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Sensors for Water Contamination in Lubricating Grease
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.ORCID iD: 0000-0002-4857-9475
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The purpose of this dissertation is to summarize the research carried out that led to the development of measurement techniques which measure the water content of lubricating grease. Calcium sulphonate complex (CaS-X) grease was used in all experiments for Papers A through E, with some additional greases used in Paper D.

A simple and effective grease mixing method for preparing grease samples was developed and tested for repeatability. The water content of these samples was also tested with time and temperature as added variables to study if and how much water will evaporate from the samples.

Additionally, three measurement principles were investigated: optical attenuation in the visible and near-infrared (NIR) region, a dielectric measurement method, and a galvanic current method.

The optical attenuation investigation found that the attenuation ratio of two wavelengths of light appear to approximate the water content of grease samples with an acceptable coefficient of determination. Additionally, aged and oxidized grease samples were measured in the experiment and were not found to affect the measurement results. The dielectric method uses the temperature dependence on the dielectric properties of water-contaminated grease to approximate the water content of the grease samples. An additional parameter of incomplete fill/coverage of the sensor has been investigated as a prestudy. The dielectric method was further optimized with computer automated measurements where an improved and miniaturized sensor was developed and used. A different method using the galvanic current between two different metals from the galvanic series was used to estimate water content as well. All three methods were found to provide measurements of water content in the prepared grease samples (ranging from 0.22% to 5.5% added water). The dielectric measurement is likely going to be better for applications requiring the possibility of measuring a larger bulk of the grease within the bearing, with the capability of using several different configurations of sensors for different types of bearings and applications. It shows promise for providing an accurate and robust system for monitoring grease condition as well as the amount of grease contained. The optical measurement will likely provide additional information; however, it will only measure small point samples within the bearing instead of the larger bulk. This could be of use though, because the sensors could be small (in the several millimeter scale) and could measure where water damage is determined to be most important to detect at. The galvanic current method was also found to provide a useful correlation to water content but may provide additional information about how corrosive the grease has become, indirectly estimating the water content.

The research contained herein has shown promise for future development for developing new grease condition monitoring tools. The optical, dielectric, and galvanic methods have their own unique challenges and may provide useful information in different applications, or perhaps be used in conjunction with each other to provide a more complete diagnostic tool.

Place, publisher, year, edition, pages
Luleå University of Technology, 2019. , p. 200
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Reliability and Maintenance Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Experimental Mechanics
Identifiers
URN: urn:nbn:se:ltu:diva-75998ISBN: 978-91-7790-439-7 (print)ISBN: 978-91-7790-440-3 (electronic)OAI: oai:DiVA.org:ltu-75998DiVA, id: diva2:1351323
Public defence
2019-11-04, D770, Luleå, 10:00 (English)
Opponent
Supervisors
Available from: 2019-09-16 Created: 2019-09-14 Last updated: 2019-10-04Bibliographically approved
List of papers
1. Mixing Grease with Water
Open this publication in new window or tab >>Mixing Grease with Water
2015 (English)Conference paper, Oral presentation only (Other academic)
Abstract [en]

The purpose of this paper is to convey a simple and effective method to mix water with grease and verify the homogeneity of the mixture using Karl-Fischer (KF) titration as the analysis tool. This is required to better develop a future water in grease sensor for on-line condition monitoring. This paper will also attempt to investigate how well KF titration functions as a tool for measuring water content in grease. Additional investigations include how the water content varies with time in grease samples open to atmosphere at different temperature. This research verifies a simple grease mixing method and investigates the water transport in water contaminated grease samples.

National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-31686 (URN)5f1feead-f874-458f-8eb1-b2172ad2a1d1 (Local ID)5f1feead-f874-458f-8eb1-b2172ad2a1d1 (Archive number)5f1feead-f874-458f-8eb1-b2172ad2a1d1 (OAI)
Conference
European Conference on Improvement in Bearing Technology : 23/02/2015 - 24/02/2015
Note

Godkänd; 2015; 20160406 (nicdit)

Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2019-09-14Bibliographically approved
2. Optical Attenuation Characterization of Water Contaminated Lubricating Grease
Open this publication in new window or tab >>Optical Attenuation Characterization of Water Contaminated Lubricating Grease
Show others...
2018 (English)In: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397X, Vol. 61, no 4, p. 726-732Article in journal (Refereed) Published
Abstract [en]

Water-contaminated grease samples are investigated with attenuation spectra in the visible and near-infrared (NIR) regions in this article. The purpose of this investigation was to identify a model with optical attenuation spectra such that the water content of grease samples could be characterized with a simple measurement setup using common methodology from the field of instrumental chemistry. The ratio between two chosen wavelengths of light appears to approximate the water content of grease samples with an acceptable coefficient of determination using a methodology to show what can potentially be done to develop condition monitoring tools. To illustrate the outlined method, a prestudy of grease aging and oxidation levels is also investigated to show that other variables do not significantly change the measurement.

Place, publisher, year, edition, pages
Taylor & Francis, 2018
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Applied Mechanics
Research subject
Machine Elements; Experimental Mechanics
Identifiers
urn:nbn:se:ltu:diva-67205 (URN)10.1080/10402004.2017.1404175 (DOI)000438157400015 ()2-s2.0-85044094152 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-08-09 (rokbeg)

Available from: 2018-01-09 Created: 2018-01-09 Last updated: 2019-09-14Bibliographically approved
3. Dielectric Thermoscopy Characterization of Water Contaminated Grease
Open this publication in new window or tab >>Dielectric Thermoscopy Characterization of Water Contaminated Grease
Show others...
2018 (English)In: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397X, Vol. 74, no 3, p. 60-73Article in journal (Refereed) Published
Abstract [en]

The temperature dependence on the dielectric properties of water-contaminated grease is investigated in this article. The purpose of this investigation was to identify the dielectric properties that could be measured to differentiate varying levels of water contamination in calcium sulfonate complex (CaS-X) grease with three different test cells with the purpose of eventually developing a grease condition sensor. Measuring the change in dielectric constant over a small temperature change yielded useful estimations of water content and amount of grease where the added water content ranged from 0.22% to about 5.5%. Additionally, other parameters such as incomplete fill/coverage of the sensors were investigated as a prestudy. The results from this set of experiments show that the measurement has potential to be developed into a condition monitoring sensor in the future.

Place, publisher, year, edition, pages
Taylor & Francis, 2018
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-65054 (URN)10.1080/10402004.2017.1333664 (DOI)000444573200001 ()2-s2.0-85045005667 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-04-16 (andbra)

Available from: 2017-08-14 Created: 2017-08-14 Last updated: 2019-09-14Bibliographically approved
4. Automated Dielectric Thermoscopy Characterization of Water Contaminated Grease
Open this publication in new window or tab >>Automated Dielectric Thermoscopy Characterization of Water Contaminated Grease
2019 (English)In: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397X, Vol. 62, no 5, p. 859-867Article in journal (Refereed) Published
Abstract [en]

Machine maintenance is important for improving machine uptime, reliability, and reducing costs. Grease is used in most rolling element bearings, and one common failure criterion is water contamination, so developing a sensor which can detect water content automatically without human input could be a useful endeavor. The temperature dependence on the dielectric properties of water-contaminated grease is investigated in this paper with computer logged instrumentation. This method has been termed Dielectric Thermoscopy (DT). Several off the shelf (two lithium, one lithium complex, and two calcium sulphonate complex) and one unadditivized lithium grease are tested with varying amounts of water contamination from 0% to approximately 5%. Another grease is tested with small increments of added water from 0% to 0.97% to test the resolution of the measurement. The purpose is to use the capacitance temperature slope (termed dielectric thermoscopy) to show correlations to the water content of the grease sample and investigate if any grease types will pose problems in the measurement. A small, custom made fringe field capacitance sensor with an integrated temperature sensor has been used for this characterization and data is logged automatically with laboratory equipment and a PC. A useable and positive correlation to water content and the DT measurement of roughly 0.5 pF per 10 °C and percentage of water is found, although it was found that some greases have different behavior than others.

Place, publisher, year, edition, pages
Taylor & Francis, 2019
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Applied Mechanics
Research subject
Machine Elements; Experimental Mechanics
Identifiers
urn:nbn:se:ltu:diva-75141 (URN)10.1080/10402004.2019.1629051 (DOI)000479625300001 ()
Note

Validerad;2019;Nivå 2;2019-08-22 (johcin)

Available from: 2019-06-28 Created: 2019-06-28 Last updated: 2019-09-14Bibliographically approved
5. Corrosion Sensor for Water Contamintated Grease
Open this publication in new window or tab >>Corrosion Sensor for Water Contamintated Grease
2019 (English)In: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397XArticle in journal (Refereed) Submitted
Abstract [en]

A simple and inexpensive corrosion sensor has been manufactured to study the corrosion rate of new and water contaminated grease using a galvanic cell. This paper shows the methodology in using this concept for any application which may require quantifying the corrosivity of a liquid or semisolid which could be applied to the surface of the sensor. Water contamination is a problem in many grease lubricated machine components, so a sensor concept was developed and a correlation between water content and the corrosion rate is shown. This method could be used to precisely study the corrosion rate of aged or contaminated lubricants and could potentially be used as a cheap and simple way to estimate water contamination of grease.

National Category
Corrosion Engineering
Identifiers
urn:nbn:se:ltu:diva-75997 (URN)
Available from: 2019-09-14 Created: 2019-09-14 Last updated: 2019-09-18

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