Vibration criteria for machinery.
Vibration criteria for machinery.
(OP)
I'm a structural engineer (who occasionally designs some frames and foundations for vibrating loads), so I thought I'd pose my question here: In a lot of literature (on dynamic loading), a lot of charts are given for acceptable vibration criteria for humans and machinery.......Question: where does that criteria come from for machinery? What is the criteria? Controlling wearing of internal parts? Cracked housing? All of the above?
Also, some people have indicated to me that this criteria originates from the UL listing or manufacturer for the machine determined through failure testing. In the case of the UL: do they figure it for individual machines or for machine categories (i.e. turbines, compressors, etc.)? I've never seen this info in a UL handbook before.
Thanks in advance.





RE: Vibration criteria for machinery.
RE: Vibration criteria for machinery.
A quick follow up question here: I've read through and I'm still not certain what the controlling criteria typically is. Is it displacement? Wear of parts? proper function of equipment? All of the above? I'm not certain if I got that (my apologies if I missed it).
RE: Vibration criteria for machinery.
RE: Vibration criteria for machinery.
I always thought that was covered by charts like the Reiher-Meister plot (i.e. that measured human perception to vibration).
In a lot of literature (that give "Criteria for vibrations of rotating machinery") there will be plots that graph frequency [on the x-axis] vs. amplitude [on the y-axis]..........where the lines intersect will be zones that fall into several categories: "Dangerous. Shut it down now to avoid danger." (or) "Faulty. Correct within 10 days to save maintenance dollars." And that just leaves me wondering [as a non-mechanical guy]: what is the danger, or what is faulty? Can the machine not run effectively with that kind of shaking? Is stuff wearing out inside?
RE: Vibration criteria for machinery.
For example NEMA MG-1 (going from memory)
< 2 mils pk/pk < 1200 cpm *
< 0.15 ips pk/0 1200 < f < 24,000 cpm *
< 0.8 g's pk/0 > 12,000 cpm *
* frequency ranges assume single-frequency sinusoidal vibration... often not the case.
A vibration analyst naturally would look not only at the "overall values" as above, but the specific frequency content and what it says about what is going on inside the machine. (0.1 ips due to rolling bearing defect is probably a concern... 0.1 ips due to unbalance is probably not). Also they look at trends and comparison to similar units. All of which is to say that predicting failure is not an exact science, so they look for deviations from what is normal. The goal is managing equipment reliability.
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: Vibration criteria for machinery.
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: Vibration criteria for machinery.
rmw
RE: Vibration criteria for machinery.
So do they typically just test equipment (to failure) to establish this criteria (and just basically sees what goes first)?
Yeah, the building (and human perception) side I know fairly well......but being structural I wasn't too sure about the charts for equipment. Thanks.
RE: Vibration criteria for machinery.
Exceptions include auxilliaries like switches and wiring, which can suffer from vibration originating exterally
Dan T
RE: Vibration criteria for machinery.
-- the equipment eventually told the plant management otherwise. Unfortunately, the pictures are proprietary and I can't share them. Wish I could as they answer pretty effectively what happens when high vibration occurs.
Patricia Lougheed
******
Please see FAQ731-376: Eng-Tips.com Forum Policies: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.