Membrane patch colorimetry: ASTM D7843, in which a conditioned oil sample is mixed with solvent and drawn through a 0.45 micron membrane. A spectrophotometer reads the color of the deposit left on the patch and reports it as a Delta E value. Most labs treat under 15 as normal, 15 to 30 as worth watching, and anything over 30 to 40 as a high varnish potential.
MPC is 38 on the gas turbine, get the varnish removal skid hooked up before the servos start sticking.
Also heard as
- MPC Delta E
- varnish potential test
Related terms
Varnish
Thin, sticky, amber-to-brown deposit from degraded oil that coats valves, bearings and coolers.
RPVOT
Rotating pressure vessel oxidation test, which rates how much oxidation life is left in an oil.
Turbine oil
Highly refined, lightly additized circulating oil built to last for years in steam, gas and hydro turbines.
FTIR
Fourier transform infrared spectroscopy, an oil test that fingerprints oxidation, contamination and additive loss.