Hi,
We are facing high vibration problem in the centrifugal compressor.

Compressor make: clark, Recycle Gas compressor,Driven by Steam Turbine,directly coupled.RPM 8585 RPM.Critical speed 7000 RPM.

We don't have any on-line monitoring system.Readings are collected using portable vibration analyzer.

Comp DE Hor-6.55 mm/sec RMS
Comp DE Ver-6.45 mm/sec RMS
Comp DE Axl-1.06 mm/sec RMS
Comp NDE Hor-1.8 mm/sec RMS
Comp NDE Ver-12.21 mm/sec RMS
Comp NDE Axl-2.9 mm/sec RMS

In all the locations we are getting only one times Running speed.

Compressor was running before at maximum of 2 mm/sec only.

What are the possible causes for this vibration.

With the given values it is difficult to answer your question. However if you can give me the following information than i will try to give the reason

1) what about the turbine vib.
2) Are the vibration increament gradual or sudden?
3) What type of coupling is there?
4) Running parametsr like discharge pressure , suction pressure , flow , suction temperature, moisture content in the gas w.r.t previous run?

Have you measured phase across the bearings and couplings if yes what is the values ?

kanti

Is this a journal bearing machine? What is the service? I know it is recycle, but recycling what? Hydrogen in a refinery? It would be nice to know if it is a fouling service.

There are a long list of things that will cause high 1X in a compressor. Without prox probes, you are not going to be able to tell much. Here are some possibilities:

Unbalance
Rub
Fouling
Broken impeller
erosion/corrosion of impeller
Coupling problem
Wiped bearing
Loose bearing
Cracked shaft
Resonance issue (critical speed shift)
Differential shaft thermal growth
Rotor bow
Improper rotor fits
Foreign object damage
Unbalance due to foreign object stuck in impeller
misalignment
pipe strain

Take your pick...

I believe in starting with the easy stuff. Check the coupling, check the alignment, and dump some wash oil through it.