high vibrations in pd pump, gearbox, motor combo on movable base 1

[jjr1111]

Have a application that flagged high for vibration and unsure how to proceeded. Vibration testing gave the following readings:
motor NDE - 1.494 ips, .11g.
pump - .365 ips, 1.02g

Pump is a PD pump is mounted to baseplate 1" thick on wheels. Gearbox and motor are direct coupled and not mounted to base plate, just overhang, and NDE motor rests on two jack screws to the attachment plate.

 

[jjr1111]

reduced speed vibration motor data

 

[jjr1111]

reduced speed acceleration data

 

[jjr1111]

Thanks for the feedback on the slack and bearing condition, I'll read through the IOM and get familiar with what that process to check for slack entails.

 

[electricpete]

Thanks for the spectra. I didn't understand the terminology reduced speed spectrum.... is that just identifying that the reading was taken on the pump end of the gearbox, or was the motor speed changed between spectra?

In your picture what the heck is going on underneath the pump and motor? It doesn't look like they are sitting flat on anything, or if they are it doesn't extend to the edges. I believe good practice is to completely support each pump and motor foot underneath. And no bolt on motor gearbox end foot I haven't seen that before... maybe an attempt to relieve stress on the mount to the gearbox? I'd think the better solution would be to shim and slign the motor to remove stresses at least in absence of large thermal growth although we don't have any analogous machine where the motor and gearbox would both be bolted to the base.

 

[FacEngrPE]

Your mounting plate as shown in the picture is way to flexible to get good vibration data. If you were using laser coupling alignment you would detect "soft foot".

The simple way to fix this is to fill the space between the floor and the plate with cement or epoxy grout. Pinning the grout to the floor is highly desirable.

Here are some useful, easy to follow directions for grouting pump base plates. 7 Steps to Grouting a Pump Base
Grouting the pump base will have the side effect of changing the resonant frequency of the piping system which should reduce the magnitude of the pipe vibrations.

 

[electricpete]

NDE motor rests on two jack screws to the attachment plate.

Now with benefit of the photo, I get the feeling it is resting on 2 jackscrews on the NDE and supported by the gearbox flange mount on the DE.

Your mounting plate as shown in the picture is way to flexible

agreed. It's a plate on stilts. The stilts can bend (which might be be expected to give directional vibration in the horizontal or axial direction), or the plate can flex.

Both the configuration above the plate and the configuration below the plate look different than any standard installation I have ever seen. Looking at that I'm not surprised that machine has high vibration. Although I am intrigued to know if it used to be lower (how much lower, and what changed)

 

[jjr1111]

Thanks for the responses, the "reduced speed" spectra was a error on my part.. I collected two sets of readings at full speed and one at a reduced speed for acceleration and velocity. I uploaded both of the full speed readings and omitted the reduced speed reading by accident.

As an update it was an exciting weekend, exciting in a bad way for us. I was on vacation but heard that the pump failed due to a drive shaft failure. I'm hoping to be able to examine the failed components tomorrow and will get a chance to see how the used pump that we had on hand is preforming in it's place. I hope to collect vibration data from it then.

 

[electricpete]

ouch, sorry to hear that. I guess it's a "learning opportunity". Let us know what you find out!