Suzhou Southern pump dialysis "pump" how to do the noise, mechanical noise from the vibration of the parts or surface, they produce adjacent media in the sound pressure fluctuations. Such as pistons, rotating unbalanced vibrations, and vibrating tube walls.
In positive displacement pumps, the noise is generally related to the pump speed and the number of pistons in the pump. Liquid pulsations are the major mechanical induced noise which, on the other hand, can also stimulate the mechanical vibrations of pump and line system components. Incorrect crankshaft counterbalances also vibrate at speed, which may loosen the anchor bolts and create a base or rail flapping sound. Other noise is related to wear of the connecting rod, worn piston pin or piston rapping noise. In centrifugal pumps, improperly installed couplings often generate noise (misalignment) at twice the pump speed. If the pump speed approaches or passes the critical speed, then noises can be generated due to high vibrations caused by imbalance or by bearing, seal or impeller wear. In the event of wear, it may be characterized by high-pitched howls. Motor noise, shaft keys, and coupling bolts may cause clearance noise. Liquid noise sources When pressure fluctuations occur directly from liquid movement, the noise source is proportionate to hydrodynamic forces. Possible sources of fluid power include turbulence, fluid separation (vortex conditions), cavitation, water hammering, flashing and the interaction of the impeller with the pump divergence. The resulting pressure and flow pulsations may not be periodic in frequency, broadband, and generally may stimulate mechanical vibrations of the line or pump itself. Then, mechanical vibration can spread the noise to the environment. In general, there are four types of pulsating sources within a liquid pump: (1) discrete frequency components produced by the pump impeller or piston (2) wide-band turbulence energy caused by high velocities (3) caused by cavitation, flash evaporation and water hammer Intermittent oscillations of broadband noise constitute impact noise. (4) Flow-induced pulsations caused by periodic vortexes may produce secondary fluctuations in pressure within the centrifugal pump as it flows through the side branches of the obstruction and pipeline system Flow spectrum changes. This is especially true when operating at off-design traffic. The numbers shown on the streamline are the positioning of the following flow process principles: Most of these unsteady flow patterns create vortices due to the interaction of the boundary layer between the high and low velocity zones in the flow field, for example due to the fluid around the obstacle The flow is either caused by the dead zone or caused by bidirectional flow. When these vortices impact the side wall, vortices, ie, vortices, translate to pressure fluctuations and can cause local oscillations of the tubing or pump components. Audible response of the pipeline system may strongly influence the frequency and amplitude of eddy current diffusion. Research has shown that eddy currents are the most intense when the systematic sounding is consistent with the natural or prevalent occurrence of noise sources. When a centrifugal pump is operated at a flow rate that is less than or greater than the best efficiency, it is common to hear noise around the pump housing. The level and frequency of this noise vary from pump to pump, depending on the level of pressure head at that pump, the required NPSH and the available NPSH ratio, and the degree to which the pump flow deviates from the ideal flow. Noise often occurs when the angle of the inlet guide vanes, impeller and housing (or diffuser) are not suitable for the actual flow rate. In addition, the main source of such noise is also considered to be recycled. (Welcome attention WeChat: Pump Friends ring) Before the liquid flows through the centrifugal pump is pressurized, the liquid must pass a pressure not greater than the existing pressure within the inlet pipe area. This is due in part to the accelerating effect of the liquid entering the impeller entry, also due to the separation of the airflow from the impeller entry vanes. If the V flow exceeds the design flow, and the accompanying blade angle is incorrect, a high speed, low pressure vortex will be formed. If the liquid pressure drops to the vapor pressure, the liquid gas flashes. The pressure in the channel will increase later. The ensuing implosion causes what is commonly called cavitation noise. In general, cavitation cracks on the non-confined side of the impeller blades cause serious damage (blade erosion) in addition to noise. At cavitation, the noise level measured on a 8000hp (5970kW) pump housing near the inlet line. Cavitation produces wide-band impacts that can excite many frequencies; however, in this case, the blade common frequency (number of impeller blades revolutions per second) and its multiples dominates. This type of cavitation noise usually produces very high frequency noise, best called "pop noise." Cavitation noise may also be heard at flows less than the design conditions, even when the available inlet NPSH exceeds the pump required NPSH, which is a baffling problem. The explanation proposed by Fraser that this very low frequency of irregular but high-intensity noise stems from the impeller inlet or impeller outlet, or two backflow, and each centrifugal pump in a decline in traffic conditions This recycling occurs. Operating under recirculation conditions compromises the pressure-bearing side of the impeller blade inlet and outlet (also for the casing guide vanes). Impact noise, irregular noise loudness increases, as well as the inlet and outlet pressure pulsation increases as the flow rate decreases can be used as proof of recirculation. Pressure auto-regulators or flow control valves can generate noise related to both turbulence and airflow separation. When these valves operate at severe pressure drops, they have high flow rates that produce significant turbulence. Although the resulting noise spectrum is very broad-band, it is characterized by a frequency centered around a corresponding Strouhal number of about 0.2. Cavitation and Flashing For many liquid pumping systems, there is typically some degree of flashness and cavitation associated with pressure control valves in the pump or delivery system. High flow rates create more severe cavitation due to greater flow losses through throttling. At the suction line of a positive displacement pump, the piston may generate high amplitude pulsations and be accentuated by the system's acoustic performance and cause the dynamic pressure to periodically reach the vaporization pressure of the liquid, even though the suction port static pressure may be greater than this pressure. As the cycle pressure increases, the bubble breaks, creating noise and impacting the system, and this can lead to corrosion as well as annoying noise. It is especially common for hot water systems (feed pump systems) to flash when hot, pressurized water is reduced in pressure by throttling (eg, flow control valves). This pressure reduction causes the liquid to suddenly vaporize, ie flash, resulting in cavitation-like noise. In order to avoid post-throttling flash phenomenon, adequate back pressure should be provided. On the other hand, the end of the pipeline should be throttled so that the flash energy is dispersed into a larger space.
【Print】 【Close】
