ASTM D7685-11
(Practice)Standard Practice for In-Line, Full Flow, Inductive Sensor for Ferromagnetic and Non-ferromagnetic Wear Debris Determination and Diagnostics for Aero-Derivative and Aircraft Gas Turbine Engine Bearings
Standard Practice for In-Line, Full Flow, Inductive Sensor for Ferromagnetic and Non-ferromagnetic Wear Debris Determination and Diagnostics for Aero-Derivative and Aircraft Gas Turbine Engine Bearings
SIGNIFICANCE AND USE
This practice is intended for the application of in-line, full-flow inductive wear debris sensors. According to (1), passing the entire lubrication oil flow for aircraft and aero-derivative gas turbines through a debris-monitoring device is a preferred approach to ensure sufficient detection efficiency.
Periodic sampling and analysis of lubricants have long been used as a means to determine overall machinery health (2). The implementation of smaller oil filter pore sizes for machinery operating at higher rotational speeds and energies has reduced the effectiveness of sampled oil analysis for determining abnormal wear prior to severe damage. In addition, sampled oil analysis for equipment that is remote or otherwise difficult to monitor or access is not practical. For these machinery systems, in-line wear debris sensors can be very useful to provide real-time and near-real-time condition monitoring data.
In-line full-flow inductive debris sensors have demonstrated the capability to detect and quantify both ferromagnetic and non-ferromagnetic metallic wear debris. These sensors record metallic wear debris according to size, count, and type (ferromagnetic or non-ferromagnetic). Sensors are available for a variety of oil pipe sizes. The sensors are designed specifically for the protection of rolling element bearings and gears in critical machine applications. Bearings are key elements in machines since their failure often leads to significant secondary damage that can adversely affect safety, operational availability, or operational/maintenance costs, or a combination thereof.
The main advantage of the sensor is the ability to detect early bearing damage and to quantify the severity of damage and rate of progression of failure towards some predefined bearing surface fatigue damage limiting wear scar. Sensor capabilities are summarized as follows:
In-line full flow non-intrusive inductive metal detector with no moving parts.
Detects both ferromagnetic and non-f...
SCOPE
1.1 This practice covers the minimum requirements for an in-line, non-intrusive, through-flow oil debris monitoring system that monitors ferromagnetic and non-ferromagnetic metallic wear debris from both industrial aero-derivative and aircraft gas turbine engine bearings. Gas turbine engines are rotating machines fitted with high-speed ball and roller bearings that can be the cause of failure modes with high secondary damage potential. (1)
1.2 Metallic wear debris considered in this practice range in size from 120 μm (micron) and greater. Metallic wear debris over 1000 μm are sized as over 1000 μm.
1.3 This practice is suitable for use with the following lubricants: polyol esters, phosphate esters, petroleum industrial gear oils and petroleum crankcase oils.
1.4 This practice is for metallic wear debris detection, not cleanliness.
1.5 The values stated in SI units are to be regarded as standard. The values given in parentheses are provided for information only.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D7685 − 11
Standard Practice for
In-Line, Full Flow, Inductive Sensor for Ferromagnetic and
Non-ferromagnetic Wear Debris Determination and
Diagnostics for Aero-Derivative and Aircraft Gas Turbine
Engine Bearings
This standard is issued under the fixed designation D7685; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
In-line wear debris sensors have been in operation since the early 1990s. There are now thousands
ofthesedevicesoperatinginawidevarietyofmachineryapplicationsaccruingmillionsofoperational
hours. Wear debris sensors provide early warning for the abnormal conditions that lead to failure.
Improved machine reliability is possible due to the enhanced sensor data granularity, which provides
better diagnostics and prognostics of tribological problems from the initiating event through failure.
1. Scope responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
1.1 This practice covers the minimum requirements for an
bility of regulatory limitations prior to use.
in-line, non-intrusive, through-flow oil debris monitoring sys-
tem that monitors ferromagnetic and non-ferromagnetic metal-
2. Terminology
lic wear debris from both industrial aero-derivative and aircraft
gas turbine engine bearings. Gas turbine engines are rotating
2.1 Definitions of Terms Specific to This Standard:
machines fitted with high-speed ball and roller bearings that 2.1.1 condition monitoring, n—field of technical activity in
can be the cause of failure modes with high secondary damage
which selected physical parameters associated with an operat-
potential. (1) ing machine are periodically or continuously sensed, measured
and recorded for the interim purpose of reducing, analyzing,
1.2 Metallic wear debris considered in this practice range in
comparing and displaying the data and information so obtained
size from 120 µm (micron) and greater. Metallic wear debris
and for the ultimate purpose of using interim result to support
over 1000 µm are sized as over 1000 µm.
decisions related to the operation and maintenance of the
1.3 This practice is suitable for use with the following
machine. (2)
lubricants: polyol esters, phosphate esters, petroleum industrial
2.1.2 control unit, n—electronic controller assembly, which
gear oils and petroleum crankcase oils.
processes the raw signal from the sensor and extracts informa-
1.4 This practice is for metallic wear debris detection, not
tion about the size and type of the metallic debris detected.
cleanliness.
2.1.2.1 Discussion—A computer(s), accessories, and data
link equipment that an operator uses to control, communicate
1.5 The values stated in SI units are to be regarded as
standard. The values given in parentheses are provided for and receive data and information.
information only.
2.1.3 full flow sensor, n—monitoring device that installs
1.6 This standard does not purport to address all of the in-line with the lubrication system and is capable of allowing
thefullflowofthelubricationfluidtotravelthroughthesensor.
safety concerns, if any, associated with its use. It is the
Also referred to as a through-flow sensor.
2.1.4 inductive debris sensor, n—device that creates an
This practice is under the jurisdiction ofASTM Committee D02 on Petroleum
electromagnetic field as a medium to permit the detection and
Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom-
measurement of metallic wear debris via permeability for
mittee D02.96.07 on Integrated Testers, Instrumentation Techniques for In-Service
Lubricants.
ferromagnetic debris and eddy current effects for non-
Current edition approved Jan. 1, 2011. Published March 2011. DOI: 10.1520/
ferromagnetic debris.
D7685–11.
2.1.4.1 Discussion—A device that detects metallic wear
The boldface numbers in parentheses refer to a list of references at the end of
this standard. debris that cause fluctuations of the magnetic field. A device
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7685 − 11
that generates a signal proportional to the size and presence of
metallic wear debris with respect to time.
2.1.5 machinery health, n—qualitative expression of the
operational status of a machine sub-component, component or
entire machine, used to communicate maintenance and opera-
tional recommendations or requirements in order to continue
operation, schedule maintenance or take immediate mainte-
nance action.
2.1.6 metallic wear debris, n—in tribology, metallic par-
ticles that have become detached in a wear or erosion process.
2.1.7 sensor cable, n—specialized cable that connects the
sensor output to the electronic control module.
2.1.8 trend analysis, n—monitoring of the level and rate of
change over operating time of measured parameters.
FIG. 1 Wear Debris Characterization
3. Summary of Practice
and rate of progression of failure towards some predefined
3.1 A full flow sensor is fitted in the oil line to detect
bearing surface fatigue damage limiting wear scar. Sensor
metallic wear debris. The system counts wear debris, sizes
capabilities are summarized as follows:
debris, and calculates debris mass estimates as a function of
4.4.1 In-linefullflownon-intrusiveinductivemetaldetector
time. This diagnostic information is then used to assess
with no moving parts.
machine health relative to cumulative debris count, or esti-
4.4.2 Detects both ferromagnetic and non-ferromagnetic
mated cumulative debris mass warning and alarm limits, or a
metallic wear debris.
combination thereof. From this information, estimates of
4.4.3 Detects 95% or more of metallic wear debris above
remaining useful life of the machine can also be made.
some minimum particle size threshold.
4.4.4 Counts and sizes wear debris detected.
4. Significance and Use
4.5 Fig.1presentsawidelyuseddiagram (2)todescribethe
4.1 This practice is intended for the application of in-line,
progress of metallic wear debris release from normal to
full-flow inductive wear debris sensors. According to (1),
catastrophic failure. It must be pointed out that this figure
passing the entire lubrication oil flow for aircraft and aero-
summarizes metallic wear debris observations from all the
derivative gas turbines through a debris-monitoring device is a
different wear modes that can range from polishing, rubbing,
preferred approach to ensure sufficient detection efficiency.
abrasion, adhesion, grinding, scoring, pitting, spalling, etc. As
4.2 Periodic sampling and analysis of lubricants have long
mentioned in numerous references (1-11), the predominant
been used as a means to determine overall machinery health
failure mode of rolling element bearings is spalling or macro
(2). The implementation of smaller oil filter pore sizes for
pitting.Whenabearingspalls,thecontactstressesincreaseand
machinery operating at higher rotational speeds and energies
cause more fatigue cracks to form within the bearing subsur-
has reduced the effectiveness of sampled oil analysis for
face material. The propagation of existing subsurface cracks
determining abnormal wear prior to severe damage. In
and creation of new subsurface cracks causes ongoing deterio-
addition, sampled oil analysis for equipment that is remote or
ration of the material that causes it to become a roughened
otherwise difficult to monitor or access is not practical. For
contact surface as illustrated in Fig. 2. This deterioration
these machinery systems, in-line wear debris sensors can be
process produces large numbers of metallic wear debris with a
very useful to provide real-time and near-real-time condition
typical size range from 100 to 1000 microns or greater. Thus,
monitoring data.
rotating machines, such as gas turbines and transmissions,
4.3 In-line full-flow inductive debris sensors have demon- which contain rolling element bearings and gears made from
strated the capability to detect and quantify both ferromagnetic hard steel tend to produce this kind of large metallic wear
and non-ferromagnetic metallic wear debris. These sensors debris that eventually leads to failure of the machines.
record metallic wear debris according to size, count, and type
4.6 In-line wear debris monitoring provides a more reliable
(ferromagnetic or non-ferromagnetic). Sensors are available
and timely indication of bearing distress for a number of
for a variety of oil pipe sizes. The sensors are designed
reasons:
specifically for the protection of rolling element bearings and
4.6.1 Firstly, bearing failures on rotating machines tend to
gears in critical machine applications. Bearings are key ele-
occur as events often without sufficient warning and could be
ments in machines since their failure often leads to significant
missed by means of only periodic inspections or data sampling
secondary damage that can adversely affect safety, operational
observations.
availability,oroperational/maintenancecosts,oracombination
4.6.2 Secondly, since it is the larger wear metallic debris
thereof.
that are being detected, there is a lower probability of false
4.4 The main advantage of the sensor is the ability to detect indicationfromthenormalrubbingwearthatwillbeassociated
early bearing damage and to quantify the severity of damage with smaller particles.
D7685 − 11
FIG. 3 Sensor Major Components (3)
debris detected. The sensor electronics perform several func-
tions including: data processing, communication control, and
Built-In-Test (BIT). Ferromagnetic and non-ferromagnetic
wear debris counts are binned according to size. Signal
conditioning using a threshold algorithm is used to categorize
the metallic wear debris that pass through the sensor on the
basis of size. Several size categories can be configured which
allow the tracking of the distribution of debris.
FIG. 2 Typical Bearing Spall
6.2 Principle of Operation—The sensor operates by moni-
toring the disturbance to the alternating magnetic field caused
by the passage of a metallic wear debris particle through the
4.6.3 Thirdly, build or residual debris from manufacturing
magnetic coil assembly as shown in Fig. 4 (12). The particle
or maintenance actions can be differentiated from actual
couples with the magnetic field to varying degrees as it
damage debris because the cumulative debris counts recorded
traverses the sensing region, resulting in a characteristic output
due to the former tend to decrease while those due to the latter
signature. The magnitude of the disturbance measured as a
tend to increase.
voltage defines the size of the metallic wear debris and the
4.6.4 Fourthly, bearing failure tests have shown that wear
phase shift of the signal defines whether the wear debris is
debris size distribution is independent of bearing size. (2-5)
ferromagnetic or non-ferromagnetic. When a ferromagnetic
and (11).
particle passes by each field coil, it strengthens the magnetic
5. Interferences
field of that coil due to the high magnetic permeability of the
particle relative to the surrounding fluid (oil). This disrupts the
5.1 Wear debris counts may be invalid due to excessive
balance of the fields seen by the sense coil, resulting in a
noise from environmental influences. See 7.4.
characteristic signal being generated as the particle passes
6. Apparatus through the entire sensing region of the sensor. The signal
looks much like one period of a sine wave where the amplitude
6.1 Sensor —Asensorsystemisidentifiedthatisathrough-
of the signal is proportional to the apparent size of the particle
flow device that installs in-line with the lubrication oil system.
and the period of the signal is inversely proportional to the
The subsections in this section provide examples for a certain
speed at which the particle passes through the sensor. For a
type of inductive debris sensor system. The sensor has no
ferromagnetic particle, the size, shape, and orientation of the
moving components.As seen in Fig. 3, the sensor incorporates
particle and the magnetic susceptibility of the material deter-
a magnetic coil assembly and signal conditioning electronics
mine the magnitude of the signal. When a non-ferromagnetic
that are capable of detecting and categorizing metallic wear
(conductive) particle passes by each field coil, the principle is
debrisbysizeandtype.Themagneticcoilassemblyconsistsof
similar except that the presence of the particle in the magnetic
three coils that surround a magnetically and electrically inert
fieldweakensthefieldduetotheeddycurrentsgeneratedinthe
section of tubing. The two outside field coils are driven by a
particle.Thisresultsinadifferenceinthesignalphaseallowing
high frequency alternating current source such that their
the processing electronics to differentiate between ferromag-
respective fields are nominally opposed or cancel each other at
netic and non-ferromagnetic particles passing through the
a point inside the tube at the center sensor coil. Signal
sensor. For a non-ferromagnetic particle, the surface area and
conditioning electronics process the raw signal from the sensor
orientation of the particle and the conductivity of the material,
and extract information about the size and type of the metallic
determine the magnitude of the signal.Also, for a given size of
particle,theamountofdisturbancecausedtothemagneticfield
The sole source of supply of the apparatus known to the committee at this time
by a ferromagnetic particle is considerably greater than that
is GasTOPS, Ltd., Polytek St., Ottawa, Ontario K1J 9J3, Canada. If you are aware
caused by a non-ferromagnetic particle resulting in the sensor
of alternative suppliers, please provide this information to ASTM International
being able to detect smaller ferromagnetic than non-
Headquarters.Your comments will receive careful consideration at a meeting of the
responsible technical committee, which you may attend. ferromagnetic particles. Note that the detection capability of
D7685 − 11
FIG. 4 Principle of Operation (12)
the sensor is limited to distinguishing ferromagnetic materials with the thickness being considerably less than the length and
from non-ferromagnetic (conductive) materials. It does not width. The particle orientation refers to the axis of the particle
have the capability to distinguish different materials of the that is parallel to the flow direction.Also shown in the graph is
same type from each other (for example, it
...
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