Vibration with axial fan 2

[AO1958]

Hi there.

please don't hate or kid me, but I am here to ask your help since I have received a more than odd question from a Customer.

Following is the question.
The subject is an air conditioning unit with an axial fan.
My customer is asking me which is the maximum level of vibration the unit can withstand.

I think this question is quite generic, nonetheless I'd need some hints to know how to start analyzing this question.

Please, can you help me ?

Thanks in advance

 

[GregLocock]

He's asking what environmental vibration the unit can be exposed to. If you are lucky the manufacturer may have defined that.

More likely, not.

Cheers

Greg Locock


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[MiketheEngineer]

Right up until it breaks!!

 

[rob768]

Depending on size and power, ISO or DIN rules (or any other) may be applicable. They do not define to what level the fan can withstand vibrations, but rather they specify maximum levels that are allowed.

 

[GregLocock]

aren't they talking about how much vibration the fan can generate, not withstand?

Cheers

Greg Locock


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[AO1958]

Hello,

many thanks for your kind answers.

To Mr GregLocock

post 1
I am working for the manufacturer, but I have never faced a question like this.
Moreover, if you google the question, I can't fine this values specified by any manufacturer.

post 2
The question is concerning the vibrations the model can withstand.
Indeed vibration can be generated either by fan or the compressor.

To Mr. MiketheEngineer

Yes, but we are talking about applications where the smallest is 7 ft large.
I can't find very difficult to find even an experimental way to test it.

To Mr. rob768
Please, could you give me some specific reference to the standards you are quoting ?

Many thanks

 

[IRstuff]

It's an absurdly open ended question, and actually doesn't deserve a response other than, "What type of vibration are you planning on applying?" Because, at the least, "vibration," in of itself, has little meaning without specifying frequency, amplitude, etc.

How would you even begin to ponder this analysis if you have no idea what the customer has in mind?

Nonetheless, refrigerated trucks have hull-mounted units that can at least withstand road vibrations.

TTFN

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[Tmoose]

My experience is that even amongst folks designing equipment or making their living doing vibration analysis the cause and effect relationship of vibration and machine condition is incorrectly linked, and sometimes outright reversed.

A major US equipment manufacturer has stated to us (somewhat after the fact, as their equipment has been failing regularly) that in order for their equipment to survive the operating environment must not exceed ANSI/AGMA 6000-B96.
I got a reply from AGMA that confirms their intent that it should be used as a guideline for mutually agreed upon acceptance testing, not for any kind of field evaluation or requirement.

 

[rob768]

as a start, ISO 10816 might be applicable

 

[jvian]

My experience has been that your requirement is my input. Meaning normally my customer would tell me that my design must meet XYZ level of vibration and I design according to that. My advice (or how I would attempt to solve your question) would be to use a uniform random vibration PSD and vary the Grms until your desing fails (via FEA). It would be an iterative and potentially very long analysis but that would be my proposal. I do however agree that the question is very generic and there could be multiple ways to approach it.

-J-