PCSA Flywheel velocity data is also showing unspecified 3.75Hz harmonics throughout and the run speed vibration seems to be modulated by 3.75Hz. Could this possibly be due to bearing movement in the housing?

More info on the machine would be useful. History, type of pump, flywheel, coupling etc

High 2x, the ratio from 1x to 2x is very high, like 10-1, this can indicate a natural frequency. There is a small mound of energy at the base of your 2x peak, this too can indicate a natural frequency. IF a bearing is loose to shaft or housing, this changes stiffness and the natural frequency. Is there a sub base under the motor? Does the 2x show up on the base also? Have seen alignment be spot on, start machine and it shows high 2x, phase shows 180 across coupling, all indications of misalignment. The sub base was rusty with minimum connection to main pump base, this was the source of the movement. Phase data taken on this machine will better identify how the machine is moving. Bump test can rule out a natural frequency.

Have you verified the shaft/s are not bent or out of round? Have you put dial indicator at top dead center of shaft/s and lift check the shaft/s? The looseness present in the data leads me to these type of tests to find the source of looseness. In some cases the base bolts or machine feet bolts are loose. Hope this helps your efforts of finding the problem

Dave

Hi Dave, thanks for your feedback. Attached are the images of the pumps. Three of them part of the primary cooling system, 4 pole, 50Hz, 1500 rpm, 200 kw fixed speed induction motor operates in a super clean environment, no rusts, no cracks in the base. NDT is done at scheduled interval on flywheel.

If it is a resonant freq. it should show up in vertical data I believe! But the high 2x is only at motor and flywheel motor end horizontal data. Phase data was never collected, shaft was not checked for roundness. Evidence of looseness is present on all pumps flywheel and pump monitoring position and has been consideredinherent to these  pumps. Only pump A motor data is showing high 2x.

Can you provide a plot with all data collection points in one plot? All location, all directions/axis

Phase data is the next step to identify what is moving or video motion amplification.

Hi Dave, please see attached vertical plot on motor and horizontal on flywheel. There is no vertical data on flywheel and no axial on any locations. As you can see, vertical vibration levels are much lower compared to horizontal and 2x is not the dominant on motor. I can put them in one plot as you suggested-either the software won't allow it or I don't know yet how to do it!

MTR NDE H  MM/SEC VERT .5MM/SEC

MTR DE H 3MM/SEC VERT .5MM/SEC

FLYWHEEL DE H 1MM/SEC

FLYWHEEL NDE 1 MM/SEC

Just putting numbers on paper shown above, large ratio from H to V on motor DE, which can indicate a natural frequency, normal ratio from H to V is 2:1, motor DE H appears there is a natural frequency at 2x rpm, motor V shows possible natural frequency near 4x rpm (vane pass, 2xLF?)

DE H and V Flywheel shows mechanical looseness and alignment, there should only be 1x and 2x present on these bearings typically. Are the time waveform peak to peak values high on the flywheel?

The 2 red arrows on the attached image, what is the black stuff on motor foot? Is that a cracked base on the left arrow?

It also appears the pump recently had bearings changed, housings are green?

General rule of thumb, machine base + its foundation should have a mass at least 2 times the weight of the machine. Your machine base could use some grout or concrete to hold your base still.

Dave

The base and foundation are perfect! Pump NDE bearing changed last Dec and yes, housings are green. Pump has 7 vanes.

Looseness has always been present and remained stable so does the TWF p-p value in line with other pumps. Motion amplification could have been very effective and revealing here I suppose.

My 25+ years of vibration analysis tells me your base is not perfect

In my experience electric motors, sitting on a concrete floor, do not vibrate, put the same motor on a weak base and vibration levels can increase 10 times higher.

The flywheel is a mass and a shaft, there should not be any turning speed harmonics 1x or 2x

The pump you state is good to go.....without data this is assumed

That leaves the base and mechanical fits. In my experience by lifting the shaft and using a dial indicator is the least intrusive to identify the source of looseness. A rule of thumb I use is no more than .003-.005" of up and down play in motor/flywheel/pump shafts. No more than .002" of shaft runout, most mechanical seals have this tolerance. Base overall vibration levels should be less than .01 in/sec/pk.

Based on the data you have provided to date, the base under the drive end of the motor is suspected "soft", the DE flywheel bearing housing has loose fits, either to the shaft/housing or bearing clearances

Dave

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Agree with fitting issue. Highly appreciate your insights Dave.