Power Plant Engineering

(4) 2-T Oil for Two Stroke Engines. From 1.04.99, on the recommendations of CPCB, the low
smoke 2T oil became effective. To prevent the use of 2T oil in excess of the required quantity premixed
2T oil dispensers have been installed in all the petrol filling stations. Sale of loose 2T oil has also been
banned from Dec. 1998.
(5) Phasing out of Grossly Polluting Vehicles. On CPCB’s recommendations initially 20 yr. old
vehicles were prohibited from plying from Dec.1998, followed by phasing out of 17 yr. old vehicles
from Nov. 1998 and 15 yr. old from Dec. 1998.
13.7 NOISE POLLLUTION AND ITS CONTROL
Of late, noise has been recognized as a pollutant which until recently was considered only as a
nuisance. The Central Pollution Control Board (CPCB) has notified the ambient noise standards in 1987
under section 20 of the Air (Prevention and Control of Pollution) Act, 1981. The noise standards specify
limits as 55dBA and 45dBA as limits for day and night time respectively for residential areas, 75 dBA
and 70dBA in the day and night time for industrial areas, and 50 dBA and 40 dBA in the day and night
for silence zones. Special campaign for reduction in use of fire crackers in Delhi have resulted in re-
duced pollution levels during Diwali in 1999.
The creation of noise creates the pollution by increasing the sound level of the atmosphere. It is
estimated that the environmental sound level is doubling in loudness after every 10 years. The increase
in sound level of the atmosphere is not the major problem presently but desirable sound level is essential
in power plants and every step should be taken to reduce the sound level of the power plants to a
tolerable level.
Heavy noise environment has extremely unpleasant effects on
people exposed to them. Continuous exposure to noise level above
100 dBA has adverse effect on hearing ability within a short time.
Therefore, in world energy conference of 1971, a study of noise sup-
pression in thermal power plants occupied a major percentage of the,
seminars conducted.
The main sources of noise in a power plant are turbo-alterna-
tors, fans and power transformers. The simple sound proofing system
consists of adequate insulation of the turbine, body and piping, with a
dashpot on the air-inlet to the fans. A moderate treatment includes a
complete casing for turbo-alternator. An intensive treatment includes
building around the turbine group and fans and complete sound-proof-
ing of the transformers and switch gears.
The tolerable sound level and time of exposure are equally important in the design of allowable
noise level in power plant. The working hours of the worker must be reduced in a highly noised area.
9
7
5
3
1
1
2
1
4 
90
95
100
105
110 115
E
x
pos
ur
e t
im
e
in hr
s
/day
Noise level in db