Twice running speed frequency
Twice running speed frequency
(OP)
Hi all,
I am measuring bearing vibration and I have been told by a colleague that twice running speed responses are indicative of a bearing fault, particularly due to misalignment or inadequate preload.
The bearing is a deep groove ball bearing with a predominant axial load and runs at a very high speed. The 2x running speed response is much higher axially, seemingly due to our use of a radial damping component.
I can't understand why this response occurs. Please tell me if you know of any online references explaining why this is, or provide one yourself.
Many thanks
Matt
I am measuring bearing vibration and I have been told by a colleague that twice running speed responses are indicative of a bearing fault, particularly due to misalignment or inadequate preload.
The bearing is a deep groove ball bearing with a predominant axial load and runs at a very high speed. The 2x running speed response is much higher axially, seemingly due to our use of a radial damping component.
I can't understand why this response occurs. Please tell me if you know of any online references explaining why this is, or provide one yourself.
Many thanks
Matt





RE: Twice running speed frequency
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It's "explanation" of a bent shaft causing 2X is arcane, but was widely held.
The cause/effect is not at all ironclad. For instance, some types of shaft couplings create 2X when misaligned, and some don't. I'd be unpacking the dial indicator and checking for mechanical runouts when referencing a good ground. Confirming Round holes and straight shafts must be the starting point.
My experience is mechanical looseness (rolling element and journal bearings) is very often accompanied by harmonics of 1X and truncated 1X wave form (same thing).
Bearing "faults" (individual spalls in races or balls" create impacts at frequencies related to dimensions, number of balls, and thus are related to rpm. Most are 3.xxx rpm or higher. Exactly 2X might be impossible.
RE: Twice running speed frequency
Walt
RE: Twice running speed frequency
"2X = misalignment" I agree.
Fe
RE: Twice running speed frequency
From a Hp Agilent brochure I quote
"The key distinguishing feature is a
high 2x component, especially in
the axial direction."
The cause is misalignment of the bearings. This brochure can be found at
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Title: Effective Machinery Measurements Using Dynamic Signal Analyzers (AN 243-1)
RE: Twice running speed frequency
In the axial direction, the only one that makes sense to me having just read it now is basically a misalignment of the bearing in its housing. So it's checking for dimensional accuracies and correctly machined bearing housing bores.
Let us know what you find out, I would be interested.