Hi,
Has anyone ever had balancing issues with a Pembril PSC 24R fluid coupling?
This coupling has to be balanced every 3 months and vibrates severely (as you can see by the global values shown below). All the energy is at 1 x rpm of motor. I've also included a picture of the equipement (rock crusher).
Just wanted to know if anyone as experience with these.

This forum has always been helpful in the past, so thanks in advance.

Wow!

Over 6 ips. Was this still in operation?

Do you do oil analysis? I wonder about cement getting in the coupling and centrifuging.

I assume from the results that you got that you have phase measurements. Have you ruled out alignment/thermal growth issues?

Good Luck

No other test were done. We got called to balance the coupling, and once we got there we were told that this coupling gets balance every 3 months. There are 2 other identical equipments, that were installed at the same time, close by with no problems.

So we balanced it, but are going back next week to do some test and find out why this coupling always get unbalanced. Phases were never stable, but we did the best we could considering the circomstance.

Just wanted to know if anybody has any experience with these types of coupling...

And it was running when we got there.

Unless I am mistaken, the 2 hydraulic cylinders are used to tighten the belts. There is probably a pivot hinge of some type on the back side. With such a large mass (motor, coupling, bearings, sheave), the lateral stiffness looks suspect. It won't take much imbalance to cause excessive vibration. Are the other units arranged exactly like this one? I would think you'd want some way to make the base "solid" once you got the belts tensioned properly.

Balance a coupling every three months, and the similar ones don't give any problems? If there are no problems with build-up of material or other appearant causes, I would look at the coupling itself. Did they ever overhauled it?
There are moving parts inside the coupling.

http://auto.howstuffworks.com/torque-converter2.htm

Also take a look at the floor the thingy is placed on. I regular visit a site w. 2 cyclocleaners where one is sitting on a cutout in the concrete floor for piping and that need balancing 3 times as often as the other as it sets up a nice resonance but it´s tricky to fix as it´s part of the building. Olov

If this fluid coupling operates like a Voith then there is a difference between the input and output coupling sections of only a few RPM depending on load. Tracking filters on analyzers like the 2120 cannot be set narrow enought to seperate the two frequencies so phase and amplitude will not be stable or correct. I have observed that reducing the oil level in the coupling has been done to increase the slip frequency during inplace balancing. But this may not be recommended by the OEM>

Have you taken high resolution spectrum (6400 line/2,000 cpm fmax) to insure seperation of the input and output rotational frequencies?