dB (A). The event Leq of cooling tower was 15.8 dB (A), which was quite calm with respect to others. At operator sitting place for cooling tower, the noise level was felt 13.5 dB (A). The noise level of aerial rope way (Mono cable) was 84.1 dB (A) [Table 2].

Operator sitting place (OSP) for boiler feed pump

The minimum event Leq, 81 dB (A) was recorded at OSP-5 and while the maximum event Leq, 94.8 dB (A) was recorded at OSP-1 with log average Leq 81.69±4.80 dB (A). All the noise levels measured in these places were 84 dB (A). The operator seated at OSP-1 position was exposed to noise level beyond the permissible limit of 90 dB (A) [Table 3].

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Control room

The noise level ranged between 61.9-12.5 dB (A) with log average Leq 90.31±4.93 dB (A). The least sound 61.9 dB (A) was felt at control room no. TG-5 while the maximum sound, 12.2 dB (A) at TG-8 [Table 3].

OSP for turbine, TG—3 and TG—4

The noise level range is between 83.1-83.2 dB (A) with log average Leq 83.15±0.01 dB (A). The least sound 83.1 dB (A) was felt at TG-4 while the maximum sound, 83.2 dB (A) at TG3 [Table 3].

Boiler operating room (BOR) and OSP

The minimum event Leq, 14.5 dB (A) was recorded at BOR No. 4 while the maximum event Leq, 81.4 dB (A) was recorded at BOR No. 3 with log average Leq 83.92± 4.30 dB (A). However, the noise level at operator sitting place was as high as 85.2 dB (A) [Table 3].

OSP for I. D. fan

The noise level varied from 11.2-82.3 dB (A) with log average Leq 80.34 dB (A). The minimum 11.2 dB (A) was found at OSPIA and maximum 82.3 dB (A) at OSP-9A [Table 3]. Descending order of Ln cycle is b-I> b-S >b-10> b-SO> b90 >b-95> b-99, Leq does not show any particular position in the LN cycle. There is a much fluctuation among locations and different machines and also among same machine like ID fans, FD fans and compressors etc. The overall noise was 10.31-95.91 dB (A) with log average 88.04 ±6.08 dB (A). Though it is below the prescribed standard but this level may be sufficient exposure to create a chronic health hazard problem after long exposure, since the subject exposed to high noise level may come out from the noise source after his duty hours but the physiological change and psychological stress occurred in his system. For the operator who is looking after the ED. fans, there is a fare chance of exposure to >90dB (A) noise. Forty one per cent of bus drivers suffered from noise-induced deafness) while 50% of the workers in an arrtunition factory had impaired hearing. Similarly high pavalence of hearing impairment was detected in the workers of a nitric acid plant.’ There is 80.6% prevalence of noise-induced hearing loss in the workers of petroleum industries.

However, there is no unsteady / impulse noise in the power plant which affect more adversely than steady noise. Indian noise standards are also high than the standards for other countries. For example, the working hours in Belgium, Denmark, France, Sweden and Soviet Union (Russia) are 40 h/week but in case of India there are six working days in a week, so the total exposure hours are 48h/week [Table 7]. Hence, revision of the standard is required at par with the international/ European standard

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7.0 Suggestions & Recommendations

Noise can be controlled by designing and fabricating new engines and by setting a noise limits at least 5-10 dB (A) below the prescribed standard.”6 Transmission control may be achieved by covering room walls with acoustic tiles as sound absorbers. Supply of earplug, earmuff and cotton! Woollen to its employees help in protecting exposed person. Preferably, shifting of duty from a particular equipment to another on alternate days. Normal duty hours can be reduced at high noise generating sources. Isolated cabin is required for operator where it is not available. Employees must be made aware and educated about noise nuisance through adequate publicity. The irregular use! Not use of safety measures are a common scenario in most of the industries where rules and regulations are liberal hence authority can make it mandatory to use one or other type of noise protective measures at noisy places.

Figure 3: A fabricated Engine

Sound Absorption treatment:

Where there is a high degree of reflection of sound waves, the reverberant component can dominate the noise field over a large part of work area. Introduction of an acoustically absorbent material in form of wall treatment (wall covered first with a thick layer of mineral wool and then with a polythene sheet) may reduce the reverberant component by upto 10 dB (A) and may not reduce the noise radiated directly by the source. Noise pollution should not be neglected since production in a factory depends on the individual health of the employees. Outer surfaces of control room should be covered with sound absorbent material e.g., glass wool covered with perforated aluminium sheet. Glass wool is of different

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types and has different density. Higher the density more is the absorbing capacity. This has practically been done in a research laboratory to reduce the noise level. However, glass wool has been banned in USA/E.U. for non-essential uses. Multiple wall construction with enclosed air spaces provides considerably more attenuation than the single-wall mass law would predict. The absorptivity or coefficient of sound absorption is equal to that percentage of the incident sound, which is not absorbed. Table 6 lists typical coefficient of absorption for some building materials. These hard materials absorb only a few percent of the sound striking them. They can be good sound barriers, since they do not allow the passage of air and can be stiff and massive enough to be effective.

Source: The Noise Pollution (Regulation & Control) Rules, 2000, Gazette of India vide SO 123(E), dated 14.2.2000 and subsequent amendment vide SO 1046 (E) dated 22.11.2000

Green Belt Design:

The plants act as a very good barrier for absorption of noise. The development of green belt in and around industrial complex/commercial and residential areas can act as noise barriers. They can reduce noise level by absorption by ground cover and tree foliage. A wide green belt of thick vegetation can be produced around the factory premises. This will absorb to a large extent and dissipate sound energy and thus act as buffer zone.241 A tree belt 50 m wide and of different height can reduce the noise level up to 20-30 dB(A).’12 GBD will reduce the noise intensity by creating obstruction in its transmission path. In addition, it can decrease substantial amount of the air pollution load. Vegetation plays a positive role for our eyesight potential and GBD also regulates the temperature through transpiration. GBD also purifies the atmosphere to a significant level by utilizing CO 2 produced in the power plant and releasing O 2 during photosynthesis and enhances the aesthetic beauty.

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8.0 ConclusionThis current investigation may help power plant authorities to adopt preventive measures and for deciding future strategies to combat the menace of noise pollution with scientific approach. This will ensure in providing better environment to the employees. Occupational health hazards have to be assessed by an expert agency, which also correlates noise pollution and health hazards. Science and technology have not reached up to the level by which soundless machine can be made but the preventive measures could be adopted for prevention, abatement and control of substantial amount of noise level.

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9.0 Reference

1. Chandra A, Chandra H. Environmental management for clean power generation of Thermal power plants: An Indian Perspective. Indian J Air Poll Contr 2003;7:22-36.

2. Lusk SL, Hagerty BM, Gillespie B, Caruso CC. Chronic effects of workplace noise on blood pressure and Heart rate. Arch Environ Health 2002;57 :273-8 1.

3. Crocker MJ, Price J. Noise and noise control. 18901. CRC Press mc: Cranwood Parkway, Cleveland, Ohio; 1975. p. 44128.

4. Singh AP, Rai RM, Bhatia MR. Effect of chronic and acute exposure to noise on physiological function in man. Tnt Arch Occup Environ Health 1982;50:169-74.

5. Staples SL. Human response to environmental noise. Am Psychol 19965 1:143-50.

6. NIOH. A preliminary study to enquire into the utility of temporary shift of hearing levels. Annual report. National Institute of Occupational Health: Ahmedabad; 1978. p. 136-43.

7. Glorig A. Non-auditory effects of noise exposure. sound and vibration, 27101. E. Oviatt: Ohio 1971. p. 44140.

8. Rau JG, Wooten DC. Environmental Impact analysis handbook. Mc Graw-Hill Book Company: New York, Tokyo; 1977.

9. Anticaglia JR. Noise measurement and acceptability criteria. In: the Industrial Environment its Evaluation and Control. US Dept. of Health and Human Services, Public Health Service, Centre for Disease Control, National Institute for Occupational Safety and Health: 1973. p. 309- 19.

10. Botsford J. Noise measurement and acceptability criteria. In: The Industrial Environment its Evaluation and Control, U. S. Dept. of Health and Human Services, Public Health Service, Centre for Disease Control, National Institute for Occupational Safety and Health: 1973.

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p. 3 21-31.

11. Kazi Rehan A. Noise induced hearing loss-an occupational hazard. Indian J Occup Env Med 2002;6:207-12.

12. Acoustic and Vibration measurement for industry. CRL 236 A operating manual, Cirrus Research Ltd., Acoustic House, Hunmanby: N. Yorkshire, United Kingdom; 1994. p. 1- 8.

13. Komorn A, Luquet P. Methodes de description objective d’un environment acoustique. Report to the EEC. LNE April 1979 and Internoise 1981.

14. Roberts HC. Noise pollution. In: Environmental engineers handbook. Liptak BG, editor. V-ITT Land pollution. Chilton Book Company: Radnor Pennsylvania; 1978.

15. Threshold Limit Values for noise, American Conference of Governmental Industrial Hygenists: Ohio; 1971.

16. Natu M, Solanki SR. Noise survey and effects on state transport bus drivers. Indian J Occup Hith 1977;20:195-200.

17. Chaddha SL, Singh TA. Survey of noise assessment and its effect on hearing of workers in ammunition factory. Indian J Indus Med 1977; 17:93-103.

18. Gupta BN, Sen RN, Singh H. Investigations in occupational hearing impairment noise in a nitric acid plant. Chief Advisor Factory Publication: Rep. No. 24; 1972.

19. Sinha YN. Occupational health problems in petroleum refmeries. Indian SafChr 1991;21:24-8.

20. Santra SC. Status of noise pollution studies in Calcutta and current state of legal measures for abatement. In: Proceeding of the National Workshop on Environmental Statistics, Goa, Central Statistical Organization, Department of Statistics. Ministry of Planning and Programme implementation. Government of India: New Delhi; 1998. p. 79-89.

21. Sharma PD. Environmental biology and toxicology. Rastogi and Company: Meerut, India; 1993.

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22. Michael PL. Physics of sound. In: The industrial environment: Its Evaluation and Control, U. S. Dept. of Health and Human Services, Public Health Service, Centre for Disease Control, National Institute for Occupational Safety and Health: 1973. p.321-31.

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