Fuels & Lubricants Magazine

1:28.4. Internal volume of the high
pressure part is 1 litre. 3 m long pipe
with 1 mm inner diameter connects
intensifier with pressure vessel. The
transformer oil was chosen, because
of a request for very low electric
conductivity of pressure liquid. Due
to the medium used, and its high
viscosity increase, the high pressure
system was able to operate reliably
up to 420 MPa only.
(except poles) by means of 1 – 3 pairs
of ultrasonic sensors with longitudinal
or transversal polarisation, see
Lokajíček and Svitek, 2015. [1]
The mechanical cup of the vessel
has 24 electric feedthroughs, what
enables to have all movable parts
located inside the vessel. Two step
motors are used there, the first for positioning/rotating
the sphere and the
second one for sensors positioning.
Transformer Oil Description
The main data of transformer oil,
which was used as power transmission
oil, are in Table 1:
Table 1
Transformer Oil Technol 2000
Kin. Viscosity at 40 °C mm 2 /s 9.62
Kin. Viscosity at 100 °C mm 2 /s 2.37
Viscosity index 41
Pour Point °C -45
Flash Point, COC °C 143
Density at 20 °C kg/m 3 874
C A
% 5
C N
% 45
C P
% 50
Regarding the data, it is low visco sity
naphtenic oil.
Figure 1: High pressure vessel with high
pressure multiplier on the left and tri axial
chamber – up.
Even higher pressure was generated
no movement of the pressure
intensifier piston of had been
monitored for a very long time. The
ambient oil temperature increased
to 30 °C approximately.
Pressure generation is controlled
by Siemens controller. High pressure
vessel has an internal volume
about 2 litres. The important part of
the vessel is measuring and positioning
head, which enables ultrasonic
sounding of spherical sample with
diameter 50 mm in any direction
The Summary of Oil
Requirements
Customer Requirements for Oil
Geology Institute specifies its
request very simple, only by low
conductivity and the oil resistance
against high pressure, but finally we
have discussed:
• Electrical conductivity as low as
possible
• The fluid should be liquid till at
least 700 MPa
• Very high VI to cover wide temperature
range
• Lifetime of the oil 1 year at least
• Oil compatibility with rubber
sealing
Oil Conductivity
Low polar, mineral base oils, PAO,
perfluoropolyether, ester oils and
silicone oils are suitable; highly polar
polyalkyleneglycol oils and water
based liquids are not suitable for it.
No data about high pressure influence
on conductivity have been
found.
Viscosity – Pressure
Relationship
The critical point, why the pressurized
system was not able to operate
at really very high pressure was
about transformer oil behaviour at
high pressures. Oil viscosity increases
with pressure exponentially till oil
Fuels&Lubricants No. 3 OCTOBER 2018 5