I acquried vibration from this pump and found high vibration around 5.6 in/sec.
This pump Model No. is A10VSO 140DR/31.

This Hydraulic pump is directly coupled with motor and pump have 9 cylinders in it.
The prominent component is Cyliner Pass Frequency(CPF) and it's harmonics.
The CPF = 9 X Pump(Motor) Running Speed.
The 2 X CPF is almost 5.0 in/sec.
What kind of problem could cause this vibration ?
Please find the attached file.

[EMAIL]
ksy9059@paran.com
ksy9059@yahoo.co.kr

20070327_Spectrum_of_hydraulic_pump.doc (42 Kb, 40 downloads) spectrum

Is this a vertical pumpset?

Check your pump demand. The 2x component could be excessive swash plate angle. Try collecting while adjusting pump output to zero and swash plate in neutral position. Does the 2x vary from one collection to the next? Do you have history?

Correct me if I'm wrong (don't know much about cylindrical compressors) but isn't second harmonic to be the highest (may be too high though) expected as impact occurs twice per shaft rev?

It's the 18th harmonic of turning speed, or the second harmonic of "cylinder pass frequency" as someone called it. There are 9 cylinders. I think the pistons move smoothly (sinusoidally) throughout their stroke and successive pistons are at the same position within their cylinder at a time difference of T/9 where T = 1/RS.

If it were something like an impact happening twice per stroke of a cylinder, we would also expect to see 4x, 6x, 8x cylinder pass frequency higher than 3x, 5x, 7x.... which is not what we see. My guess is whatever it is happens once per stroke of cylinder. Only the TWF would show for sure.

We had a problem with similar type pumps developing pressure pulsations at one times cylinder pass frequency... the problem was resolved by adjusting the system accumulators. I'm not sure if pressure pulsations could result in 2*cylinder pass, but it wouldn't hurt to check. I would suggest to take a quick check if there are pressure pulsations and whether these frequencies show up heavily on the discharge piping.

This message has been edited. Last edited by: electricpete,

Pete
in the alternative movement, piston or cilinders, the movement isn't pure sine. There is a strong 2x of mass force. At car engine are applied several corretions for minimize the 2x. In pumps no. Is normal 2x, I dont know if is big as 5.6.

Ricardo Góz from Brazil

Thanks for the comment. If the cyclinders were driven by a crankshaft, then I can imagine very nonuniform movement of the pistons. But if this pump is the same as I'm thinking, the pistons rods are driven by a tilted circular plate which is almost perpendicular to the shaft but tilted slightly (is that correct?). If you track the position of a point on the circumference of that circular plate as it rotates, the axial movement is sinusoidally.

I could be wrong... always open to hear more.