1. Noise and Noise Propagation

  2. The Noise Producers

    • Engines

    • Compressors

    • Expanders &Turbines

    • Aerial Coolers

    • Piping

    • Flares

  3. Tonal Characteristics

  4. Attenuation Techniques

    • Silencers

    • Berms and Dykes

    • Source Treatment

    • Variable Speed Drives (VSD)

    • The Stack Induced Draft Air Cooler (SIOAC)

  5. Recommendations - Designing for a Quiet Plant

Gas Plant Environmental Noise

In September 1988 the Energy Resources Conservation Board (ERCB) whichregulates the Alberta Oil and Gas Industry tightened its environmental noiseguidelines by a factor X10. New nighttime maximum permissible noise levels aslow as 40dBA are now enforceable in rural areas. The directive is retroactivelyapplicable upon residential complaints and necessitated the use of radicalinnovations for industry to comply. Aerial coolers contribute substantially toplant noise and this paper discusses abatement in general and two novelapproaches taken by Amoco in particular. The use of variable speed fan drivesand stack induced draft coolers are examined in detail.

Noise and Noise Propagation
The Parameters

Noise is measured on the decibel scale (dB). There are two distinct commonreference scales, the Sound Power Level, which is base referenced to10−12 Watts and Sound Pressure Level, which is base referenced to 2 × 10−5 N/m2. Decibelsthemselves are in effect only a logarithmic ratio with no absolute meaningwithout these reference bases. Every 10dB increase represents a X10 foldincrease. Therefore, 20dB represents a x100 fold and 30dB a x1000 fold increaseetc.

To distinguish between Sound Power and Sound Pressure Levels, consider thata given piece of equipment (e.g. compressor) in the steady state generates afixed Sound Power Level but that the microphone and human ear respond to Sound Pressure Leve1 which decreases (as roughly the square of distance) as thereceptor moves away from the noise source.

Figure 1 lists a whole range of commonly heard noises and their approximatesound pressure levels. Figure 2 shows the logarithmic nature of decibels. Notethat only ±3dB represents a doubling/halving of sound level regardless of theabsolute decibel level.

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