Noise rotational

This research examines the feasibility of a technique based upon the CT principle using a microfocus X-ray source with an image intensifier while the examined object is being rotated The attainable enlargement is up to 200. The data to be processed is collected from the whole surface of the image intensifier by a frame grabber and noise suppression is performed. 

Uses. In architectural and industrial appHcations vibrational isolators are used to reduce transmission of vibration into building stmctures from rotating or reciprocating machinery, such as ventilating fans, pumps, chillers, industrial machinery, and the piping and ductwork coimected to this equipment (6). Vibration isolators also can be used to isolate vibration-sensitive equipment or noise-sensitive areas from sources of vibration. Examples are special pneumatic isolators to protect electron microscopes, and isolators used to support floating concrete floors in recording studios. 

Most rotating equipment includes electric motors or steam dryers that generate noise at a constant frequency. Air cooler fans are a source of noise that can be reduced by lowering the fan speed and increasing the number of blades. Pump motor noise can be reduced by including a shroud or fan cover that is accurately lined. Centrifugal compressor noise reduction can be achieved by blade design and the use of compressor pulsation noise reduction, silencers, and vibration isolation. 

ISO 1680-1, Acoustics - Test code for the measurement of airborne noise emitted by rotating electrical machinery... 

Guidelines on t ualily management and quality system elements Test code for the measurement of airborne noise emitted by rotating electrical machines Engineering method for free field conditions over a reflecting plane Survey method Determination of sound power levels of noise sources 14004/1991 BS EN ISO 9004/1994-1/1994 BS 7458-1/1991 BS 7458-2/1991 B.S 4196 9004/1987 1680-1/1986 1680-2/1986. 3740... 

Improved rotor dynamic stability. The active magnetic bearing s ability to vary stiffness and damping permits rotation about the rotor s inertial axis, eliminating vibration and noise. 

The movement of large volumes of cooling air is accomplished by the rotation of large diameter fan blades rotating at high speeds. As a result, noise due to air mrbulence and high fan tip speed is generated. 

The primary limitation of a HAZOP study is the length of time required to perform it. Because the study is designed to provide a complete analysis, study sessions can be intensive and lii ing. HAZOP studies typically do not look at occupational hazards (e.g., electrical equipment, rotating equipment, hot surfaces) or chronic hazards (e.g., chronic chemical exposure, noise, heat stress). For experience with HAZOP see Swann (1995). 

Ventilation noise originates primarily from fans and the air turbulence generated inside ducts and around supply air and exhaust air terminal devices. The appearance of the noise is, of course, affected by factors such as the speed of rotation and the power of the fan, and by how the fan is stabilized or in other ways acoustically insulated. The noise level and the frequency characteristics are also largely derermined by the velocity of the air inside ducts and around terminal devices, where factors such as the dimensions and appearance of the ducts and terminal devices may play a decisive role in the appearance of the noise. 

Systematic studies have been carried out for the purpose of studying how low-frequency tones, broad-band components, and/or time fluctuations in ventilation noise interfere w ith disturbance reactions, In one of these studies, the respondents were exposed to ventilation noise that is representative of the noise encountered in office premises. The respondents were asked to use a rotating potentiometer to set the most acceptable noise level and the least acceptable noise level for each noise, taking account of comfort, disturbance, and performance, w hile performing their work at the same time. The noise level was maintained at a constant level of 40 d.B(A). 

Fan laws The equations that describe the relationship between fan flow rate, pressure, density, power, size, rotation speed, and noise levels. 

Sound rating The manufacturer s rating of the noise level produced by an item of rotating or reciprocating plant. 

The siting, as well as the selection of type of tower, can be critical. Rotating the tower, shielding the motor, use of baffles can all help in meeting environmental noise requirements. If in doubt, consult your cooling tower designer. 

The spur gear is the least expensive of all gears to manufacture and is the most commonly used. It can be manufactured to close tolerances and is used to connect parallel shafts that rotate in opposite directions. It gives excellent results at moderate peripheral speeds and the tooth load produces no axial thrust. Because contact is simultaneous across the entire width of the meshing teeth, it tends to be noisy at high speeds. However, noise and wear can be minimized with proper lubrication. 

Turbulent or unbalanced media flow (i.e., aerodynamic or hydraulic instability) does not have the same quadratic impacts on the vibration profile as that of load change, but it increases the overall vibration energy. This generates a unique profile that can be used to quantify the level of instability present in the machine. The profile generated by unbalanced flow is visible at the vane or blade-pass frequency of the rotating element. In addition, the profile shows a marked increase in the random noise generated by the flow of gas or liquid through the machine. 

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