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hriveraq

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HIJOS:
  
Tengo un tamiz vibratorio que gira a 900 CPM, su frecuencia de giro se obtiene en todos los equipos del edificio, como los motores reductores. ¿Cuál crees que sería la mejor eliminación de esta frecuencia? ¿Se me ocurre que podría mejorar la amortiguación de los resortes? Espero tus comentarios
20160602_151258.jpg  20160602_151555.jpg  Espectro.jpg  placa moto reductor.jpg  Reductor.jpg

Walt Strong

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Perhaps someone can translate OP to English? The vibration at shaker speed appears to be low, but measurement location-direction was not specified. Is there a machine vibration problem present, or just photos of an impressive new shaker with damping?

Walt
hriveraq

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I have a vibration shaker that rotates at 900 CPM vertical , its turning frequency is obtained in all the equipment of the building, such as reducing motors. Which do you think would be the best elimination of this frequency.It occurs to me that I could improve the damping of the resorts?I await your comments
electricpete

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Reply with quote  #4 

>> hriveraq wrote: I have a vibration shaker that rotates at 900 CPM vertical , its turning frequency is obtained in all the equipment of the building, such as reducing motors. Which do you think would be the best elimination of this frequency.It occurs to me that I could improve the damping of the resorts?I await your comments

 

It looks like the machine already sits on spring isolators.  If the resonant frequency of the machine on isolators is significantly below running speed, then it should’t transmit much force below the machine.  Rather than looking at damping, I'd investigate why the isolation doesn't appear to be working.  For example are  the isolators are bottomed out.  Check if there is anything rigid connected from the frame to foundation in parallel with the springs (which could defeat the purpose of the springs).  Perhaps try bump test with machine secured to see if the resonant frequency is in fact sufficiently below running speed (do an operating deflection shape of the platform while running to see if it’s pure vertical or rocking, and attempt to excite that same shape during the impact).

Walt Strong

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This looks like a new installation. First verify that it was installed correctly; especially the primary foundation for the shaker and conveyor supports. Next check for any vibration short circuits where a rigid link incorrectly connect (or touch) the shaker to the stationary structure; such as pipes and electrical conduit or lateral stabilizers. Some shaker designs can change the amount of vertical motion compared to the desired horizontal motion. Make sure that shaker motion is calibrated for the product and flow rate. Is the motor operated with variable speed with VFD drive? If yes, the try a change of speed. These checks and corrections are essential before considering the need for vibration control.

Walt
RRS_Dave

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Reply with quote  #6 
I agree with EPete and Walt, I've seen a lot of electrical conduit put in that was supposed to have a loop of seal tite or similar to allow for movement, and instead had rigid all the way. Also shipping braces not removed. Lot's of things like that get overlooked in the rush to get it running.
OLi

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Reply with quote  #7 
Steel springs only as isolators do have very little damping some or most brands offer steel wool or rubber inserts in the springs do improve on that at an extra cost.
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John from PA

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Quote:
Originally Posted by Walt Strong
Perhaps someone can translate OP to English? The vibration at shaker speed appears to be low, but measurement location-direction was not specified. Is there a machine vibration problem present, or just photos of an impressive new shaker with damping?

Walt



Translation:

I have a vibrating screen that rotates at 900 CPM, its rotation frequency is obtained in all the equipment of the building, such as reducing motors. What do you think would be the best elimination of this frequency? Can I think that it could improve the damping of the springs? I await your comments
MarkL

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Reply with quote  #9 
Quote:
Originally Posted by John from PA



I have a vibrating screen that rotates at 900 CPM, its rotation frequency is obtained in all the equipment of the building, such as reducing motors. What do you think would be the best elimination of this frequency? Can I think that it could improve the damping of the springs? I await your comments



Funnily enough I’ve a similar issue in a magna-cite plant I do monthly surveys in. On a few machines in a certain area of the plant one of the vibrating screens dominates the readings on anything nearby. I’ve been telling customer about it for years but they haven’t shown any initiative to fix the issue so I just remind them each time I report on the machines in question. I cannot get in at the workings of the machine so unsure exactly how it’s connecting to the plant structures to cause the excitation but it’s at a constant 900 rpm which I know is the speed of the italvibriss screen motors.
fburgos

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I'll try to do my best.

Quote:
Originally Posted by electricpete

It looks like the machine already sits on spring isolators.  If the resonant frequency of the machine on isolators is significantly below running speed, then it should’t transmit much force below the machine.  Rather than looking at damping, I'd investigate why the isolation doesn't appear to be working.  For example are  the isolators are bottomed out.  Check if there is anything rigid connected from the frame to foundation in parallel with the springs (which could defeat the purpose of the springs).  Perhaps try bump test with machine secured to see if the resonant frequency is in fact sufficiently below running speed (do an operating deflection shape of the platform while running to see if it’s pure vertical or rocking, and attempt to excite that same shape during the impact).

Al parecer la maquina ya se encuentra montada sobre aisladores, si la frecuencia resonante de la maquina sobre los aisladores es significativamente menor a la frecuencia/velocidad de operación, entonces no deberia transmitir mucha fuerza bajo la maquina. En vez de mirar hacia el amortiguamiento, yo investigaria porque los aisladores no parecen estar funcionando. Por ejemplo si los aisladores estan "vencidos/en las ultimas". Verifica si existe alguna conexión rigida desde el marco a la fundición en paralelo a los resortes (lo que anularia el proposito de los resortes). Quiza intenta realizar una prueba de impacto con la maquina asegurada para observar si la frecuencia resonante es en realidad lo suficiente menor a la freuencia de operación (haz un analisis de modo de defleción de operación (ODS) a la plataforma cuando trabajan para ver si es un movimiento puramente vertical o oscilante (rocking motion) e intenta excitar esa misma forma durante la prueba de impacto)



Quote:
Originally Posted by Walt Strong
This looks like a new installation. First verify that it was installed correctly; especially the primary foundation for the shaker and conveyor supports. Next check for any vibration short circuits where a rigid link incorrectly connect (or touch) the shaker to the stationary structure; such as pipes and electrical conduit or lateral stabilizers. Some shaker designs can change the amount of vertical motion compared to the desired horizontal motion. Make sure that shaker motion is calibrated for the product and flow rate. Is the motor operated with variable speed with VFD drive? If yes, the try a change of speed. These checks and corrections are essential before considering the need for vibration control.

Walt

Esto parece una instalación nueva. Primero verifica que fue instalado correctamente; especialmente a la base primaria del vibrador y los soportes del transportador. Siguiente verifica por cualquier "corto circuito de vibración" donde un camino rigido incorrectamente conecta (o toca) el vibrador con la estructura estacionaria; como lo son tuberias y conductos electricos o estabilizadores laterales. Algunos diseños de vibradores pueden cambiar la cantidad de vibración verical comparado con el movimiento horizontal deseado. Asegurate que el movimiento del vibrador esta calibrado para el producto y flujo. ¿Es el motor operado por un variador de frecuencia? si asi fuese, intenta cambiar la velocidad. Estas verificaciones y correciones son esenciales antes de considerar la necesidad de controlar la vibración.




Quote:
Originally Posted by RRS_Dave
I agree with EPete and Walt, I've seen a lot of electrical conduit put in that was supposed to have a loop of seal tite or similar to allow for movement, and instead had rigid all the way. Also shipping braces not removed. Lot's of things like that get overlooked in the rush to get it running.


concuerdo con Epete y Walt, he visto muchos conductos electricos instalados que supuestamente deberian haber tenido un "lazo/vuelta" de sealtite o similar que permitan el movimiento, que en su lugar tenian conductos rigidos a todo lo largo. Tambien si las abrazaderas de transporte no fueron removidas. muchas de esas cosas se pasan por alto con la premura/prisa de entrar en operación


Noknroll

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an iron ore processing plant I worked at had banks of 5 or 6 of these together on 1 level of the plant and same as MarkL they transmitted to other equipment, conveyor pulleys etc nearby. when they all came into phase they even sent a big old beat frequency through the air to demountable buildings a hundred meters away.
MarkL

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Reply with quote  #12 
Sounds like fun Nok.......
fburgos

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Reply with quote  #13 
Quote:
Originally Posted by MarkL

Funnily enough I’ve a similar issue in a magna-cite plant I do monthly surveys in. On a few machines in a certain area of the plant one of the vibrating screens dominates the readings on anything nearby. I’ve been telling customer about it for years but they haven’t shown any initiative to fix the issue so I just remind them each time I report on the machines in question. I cannot get in at the workings of the machine so unsure exactly how it’s connecting to the plant structures to cause the excitation but it’s at a constant 900 rpm which I know is the speed of the italvibriss screen motors.

Es gracioso tengo un problema similar en una planta de magna-cite donde realizo monitoreos mensuales. en algunas maquinas en cierta area de la planta una de las cribas vibratorias domina las lecturas en cualquier cosa cercana. Durante años se lo he dicho al cliente pero no han mostrado ninguna iniciativa de arreglarlo, entonces solo se los recuerdo en cada reporte de la maquina en cuestion. No puedo ingresar al area de dicha machina por lo que no estoy seguro de como exactamente se conecta a la estructura de la planta para causar esa excitación pero es a 900rpm constantes el cual se que es la velocidad de giro de los motores en esas cribas Italvibriss



Quote:
Originally Posted by Noknroll
an iron ore processing plant I worked at had banks of 5 or 6 of these together on 1 level of the plant and same as MarkL they transmitted to other equipment, conveyor pulleys etc nearby. when they all came into phase they even sent a big old beat frequency through the air to demountable buildings a hundred meters away.


En una planta de procesamiento de mineral de hierro en la que trabajé tenía bancos de 5 o 6 de estos juntos en 1 nivel de la planta y al igual que MarkL, la vibración se transmite a otros equipos cercanos, transportadores, poleas, etc. Cuando todos entraban en fase, enviavan una frecuencia de golpeo atravez del aire por todos los edificios desmontables a cientos de metros de distancia



PS. Hey Noknroll, how could you notice this air beat mid air? like a bass in a concert, did you get a chance to measure ir with a sound pressure level?
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