Assessment and control design for steam vent noise in an oil refinery.
BACKGROUND
Noise is one of the most important harmful agents in work environment. Noise pollution in oil refinery industries is related to workers' health. This study aimed to determine the overall noise pollution of an oil refinery operation and its frequency analysis to determine the control plan for a vent noise in these industries.


METHODS
This experimental study performed in control unit of Tehran Oil Refinery in 2008. To determine the noise distributions, environmental noise measurements were carried out by lattice method according to basic information and technical process.  The sound pressure level and frequency distribution was measured for each study sources subject separately was performed individually. According to the vent's specification, the measured steam noise characteristics reviewed and compared to the theoretical results of steam noise estimation. Eventually, a double expansion muffler was designed. Data analysis and graphical design were carried out using Excel software.


RESULTS
The results of environmental noise measurements indicated that the level of sound pressure was above the national permitted level (85 dB (A)).  The Mean level of sound pressure of the studied steam jet was 90.3 dB (L). The results of noise frequency analysis for the steam vents showed that the dominant frequency was 4000 Hz. To obtain 17 dB noise reductions, a double chamber aluminum muffler with 500 mm length and 200 mm diameter consisting pipe drilled was designed.


CONCLUSIONS
The characteristics of steam vent noise were separated from other sources, a double expansion muffler was designed using a new method based on the level of steam noise, and principle sound frequency, a double expansion muffler was designed.
Department of Occupational Hygiene, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
Mohammad Reza
MR
Monazzam
Rostam
R
Golmohammadi
Maryam
M
Nourollahi
Samaneh
S
Momen Bellah Fard