position of accelerometers
position of accelerometers
(OP)
An accelerometer is fit on the bearing housing at an angle of 45 deg to the horizontal plane, and measures an acceleration of 0.3g(rms). How can i calculate the values in horiz. and vertical planes? Further, is there any advantage in mounting the accelerometer in an inclined plane (45deg)?





RE: position of accelerometers
The following website has some information on mounting the accelerometer. I never used the 45* angle method. I machined off the vertical and horizontal plane on the housing and mounted the contacts flush with the surface.
I used these on 1200HP+ dc mill motors though....which gave me good repeatable results. It however, may not be right for you.
http://www.ctconline.com/
Carl
RE: position of accelerometers
http://www.ctconline.com/
Carl
RE: position of accelerometers
There's no trigonometric way to divide one reading at 45° into horizontal and vertical components. I don't believe that there is any advantage to using only sensing in the 45° direction. More commonly, of course, people use vertical and horizontal as "standard."
regards.. kv
RE: position of accelerometers
machinedoctor
RE: position of accelerometers
A major turbine manufacturer only has a probe located at the 45 degree plane. This way there are fewer instruments to calibrate and fewer costs. Again I would recommend using the manufacturers installed instrumentation (i.e. least cost) augmented with your own predictive maintenance program.
RE: position of accelerometers
I prefer horizontal and vertical for most applications. And axial is added for troubleshooting.
RE: position of accelerometers
However, we know that differing causes of vibration give a resultant that is often direction specific. As almost everyone here has stated, it is best to take the readings in 2 radial directions but much more important is to be repeatable - make sure you always take the readings at the same place. Personally, I always try and take one reading in the load zone (thanks Ilangford) and at least one other as close to the perpendicular to the first reading as possible.
The practice of taking readings at 45' appears to have started with the gas turbine and centrifugal compressor community. This was done so that true orbits could be taken of the shaft using the built in displacement probes without having to worry about the gravitational effect on the shaft. This works excellently for checking alignments with vibration as well as looking for shaft whirl, rub or even a rotating stall on a centrifugal compressor element.
My point, Kashnap, is don't worry too much about convention when you are taking readings with a portable vibration analyzer but use your engineering experience and good old common sense.