Causes and Control of Boiler Feed Pump Noise
Boiler pump noise is a reflection of the characteristics of the working state of the pump, the Boiler pump noise, mainly by the various parts of the pump parts or pump flow of media generated. Reduce the noise, it is necessary to carefully analyze the noise generated by the sound source to improve the structure of the sound source or medium motion.
1, the main causes of noise in the following areas:
1) mechanical noise
Multi-stage centrifugal pump with the guide vane, rigid or guide the population at the cross-sectional area and the entrance edge thickness with unreasonable, it may cause a larger vibration generated by the pump noise.
Second, the pump rotor parts and non-rotating between the pump, due to contact friction, will also produce higher frequency noise.
Due to the external structure of the boiler feed water pump and the installation of the problems arising from.
For example, the design of the pump base is unreasonable, rigidity, the bottom of the concrete filled with defects, the formation of "hollowing phenomenon", there is the pump and the motor is different, causing the rotor vibration and noise. Externally generated noise, easy to find, and easier to eliminate.
2) aerodynamic noise
Is generated by the rotation of the motor fan and the rotor in the air, mainly with the number of blades of the fan and the relative velocity of the air flow (public number: pump housekeeper).
For water-cooled motors, this fan-induced noise can be eliminated.
3) Electromagnetic noise (mainly generated by the motor)
Voltage instability caused by electromagnetic vibration;
Rotor eccentric air gap is not uniform, so that electromagnetic noise increases;
The motor winding is faulty, causing the magnetic field to be unbalanced, causing the motor to produce a low roar;
Asynchronous motor rotor has broken bar, the motor torque is reduced, the load current is low when the high, low noise occurs when high.
4) hydraulic noise
Generally, centrifugal pumps are much more powerful than mechanical noise.
There are five main aspects of the hydraulic noise source: the noise caused by the impeller of the pump impeller, the noise caused by the cavitation, the noise caused by the uneven velocity distribution at the inlet of the impeller, the noise caused by the eddy current and the noise caused by the surge phenomenon.
When the pump is running in the highest efficiency zone, the noise is the smallest, deviating from the design condition, the sound level of the noise is large, and the destructive is also very serious.
2, the pump produces noise control
1) Start with the design of the pump
During the design of the pump, pay attention to the number of impeller blades and the number of leaves of the guide vane, should be mutually prime number to avoid resonance, and the impeller and guide vane, volute radial reasonable gap. From the structural and hydraulic design to reduce the noise source, to ensure the superiority of congenital control sound source.
2) the rationality of installation and operation
Install the strict implementation of the installation process, anti-production sound source.
Operation to pay attention to exhaust (emptying), to ensure that the allowable suction on the height or to ensure that the necessary NPSH NPSHr, control the minimum flow of the pump, and pump overload flow operation.
3) take protective measures to prevent the spread of noise
The noise of the pump is transmitted through two main ways, respectively, through airborne airborne noise and through the floor walls and ceilings that propagate structural noise, taking effective measures after the pump system noise has been reduced.
In the installation, in the support part of the pipe rack can play anti-vibration effect of the gasket, such as rubber mats and cotton fabric, increase the basis of the design and set the wall.
In addition, in the pump, the motor set around the noise hood. Sound insulation can be used to make sound insulation material manufacturing, this method is easy to do, quick results. Foreign, domestic use of this approach to solve the noise of ultra-standard units of the noise back to the title.
4) No pulsation muffler
Made in a foreign country double-cylinder pulseless muffler, there are two types of expansion and phase mutual interference, as shown in the figure shows the shape of this pulseless muffler. The installation of this pulseless muffler in the device, received a significant effect.
Frequency noise generated by pump pulsation The noise of this ratio is almost completely attenuated by the installation of a pulseless muffler.
3, noise measurement and evaluation methods
China has published GB10890 pump noise measurement and evaluation methods.
The standard stipulates that in the selection method, should be preferred to use the sound power level method, when the conditions are not available with sound pressure level method. Controversial sound power level prevail.
For the determination of sound power level, there are provisions such as measuring surface, measuring point position, measuring instrument, background noise and environmental noise correction.
1, the main causes of noise in the following areas:
1) mechanical noise
Multi-stage centrifugal pump with the guide vane, rigid or guide the population at the cross-sectional area and the entrance edge thickness with unreasonable, it may cause a larger vibration generated by the pump noise.
Second, the pump rotor parts and non-rotating between the pump, due to contact friction, will also produce higher frequency noise.
Due to the external structure of the boiler feed water pump and the installation of the problems arising from.
For example, the design of the pump base is unreasonable, rigidity, the bottom of the concrete filled with defects, the formation of "hollowing phenomenon", there is the pump and the motor is different, causing the rotor vibration and noise. Externally generated noise, easy to find, and easier to eliminate.
2) aerodynamic noise
Is generated by the rotation of the motor fan and the rotor in the air, mainly with the number of blades of the fan and the relative velocity of the air flow (public number: pump housekeeper).
For water-cooled motors, this fan-induced noise can be eliminated.
3) Electromagnetic noise (mainly generated by the motor)
Voltage instability caused by electromagnetic vibration;
Rotor eccentric air gap is not uniform, so that electromagnetic noise increases;
The motor winding is faulty, causing the magnetic field to be unbalanced, causing the motor to produce a low roar;
Asynchronous motor rotor has broken bar, the motor torque is reduced, the load current is low when the high, low noise occurs when high.
4) hydraulic noise
Generally, centrifugal pumps are much more powerful than mechanical noise.
There are five main aspects of the hydraulic noise source: the noise caused by the impeller of the pump impeller, the noise caused by the cavitation, the noise caused by the uneven velocity distribution at the inlet of the impeller, the noise caused by the eddy current and the noise caused by the surge phenomenon.
When the pump is running in the highest efficiency zone, the noise is the smallest, deviating from the design condition, the sound level of the noise is large, and the destructive is also very serious.
2, the pump produces noise control
1) Start with the design of the pump
During the design of the pump, pay attention to the number of impeller blades and the number of leaves of the guide vane, should be mutually prime number to avoid resonance, and the impeller and guide vane, volute radial reasonable gap. From the structural and hydraulic design to reduce the noise source, to ensure the superiority of congenital control sound source.
2) the rationality of installation and operation
Install the strict implementation of the installation process, anti-production sound source.
Operation to pay attention to exhaust (emptying), to ensure that the allowable suction on the height or to ensure that the necessary NPSH NPSHr, control the minimum flow of the pump, and pump overload flow operation.
3) take protective measures to prevent the spread of noise
The noise of the pump is transmitted through two main ways, respectively, through airborne airborne noise and through the floor walls and ceilings that propagate structural noise, taking effective measures after the pump system noise has been reduced.
In the installation, in the support part of the pipe rack can play anti-vibration effect of the gasket, such as rubber mats and cotton fabric, increase the basis of the design and set the wall.
In addition, in the pump, the motor set around the noise hood. Sound insulation can be used to make sound insulation material manufacturing, this method is easy to do, quick results. Foreign, domestic use of this approach to solve the noise of ultra-standard units of the noise back to the title.
4) No pulsation muffler
Made in a foreign country double-cylinder pulseless muffler, there are two types of expansion and phase mutual interference, as shown in the figure shows the shape of this pulseless muffler. The installation of this pulseless muffler in the device, received a significant effect.
Frequency noise generated by pump pulsation The noise of this ratio is almost completely attenuated by the installation of a pulseless muffler.
3, noise measurement and evaluation methods
China has published GB10890 pump noise measurement and evaluation methods.
The standard stipulates that in the selection method, should be preferred to use the sound power level method, when the conditions are not available with sound pressure level method. Controversial sound power level prevail.
For the determination of sound power level, there are provisions such as measuring surface, measuring point position, measuring instrument, background noise and environmental noise correction.
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