Vane Pass Frequency

This relates to VPF as found in vibration spectrum.

<...6 vanes...> times <...1000 RPM...> divided by <...100Hz...> is, er (tap, tap, tap, press equals...) 60Hz, which is a commonly-used mains frequency. One might reasonably expect a vibration at this frequency.

It looks like one <...vane...> is out of balance and the <...200Hz...> signal is merely its second harmonic.

• Is there a barnacle stuck to one of the vanes, perhaps? Or is one of them bent or chipped? Or is an unintended solid jammed between two of them?

One might sieze an opportunity to dismantle the pump, inspect, clean and re-balance the rotor or, as an alternative, install the strategic spare and get the original overhauled appropriately, perhaps.

VPF=1000X6X2=12000CPM=200HZ. I am getting peak at 200 Hz as well as 100 Hz . 100Hz is 0.5VPF. The casing is double volute.

And?

Is 0.5VPF is a normal phenomenon. How and why it is coming in spectrum.

Once the possibilities in #2⇑ have been eliminated it will be time to look deeper.

Vane passing induced vibration is caused by pressure pulsations in the diffuser (or volute) being transmitted to the pump housing and the bearings. Some vibration will also be transmitted to the bearings via the shaft.

Not knowing the details of the pump, system or vibration spectrum, I would suggest that your dominant peak at 200 Hz is almost certainly vane passing. The 100 Hz is not uncommon and could be attributed to some sort of flow disturbance/pressure pulsation occurring due to opposite impeller vanes passing the two cutwaters simultaneously.

The usual way to solve the vibration problem if it severe enough to warrant correction is to increase the clearance between the impeller vanes and the cutwater (or volute vanes). This clearance, often referred to as clearance B in the literature should be around 6% (up to 10% if needed) of the impeller vane diameter (not the shroud diameter).

Increasing this clearance will have only a very small effect on efficiency.

The vanes are staggered, often used in paper making to reduce pulsation in the forming equipment. The cut waters would be symmetrical, normally, so wouldn’t generate a different frequency. Double suction is unusual for a vertical pump, typically end suction...