I have normally found that hydraulic pumps have a signature with no. pistons x RPM and that when they go bad there is a change in the pattern of multiples, what I have seen, normally increasing level at some multiple. In some case it´s always the same position.... both multiple and piston. Today I have one that is kind of the opposite. One pump of several to a big brass tube press has increased ISO levels for 8-12 months and have a increased trend compared to the next identical twin pump. It has however reduced multiple content/levels. I have a idea why that could be but would like to hear if my logic is something that is shared or known by others. These 2 units are of the adjusting kind and have likely 7 pistons and possibly RexRoth´s 1480RPM. Olov

I do a lot of hydraulic pumps but mostly ones with an altered fluid so as not to contaminate product. And they produce a lot of high vibs at piston cycle with many harmonics. This leads me to try to weight on exact known facts about the bearings as generally it'll keep running until bearing failure. It also prompts me to do visual inspections and try to acquire records.

Attaching a comparison FFT. P2 has increasing ISO levels for some time so my idea was that as it has less than normal multiples it doesn´t have the same umpfh and not giving the same transients and thereby is leaking more or worn more? As they are pressure controlled it must turn on more and work harder or leave more work to the other pump possible? Olov

GusFFT.doc (32 Kb, 8 downloads) HyPump