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Electrostatic Cleaning of
Hydraulic and Lubricating
It will be difficult to write up exact chemical formulas for the
potential chemical reactions in hydraulic and lubricating oils.
However, we do know something about what is going on.
Oxidation is a process where the hydrocarbons are attacked by
oxygen and are broken down to different oxygen rich molecules
such as hydroperoxide, alcohols and organic acids. This process
can be described in a simplified manner as;
RH + [HEATH] -> R* + H
Where RH represents a hydrocarbon molecule consisting of a
reactant (R) and a hydrogen atom (H). If the necessary amount
of heath energy is available, will the hydrocarbon molecule be
cleaved and a free energy rich radical (R*) and a free hydrogen
atom will be created. The energy rich radical (R*) can bond to
an oxygen molecule and establish an energy rich peroxide.
R* + O2 -> RO2
This peroxide can in turn react with the hydrocarbon and a
hydroperoxide and create a new energy rich radical.
RO2 -> ROOH + R*
The reactions above are by no means exact, but they give us an
indication about the reactions that may occur in the fluid. Most
importantly, they give the chemical engineer the possibility to
take qualitative precautions towards obtaining a system in
equilibrium and give the system a long life.
•Reduce the amount of reactive material. To
initiate the oxidation process, oxygen must be
available. Both air and water can supply oxygen,
and should be eliminated from the system
•Reduce the amount of catalytic material.
Catalytic material, in this context will primarily
be copper and iron.
•The oxidation process is endothermal, i.e.
heath is necessary. If the operational process is
kept below 65 0C, oxidation will only rarely be a
problem in modern oils, which is given oxidation
•Add an inhibitor. This is normally done, but it is
important not to exceed the recommended
temperature if these inhibitors should have the
desired effect. It is also important that the oil is
free from catalytic material. These inhibitors
only slow down the oxidation process, and will
eventually not have any effect.
A few hours after stop
10-15 hours after stop
Cleaning of Hydraulic
and Lubricating Systems
Reduce the amount of reactive material, i.e.
Reduce the amount of chemical compounds
that can act as reactive material
Reduce the amount of catalytic material,
Forces acting on a
particle in an
Cleaning do the job.
Do not remove additives
Operating time, hours
0 2 4 6 8 10 12 14 16 18
O p e ra tin g time , h o u rs
0 24 73 122 169 217 265 314 361 409 457 505 526 575
0 , 0 2 8
0 , 0 3
0 , 0 3 2
0 , 0 3 4
0 , 0 3 6
0 , 0 3 8
0 , 0 4
0 , 0 4 2
O p e r a tin g tim e , h o u r s
1 2 2
1 6 9
2 1 7
2 6 5
3 1 4
3 6 1
4 0 9
4 5 7
5 0 5
5 2 6
5 7 5
P , [% ]
Z n , [% ]
Operated in 600 hours on a Tellus T32 (Shell)
Welfare of hydraulic and lubricating systems. Contamination Control