Hi, there

I am experiencing deposit on the bearing of a recip compressor (5 stages , 42 bars).The deposit occur over a period of 6-12 months. At 12 months it is such that it impairs the free rotation of the shaft at start up. Sump, packing and cylinders are lubricated with PAG. There is the possibility that a little compressed gas seeps through packing. The compressed gas is a water wet CO2. However insoluble presence in the oil is less than 0.1%, monitored regularly. Oil temp is 50C. The same deposit is found on main bearing and big end whatever the compression stage No unusual wear. Oil in good condition, low TAN, in specs viscosity (ISO VG 220). The deposit was analysed and appeared to be organic carbonaceous no trace of metal.

Have you experienced similar issue ? thanks

Hi Pepelepew

I sent your question on the Mr Joe Ban from J&M Specialized Products, J&M manufacture Polyfluoroether Oxygen approved lubricants,
This is his view of what could be occurring, We hope this assists

Regards Rob S



First, CO2 will not readily show up in TAN tests as it is a weak acid.
I am not surprised by the formation of Organic Carbonates using that oil.
In the normal operating condition, and degradation occurring with the oil, (cracking), the CO2 is used up with by-products to form the organic carbonates, and because of the breakdown products being constantly removed from the oil as insoluble materials, the balance of oil appears OK.
The oil does not dissolve the newly formed Carbonates, and normal tests will not identify any abnormalities in the oil as the material being formed is sediment.
There is another problem, that the reaction "cracking" of the oil, is catalysed by various metals, and deposits will occur on surfaces that are contributing to the Catalytic "cracking" process even though there is Organic Carbonates being deposited, there is a bonding occurring on surfaces of the metals with the Carbonates.
You need to examine fairly close detail the surface structure of the surfaces where the deposits have occurred.
My guess is that there will be evidence of surface metal crystal structure evident.
Would be interested in picture of surfaces affected.
The organic Carbonates can be studied by IR spectroscopy to determine structure, and if can be dissolved with suitable solvent, the molecular composition can be determined by GCMS or HPLC Mass spectra analysis which should identify organic composition.

Regards Joe

Thank you Joe and Rob. S your comments are highly valuable.