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It is shown that the vibration transfer and working medium pressure pulsations through vibration-isolating pipeline junctions of various plants may increase by two or three orders of magnitude with an increase in the vibration frequency and in the presence of incompressible working fluid. The results of research of the found physical models that determine this phenomenon are presented. The experimental results for a spatial three-component broadband active vibration-protection system (AVS) for vibration damping beyond the vibration isolation junction with liquid are considered. An experimental plant scheme for studying the simultaneous spatial active damping of dynamic forces, vibrations and pressure pulsations downstream from the junction has been given. Calculated dependences of the maximum efficiency of considered AVS on frequency are obtained. Efficient active damping of forces is shown to be attainable in an open loop without feedback. While damping in an open loop at the experimental plant, the efficiency of active damping of dynamic forces is obtained in three directions up to 10 dB or more in the frequency range from 5 to 800 Hz (more than seven octaves). The analysis of scientific publications reveals the uniqueness of this result. In this case, there are no zones of negative efficiency outside the active damping frequency range, which appear while using other methods of active damping. [ABSTRACT FROM AUTHOR]

Airborne noise (AN) levels were measured at workshops in the premises of boiler and turbine compartments (BTCs) of the Mosénergo heating and power plants (HPPs) for T-250/300-240 turbine units and their auxiliary equipment, and the results were analyzed. During the simultaneous operation of the equipment, the primary sources of elevated AN levels were identified. Despite the apparent popularity, simplicity, and extent of examination of the problem, it is yet to be resolved at thermal power plants (TPPs), although the primary sources of noise at TPPs and means of controlling them have long been known and detailed in the literature. An important result inferred from the measurements and their analysis was the absence of a completely diffused AN field in the BTC premises. This enabled us to establish the locations of the sources of elevated AN levels (e.g., location of the brush assembly of a generator exciter), and it suggested that the installation of local soundproof casings can provide necessary reduction in AN levels. Further, it indicated that possible solutions for reducing noise at the BTC workshops of HPP include the improvement of sound proofing and absorption utilizing new, highly effective scientific and technical developments. Particularly, the issue can be mitigated by employing a new, low-frequency, heavy rubber coating. The data and recommendations obtained for the T-250/300-240 turbine units can be used for other types of turbine units at Russian TPPs with similar equipment. [ABSTRACT FROM AUTHOR]