Ventilation noise enclosures

Design controls that could be used, such as isolation, enclosure, ventilation, noise, or radiation barriers. 

Other considerations are (I) proper ventilation and discharge enclosures, (2) provision for relief of internal explosion, (3) vibration isolation (shock mounts), (4) remote operation of charge and discharge, (5) noise during operation. 

In addition, they are usually constructed without isolation valves on the fuel supply lines. As a result the final connection in the pipework cannot be leak-tested. In practice, it is tested as far as possible at the manufacturer s works but often not leak-tested on-site. Reference 32 reviews the fuel leaks that have occurred, including a major explosion at a CCGT plant in England in 1996 due to the explosion of a leak of naphtha from a pipe joint. One man was seriously injured, and a 600-m chamber was lifted off its foundations. The reference also reviews the precautions that should be taken. They include. selecting a site where noise reduction is not required or can be achieved w ithout enclosure. If enclosure is essential, then a high ventilation rate is needed it is often designed to keep the turbine cool and is far too low to disperse gas leaks. Care must be taken to avoid stagnant pockets. 

Enclosure, isolation, separation, or other controls for hazardous sources (noise, gaseous or particulate contaminants, etc.) Exhaust ventilation, hoods, or cabinets for hazardous contaminants. 

Ver, Istvan L., and Leo L. Beranek, eds. Noise and Vibration Control En neering Principles and AppUcor tions. 2d ed. Hoboken, N.J. John Wiley Sons, 2006. Details sound absorption, passive silencers, enclosures, vibration isolation and damping, machinery and heating, ventilation, and air-conditioning (HVAC) noise control, and active noise suppression. 

Enclosures which give an attenuation of between 10 and 30dBA are the most satisfactory solution since they will control both the direct field and reverberant field noise components. In enclosing any source, the provision of adequate ventilation, access and maintenance facilities must be considered. A typical enclosure construction is shown in Figure 20. W. The main features are an outer heavy wall with an inner lining of an acoustically absorbent material to minimise reverberant build-up inside the enclosure. An inner mesh or perforate panel may be used to minimise mechanical damage. 

Compressors, pumps Vibration-isolated mounting in enclosed soundproofed rooms. Machines preferably separated from one another by partitions or with individual enclosures. Ventilation or air intake openings of such rooms should have louvred sound attenuators. Intake and outlet silencers for the compressors. Pressure pipelines to have sound-damping expansion joints and acoustically sealed wall inlets. Pressure release pipelines to have silencers. Additional sound insulation for compressed air pipelines to suppress rushing noises. Sound-insulated enclosed portable compressors represent the current "state of the art" for use in quarrying operations. 

Mills Acoustic enclosure of the mill shell obstructs heat dissipation and makes inspection difficult, i. e., is not satisfactory. Boltless liner plates on rubber backing, or rubber liners, do not sufficiently reduce noise emission. A commonly employed and generally satisfactory solution is as follows Whole grinding plant with all its noise sources (mill, drive, air separator, conveyors, elevators, filters, etc.) accommodated in a closed sound-insulated building with central control room for operators and with additional ventilation (see Funke, 1969 and 1973, Techn. Merkblatt, Bundesverband der Deutschen Kalkindustrie, 1975). 

Machinery enclosures Walls of acoustic enclosures should consist of heavy but flexible panels lined internally with sound-absorbing material. Adequate ventilation, demountability of the enclosure for repairs, and arrangements for operating and/or observing the machine to be provided. If hot gas fans are acoustically enclosed, the surface of the fan casing should additionally be heat-insulated. For information on design and performance of enclosures for noise control see VDI2711. 

Electric motors Motors with low speeds are preferable. Big motors to be water-cooled rather than air-cooled. Direct drive by four-pole or variable-speed motors. Choose motor types with low noise emission. Fan blading to have irregular pitch. If necessary, motor enclosure to be provided with special silenced ventilation. Internal combustion engines (e.g., for driving quarry machinery) Exhaust noise can be reduced by using amply dimensioned absorption and reflection silencers. Enclosure of the engine with ventilation system equipped with inlet and outlet silencers and ducts lined with sound-absorbing material (see Funke, 1977). 

The outer frame is a simple fabricated enclosure that supports either the air inlets and silencers if the unit is open-ventilated (Fig. 6.33) or the roof and cooler enclosure if the unit is totally enclosed water-to-air-cooled. The outer frame further acts as an air guide to complete the ventilation paths, and as a sonndproof enclosure to keep noise levels low. Since the rotor is pedestal mounted, the end shields are very simple structures. As with the inner frame, the outer frame is designed to be free of resonances in the range of operating frequencies. 

---