BCM-MS, BCM-LS
Since the characteristics measured in phase I do not change, the RUL also cannot be determined based on characteristics. During
this phase, however, the RUL can be estimated based on the thermal stress at the measuring point. This is permissible so long as
the temperature is the decisive stress factor for the oil and decisive in the aging rate (Arrhenius law). The sensor continuously
detects a temperature histogram for this purpose. Furthermore, data can only be transmitted for comparable applications and
the same types of oil.
NOTICE! We will gladly assist you with the necessary parameter settings for calculating the RUL based on thermal stress (Phase
I). Please contact Bühler Technologies GmbH Service.
1.2.11 Scope And Basic Parameters For Automatic Condition Analysis And RUL
Calculation
Some basic parameters must be taken into account for the automatic condition analysis:
– Changes in the condition can only be determined if the information is included in the measured parameters. For example,
the measured parameters typically do not provide any information about the depletion of antioxidants.
– Individual critical changes in the oil can overlap in extreme cases so the resulting overall change does not reflect this condi-
tion.
– The respective conditions or condition changes have detection limits where the underlying signal changes or change gradi-
ents are not detected.
– The automatic condition analysis can be distorted due to cross-influences.
– The RUL calculation is only a rough estimate. In open systems with uncontrollable contamination and systems with strongly
varied operating conditions the uncertainty of the characteristics information increases. The parameter settings further
greatly affect the results.
– A purely mathematical estimate of the RUL based on measured burden factors cannot predict spontaneous condition
changes.
Overall, a sufficient data volume and purposeful parameter settings will typically yield a satisfactory accuracy and prediction of
the aging process.
1.2.12 List Of All Measured And Derived Parameters
The 5 original characteristics above are measured to define the oil condition. These parameters and their meaning are again lis-
ted in the table below.
#
Parameter
Abbre-
viation
Unit
Explanation
1
Operating hours
Time
h
runs when powered
2
Temperature
T
°C
Oil temperature
3
Relative permittivity (rel. DK)
P
-
Fluid polarity. Fresh oils differ in P and can therefore be distinguished.
Furthermore, P changes with oil aging.
4
Conductivity
C
pS/m
Fresh oils differ in C and can therefore be distinguished. Furthermore,
C changes with oil aging.
5
rel. oil humidity
RH
%
Rel. humidity between 0 and 100 %
61
Liquid level
L
%
Liquid level between 0 and 100
Tab. 1:
Original characteristics determined
The parameters depend on the temperature, which is compensated by the sensor. This compensation involves two additional
temperature gradients used to assess the condition.
#
Original parameter
Derived characteristic
Abbreviation
Unit
Explanation
1
P
PTG
1/K
rel. DK - temperature gradient
2
C
CTG
(pS/m)/K
Conductivity - temperature gradient
3
RH
HTG
%/K
rel. oil humidity - temperature gradient
Tab. 2:
Derived temperature gradients
The sensor uses the original parameters P, C and RH as well as the determined temperature gradients PTG, CTG and HTG to cal-
culate the temperature-compensated parameters P40 and C40 and H20, H40 in the same unit as the respective original para-
meter.
NOTICE! The accuracy of determining PTG, CTG and HTG as well as the quality of the temperature compensation depend on the
fluid.
6
Bühler Technologies GmbH
BE150104 ◦ 03/2021
