Noise emission

Noise can constitute a danger to health, and therefore adequate precautions must be taken to protect personnel who are required to be in such an environment. The Health and Safety at Work, etc. Act 1974 has the power to control noise emissions, but the subject is complex. If it is anticipated that noise will exceed acceptable levels then... 

Noise emission control is another area where the application of electronics goes hand in hand with environment protection. Special electronic circuits on DC motors ensure that the noise level can be reduced at the source rather than through costly insulation. 

Does the organisation seriously address the subject of noise emissions Does the organisation maintain valid training certificates proving that personnel are trained regularly in the handling of hazardous materials ... 

Lower capital and operating costs, up to 50% less than traditional dehumidifiers low-pressure drops low noise emissions [47] Water deoxygenation and carbonation carried out simultaneously in the same device lower capital cost and CO2 consumption over 10 times reduction in size [5]... 

External verification carried out by Arthur D. Little. Random inspections of six sites in different countries (two visited, four by telephone) to assess the completeness of the methods of recording data, and consistency during transfer for consolidation. Bayer has implemented their recommendations from the last validation. 1999 recommendations are to improve information flow within Bayer, to include noise emissions in the questionnaire, and to compile data on below-ground information in more detail. 

But how different can the Vl and Vn scans be In fact, the above two equations have inspired a rather misleading statement often found in related literature — if the noise emission is predominantly DM, the Vl and Vn scans will look almost the same. The scans also look identical if the noise is predominantly CM. And if the Vl and Vn scans look very different, that implies that both CM and DM emissions are present. However, in the case of an off-line power supply, this statement is clearly not true. Because, that would imply that somehow the emissions on the L and N lines are different. However, we know that in any typical off-line power supply (with an input bridge rectifier), the L and N lines are... 

Let us see what all this nets us. Suppose by suitable design we have achieved compliance at the lowest frequency. So, if the switching frequency is less than 150 kHz, that would mean that we have about 2 mV (66 dBpV) of noise emissions at 150 kHz (see Table 9-1). Now let us go in the reverse direction that is, from low frequency to high frequency. This is what happens (see Figure 14-8) ... 

Noise emissions from gas-turbine engines, resulting from unsteady flow interactions with rigid and moving surfaces (compressor and diffuser noise) and from combustion (core noise), must also be reduced without sacrificing performance. Studies addressing simultaneous pollutant and noise emission reductions are rare. The current study may lead to a better understanding of the coupled acoustic and pollutant behavior of advanced combustor concepts. 

Swirling flows are inherently three dimensional. The authors current PIV system measures only two velocity components. A newly acquired stereoscopic PIV system will be used to characterize the 3D flowfield. In addition, pollutant characteristics of high-pressure partially-premixed swirling flames will also be obtained. Together with the PIV velocity and acoustic measurements, a full characterization of both pollutant and noise emissions from such flames will be achieved. It is believed that this will help improve the fundamental understanding of these types of emissions from modern gas-turbine combustors and will provide a valuable database for validating LES models. 

A combined experimental and computational research program investigating the role of partial premixing and swirl on pollutant and noise emissions from aeropropulsion gas-turbine engines is being performed by Frankel and his coworkers at Purdue University (Chapter 1). The diagnostics include PIV, microphone arrays, and gas analyzers in multiswirl and trapped-vortex combustors. 

Test flare at John Zink test site in Tulsa. Combustion of identical fuel flow rates with different degrees of mixing. Total noise emissions of the flame in the left picture are about 5 dB higher than for the flame in the right picture. 

A central problem of the approach described above certainly lies in applying it to a whole flare system instead of the combustion process alone. Doing so means that TAB becomes a "lumped parameter" incorporating all effects that have an impact on the acoustical behavior of the flare (i.e., noise emissions from valves, injectors, smoke suppression devices etc.) as well as any noise control measures installed. Other... 

Another problem with using the TAB concept to predict combustion noise is that it does not take the frequency characteristics of the noise emissions into account. Frequency characteristics are very important for the design of adequate noise control measures and will also determine the human perception of the noise emissions since the ear s sensitivity for noise is frequency-dependent (see Section 8.1). 

In summary, it can be concluded that the TAB concept applied to flare systems will usually only allow a very rough estimate of the actual noise emissions and the associated effect of these emissions on persons in the neighborhood of the flare. In some cases, the results can even be completely off the real situation. A key issue in developing reliable noise prediction tools for flares fhaf are more generally applicable in a broad range of operating conditions lies in a proper treatment of fhe individual sources that contribute to the overall noise emissions of a flare system. 

The following individual sound sources can contribute to the overall noise emissions of flares ... 

In such cases, enclosed flares may provide one solution. Enclosed flares are designed to completely hide a flare flame in order to reduce noise and thermal radiation levels. The design of these flare systems typically consist of an insulated enclosure with a wind fence around the perimeter as shown in the photograph in Figure 8.28. These types of flares can substantially reduce noise emissions as compared to open elevated flares. 

Example for the noise emissions of a steam control valve of a steam-assisted elevated flare. A-weighted sound power level L , as in Figure 8.32 of the flare with standard control valve and uninsulated piping and with low noise valve and acoustically insulated steam pipes. 

Figure 8.36 shows an example for the noise emissions of a steam control valve located at the base of a... 

Noise emission level dB(A) level measured at a specified distance and direction from a noise source, in an open environment, above a specified type of surface. Generally follows the recommendation of a national or industry standard. 

Miiller-BBM GmbH. "Noise Emissions of Different Flare Systems—Field Measurements Taken in Various Refineries and Petrochemical Plants." Proprietary data, 1900-2004. 

Verein Deutscher Ingenieure. "VDI 3732—Characteristic Noise Emission Values of Technical Sound Sources— Flares." VDI guideline, 1999. 

Noise emissions are becoming increasingly important. With some refineries located near populated areas, it is important to keep noise to a minimum. Burner testing is usually conducted on a single burner and noise emissions are usually measured at a distance of approximately three feet from the burner air inlet. Data collected during the test includes an overall A-weighted sound pressure level and the sound level at each octave... 

The unique features of HiTAC flames are now provided. Specifically we provide information on the flame stability, thermal field uniformity, NO, and noise emission levels. For other benefits, the reader is referred to the only book available on the subject. High Temperature Air Combustion From Energy Conservation to Pollution Reduction [8]. 

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