Page 79 - Electric

• As a turbine oil oxidises it forms by-products which are highly polar - these include organic acids, ketones, aldehydes
• The polar by-products react with each other and form higher molecular weight polymeric species (dimers/trimers)
• The Turbine base oil has finite solvency and will hold these higher MW species in solution - this is temperature dependent
- higher T’s give greater solvency

…once saturation point is reached, the by-products have such a high molecular weight and polarity, they can no longer be
held in solution and they drop-out as sludges (still “wet”) initially, in the cooler spots in the lube system
Metal surfaces typically are dipolar and hence attract polar molecules from the relatively non-polar lubricants, especially in
cooler areas The continued action of cross links and heat dries sludges out to form varnishes or lacquers
As these species reach a point of saturation they will effectively plate out in cooler areas of the turbine such as guide vanes,
servo valves and in bearings or gears. While it may cause a visual issue on bearings it often will not lead to a system shutdown
unlike the case of a hydraulic servo valve trip.

Shell new technology (Gas-to-liquids (GTL))

CATALYTIC PROCESS TO CONVERT GAS TO OIL PRODUCTS

Stage 1: Stage 2: Stage 3:
Gasification Synthesis Hydro-Cracking and Separation
SYNGAS
+ + + CR ACKING
HYDR O-
C ATALYST

Methane Oxygen Hydrogen Carbon F ischer Tropsch Wax + Water
(natural gas) (from air) Monoxide

January-February 2018