Spatial Active Damping of Vibrations, Vibration Forces, and Pressure Fluctuations Transferred via Expansion Joints in Liquid-Filled Pipelines

An analysis from the results of investigation into spatial active damping of pressure fluctuations, vibrations, and vibration forces transferred from power facilities via expansion joints in their piping is presented. Vibration transfer from power facilities via piping can be several orders of magnitude greater than along the support structures. This fact should be kept in mind in designing vibration isolation of power equipment from the foundation and the environment through pipelines in the power and transport engineering, shipbuilding, and in oil and gas pipelines in pumping stations. To reduce the transfer of vibrations via a pipeline by means of vibration-isolating expansion joints, it is necessary to decrease their structural stiffness and the forces induced by fluctuations of the working fluid pressure in an expansion joint in a wide frequency band using structural or active methods. A review of the available publications has not revealed, except for the studies performed within the scope of this investigation, any analysis of the interaction between the fluid fluctuations and vibration in the expansion joints or information on reducing the transfer of vibrations and pressure fluctuations via expansion joints in liquid-carrying pipelines. The effectiveness of various multichannel spatial active vibration protection systems whose feedback circuit includes regulators in the form of standard band-pass filters has been studied experimentally. The effect that the interaction of active vibration force damping channels has on the damping efficiency, which may be caused by the cross sensitivity of three-component vibration force sensors during damping of the vibration forces, has been revealed. The active spatial vibration damping of a pipeline downstream of the expansion joint has also demonstrated the interaction of active vibration damping channels resulting in a noticeable change in the damping effectiveness. The effectiveness of the investigated options varied from 10 to 32 dB (reducing fluctuations, transfer of vibration, and forces transmission by 3–30 times) both at individual frequencies and in frequency bands in the range between 10 and 500 Hz.