MASTER's THESIS Real-Time Lubricant Ageing Analysis

2010:135 CIV MASTER'S THESIS

Real-time lubricant ageing analysis - first step towards a Tribotronic system

Prashant Rana

Luleå University of Technology MSc Programmes in Engineering Electrical Engineering Department of Applied Physics and Mechanical Engineering Division of Machine Elements

2010:135 CIV - ISSN: 1402-1617 - ISRN: LTU-EX--10/135--SE 2 Preface

This is the final report of a master thesis project carried out as a Research Trainee at the Division of Machine Elements at Lule˚aUniversity of Technology, Sweden 2009/2010. I would like to thank my supervisor, Dr. PärMarklund, for his help and guidance throughout this project. I would also like to express my gratitude to Kim Berglund, Ph.D. student at Division of Machine Elements. I thank Prof. Staffan Lundströmand Prof. Roland Larsson for giving me the opportunity to work on this project. I would also like to thank my parents and my brother for their support during this project.

Prashant Rana Lule˚a,September 2010 4 Abstract

The operating performance and reliability of tribological systems at present are main- tained by employing periodic or online diagnostic techniques. These techniques have of course been effective in enhancing the performance, reliability and durability of various systems. However, these systems invariably have to be shutdown for tak- ing the necessary corrective action based on a system’s condition. This approach is usually considered passive and presently there are not many active methods which enable corrective action in situ to maintain the desired performance, reliability and durability of complex technological systems. The Division of Machine Elements at Lule˚aUniversity of Technology has recently coined a new term Tribotronics. It is essentially based on combining the knowledge of tribology and electronics for actively controlling and optimising the performance, reliability and durability of modern technological systems. Tribotronics at present is just an idea and a lot of Research and Development work will have to be carried out for developing viable and reliable Tri- botronic systems. This thesis is thus a first step towards developing a Tribotronic system in the long run. As is well known, a lubricant plays a very crucial role in controlling (minimising) friction and wear in machines. The deterioration of its properties during ageing can therefore significantly influence the performance, reliability and durability of technological systems. There are of course several laboratory tests to analyse and measure the changes in properties of used lubricants but the understanding of their the ageing during service is far from satisfactory. There is thus a clear need to developed some techniques or systems to monitor, and analyse in situ the ageing behaviour of a lubricant during use. This work has focused on the development and implementation of a Tribotronic Diagnostic System (TDS) to monitor the ageing of lubricant in the Haldex Limited Slip Coupling (HLSC) test rig available at Tribolab, at Lule˚aUniversity of Technology. A fluid property analyzer has been used in developing the prototype of the TDS. A LabVIEW measurement interface has also been developed to measure and analyse various lubricant parameters. For understanding the ageing behaviour of the lubricant, the changes in the lubricant viscosity and dielectric properties during its use in the HLSC test 6 rig incorporating the TDS have been monitored. The viscosity of the aged lubricant samples were also measured by using Bohlins rheometer in order to compare and check the reliability of results obtained by using the TDS system. In addition, co- relation of ageing of the lubricant to friction between the clutch plates in the HLSC has also been discussed in this report. The results of this study have shown that it is possible to actively measure the ageing behaviour of a lubricant by using the TDS. Contents

1 Introduction 9

2 Aim and scope of work 13

3 Investigated System 15 3.1 Wet clutch test rig ...... 17

4 Tribotronic diagnostic system 19 4.1 The sensor system ...... 20 4.2 The sample control unit ...... 22 4.2.1 Pump control ...... 25 4.3 The measurement interface ...... 26 4.3.1 Programming the LabVIEW user interface ...... 26

5 Experimental procedure 29 5.1 Lubricant samples used for measurement ...... 29 5.1.1 Ageing of the lubricant samples ...... 30 5.2 Tribological parameters observed ...... 31 5.3 Measurement procedure with TDS ...... 31 5.4 Measurement procedure with Bohlins CVO100 ...... 31

6 Results and discussion 33 6.1 Initial measurements ...... 33 6.1.1 Short measurements ...... 37 6.1.2 Theoretical model ...... 38 6.1.3 Short vs long measurement sequences ...... 38 6.2 Comparisons between TDS and Bohlins CVO100 ...... 40 6.2.1 Possible cause of deviations in measurements ...... 42 6.3 Results obtained ...... 44

7 8 CONTENTS

6.3.1 PAO results ...... 45 6.3.2 Mobil 5W40 results ...... 45 6.3.3 LSC301 results ...... 45 6.3.4 Summary of results ...... 51

7 Conclusions 53

8 Future work 55

Bibliography 56

Appendix 59

A The FPA Studio Interface 59 A.1 FPA Studio Interface overview ...... 59 A.2 Setup Tab ...... 59 A.3 Data acquisition tab ...... 60 A.4 Graphics section ...... 61

B Drawings 63 B.1 Pump holder ...... 63 B.2 Sensor holder ...... 65

C National Instruments I/O module 67 Chapter 1

Introduction

We find ourselves in an era today, where we are, more than ever dependent on automated electro-mechanical systems. Hence, the importance of these systems to be more reliable and efficient has also increased over the years giving rise to a need of more accurate condition monitoring. The electro-mechanical systems today are an integration of several moving machine components, which often come into contact. Whenever there is a mechanical contact and relative motion between the components of the system, it gives rise to friction. Friction is an energy dissipating process and impairs the efficiency of machines. Wear leads to shortened machine life and premature failure of machine components. Machine failure in industries implies interrupted production that in turn results in huge economical losses. To minimize the impact of friction and wear on the machine performance, lubrication is usually employed. Efficient and effective design of machines and commonly lubricated contacts is enabled by tribology. The earliest friction laws were first proposed by Leonardo da Vinci [1], but tribology as a term was used widely following ”The Jost Report” in 1966 [2], which showed that huge economical losses were reported annually due to friction, wear and corrosion. Since then, machine design has been integrated with tribological practices that have lead to design of machines that are more efficient and more reliable. This in turn has lead to economical savings as well as lower consumption of materials and energy. The latter has a positive affect on the environment, which is an ever- growing issue. Figure 1.1 shows an example of how design integrated with tribology has helped to manufacture efficient rolling element bearings over time. The rolling element bearing to the right in Figure 1.1 have better efficiency, and is more reliable than the 50 year old bearing even though the weight is almost one fourth.

9 10 CHAPTER 1. INTRODUCTION

Figure 1.1: Development trend of rolling element bearings (courtesy of SKF ERC)

All mechanical and electro-mechanical systems require maintenance from time to time as various components interacting in a system often wear out. Condition monitoring is the process of monitoring a parameter of condition in machinery, such that a significant change is indicative of a developing failure and replacing the components of the system once they no longer can perform their task. Conventional forms of condition monitoring systems are often very rudimentary. One of the major forms of monitoring the condition of a system is visual inspection by maintenance professionals and experienced operators. Visual inspections have certain limitations as defects in machine parts such as micro-cracks can not be seen by the naked eye and are first discovered when it is too late and the condition of the system is beyond repair. Vibration analysis is another way of monitoring the condition of the system. The level of vibration can be compared with historical baseline values such as former start- ups and shutdowns, and in some cases established standards such as load changes, to assess the severity. Other practices involve detecting temperature changes, listening for unwanted noise levels, time/count based service intervals which involve maintenance of the system without having an actual knowledge of the current state of the system. Practices for condition monitoring involving visual inspection, vibration analysis , etc., are both labour and cost intensive and often require a complete shutdown of the system for inspection. Tribotronics, or active tribology aims at monitoring the tribological parameters of a system in real-time. Tribotronics aims at having an accurate and active knowledge of the state of the system [3]. The term tribotronics was coined at the Division of Machine Elements at Lule˚aUniversity of Technology. It aims at 11 the integration of tribology and electronics by having a sensor system to actively study the tribological parameters of a system during operation and simultaneously take necessary corrective action. The definition of tribotronics may resemble that of a mechatronic system but there exists essential differences. Most mechatronic systems use only information from inputs and functional or useful outputs of a mechanical system to control its operation. The functional outputs include rotational speed, torque, load , etc. The main principle of tribotronics is to use additional so-called loss outputs such as friction, wear, vibration, etc. The purpose of tribotronics is to control these loss outputs and by doing so considerably improve performance, efficiency and reliability of the tribological units and that of the entire machinery. In contrast to the usual methods of condition monitoring, tribotronics help determine the actual state of the system. It promises to be less labour intensive as the whole system is more or less automated and even helps predict the future trend of the machinery. Further, a system shut down is not required to study the condition of various parts when a tribotronic system is used and helps to determine the exact service interval for the system. Knowledge of the exact service interval would in turn prove to be economically beneficial as one would have an accurate idea as to which parts in the system need to be replaced which saves on inspection time. As mentioned earlier, lubrication is often employed to control friction and wear. Hence, the study of ageing of the lubricant is extremely important, as it is the first step to counter the forces of friction and wear. Having an accurate knowledge of the state of the lubricant would help prevent frictional losses and/or failures long before they can occur. 12 CHAPTER 1. INTRODUCTION Chapter 2

Aim and scope of work

As stated earlier, ‘tribotronics’ is a new concept recently introduced by the Division of Machine Elements at Lule˚aUniversity of Technology. It is based on combining the knowledge of tribology and electronics for in situ measurement of selected variables of the tribological system and their control in such a way as to optimise their performance and durability. It has also been seen that a lubricant is one of the crucial elements of a lubricated tribological system in view its role in controlling friction and wear of different machine components. The deterioration of lubricant properties due to ageing in a particular tribological system can therefore significantly influence its performance, reliability and durability. Tribotronics at present is merely a concept. This work is thus a first step towards developing tribotronic system. The aim of this work is to develop a sensor system to monitor the ageing of the lubricant in the Haldex Limited Slip Coupling (HLSC) test rig as a precursor to creation of a full-fledget tribotronic system. By understanding the ageing mechanisms of the lubricant used in the HLSC, we can evaluate the cause of the lubricant degradation and also optimise the performance of the system. The HLSC is a wet clutch that is electronically controlled. The torque output is governed by the control system. The ageing of the lubrication implies a change in the coefficient of friction. Hence, if the change in the coefficient of friction is known, the torque output can be regulated accordingly.

13 14 CHAPTER 2. AIM AND SCOPE OF WORK Chapter 3

Investigated System

The objective of this project is to investigate the ageing mechanism of the lubricant for a wet clutch system used in All Wheel Drive(AWD) systems for car. The wet clutch system investigated here is the Haldex All Wheel Drive system. The major component of the Haldex All Wheel Drive (AWD) system for vehicles is the Haldex Limited Slip Coupling(HLSC) [4]. It consists of an electronically controlled, disc-type wet clutch mounted between the propeller shaft and rear differential of these vehicles. The torque transfer to the rear axle is controlled by the wet clutch. Sensors monitor the speed difference between the front and rear axles of the vehicle. An electronically controlled hydraulic pressure from a hydraulic pump actuates the clutch. Figure 3.1(a) shows a picture of the HLSC and Figure 3.1(b) shows the schematic of the HLSC. The Haldex AWD has several advantages over the traditional transmission systems. The torque transfer to the rear axle is controlled efficiently. This allows the system to work along with other control systems of the vehicle, such as the Anti- lock Braking System (ABS), the Traction Control System (TCS) and the Electronic Stability Program (ESP). The HLSC in particular works irrespective of wheel size, tire dimensions or air pressure, which may make other AWD systems malfunction. To obtain a high power density of the clutch while still keeping the cost down, a sintered bronze friction material is used in combination with separator discs made of hardened steel. The lubricant used in this application is a tailor made semisynthetic fluid with a special additive formulation.

15 16 CHAPTER 3. INVESTIGATED SYSTEM

(a) Haldex Limited Slip Coupling

(b) Haldex Limited Slip Coupling,generation 1-3 (Schematic)

Figure 3.1: Overview of the Haldex Limited Slip Coupling 3.1. WET CLUTCH TEST RIG 17 3.1 Wet clutch test rig

Previous work on the HLSC involved testing the lubricant in a wet clutch test rig. The wet clutch test rig simulates the working conditions of the HLSC and is designed to test the limits of the material and lubricant and to give an idea of the lifetime of both the lubricant and the components involved. An overview of the wet clutch rig is shown in Figure 3.2.

Figure 3.2: A schematic of the wet clutch test rig

In his research, Berglund [5] showed that it is possible to study the ageing of lubricant by monitoring the changes in its tribological parameters. The research also showed that it is possible to co-relate the increase in friction levels to the ageing of the lubricant. The focus of this project is to design a system that would be able to monitor the changes of the tribological parameters such as viscosity, density and dielectric constant of the lubricant used in the wet clutch rig in real time. Real-time monitoring of the lubricant’s tribological parameters ensures active knowledge of the state of the lubricant thus foreseeing the condition of the lubricant and deterioration in its lubricating properties. Hence it would help us deciede to modify the torque output in the HLSC when required. 18 CHAPTER 3. INVESTIGATED SYSTEM Chapter 4

Tribotronic diagnostic system

As stated earlier, Tribotronics aims at the integration of tribology and electronics by employing sensor systems. The main purpose of these sensor systems is to actively study the tribological parameters of a system during operation and simultaneously take necessary corrective action. Hence a Tribotronic system can be seen as a combination of a diagnostic unit; which performs real-time measurements of the required tribological parameters, and an actuator unit which takes the necessary corrective action based on the measurements recieved from the diagnostic unit. In this project, a diagnostic unit has been developed as a precursor to developing a complete Tribotronic system. The diagnostic unit developed here is a sensor system that monitors the ageing of a lubricant by measuring the changes in its tribological parameters in real-time. The diagnostic unit has been designed to be portable that can easily be adjusted to suite the requirements of diﬀerent applications. This unit will eventually be fully integrated in the Tribotronic system. The tribological system in this project is a Haldex Limited Slip Coupling(HLSC). This Tribotronic Diagnostic System (TDS) has been designed to monitor changes in the tribological parameters of the lubricant used in HLSC in real time. The TDS extracts a sample of lubricant from the HLSC, directs it to the sensor system for measurement of its tribological parameters, and then re-directs the lubricant back in to the HLSC. A schematic diagram of the system can be seen in Figure 4.1. The TDS consists of various sub-systems interacting with each other in desired manner. The main sub-systems involved in the TDS are: • The sensor system • The sample control unit • Measurement interface

19 20 CHAPTER 4. TRIBOTRONIC DIAGNOSTIC SYSTEM

Wet clutch test rig

Air vent

Inlet Sample Extraction channel

Outlet

FPA

Pump control unit Computer

Figure 4.1: System overview

4.1 The sensor system

To analyze the lubricant sample, some suitable sensors are required to monitor its tribological parameters. A Fluid Property analyzer(FPA) manufactured by Measurement- Specialties of France was selected for use in developing the proposed tribotronic diagnostic system. This FPA enables in measuring viscosity, dielectric constant, density and temperature of fluids [6]. The FPA tuning fork is made of piezoelectric material that is mono-crystalline quartz. The tuning fork is a single structure with two tines that are metallized with thin film electrodes that permit the crystal to res- onate when energized. When the tuning fork resonator is energized, the frequency is scanned at its natural resonant frequency in fluids. The change in the resonator’s complex impedance at the resonant frequency is the signal used to determine the fluid’s viscosity, density and dielectric constant. The interface provided for measurement presents graphs showing the real time measurements. Furthermore, the communication protocol via the 9-pin RS-232 (serial port) makes the FPA compat- ible with most computers. More information about the sensor interface is given in Appendix A. The FPA is shown in Figure 4.2(a) and Figure 4.2(b) shows a block diagram along with the sensor control unit. The optimal temperature range of this FPA is between 10 ◦C and 120 ◦C. To prevent any damage to the sensor, a k-type thermo couple was used to measure the temperature of the lubricant before measuring with the sensor. The sample is then extracted only if the temperature of the lubricant is within the interval mentioned above. The thermocouple was connected to the computer using a National 4.1. THE SENSOR SYSTEM 21

(a) Fluid property analyzer (FPA2400BST)

(b) Fluid Property analyser (Block Diagram)

Figure 4.2: Overview of the Fluid Property Analyzer 22 CHAPTER 4. TRIBOTRONIC DIAGNOSTIC SYSTEM instruments input/output module. More information about the module can be found in Appendix C.

4.2 The sample control unit

Once the sensor system had been conﬁgured according to the requirements, a sample control unit was designed. The system had to be able to extract a lubricant sample while the test rig was under operation. To extract the sample from the system, an oil pump provided by Haldex was used as seen in Figure 4.3. The oil pump is the same as the one found in generation III Haldex AWD systems. The power requirements of the pump and how these are met including remote control of the pump are discussed in section 4.2.1.

Figure 4.3: The Haldex oil pump 4.2. THE SAMPLE CONTROL UNIT 23

The lubricant sample was transported through the system using small diameter tubes. To be able to connect the tubing and maintain a ﬂow of the lubricant through the system, a holder was designed for the pump with an inlet connected to the tribological system to extract the oil and an outlet directing the ﬂow of the oil towards the sensor. The holder was specially made to suite the dimensions of the HLSC oil pump. Once the dimensions of the pump were known, a schematic of the holder was drawn using a Computer Aided Design (CAD) program. Using the CAD drawings, the holder was manufactured from a solid block of steel. Figure 4.4 shows a picture of the pump holder. The mechanical drawing for the pump holder can be found in Appendix B.1.

Figure 4.4: Pump Holder 24 CHAPTER 4. TRIBOTRONIC DIAGNOSTIC SYSTEM

Similarly, another holder was designed for the sensor to provide optimal conditions for measurement. This also had an inlet to receive the oil from the pump and an outlet that directs the oil back into the tribological system. In order to avoid any possible damage to the sensor due to high inlet oil ﬂow velocity, the outlet was positioned close to the sensor and much far below the inlet. To be able to release any air trapped within the extracted oil sample, a vent was designed and integrated in the sensor holder. This was done to avoid any measurement errors caused by air present in the lubricant. Any air trapped as bubbles in the extracted sample could thus easily escape through this vent before reaching the sensor. The vent can be opened manually before starting each measurement. Figure 4.5 shows a picture of the sensor holder. The mechanical drawing for the sensor holder can be found in Appendix B.2.

Figure 4.5: Sensor Holder 4.2. THE SAMPLE CONTROL UNIT 25

4.2.1 Pump control To operate the HLSC pump, a voltage of 12 V and a current of 2.2 A is required. The serial port (RS-232) is a universal communication port found on almost all computers today. A standard PC serial port has 9 pins. Pin 4 - DTR (data terminal ready) and Pin 7 - RTS (request to send) can be used to control a relay. The pins 4 and 7 can be set high or low. When set high, they each reach a voltage to about +12 volts and -12V when set to low. Setting the pins high and low is done with help of a program designed in LabVIEW. More about the working of the program can be found in section 4.3.1. Hence the voltage requirements to operate the pump were fulﬁlled. But since the serial port only provides a current of 0.5 mA, the signal had to be ampliﬁed to meet the requirements of the pump. This was done using a simple circuit consisting of a diode, a resistor and a transistor. The idea is to amplify the signal just enough to power a regular relay (12V/30A) which in turn would be able to power the pump. An overview of the circuit is shown in Figure 4.6.

Figure 4.6: The pump control unit 26 CHAPTER 4. TRIBOTRONIC DIAGNOSTIC SYSTEM

As seen in Figure 4.6, the serial port of the computer is connected to the circuit through pins 4 and 5. The diode helps ﬁlter the signal. If a negative voltage is applied, it does not transmit any signal to the relay keeping it in the normally open state. If the computer provides with +12 V it is transmitted via the diode and through the resistor to the transistor. The transistor in turn ampliﬁes the current enough to power the relay switching it from normally open position to normally closed. This in turn powers the pump.

4.3 The measurement interface

There are two main measurement interfaces. The ﬁrst interface was designed to give an overview of the system in general and the second interface focused on the measurements done by the sensor. To design the ﬁrst measurement interface, LabVIEW was chosen for the task as it provides a simple interface for graphical programming and design of Graphical User Interface (GUI). Further, one can log the measurements with ease and also present them in real time.

4.3.1 Programming the LabVIEW user interface The program is designed according to the algorithm described in the ﬂowchart in Figure 4.7.

False

Check Measure/ Start 10 < temp < 125 End Log data temperature True

Start Pump Measure Save data

Figure 4.7: Flow chart describing the program algorithm

As seen in the flow chart, the first thing the program checks for is whether the temperature of the oil in the tribological system is in the correct interval (between 10 ◦C and 120 ◦C). The temperature check is done in order to avoid any damage 4.3. THE MEASUREMENT INTERFACE 27 to the sensor. The temperature is measured using a k-type thermo element. The thermo element returns an integer value. If the temperature of the lubricant in the tribological system is not in the correct interval, the program keeps checking the temperature continuously and no further action is taken. If the temperature of the lubricant is in the correct interval, the program switches on the pump to extract a sample, directs it towards the sensor for measurement and executes the second measurement interface, the FPA Studio Software. More information about the FPA studio Software can be found in Appendix A. The data is then saved in a file marked with a time and date stamp and is later analyzed using MATLAB. A layout of the Graphical User Interface(GUI) is shown in Figure 4.8.

Figure 4.8: Layout of the GUI designed in LabVIEW 28 CHAPTER 4. TRIBOTRONIC DIAGNOSTIC SYSTEM Chapter 5

Experimental procedure

To see if the Tribotronic Diagnostic System(TDS) is able to measure the changes in the tribological parameters of lubricants, various lubricant samples were chosen. Since ageing of lubricant occurs over time, measurements were made on lubricants with diﬀerent levels of ageing to be able to study the changes in the tribological parameters of the lubricant.

5.1 Lubricant samples used for measurement

Various lubricant samples were measured using the TDS. Lubricant samples with diﬀerent levels of ageing measured with the tribotronic diagnostic system are listed in Table 5.1 below:

Lubricant Ageing levels LSC301(dry-TOST) 0 hours 408 hours LSC301(aged in oven,120 ◦C) 0 days 30 days PAO (with presence of Fe/Cu, Aged in oven 120 ◦C) 0 days 30 days Engine oil(Mobil 5W40, Aged in oven 120 ◦C) 0 days 30 days Engine oil(Mobil 5W40, Car test) 0 days 10000 kms

Table 5.1: Lubricant samples used in the experiments

29 30 CHAPTER 5. EXPERIMENTAL PROCEDURE

LSC301 The lubricant in focus during these measurements was the LSC301, a lubricant tailor made to meet the lubrication requirements of the HLSC. Unfortunately, little can be revealed about its composition and additive content in view of the proprietary aspects.

Poly-Alpha-Olefin(PAO) Poly-Alpha-Olefin(PAO) is a synthetic base oil in which all the molecules are very similar to each other. The process for making synthetic base oils is to start with a chemical called an olefin and make new molecules by attaching them to each other in long chains. This lubricant has been studied as it has one of the most basic chemical composition and does not contain viscosity index modifiers or long chain polymer molecules.

Mobil Super 3000 X1 5W40 The Mobil Super 3000 X1 is a premium synthetic engine oil, designed to provide protection and enhance performance. Mobil Super 3000 X1 is designed to provide wear protection, engine cleanliness as well as high and low temperature protection. This lubricant was included for studies as it has a more complex chemical composition than the lubricant PAO but not as complex as the lubricant LSC301.

5.1.1 Ageing of the lubricant samples The ageing of the lubricant samples was done in following ways.

• The ﬁrst was a modiﬁed dry-TOST(Waterless Turbine Oil Oxidation Stability Test) ASTM D 943. It is a standard test to evaluate oxidational stability of lubricants. Oxygen is passed through the lubricant at a rate of 3.5 liters/hour in the presence of an iron-copper catalyst at 120 ◦C for a certain time period [5]. The lubricant samples studied in this project had an oxidation level of 0 hours i.e. fresh oil and 408 hours as can be seen from Table 5.1. This ageing method was only used for the lubricant LSC-301.

• The second method of ageing the lubricant samples was similar to the dry- TOST. The lubricant samples were oxidized by heating them in an oven for a period of 30 days at a constant temperature of 120 ◦C and with the presence of iron-copper as catalyst. The changes in tribological parameters were studied 5.2. TRIBOLOGICAL PARAMETERS OBSERVED 31

and compared with those measured on the fresh lubricant. The major diﬀerence between ageing the lubricant samples in oven and dry-TOST ageing is that oxygen is not passed through the lubricant while ageing the sample in oven. Further, the amount of the catalyst (iron-copper) is not same as in dry-TOST. This method of ageing was used on all lubricants.

• The engine oil Mobil Super 3000 X1 5W40 was also compared to a used engine oil. This used engine oil had been used in a diesel engine car which had run 10,000 kilometers. This test was relevant as Mobil Super 3000 X1 5W40 is used as engine oil in cars.

5.2 Tribological parameters observed

Changes in two tribological parameters of the lubricant samples were the focus of these measurements; viscosity and dielectric constant. Observation of the change in viscosity of the lubricant is extremely important as changes in viscosity can cause excessive energy consumption to overcome viscous friction or loss of oil ﬁlm causing excessive wear and other severe damages to a technological system [7] . Likewise, a change in the dielectric constant indicates either contamination, or a change in the chemistry of the lubricant [8]. An active knowledge of the viscosity and the dielectric constant of the lubricant in combination should help to understand the ageing mechanism of the lubricant.

5.3 Measurement procedure with TDS

The measurements on the lubricant samples were made using the TDS over a time period of 2 hours. In between measurements, heptane was passed through the tribotronic diagnostic system to clean the traces of the last lubricant sample that was present in the system. Later, the heptane was allowed to dry and a small amount of lubricant sample to be measured is passed through the system to remove the ﬁnal traces of heptane before starting a new measurement.

5.4 Measurement procedure with Bohlins CVO100

Since the FPA sensor used in the TDS had never been used before its credibility was checked with other equipment present in the laboratory. The Bohlins CVO100 rheometer had been used to measure viscosity of ﬂuids and had always provided 32 CHAPTER 5. EXPERIMENTAL PROCEDURE with reliable measurements. It is a ﬂexible rheometer system suitable for research, product development and quality control. Figure 5.1 shows a picture of the Bohlins CVO100 rheometer.

Figure 5.1: The Bohlins CVO100 rheometer

The Bohlins CVO100 is a laboratory device used to measure the way in which a liquid, suspension or slurry ﬂows in response to applied forces [9]. To measure the viscosity of the lubricant with help of Bohlins CVO100 Rheometer, the cone and plate measuring geometry has been chosen, 20 mm in diameter cone with an angle of 1 ◦. The test temperature is controlled by PELTIER. Peltier systems are temperature control units and feature high heating and cooling rates and excellent temperature accuracy, which is an essential requirement for reliable rheological measurements.The plate is rotated and the force on the cone is measured. The temperature interval was 23 ◦C to 43 ◦C and 18 samples were chosen by linear interpolation. Pre-shear has been applied, 15 Pa for 15 seconds. The applied shear stress was between 0.2387 to 10 Pa and 20 samples were applied according to linear interpolation. Each shear is applied for a user set time and the shear rate, shear stress and viscosity are recorded for each value. The viscosity is calculated by shear stress divided by shear rate, that is, Newtonian model has been applied. The results from the measurements made on the lubricant samples, both from the Tribotronic diagnostic system and the Bohlins CVO are discussed in Chapter 6. Chapter 6

Results and discussion

Understanding the ageing mechanism of a lubricant is a complex task. There are many factors and changes in various tribological and non tribological parameters to be considered to accurately determine a trend in ageing of a lubricant. To be sure that the optimal measurement procedure and equipment were chosen, tests were done using several lubricants to verify the functionality of the experimental setup. As a ﬁrst step, the results obtained from the experiments show the changes in two of the major tribological parameters, viscosity and the dielectric constant, which help determine the ageing of the lubricants.

6.1 Initial measurements

The difference between the viscosity of the LSC301 with ageing levels of 0 and 408 hours(dry-TOST) were compared. Figure 6.1 shows the comparison between the two measurements during a long measurement cycle for a period of 2 hours. As seen in Figure 6.1, viscosity of LSC301 at oxidation level 408 hours is relatively higher than that of the oxidation level 0 hours i.e. fresh oil. A significant increase in viscosity may cause loss of oil film causing excessive wear. It may even result in increased mechanical friction causing excessive energy consumption and heat generation due to mechanical friction. Other results may involve internal or external leakage and increased sensitivity to particle contamination due to reduced oil film. It may even cause oil film failure at high temperatures, high loads or during start-ups or coast-downs. Changes in the dielectric constant were also studied. Figure 6.2 shows the comparison between the dielectric constant of the LSC301 lubricant at different oxidation levels. As seen in Figure 6.2, the dielectric constant of the LSC301 has increased for

33 34 CHAPTER 6. RESULTS AND DISCUSSION

28 Fresh LSC301 LSC301 408 hours(dry−TOST) 26

20 Viscosity(cP)

12 30 32 34 36 38 40 42 Temperature(deg Cel)

Figure 6.1: Comparison between viscosity measurements of LSC301 lubricant at diﬀerent levels of ageing(0 hours and 408 hours, dry TOST)

higher ageing level. An increase in the dielectric constant of a lubricant may indicate the presence of contaminants or a change in lubricant’s chemistry. Further, as seen in both Figure 6.1 and Figure 6.2, even though there is no external heat supply, the temperature of the lubricant sample increases from around 20 ◦C to about 45 ◦C during the course of measurement, i.e. 2 hours. This change in temperature was caused by the oil pump. It was suspected that the change in temperature might cause degradation of the lubricant sample. The phenomenon was further studied by examining a lubricant sample (LSC301 with oxidation level at 0 hours) and the tribological parameters of the sample were measured several times using the TDS. The comparison between the ﬁrst, second and third measurement on 6.1. INITIAL MEASUREMENTS 35

2.32 Fresh LSC301 LSC301 oxidation level 408 hours(dry−TOST)

2.3

2.28

2.26 Di−electric constant 2.24

2.22

2.2 30 32 34 36 38 40 42 Temperature(deg Cel)

Figure 6.2: Comparison between dielectric constant measurements of LSC301 lubricant at different levels of ageing(0 hours and 408 hours, dry TOST) the lubricant sample are shown in Figure 6.3. As seen in Figure 6.3, some degradation in the tribological parameters of the LSC301 lubricant has occurred between the first and the second measurement. According to the second and third measurements, the viscosity and the dielectric constant of the lubricant has increased. This phenomenon of increase in viscosity and dielectric constant of the lubricant after the course of a measurement was confirmed by conducting several measurements. 36 CHAPTER 6. RESULTS AND DISCUSSION

26 Test 1 Test 2 24 Test 3

Viscosity(cP) 18

12 30 32 34 36 38 40 42 Temperature(deg Cel)

(a) Comparison of viscosity on fresh LSC301 lubricant

2.23 Test 1 Test 2 Test 3 2.225

2.22

2.215 Di−electric constant

2.21

2.205 30 32 34 36 38 40 42 Temperature(deg Cel)

(b) Comparison of dielectric constant on fresh LSC301 lubricant

Figure 6.3: Comparison of viscosity and dielectric constant between test 1 and test 2 on LSC301 lubricant at ageing level 0 hours 6.1. INITIAL MEASUREMENTS 37

6.1.1 Short measurements Since the oil pump was influencing the lubricant sample and hence the measurements during the longer measurement sequences, a new measurement procedure was devised. Short measurements were done over a course of 1 to 1.5 minutes instead and more frequently. Instead of using the pump constantly, it was switched off between each measurement, hence reducing its effect on the temperature of the lubricant sample extracted. The results from the short measurements are shown in Figure 6.4.

37 Test 1 Test 2 36 Test 3

32 Viscosity(cP)

27 22.9 23 23.1 23.2 23.3 23.4 23.5 23.6 23.7 23.8 23.9 Temperature(deg Cel)

Figure 6.4: Comparison between short measurements test 1, test 2 and test 3 on LSC301(Fresh lubricant) 38 CHAPTER 6. RESULTS AND DISCUSSION

As seen in Figure 6.4, there is a much smaller change in viscosity when measurements are taken over shorter time intervals than when they are taken over a period of 2 hours. Since the short measurements did not provide with viscosity measurements at larger temperature interval, a theoretical model was designed to be able to obtain viscosity values at any desired temperature. The theoretical model is discussed in more detail in section 6.1.2.

6.1.2 Theoretical model The expression used by Roelands (1966) [10] to describe the eﬀect of temperature on viscosity is given as:

log(log η + 1.200) = −So log(1 + tm/135) + log Go (6.1)

Where:

η = absolute viscosity, cP

tm = temperature, C

Go = dimensionless constant indicative of viscosity grade of liquid

So = dimensionless constant that establishes slope of viscosity-temperature rela- tionship

As seen in the equation, the dimensionless constants Go and So are the two un- known variables. Using the measurements done over a shorter period of time and equation 6.1, theoretically, we are able to obtain viscosity values for any temperature interval which may be required. Figure 6.5 shows a comparison between the theoretical model and actual viscosity measurements on the non-oxidized lubricant PAO with the TDS. As seen in Figure 6.5, the values obtained from the theoretical model based on short measurements from TDS are very similar to the actual measurements.

6.1.3 Short vs long measurement sequences As discussed in section 6.1.1, shorter time period for measurements are optimal to study the tribological parameters. Using a shorter time period resulted in more accurate measurements, as the eﬀect of the oil pump on the temperature of the lubricant sample was negligible. During the measurements over a long period of 6.1. INITIAL MEASUREMENTS 39

32 Bohlin CVO measurements Theoretical model using short measurements from TDS

Viscosity(cP) 24

18 30 32 34 36 38 40 42 Temperature (deg Cel)

Figure 6.5: Theoretical model based on short measurements from TDS compared to viscosity measurements from Bohlins on lubricant LSC301(Fresh lubricant)

time, we observed the oil pump might be causing degradation of the lubricant sample being measured. By switching the pump oﬀ and using a shorter time period between measurements, we were able to avoid this problem. Even though the system is designed to provide with real-time measurements, there may be some cases that a machine or a tribological system in need of condition monitoring has to be shut down while measurements are being taken. In such cases, shorter measurements will prove to be very useful, as it would save time. A system stop at an industry often implies huge economical losses. Though the short measurements have their beneﬁts, they have one major drawback. Short measurements are taken at regular time intervals and not in real time. Hence, one would not have active knowledge of the state of 40 CHAPTER 6. RESULTS AND DISCUSSION the system between measurements and this end the scope of active counteraction in case it is required to avoid damage to the system. This however is not an issue when measuring on this kind of lubricant since the change in its properties is very slow. To have an accurate idea of the state of the lubricant and avoid its degradation caused by the oil pump, the measurements should be taken more frequently. However, short measurements do not provide a a relation between temperature and the di-electric constant of lubricants being measured. The temperature of the lubricants being measured needs to be controlled or a theoretical model(similar to theoretical model for viscosity discussed in section 6.1.2) needs to be established to utilize short measurements to be able to study the change in di-electric constant of lubricants. Hence, in this project, the long measurements have been chosen to study the changes in tribological parameters of lubricants.

6.2 Comparisons between TDS and Bohlins CVO100

The viscosity measurements made on various lubricant samples with help of the TDS could be compared to the viscosity measurements made on the same lubricant with help of the Bohlins CVO. Figure 6.6 shows a comparison between the viscosity measurements done by the bohlins and the TDS on the lubricant LSC 301 at two diﬀerent ageing levels levels, 0 hours, i.e. fresh lubricant and at 408 hours (dry- TOST ageing method). As seen in the Figure 6.6, the viscosity measurements made with help of the TDS do not concur with the measurements made with help of the Bohlins CVO. Further, while the TDS measurements show a decrease in viscosity of the lubricant LSC 301 with increase in oxidation level, the bohlins measurements give the contrary result. Since the measurements were done with the same lubricant sample, there should not be a diﬀerence between the measurement results. 6.2. COMPARISONS BETWEEN TDS AND BOHLINS CVO100 41

32 BI CVO−Fresh LSC301 30 BI CVO−LSC301 408 hours(dry−TOST) TDS−Fresh LSC301) TDS−LSC301 408 hours(dry−TOST) 28

22 Viscosity (cP) 20

12 30 32 34 36 38 40 42 Temperature (Deg Cel)

Figure 6.6: Comparison between the viscosity measurements done by the Bohlins and the TDS on the lubricant LSC 301 42 CHAPTER 6. RESULTS AND DISCUSSION

6.2.1 Possible cause of deviations in measurements One theory as to why there is diﬀerence between the viscosity measurements between the Bohlins and the TDS is the permanent and temporary viscosity loss that often occurs in the polymer-containing lubricants. The lubricant’s viscosity modiﬁers are long-chain molecules that lessen the change of viscosity with temperature variance. In the past, the polymer additives (used to thicken the oil) were sometimes susceptible to viscosity loss [11]. These polymer molecules are severely distorted when the lubricant is subjected to high shear stress. The higher the shear stress, the lower the viscosity until a stable region is reached. If the shear stress breaks the polymer molecules the process is irreversible and a permanent viscosity loss has occurred. Figure 6.7 shows a schematic of mechanical polymer degradation that results in permanent viscosity loss.

Figure 6.7: Schematic of mechanical polymer degradation

Figure 6.8: Relation between shear rate and viscosity 6.2. COMPARISONS BETWEEN TDS AND BOHLINS CVO100 43

As long as the shear stress does not break the molecules, the process is reversible and is known as temporary viscosity loss. A relation between shear rate and viscosity is shown in Figure 6.8 [12]. Figure 6.8 also shows that the increase in shear rate does not aﬀect the viscosity of the base oil. Tests were conducted on the base oil PAO to conﬁrm the theory and the results obtained between the measurements made with the tribotronic diagnostic system and the Bohlins CVO are shown in Figure 6.9.

34 FPA Measurements PAO Bohlins measurements PAO 32

26 Viscosity (cP) 24

18 30 32 34 36 38 40 42 Temperature (Deg Cel)

Figure 6.9: Comparison between measurement results from TDS and Bohlins CVO on the lubricant PAO 44 CHAPTER 6. RESULTS AND DISCUSSION

As seen in the Figure 6.9, the viscosity measurements made with help of the TDS do concur with the measurements made with help of the Bohlins CVO. Hence, the temporary and permanent viscosity loss may be the main reason for diﬀerences between measurement results obtained from the two measurement systems, though further investigation is still required to conﬁrm this theory.

6.3 Results obtained

In this section, we compare the results from the measurement in the TDS on fresh and aged lubricant samples mentioned in Table 5.1. As mentioned earlier in section 5.2, the changes in viscosity and the di-electric constant have been studied. The change in the viscosity of a lubricant is related to oxidation and shearing and may cause excessive energy consumption to overcome viscous friction or loss of oil film causing excessive wear and other severe damages to a technological system. A change in di-electric constant of a lubricant indicates either the contamination, or a change in the chemistry of the lubricant. Hence, the viscosity and di-electric constant are relevant and important parameters for understanding the ageing mechanism of a lubricant. The measurement results shown in this section have been obtained using the long measurement duration. The viscosity and di-electric constant of fresh lubricant have been compared with that of the aged lubricant sample. The level of ageing for each lubricant can be found in Table 5.1. Even though we have seen that the short measurements are better as they do not affect the lubricant sample being measured, long measurements have been carried out to study the changes in both viscosity and di-electric constant simultaneously from the same test. Although the viscosity of a lubricant sample can be theoretically predicted for any temperature, a theoretical model of di-electric constant has not yet been developed. Long measurements were thus necessary to study the relation between temperature and di-electric constant of lubricants. Three different lubricants were chosen and changes in their viscosity and di- electric constant with increased ageing levels were studied. The lubricants were chosen based on the complexity of their chemical composition as well as based on their additive content. As we have seen in section 6.2.1, the additive content in a lubricant may result in faulty measurements. The aim is therefore to start with a lubricant having simple chemical composition and later on conduct measurements on lubricants containing additives. The lubricant PAO has one of the most basic chemical composition and does not contain viscosity index modifiers or long chain polymer molecules. The Mobil Super 3000 X1 is a premium synthetic engine oil. 6.3. RESULTS OBTAINED 45

It contains additives designed to provide protection and enhance performance. The chemical composition of Mobil Super 3000 X1 is more complex compared to the PAO, but relatively simpler to that of LSC301. The LSC301 is a transmission lubricant tailor made to meet the lubrication requirements of the HLSC and has an extremely complex chemical composition and contains several additives. As mentioned earlier, the aim of this project is to study the changes in viscosity and di-electric constant of the LSC301 lubricant and to be able to understand its ageing mechanisms. Results from all lubricants are shown and discussed brieﬂy from section 6.3.1 to 6.3.3 and are discussed in detail in section 6.3.4.

6.3.1 PAO results The lubricant PAO was aged in oven for a period of 30 days in presence of iron- copper catalyst. A comparison between the viscosity and the di-electric constant of the fresh and aged PAO is given in Figure 6.10. As can be seen from Figure 6.10, there is an increase in both viscosity and the di-electric constant of the lubricant with ageing.

6.3.2 Mobil 5W40 results The engine oil Mobil Super 3000 X1 was aged using two methods. The ﬁrst sample was aged in an oven for a period of 30 days in presence of iron-copper catalyst. The second sample was aged in a diesel engine car which had driven 10000 kilometers. A comparison between the viscosity and the di-electric constant of the fresh and aged Mobil Super 3000 X1 is shown in Figure 6.11 and Figure 6.12 respectively.

6.3.3 LSC301 results The lubricant is used in the HLSC. The ageing trend of the lubricant is therefore the main focus of this project. This lubricant was aged using two methods i.e., by the dry-TOST method and in an oven. The details of the ageing methods have earlier bee described in section 5.1.1. The comparison of the viscosity and the di-electric constant of the fresh and aged lubricant samples measured by the two aging methods are given in Figure 6.13 and Figure 6.14 respectively. As seen from Figure 6.13 and Figure 6.14, the viscosity and the di-electric constant of the lubricant increased with increased ageing levels. 46 CHAPTER 6. RESULTS AND DISCUSSION

36 Fresh PAO PAO oven 30 days 34

26 Viscosity(cP)

18 30 32 34 36 38 40 42 Temperature(deg Cel)

(a) Comparison of viscosity on PAO lubricant(Aged in oven)

2.205 Fresh PAO PAO oven 30 days 2.2

2.195

2.19

2.185

Di−electric constant 2.18

2.175

2.17

2.165 30 32 34 36 38 40 42 Temperature(deg Cel)

(b) Comparison of di-electric constant on PAO lubricant(Aged in oven)

Figure 6.10: Comparison of viscosity and di-electric constant on PAO lubricant between fresh lubricant and aged in oven(30 days) 6.3. RESULTS OBTAINED 47

65 Fresh Mobil 5W40 Mobil 5W40 aged in oven(30 days)

50 Viscosity(cP)

35 30 32 34 36 38 40 42 Temperature(deg Cel)

(a) Comparison of viscosity on Mobil 5W40 lubricant(Aged in oven)

85 Fresh Mobil 5W40 80 Car test(10000 kms)

60 Viscosity(cP) 55

35 30 32 34 36 38 40 42 Temperature(deg Cel)

(b) Comparison of viscosity on Mobil 5W40 lubricant(Car test)

Figure 6.11: Comparison of viscosity on Mobil 5W40 lubricant between ageing in oven and ageing in car 48 CHAPTER 6. RESULTS AND DISCUSSION

2.5 Fresh Mobil 5W40 Mobil 5W40 aged in oven(30days) 2.45

2.4

2.35

2.3

Di−electric constant 2.25

2.2

2.15

2.1 30 32 34 36 38 40 42 Temperature(deg Cel)

(a) Comparison of dielectric constant on Mobil 5W40 lubricant(Aged in oven)

2.5

2.45

2.4

2.35 Fresh Mobil 5W40 Car test(10000 kms) 2.3

Di−electric constant 2.25

2.2

2.15

2.1 30 32 34 36 38 40 42 Temperature(deg Cel)

(b) Comparison of di-electric constant on Mobil 5W40 lubricant(Car test)

Figure 6.12: Comparison of di-electric constant on Mobil 5W40 lubricant between ageing in oven and ageing in car 6.3. RESULTS OBTAINED 49

28 Fresh LSC301 LSC301 408 hours(dry−TOST) 26

20 Viscosity(cP)

12 30 32 34 36 38 40 42 Temperature(deg Cel)

(a) Comparison of viscosity on LSC301 lubricant(dry-TOST)

28 Fresh LSC301

26 LSC301 oven 30 days

20 Viscosity(cP)

12 30 32 34 36 38 40 42 Temperature(deg Cel)

(b) Comparison of viscosity on LSC301 lubricant(Aged in oven)

Figure 6.13: Comparison of viscosity on LSC301 lubricant between dry-TOST and oven 50 CHAPTER 6. RESULTS AND DISCUSSION

2.32 Fresh LSC301 LSC301 oxidation level 408 hours(dry−TOST)

2.3

2.28

2.26 Di−electric constant 2.24

2.22

2.2 30 32 34 36 38 40 42 Temperature(deg Cel)

(a) Comparison of dielectric constant on LSC301 lubricant(dry-TOST)

2.224 Fresh LSC301 LSC301 oven 30 days 2.222

2.22

2.218

2.216

2.214 Di−electric constant 2.212

2.21

2.208

2.206 30 32 34 36 38 40 42 Temperature(deg Cel)

(b) Comparison of dielectric constant on LSC301 lubricant(Aged in oven)

Figure 6.14: Comparison of dielectric constant on LSC301 lubricant between dry- TOST and oven 6.3. RESULTS OBTAINED 51

6.3.4 Summary of results As seen in section 6.3, the ageing of lubricants in an oven is not really adequate as the changes in viscosity and di-electric constant are very small compared to the changes in lubricants aged with help of dry-TOST or aged in car. The only exception is the decrease in di-electric constant of the lubricant Mobil Super 3000 X1 when aged in oven, Figure 6.12(a). If we compare these results with those of aged in car shown in Figure 6.12(b), we see that the decrease in di-electric constant is very small compared to the increase in di-electric constant of the lubricant aged in car. This decrease may probably be attributed to the ageing the sample in the oven. As discussed earlier, ageing in oven is not an adequate ageing method and hence this measurement may not depict the actual trend of the change in di-electric constant of the lubricant. Further, the viscosity and the di-electric constant of lubricants tend to increase with increase in ageing level for measurements on the lubricant samples PAO, and Mobil Super 3000 X1 and LSC301.

An increase in viscosity of a lubricant may imply:

• Excessive heat generation may result in oil oxidation, sludge and varnish build- up.

• Gaseous cavitation due to inadequate oil ﬂow to pumps and bearings.

• Excess energy consumption to overcome ﬂuid friction.

• Poor cold-start pumpability.

Likewise, an increase in di-electric constant of a lubricant may imply:

• The presence of contaminants in the lubricant, such as water or particles.

• Changes in chemistry of the oil such as additive depletion or oxidation.

To study the ageing mechanisms, and to accurately determine a trend in ageing of lubricants, we need to study lubricant in actual ﬁeld-tests. Ageing the lubricant samples in oven is not an adequate ageing method. Further, the study of changes in viscosity and the di-electric contants of lubricants by itself is not enough to be able to refer to ageing of the system. Changes in these tribological parameters need to be co-related to other functional parameters such as speed, torque etc. It is only then the Tribotronic Diagnostic System can be adjusted to perform optimally and lead to the development of a complete Tribotronic System. 52 CHAPTER 6. RESULTS AND DISCUSSION Chapter 7

Conclusions

The main conclusions from this master thesis are:

• It is possible to actively monitor the changes in viscosity and di-electric constant of the lubricant in the investigated system.

• The monitored changes in tribological parameters can be used together with friction measurements in order to co-relate ageing of lubricant to friction hence actively control the state of the application.

• The viscosity and di-electric constant of a lubricant increase with generally increase in ageing level as the changes in tribological parameters of lubricants aged in oven .

• Ageing of lubricant in oven is not an adequate ageing method. Real ﬁeld-tests are required with lubricants to accurately plot the ageing trend of the lubricant.

• Polymer degradation may be the main cause of discrepancies of viscosity measurements between the TDS and other measurement instruments.

53 54 CHAPTER 7. CONCLUSIONS Chapter 8

Future work

• Investigate the eﬀect of TDS on polymer containing lubricant.

• Use the Tribotronic Diagnostic System(TDS) to monitor behaviour of ageing tests in wet clutch test rigs. Changes in tribological parameters of lubricants have to be studied in real ﬁeld-tests to accurately understand the ageing mechanisms of lubricants.

• Use measurement results from TDS to change control software of clutch to compensate for ageing of the lubricant.

• Establish a theoretical model for changes in di-electric constant similar to the theoretical model for viscosity to be able to utilize the short measurements for the di-electric constant as well.

55 56 CHAPTER 8. FUTURE WORK Bibliography

[1] B. Bhushan, “Introduction to tribology,” Book, 2002.

[2] P. Jost, “Lubrication(tribology) - a report on the present position and industry’s needs,” England, Department of Education and Science, H.M. Stationary Oﬃce, 1966.

[3] S. Glavatskih and E. H¨oglund,“Tribotronics-towards active tribology,” Tribol- ogy International, vol. 41, no. 9-10, pp. 934–939, 2008.

[4] P. Marklund, “Wet clutch tribological performance optimization methods,” Lule˚aUniversity of Technology, 2008.

[5] K. Berglund, P. Marklund, and R. Larsson, “Lubricant ageing eﬀects on the friction charecteristics of wet clutches,” Lule˚aUniversity of Technology, 2010.

[6] J. Milpied, M. Uhrich, B. Patissier, and L. Bernasconi, “Applications of tuning fork resonators for engine oil, fuel, biodiesel fuel and urea quality monitoring,” SAE International Journal of Fuels and Lubricants, vol. 2, no. 2, pp. 45–53, 2010.

[7] M. Barnes, “Oil viscosity - how it’s measured and reported,” Machinery Lubri- cation, 2002.

[8] A. A. Carey and A. J. Hayzen, “The dielectric constant and oil analysis,” Ma- chinery Lubrication, 2001.

[9] “Bohlin instruments. rheological measurements on drilling mud and a crude oil,” Industrial Lubrication and Tribology, vol. 54, no. 1, pp. 26–30, 2002.

[10] B. J. Hamrock, S. R. Schmid, and B. O. Jacobson, “Fundamentals of ﬂuid ﬁlm lubrication,” Book, 2004.

57 58 BIBLIOGRAPHY

[11] W. Scraba, “All about oil viscosity and api classiﬁcations,” autoMedia.com, 2000.

[12] Blackie, “Chemistry and technology of lubricants,” Book, 1997. Appendix A

The FPA Studio Interface

A.1 FPA Studio Interface overview

The sensor has its own interface that in turn is executed via the program designed in LabVIEW once all the pre-conditions have been met. A layout of the FPA studio interface is shown in the Figure A.1. FPA Studio is a real-time operating software that allows the viscosity, density, di- electric constant and temperature measured by the FPA to be displayed in an easy to use graphical user interface (GUI). The FPA Studio software permits the continuous recording of measured values to be stored in a text ﬁle for subsequent data analysis by standard spreadsheet manipulation programs. The FPA is directly connected to a PC using the ModBus protocol conﬁgured with communication software.

A.2 Setup Tab

The “Setup” tab contains basic information related to the FPA in use. The “Com- munication” section displays the communication type and the COM port number through which the FPA is linked. The “FPA Identification” section contains important information about the FPA that is connected and in communication with the PC. This information includes the FPA serial number, last revision and factory cali- bration dates. The “Host Date” is the internal date and hour of the FPA in current use and is displayed with the following format: “MM/DD/YYYY hh:mm:ss”. If the FPA auto-connection box is ticked, then the COM port number is automatically set. All the information related to the “FPA Identification” tables is also already entered. This information cannot be modified.

59 60 APPENDIX A. THE FPA STUDIO INTERFACE

Figure A.1: Layout of the FPA studio interface

A.3 Data acquisition tab

The “data acquisition” tab allows operators to set-up and to customize the acquisition. The sub sections “Duration” and “Acquisition Parameters” sections are linked together. First, operators have the choice between making a continuous acquisition or identify a speciﬁc acquisition interval with “Fixed Period”. If “Continuous” is selected, the acquisition will run until it is manually stopped by the operator. In “Continuous” mode, the operator may designate a delay time between each scan. If “Fixed Period” is selected, the acquisition will run until a designated period of time is achieved. Indicate the total duration of the acquisition in “Amount of time” and the interval between two points below in “Time interval between samples”. Figure A.2 shows a layout of the data acquisition tab. It is not possible to put a time interval shorter than a minute. If the time interval is set to zero, then the FPA will automatically acquire data and report a measured A.4. GRAPHICS SECTION 61

Figure A.2: Layout of the Data Acquisition tab physical property and temperature about every 30s.

A.4 Graphics section

The Graphic section enables the operator to observe the acquired data in a real- time mode. The digital display fields always display the most recently acquired data while the charts display the aggregate of historical and current measured parameters. Both are updated during the FPA data acquisition. An example of an active FPA acquisition is shown in Figure A.3 . When the acquisition or the downloading of data from internal memory is finished, the measured parameters are saved in the text file. The file in an excel spreadsheet shows the list of all saved values, ranged in 7 columns. The first column refers to the date and time of acquisition: MM/DD/YY and HH/MM/SS. Then dynamic viscosity values are indicated in cP, next to density values in gm/cc. Dielectric constant appears in the 5th column, as indicated by “Dielectric”. Finally, temperatures in ◦C are displayed, next to “DeltaT” which reveals if any temperature variation has occurred during the acquisition. Figure A.4 shows a layout of the data log. 62 APPENDIX A. THE FPA STUDIO INTERFACE

Figure A.3: An active FPA data acquisition

Figure A.4: Layout of the data log Appendix B

Drawings

B.1 Pump holder

63 1 2 3 4 5 6

Rev Revision note Approved by - date

11,8

26,1 26,5 2XM6 förborras 5 15 6 A A 15 12,5 11,8 4,6 38 70

B 40 B

C 54,5 C

100

1 1 1 PUMPHOLDER

Item Quantity Title, designation, material, dimension, etc Weight Article No/Reference

Title Title Drawing Number Edition Sheet Number nix nix 1 2 5 6 B.2. SENSOR HOLDER 65 B.2 Sensor holder

Appendix C

National Instruments I/O module

67 Technical Sales Sweden 08 587 895 00 [email protected]

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