ML
www
.
machinerylubrication.com
|
September - October 2020
|
19
ML
because of the higher amount of oil-soluble
varnish in the second sample, the proba-
bility of sediment contamination is higher
at the critical points within the second gas
turbine at the thermal power plant.
Importance of particle
counting report:
Most oil labs currently use laser particle
counters calibrated in accordance with
ISO4406:99 to count suspended parti-
cles within the oil. In this standard, only
suspended particles larger than 4 microns
are examined and counted. Field observa-
tions have shown that high contamination
of turbine oil with particulate matter can
contribute to profound errors in MPC
varnish potential test results.
erefore, it is important to consider
particle counts when evaluating MPC
values. Clearly, calculating the R index and
thus removing insoluble particles from the
varnish potential test results can be of great
value to analysts.
Conclusion:
ough this article is a critique of defi-
ciencies in the ASTM D7843 standard, it
is still available and viable as a powerful
and reliable tool. Analysts' attention to the
test results and the issues mentioned in
this article can help to mitigate misunder-
standings and errors in the final analysis.
Focusing only on the numerical value of
MPC tests can be misleading and could
lead to costly, inaccurate and ineffective
decisions.
e smart choice is to supplement your
particle counting results with the R index
presented here in order to ensure useful
analysis of MPC value.
ML
REFERENCES
• Dr. A. Sasaki, CPA newsletter
(October 2015)
• US Patent NO. 8,390,796B2 (Mar. 5,
2015)
• Andy Sitton, Focuslab.
• Machinery Lubrication Magazine.
(6/2014)
• The varnish issue: strategies for
successful monitoring and acceptable
level.
• Dr. H. Tubisu. Dr. A. Sasaki.
• Review of varnish problems of modern
gas turbines.
• Society of tribologists and lubrication
engineers annual meeting. (2010)
