Unwanted machine vibration is the first asymptote for machine failures that is so true especially when it comes to rotary machines such as centrifugal pumps and compressors. However, the case with centrifugal pump is so crucial. Anyway, I'm not going to talk about how vibration could be a health killer since this is not the purpose of this article.
For more metal rubber damperinformation, please contact us. We will provide professional answers.
The vibration isolator is playing a great role to keep our rotating machine alive. The following video shows the disastrous effect of vibration:
There are many types of vibration isolators based on application. However selection principle is still the same for all of them, the following slide shows most types:
Selection of Vibration Isolator
Passive isolator selection requires knowing rotation speed and weight. In general, there is another parameter is called Transmissibility (T) that is calculated from the natural frequency of the isolator, frequency of the machine, and damping.
w/wn of √2 is a region of the selection of a good isolator, the more it goes to the the more better isolator we have.
In practice we attend to a percent reduction that is given as standards acooring toindustry where the rotatining machine serves.
The following equation shows how to determine the frequency base on static deflection and percent of reduction in vibration:
It is good to mention that the perecent of reduction itself depends on the transmibility factor. The equation (2) in above figure shows how to calculate the percent of reduction.
However as I said before usually we don't need to calculate the percent of reduction instead we use the stand values given by vibration control per industry.
If you are looking for more details, kindly visit bakelite handwheel supplier.
The chart in the previous figure shows the three parameters rotating speed (RPM), static deviation, and percent of reduction to vibration. It is usually used by vibration isolators manufacturers to make the selection for best vibration isolator.
The final step is to determine the required stiffness, the following equation is very useful to calculate the stiffness for passive isolator:
Design Example
350 lb machine with 300 RPM needs to get vibration reduction of 60%.
It is good to mention that the 60% is modulos when it comes to vibration reduction, however the case could be different based on application as mentioned earlier, i.e. 90% vibration reduction.
Step (1): Use the ( freq,. Vs Static deflection chart) to determine the static deflection
The above figure shows the how to determine the amount of deflection in inches. This is very important to know amount of travel the isolator has to goes through it.
Step (2): Determine the stiffness, the is very straightforward process. We devivde the weight by the travel distinacen (static deflection). The shown below figure shows the calculations:
Manufacturer Catalog
Considering the previous example we have 1.4" (35 mm) defelection , 350 lb (158 kg), and 300 RPM (5 Hz). While the deflection of 1.4"(35) could be very large for most of equipment we can go to lower value, however we have to consider the weight and speed of rotation as critical values. The following figure shows selection of Hydruolic Cone 31 70Sh.
Further Know-Hows:
Want more information on buy round rubber gasket seals? Feel free to contact us.