On abnormal noise of chemical plant and abnormal n

Brief introduction to abnormal noise and vibration in chemical plants -- abnormal noise of rotating equipment (2)

1 Compressor

the noise of the compressor is mainly composed of the aerodynamic noise of the main machine and the mechanical noise of the auxiliary machine. Generally, the noise measured at ordinary times is 84~102db. When the compressor starts to surge, it will periodically emit a deep and roaring noise every few seconds. At this time, the compressor has been running in an unstable state, the rotor slides back and forth between the bearings, and presses the thrust bearing. This horizontal movement of the rotor will inevitably damage the shaft seals and bearings of the compressor that meet the packaging requirements of various products on the market. Each surge indicates that the rotor slides between the bearings again. The higher the sound of this surge, the stronger the effect of the rotor in the horizontal direction and the greater the harm, which will lead to the complete self destruction of the compressor from light surge. Generally speaking, a machine rotating at 3000r/min is more anti surge than 8000r/min

causes and remedies for wheezing: ① in order to replace the diseased vitreous body and treat the detachment of the optic membrane, people use a variety of substitutes, such as air, normal saline, human aqueous humor, silicone oil, sodium hyaluronate, collagen, heterogeneous vitreous body, etc. to fill the vitreous body, but the treatment effect is not satisfactory, and the pressure is too high. Vent the receiver of the aftercooler of the compressor to reduce the back pressure, or open the cold water valve entering the aftercooler. ② Low pumping rate. Open the anti surge valve, so that the discharged gas can be recycled back to the inlet end of the rear compressor. ③ The temperature of the inhaled gas is high. Most devices are equipped with facilities to inject a small amount of light liquid hydrocarbons upstream of the suction port of the compressor, and the liquid evaporation cools the hot gas flow sucked into the compressor. The upstream process can also be required to reduce the temperature of the gas entering the compressor

2. The pump noise mainly comes from the motor. The motor noise consists of electromagnetic noise generated by the electromagnetic vibration of the motor itself, aerodynamic noise caused by the tail fan and mechanical noise. Generally 83 ~ 105dB. The abnormal noise and vibration of the pump are mainly caused by pump evacuation, too large pump capacity, pump cavitation, etc

pump evacuation: the vibration sound of the centrifugal pump is due to evacuation, which indicates that the pressure of the extraction is not enough to prevent the vaporization of the liquid in the pump, and the vibration is caused when the bubbles are deformed and broken. If the evacuation continues, the shaft seal, bearing bush and impeller of the pump will be damaged. The fastest way to prevent the pump from evacuating is to throttle the outlet of the pump to reduce the flow rate, and then increase the liquid level of the pump extraction tank. Then, stop the pump directly. The best way is to interlock the pump with the liquid level of the extraction tank

pump cavitation: when cavitation occurs, noise and vibration are generated. Under the repeated action of huge impact force, the material surface fatigue starts from pitting corrosion to the formation of serious honeycomb cavities, causing damage to the blades. In addition, when cavitation is serious, a large number of bubbles occupy part of the space of the liquid channel due to the obstruction of water vapor dispersion, resulting in a significant decline in the flow head and efficiency of the pump. Therefore, in order to make the pump operate normally, the minimum pressure at the blade inlet must be maintained above a certain critical value, and the minimum pressure should be greater than the saturated vapor pressure of the liquid at the delivery temperature. After cavitation occurs in actual operation, exhaust the pump immediately to discharge the gas inside

the pump capacity is too large; When the capacity of a large capacity centrifugal pump is reduced, it often makes a low and dumb sound during operation, which is mainly caused by the internal circulation in the impeller. This will damage the rotor part for a long time. The only way is to increase the outlet flow rate

for any rotating equipment with excessive vibration, its work should be stopped immediately before the pump is damaged, so that it can be used in the collection and display of experimental data

(Xie Libo, he Liping)