Nozzle noise

The system includes two heat exchangers which are automatically cleaned by special noise nozzles. Every second month we have to clean them more thoroughly with compressed air, which requires a couple of hours for two men. 

Flare stack sizing and pressure drop is included with considerations of pressure drop through the safety valve headers, blowdown drums, flare headers, seal drum, etc. Elevated flare tips incorporating various steam injection nozzle configurations are normally sized for a velocity of 120 m/s at maximum flow, as limited by excessive noise and the ability of manufacturers to design tips which will insure flame stability. This velocity is based on the inclusion of steam flow if injected internally, but the steam is not included if added through jets external to the main tip. 

Smokeless Steam Inspirating Air Coanda effect nozzles are used to inspirate air into the mixing chamber. Claim high efficiency of steam use. Claim low steam noise. Complex nozzles are a high-cost component. Brochure shows much R D back-up of basic design, in marked contrast to those of other vendors. Coanda effect is well understood and widely used, therefore working principle is well established. 

LVHV nozzles can create problems that may be sufficiently severe as to prevent their use, usually in the form of ergonomic encumbrances and excessive noise. These problems can be dealt with, to limited extents, and LVHV applications can be effective. It must also be understood that dust control by 1..VHV systems is ultimately limited. No ventilation control measure can ensure sufficient worker protection down to extraordinatily low acceptable dust levels. Worker protection must always be confirmed by industrial hygiene monitoring and evaluation, and administrative control measures such as respiratory protection may be necessary. 

FIGURE 10.26 Noise characteristics for experimental LVHV exhaust nozzles,... 

Figure 10.26 also presents comparisons of nozzle noise potentials, two-dimensional plots of constant noise (dBA) levels in proximity to the experimental LVHV nozzles. Noise potentials for a plain circular nozzle,... 

Consider nozzle noise levels and control measures. 

Continuous, surface blowdown arrangements employ a multistage nozzle valve that permits the BW to expand and flash gradually and safely across each successive orifice and chamber with almost no noise. This effect reduces the flow velocity and virtually eliminates the risk of wire drawing. The BD valve is provided with a regulating lever and calibrated dial (or an electric actuator) for either manual or automatic BD rate adjustment. Continuous blowdown arrangements are entirely suitable for incorporation into FSHR systems. They are commonly employed for WT boilers. 

Flare noise (roar of combustion) is the most serious because it is elevated and the sound carries. The flare can be located at a remote distance from the operating unit or surrounding community. Noise of steam injection into the burner can be reduced by using multiple nozzles. Furnace noise from air intake, fuel systems, and combustion blower forced draft/induced draft (FD/ID) fans can be reduced by acoustics. The plot plan should be evaluated for noise generation and to find the means of alleviating or moving noise to a less sensitive area. 

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