evaluation of fire resistant hydraulic fluid to replace conventional mineral oil in nuclear industry

Dissertation Titled

―Evaluation of Fire Resistant Hydraulic Fluid to Replace

Conventional Mineral Oil in Nuclear Industry‖

Submitted

in partial fulfilment of

the requirements of the degree of

M. Tech. (Mechanical Engineering with

Specialization in Machine Design)

By

Zeeshan Ahmad

(132090007)

2014-2015

Under the guidance of

Dr. V.M.Phalle

Department of Mechanical Engineering

Veermata Jijabai Technological Institute

(Autonomous Institute Affiliated to University of Mumbai)

Mumbai 400019

Certificate

This is to certify that Zeeshan Ahmad Rizwan Ahmad (ID. No. 132090007) has completed

the dissertation titled ―Evaluation of Fire Resistant Hydraulic Fluid to Replace

Conventional Mineral Oil in Nuclear Industry‖ to our satisfaction, as a partial fulfilment of

award of degree of M. Tech. Mechanical Engineering (Specialization in Machine Design)

under University of Mumbai.

Dr. V.M.Phalle

Supervisor

Department of Mechanical Engg.

V.J.T.I., Mumbai

Mr N. L. Soni

External Supervisor

Head, Fluid Power & Tribology Section

Refuelling Technology Division

Dr. Sanjay M.G.

Head


V.J.T.I., Mumbai

Dr. O. G. Kakde Director,

V.J.T.I., Mumbai

Evaluation of Fire Resistant Hydraulic Fluid to Replace Conventional Mineral Oil in Nuclear Industry

Zeeshan Ahmad

iii

Certificate of Approval

The dissertation on “Evaluation of Fire Resistant Hydraulic Fluid to Replace

Conventional Mineral Oil in Nuclear Industry” submitted by Mr. Zeeshan Ahmad

Rizwan Ahmad (ID. No. 132090007) is found to be satisfactory and is approved for the

Degree of Master of Technology in Mechanical Engineering with specialization in Machine

Design under University of Mumbai.

Dr. V.M.Phalle

Supervisor


V.J.T.I., Mumbai (External Examiner)

Date:

Place: Mumbai


Zeeshan Ahmad

iv

Acknowledgment

First and foremost I would like to thank Dr. V.M.Phalle, Associate Professor & TPO,

Mechanical Engg. Dept., VJTI Mumbai, for his guidance, support and encouragement

throughout this work.

I thank Bhabha Atomic Research Centre, Trombay, Mumbai for giving me this

internship opportunity to carry out a research of this magnitude.

My sincere thanks to Mr N. L. Soni, Outstanding Scientist, Head-Fluid Power and Tribology

Section, Refuelling Technology Division, Mr. P. K. Mishra, Scientific officer (E), Mr. P. K.

Limaye, Scientific officer (H), Mr. Shiju Verghese Scientific officer (E), Mr. S.

Pandharikar, Scientific officer (F), and the entire Team, Bhabha Atomic Research Centre,

Mumbai for being supportive and giving me the freedom to experiment my ideas. Their

guidance and continuous encouragement throughout this period was invaluable for my

success. I am grateful to them for their advice and endless support in all parts of this

dissertation.

Last but not least, I would like to thank my family and friends for motivating and

having faith in me.


Zeeshan Ahmad

v

Declaration of the Student

I declare that this written submission represents my ideas in my own words and where

others' ideas or words have been included, I have adequately cited and referenced the original

sources.

I also declare that I have adhered to all principles of academic honesty and integrity and

have not misrepresented or fabricated or falsified any idea / data / fact / source in my

submission.

I understand that any violation of the above will be cause for disciplinary action by the

Institute and can also evoke penal action from the sources which have thus not been properly

cited or from whom proper permission has not been taken when needed.

Zeeshan Ahmad

M.Tech (Machine design)

Roll No.: 132090007

Date:


Zeeshan Ahmad

vi

Abstract

Hydraulic systems are extensively used in DAE like fuel handling control of various

reactors, reprocessing plants, nuclear waste management systems; nuclear fuel extrusion

presses and uranium mining etc. in many applications surrounding temperatures are high.

Conventional hydraulic oil manufactured from petroleum based fluid has poor fire resistant

characteristics and in high temperature applications this type of oil may be a big fire hazard.

Also, in some applications like AHWR fuelling machine snout, where ambient temperature is

quite high, lack of adequate cooling system may result in increase in operating temperature of

working hydraulic fluid leading to the loss of viscosity and hence lubrication apart from

thermal degradation of the hydraulic fluid. Petroleum based hydraulic fluids have poor

viscosity index and have limit in being used only up to 65oC. To reduce the fire hazards, non-

flammable hydraulic fluids are best suited. Apart from the above difficulties gamma radiation

is the most severe operating condition in nuclear industry. So degradation of hydraulic fluid

because of gamma radiation will be dangerous and hazardous for the entire environment near

the nuclear reactor. In view of this it is essential to explore and evaluate synthetic hydraulic

fluid generally called as Fire Resistant Hydraulic Fluid (FRHF) for the utilization in fuelling

machine of AHWR as well as other hydraulic applications of DAE. There for this thesis work

mainly based on the evaluation and comparison of the properties of Fire resistant hydraulic

fluid and Petroleum based mineral oil.

Keywords: Evaluation of fire resistant hydraulic fluid, Radiation resistant lubricant, friction,

Wear, Viscosity measurement


Zeeshan Ahmad

vii

TABLE OF CONTENTS 1. Introduction ........................................................................................................................ 1

Objective ................................................................................................................................ 2

Summery ................................................................................................................................ 2

2. Literature Review ............................................................................................................... 4

2.1. Classification of Hydraulic Fluids [1]

...................................................................... 4

2.1.1. Classification by Physical Properties ................................................................ 5

2.1.2. Classification by Chemical Properties .............................................................. 5

2.1.3. Classification by Operating Characteristics ...................................................... 5

2.1.4. Classification into Petroleum or Nonpetroleum Hydraulic Fluids ................... 6

2.1.5. Classification by Fire-Resistance ...................................................................... 7

2.2. Classification of Fire-Resistant Hydraulic Fluids, Their Properties and Uses [2]

.. 7

2.2.1. Introduction ....................................................................................................... 7

2.2.2. Fire Hazards ...................................................................................................... 8

2.2.3. Fire Resistance and Fire-Resistant Fluids ......................................................... 9

2.2.4. Fire-Resistant Hydraulic Fluid Types for Industrial Applications ................... 9

2.3. Properties of Hydraulic Fluids and Their Effect on System Performance [6]

........ 10

2.3.1. Density (ρ) ...................................................................................................... 11

2.3.2. Viscosity ......................................................................................................... 12

2.3.3. Viscosity Index [1]

........................................................................................... 13

2.4. Requirements for Fire-Resistant Hydraulic Fluids [7]

........................................... 14

2.5. Tribological Properties of Hydraulic Fluids.......................................................... 15

2.5.1. Lubrication Properties ..................................................................................... 15

2.5.2. Wear or Surface Damage ................................................................................ 18

2.5.3. Prevention of Wear ......................................................................................... 19

2.5.4. Test Methods for Lubricating Properties ........................................................ 20

2.6. Effect of Gamma Radiation on Properties of Hydraulic Fluid.............................. 24


Zeeshan Ahmad

viii

3. Tribological Evaluation of Hydraulic Fluids .................................................................... 27

3.1. Apparatus and Materials........................................................................................ 27

3.2. Experimental Procedure ........................................................................................ 28

3.2.1. Standard Testing Method ................................................................................ 28

1. Test Procedure .................................................................................................... 29

2. Test Parameters................................................................................................... 30

3.3. Measurement and Calculation of Wear [23] [24]

....................................................... 30

3.3.1. Wear Measurement of Ball Specimen ............................................................ 31

3.3.2. Wear of Flat Specimen ................................................................................... 32

3.3.3. Results and Discussion ................................................................................... 32

4. Gamma Irradiation of Hydraulic Fluids ........................................................................... 39

4.1. Measurement of Properties of Synthetic Fire Resistant Hydraulic Oil (Oil-A) .... 39

4.1.1. Effect of Gamma Radiation on Kinematic Viscosity ..................................... 39

4.1.2. Effect Of Gamma Radiation On Viscosity Index .......................................... 40

4.1.3. Appearance of Oil after Gamma Irradiation ................................................... 40

4.2. Measurement of Properties of Petroleum Based Hydraulic Fluid (Oil-B) ............ 40

4.2.1. Effect of Gamma Radiation on Kinematic Viscosity ..................................... 40

4.2.2. Effect Of Gamma Radiation On Viscosity Index .......................................... 41

4.2.3. Appearance of Oil after Gamma Irradiation ................................................... 41

5. Conclusion and Future Scope ........................................................................................... 42

5.1. Conclusion ............................................................................................................. 42

5.2. Future Scope .......................................................................................................... 43

6. References ............................................................................................................................ 45

Appendix I ................................................................................................................................ 47


Zeeshan Ahmad

ix

LIST OF FIGURES

Figure 2.1 Coefficient of friction Vs. Stribeck parameter ....................................................... 17

Figure 2.2 Five bench-type friction and wear testers ………………………………………………….…..24

Figure 3.1 Measurement of plate and ball wear scar marks ................................................... 30

Figure 3.2 Lubrication regimes ............................................................................................... 37

Figure 3.3 Reciprocating wear & friction machine PLINT TE 70 .......................................... 47

Figure 3.4 Typical photographs indicating ball wear .............................................................. 47

Figure 3.5 3D profile of wear scar on SS-52100 steel flat sample .......................................... 47

Figure 3.6 Stribeck curve of Oil-A and Oil-B ......................................................................... 48

Figure 3.7 Effect of temperature on coefficient of friction 15 N / 10 Hz ................................ 48



Figure 3.10 Load vs. wear rate of ball 27oC /10 Hz ................................................................ 50

Figure 3.11 Load vs. wear rate of ball 65oC /10 Hz ................................................................ 50

Figure 3.12 Load vs. wear rate of plate 27oC /10 Hz .............................................................. 51

Figure 3.13 Load vs. wear rate of plate 65oC /10 Hz .............................................................. 51

Figure 4.1 Percentage change in kinematic viscosity of Oil-A ............................................... 52

Figure 4.2 Viscosity index vs. gamma radiation dose ............................................................. 52

Figure 4.3 Change of appearance with gamma radiation dose ................................................ 52

Figure 4.4 Percentage change in kinematic viscosity of Oil-B ............................................... 53

Figure 4.5 Viscosity index vs. gamma radiation dose ............................................................. 53

Figure 4.6 Change of appearance with gamma radiation dose ................................................ 53


Zeeshan Ahmad

x

LIST OF TABLES

Table 2.1 Possible ignition sources ........................................................................................... 8

Table 2.2 ISO Classification of fire-resistant hydraulic fluids and their composition .............. 9

Table 2.3 Units of dynamic viscosity ...................................................................................... 12

Table 2.4 Units of kinematic viscosity .................................................................................... 13

Table 2.5 Radiation resistance of hydraulic fluids .................................................................. 25

Table 3.1 Test conditions for Oil-A and Oil-B ........................................................................ 28

Table 3.2 ASTM std. parameters Vs. parameters used for this test ........................................ 30

Table 3.3 Experiment data for hydraulic Oil-A and Oil-B ...................................................... 33

Table 3.4 Experiment results of OIL-A and Oil-B .................................................................. 34

Table 4.1 Percentage change in kinematic viscosity of radiated oil sample from fresh oil .... 39

Table 4.2 Viscosity index of Oil-A ......................................................................................... 40

Table 4.3 Percentage change in kinematic viscosity of radiated oil sample from fresh oil .... 41

Table 4.4 Viscosity index of Oil-B .......................................................................................... 41


Zeeshan Ahmad

xi

NOMENCLATURE

Oil-A Polyol Ester based synthetic Fire Resistant Hydraulic Fluid (FRHF) of

viscosity grade 68

Oil-B Petroleum based mineral hydraulic fluid of viscosity grade 68

ρ Density

m Mass

v Volume

η Dynamic Viscosity

υ Kinematic Viscosity

V.I Viscosity Index

η*V/P Stribeck Parameter

V Sliding Velocity

P Load/ Pressure

Vb Volume Loss of Ball Specimen

D Wear Scar Diameter of Ball

R Radius of Ball

k Wear Rate

L Sliding Distance

Vf Volume Loss of Plate Specimen

l Length of Wear Scar on Plate

w Width of Wear Scar on Plate

d Depth of Wear Scar on Plate


Zeeshan Ahmad

xii

Organization Profile

Bhabha Atomic Research Centre (BARC), Trombay has already made its impressions in

the world of science as one of the unique nuclear research institution where high quality

research and development is taking place in the areas of nuclear reactor design and

installation, fuel fabrication, chemical processing of depleted fuel and also acquired sufficient

expertise in the development of radioisotope application techniques in medicine, agriculture

and industries. Basic and advanced research investigations were in full progress in nuclear

physics, spectroscopy, solid state physics, chemical and life sciences, reactor engineering,

instrumentation, radiation safety and nuclear medicine etc. In a nutshell, BARC provides a

broad spectrum of scientific and technological activities extending from basic laboratory

bench scale research to scale up plant level operations and its functional domain covers all

walks of science and technology – stretching from classical school of thoughts to the

emerging novel fields of interest. The core mandate of this institution is to provide Research

and Development support required to sustain one of the major peaceful applications of nuclear

energy viz. power generation. This includes conceptualization of the programs, finalization of

the design of the reactor and the peripheral components, preparation of computer generated

working models and their evaluation studies under simulated reactor running conditions,

identification, and selection and testing of materials and components for their risk analysis

under extreme conditions of reactor operating environments, development and testing of new

reactor fuel materials etc. Besides, BARC also extends its expertise to chemical processing of

spent fuels, safe disposal of nuclear waste besides developing new isotope application

techniques in industries, medicine, agriculture etc. Advanced frontline research in physical,

chemical and biological sciences are intensely being pursued in BARC in order to give the

nation a cutting edge in the fields of science and technology at the international levels. Thus,

BARC is a multifaceted institution wherein the in house research findings were further

translated into the development stage and finally through successful demonstration phase is

taken for deployment in the respective fields. Advanced equipment and instruments, well set

laboratories, vibrant ambience and availability of expertise from all fields of science and

engineering are the unique features of BARC committed in taking the nation to the new

horizons of knowledge and development.


Zeeshan Ahmad

1

1. Introduction

The two main functions of hydraulic fluids are (a) to transmit power efficiently and (b)

to lubricate components. Petroleum based oils are excellent in meeting these requirements but

has the disadvantage of being combustible. Hydraulic systems are extensively used in DAE

like fuel handling control of various reactors, reprocessing plants, nuclear waste management

systems; nuclear fuel extrusion presses and uranium mining etc. Depending on the

requirements, various hydraulic fluids like petroleum based hydraulic fluids, invert emulsions

like oil in water and water in oil, water etc. are used in the hydraulic systems of DAE. Apart

from this, AHWR fuelling machine being a vertical assembly due to vertical reactor coolant

channels, any leakage of mineral based hydraulic oil (having flash point of 210 OC and fire

point approximately 230 OC) from the snout actuators in an environment of 285

OC (area

below the deck plate) will be a potential fire hazard. Even water based fire resistant hydraulic

fluids are also not suitable because of high vapour pressure and the additive oils are not fire

resistant. For these reasons fire resistant hydraulic fluids (FRHF) are now being employed in

such industries as nuclear, mining, die-casting and steel making where fire hazards exist,

Other factor now being considered in DAE application is degradation of oil because of

gamma irradiation. Petroleum based i.e. mineral based hydraulic fluid is predominantly used

in several nuclear facilities in system working in radioactive environment (which is not found

in general industries) consisting of Gamma and neutron irradiation. The effect of gamma and

neutron irradiation on these hydraulic fluids has never been evaluated in India. When a

system is used in radioactive environment, it may undergo several changes like change in

viscosity, chemical composition, acidity level etc. A research has been carried out to study

and compare the effect of Gamma radiation on the properties of polyol ester based fire

resistant hydraulic fluid (FRHF) of synthetic type and petroleum based mineral oil. For this

purpose both hydraulic fluids has been gamma irradiated at radiation level of 50 MRad inside

a Gamma Chamber located at ISOMED, south side of BARC. But for the future study and

scope of this thesis more oils need to be gamma irradiated at different radiation levels and

other properties like TAN NO., oxidation stability etc. need to be evaluated. This thesis work

discusses the effects of (50 MRad) gamma radiation on viscosity and tribological

characteristics of the fluids at various conditions.


Zeeshan Ahmad

2

Objective

Study of different types of hydraulic fluids and their properties and selection of fire

resistant hydraulic fluid based on previous data available and system requirements.

Study of tribological behaviour of different hydraulic fluid and selection of standard

method of evaluating tribological properties based on our requirements.

Preparation and submission of report on tribological behaviour of hydraulic fluids.

Conclusion based on experimental data of both the hydraulic fluids.

Planning and preparation of sample for gamma radiation of hydraulic fluids inside a

gamma chamber located at ISOMED, south side of BARC.

Measurement of viscosity, viscosity index of radiated oil samples at different

temperatures and conclusion based on experimental data.

Summery

This section gives the summary of the work done in this project. It briefly covers the

literature reviewed, the measurement of properties of radiated oil samples and the tribological

evaluation of radiated oil samples.

Literature Reviewed

Essential sources of data as listed in the reference section were reviewed, which include

substantial information on concentrated efforts towards

Study of different types of hydraulic fluids

Selection of fire resistant hydraulic fluid

Study of properties of hydraulic fluids and their effect on system performance

Study of different tribological test methods as per ASTM and ISO standards

Study of effect of gamma radiation on properties of hydraulic fluids

The Tribological Evaluation of Hydraulic Fluids

This point covers the experimental work carried out to evaluate the wear characteristics

of fresh as well as gamma irradiated polyol ester based FRHF of synthetic type and Petroleum

based mineral oil of viscosity grade 68 at different test conditions. The tests were carried out

on Reciprocating Sliding Wear & Friction Machine (Plint TE-70). Bearing steel plate SS-

52100 and bearing steel balls SS-52100 of 1/2 inch diameter were used as fixed specimen and

moving specimen respectively. Optical microscopic examinations were carried out to measure


Zeeshan Ahmad

3

wear scar on Ball specimen and 3 D profiles of flat sample wear scars were done, which were

used to calculate the Wear rate.

The Measurement of Properties of Gamma Radiated Oil Samples

Hydraulic fluid is the medium of power transmission in hydraulic equipment. Properties

of hydraulic fluid greatly affect the performance of equipment/ system, so knowledge of

properties of hydraulic fluid is very important. Out of several properties, viscosity is an

important property. Viscosity of fluid affects leakage, efficiency and energy consumption in

the system. To study the effect of Gamma radiation on viscosity of hydraulic fluid, polyol

ester based fire resistant hydraulic fluid (FRHF) of synthetic type and petroleum based

hydraulic fluid has been gamma irradiated at 50 MRad radiation level. The dynamic viscosity,

kinematic viscosity, has been evaluated for these irradiated fluid samples using Anton Paar

rotational Stabinger viscometer SVM – 3000 available in Chemistry Division (ChD). Apart

from this, the effect of Gamma radiation on viscosity index (VI) and appearance of fluids has

also been evaluated.


Zeeshan Ahmad

4

2. Literature Review

The hydraulic fluid is an essential and important component of any hydraulic power or

control system. No other component of the circuit must perform as many functions or meet as

many requirements as the hydraulic fluid. The hydraulic fluid must not only provide a

medium for efficient power transmission, but it must also lubricate, cool, protect from

corrosion, not leak excessively, and perform numerous other functions depending on the

system design. However, even if a hydraulic fluid can adequately perform these system

functions, it may still be less than satisfactory in terms of usage and compatibility factors. In

many hydraulic systems, it is necessary that the hydraulic fluid be nontoxic and fire-resistant.

It must be compatible with the structural materials of the system. The hydraulic fluid should

exhibit stable physical properties during a suitable period of use. It should be easy to handle

when in use and in storage, and it is desirable, of course, that it be readily available and

inexpensive. The selection of a hydraulic fluid is further complicated by the vast number of

liquids currently available. These range from water and mineral oils to special purpose

synthetic liquids. It is thus necessary for the system designer to have at least an elementary

understanding of the terminology prevalent in the specification of hydraulic fluids.

2.1. Classification of Hydraulic Fluids [1]

A wide range of liquids is available for use in hydraulic systems, and it is desirable to

employ a classification system to assist those using hydraulic fluids to determine if a liquid

under consideration may function satisfactorily for a particular application. However, the task

of selecting the most meaningful classification system is complicated by several factors. The

areas of application of hydraulic systems and the type of equipment used have become so

diverse that a classification useful in one area of application has little or no meaning in

another. In addition, the increasing number and types of hydraulic fluids available add to the

complexity of the task. In simple, low performance hydraulic systems, where operating

parameters are not severe, almost any liquid-water, water-based liquids, natural petroleum

products, or the more sophisticated synthetic liquids-may be used with varying degrees of

satisfaction. In other areas, where the operating parameters are very severe, only a limited

number of liquids may be considered and selection must be made with considerable care. In

addition, there are liquids which are used primarily for purposes other than as hydraulic

fluids, but which have properties permitting them to be employed for the latter purpose in

many applications. Because of the wide and vastly different areas of application, it is not


Zeeshan Ahmad

5

surprising that hydraulic fluids have been classified by many different systems based on their

different characteristics such as physical properties, chemical types, operating capabilities,

utility, or specific applications. Although none of these groupings fully describe the properties

of a hydraulic fluid, they are still employed and assist in selecting fluids for use in specific

areas.

2.1.1. Classification by Physical Properties

A classification based on viscosity ranges was one of the earliest methods used since

petroleum products were the only hydraulic fluids widely used and viscosity was the most

important property of this class of hydraulic fluids. The viscosity method is accepted and used

as a means of classifying petroleum base hydraulic fluids by the fluid manufacturers, the

automotive industry, hydraulic component manufacturers, and hydraulic system designers and

builders. Hydraulic fluids grouped in this manner are generally specified as suitable for use in

a given application within a specified viscosity range. However, in the case of nonpetroleum

base synthetic fluids, a classification based on viscosity range alone is not sufficient because

of the importance of other properties.

2.1.2. Classification by Chemical Properties

Chemical classification of hydraulic fluids is extensively used by technical personnel,

such as chemists and petroleum engineers. Chemical classification assists them in predicting

general characteristics of a new hydraulic fluid or in developing a new hydraulic fluid for a

specific application. In chemical compounds such as hydraulic fluids, the physical properties

are dependent upon the compound structure and, accordingly, the physical properties of two

chemically similar fluids may not be the same. Within a given class of hydraulic fluids where

the chemical properties are similar, the physical properties of these fluids may vary greatly.

2.1.3. Classification by Operating Characteristics

When classifying hydraulic fluids according to operating characteristics, the most

common operational parameters used are the temperature limits and the fire-resistant

characteristics of the hydraulic fluid. The aerospace industry and the Air Force are the

principal users of the classification system based on operational temperatures and have

established the following system types:

Although this classification system has proved valuable and useful to some users, it

does not identify other properties of the liquids and one type may include several chemical

classes. Type I liquids include some petroleum hydrocarbons, phosphate esters, silicate esters,


Zeeshan Ahmad

6

emulsions, water-base liquids, polyalkylene glycols, and halogenated hydrocarbons. Type II

liquids include petroleum hydrocarbons and silicate esters.

Type I :- 65° to 160°F

Type II :- 65° to 275°F

Type III :- 65° to 400°F

Type IV :- 65° to 550°F

Type V :- 0° to 700°F

Type VI :- +40° to 1,000°F (Proposed)

Type III liquids include the deep dewaxed highly refined hydrocarbons, synthetic

hydrocarbons, silicate esters, and silicones. Type IV liquid requirements have not been fully

met by any class of fluids. However, the deep dewaxed highly refined mineral oils covered

under MIL-H 27601A (-40° to + 550°F) closely approach the Type IV requirements. Type V

and VI fluids have not been completely defined or tested. Some potential candidate fluids for

Type V are polyphenyl ethers, perfluoroalkylesters, and specially refined hydrocarbons.

Liquid metals have some potential for satisfying Type VI requirements. In general, there are

commercial hydraulic fluids readily available which operate satisfactorily over the

temperature ranges of Types I, II, and III hydraulic systems. However, for the higher

temperature ranges of Types IV, V, and VI, only a limited number of fluids are available and

those are usable only for relatively short durations. Extensive research programs are being

conducted to develop fluids (and components) which will be usable in Types IV, V, and VI

hydraulic systems. Classification of hydraulic fluids and systems based on operational

temperature ranges is not satisfactory in many cases, such as in industrial systems, since there

is no need for a -65°F operational temperature requirement. However, it is important that

every hydraulic fluid have a definite operational temperature range established. Knowledge of

these temperature limits is necessary in selecting a hydraulic fluid for a specific application.

2.1.4. Classification into Petroleum or Nonpetroleum Hydraulic Fluids

One of the most widely used classifications of hydraulic fluids is based on a separation

into two general classes-petroleum and nonpetroleum. However, the petroleum class

hydraulic fluids may contain additives, even synthetic additives, without changing their

classifications. The nonpetroleum and/or synthetic class of hydraulic fluids includes a

considerably wider range of liquids since it contains those derived from nonpetroleum base


Zeeshan Ahmad

7

liquids (water, castor oil) as well as the synthetic base liquids produced by major chemical

reactions, although the base material for some of these liquids may be a petroleum product.

2.1.5. Classification by Fire-Resistance

Hydraulic fluids can be classed as flammable or fire-resistant. However, this

classification is somewhat arbitrary since the degree of flammability depends on both the

specific fluid and the definition of "flammability". Generally, fire-resistant hydraulic fluids

are of three types-synthetic fluids, water-based fluids, and emulsions. Fire-resistant synthetic

fluids are fire-resistant because of their chemical nature and include phosphate esters,

chlorinated hydrocarbons, halogen-containing compounds, organophosphorus derivatives, and

mixtures of similar materials. The water-base fluids are solutions of various natural or

synthetic materials in water, and depend upon their water content for fire-resistance. Glycols,

polyglycols, and mixtures containing additives are the most common hydraulic fluids of this

type. Emulsion-type hydraulic fluids also depend upon water content for fire-resistance and

are water-in-oil mixtures made from petroleum hydrocarbons, but may contain various

additives to provide other desirable properties.

2.2. Classification of Fire-Resistant Hydraulic Fluids, Their

Properties and Uses [2]

2.2.1. Introduction

The development of fire-resistant hydraulic fluids commenced towards the end of the

Second World War, as a result of a search by the US military for less flammable fluids [3]

,

particularly for aircraft hydraulic applications. The investigations identified water-glycol

fluids and phosphate esters as the most promising candidates for further research [4]

, and this

stimulated independent interest in their potential for general industrial usage. Since that time,

the industrial market for fire-resistant hydraulic fluids has expanded significantly and

undergone many changes. Some fluids, for example polychlorinated biphenyls, have come

and gone. Others, like the high water content fluids (particularly micro-emulsions and

chemical solutions) have been steadily developed and taken an increasing share of the market

for aqueous-based fluids. In the field of non-aqueous fluids, certain carboxylate or polyo1

esters have competed very successfully with phosphates. The changes continue into the

1990s, the latest resulting from the development of new spray ignition tests which will

probably influence a move away from polyol esters. These developments have taken place

against a backdrop of increasing severity in equipment operating conditions and, at the same


Zeeshan Ahmad

8

time, a greater emphasis on workplace safety, including the handling and use of chemicals.

The transportation and disposal of waste material is also the subject of a growing volume of

legislation, and is therefore of considerable concern to the customer. In view of the continuing

technical developments and the complexity of environmental legislation, it is appropriate to

review and compare the performance of the different fire-resistant fluids that are currently in

wide commercial use.

2.2.2. Fire Hazards

Many modern industrial processes involve high temperatures that represent a fire

hazard. Some common primary sources of ignition are listed in Table 1. As dangerous

processes become increasingly automated, hydraulic systems become more widely used and

manning levels are reduced. As a result, fire becomes an ever greater risk. When a source of

ignition comes into contact with a flammable fluid, e.g. as a result of a leak or spray, then the

risk of fire is considerable. In some cases, small fires can become major incidents through

secondary fire hazards, which can include fluid soaked into lagging, packaging, or other waste

material. The most frequently used hydraulic fluid is mineral oil but, in the vicinity of high

temperatures, it poses a major fire hazard. The use of mineral hydraulic oil in applications

involving temperatures greater than 250oC, or in the vicinity of such high temperature

processes, is highly dangerous. Many severe fires have been caused by escaping oil, usually in

the form of a mist or jet, arising from the failure of a high-pressure hose or pipe. The ignition

source need not be adjacent to the leak; the atomised mist or spray can travel considerable

distances, e.g. up to 12 metres (40 feet) from a leak in a system operating at a pressure of 70

bar, and systems operating at 350 bar are now quite common. The most serious consequences

occur when the escaping oil is ignited by a remote heat source and the fire propagates back to

the leak, resulting in a flamethrower effect, with potentially lethal consequences for personnel

in the vicinity.

Table 2.1 Possible ignition sources

Hot surfaces Localised ignition sources

Hot/molten metal Naked flames

Steam pipes Electric arcs

Flue pipes Frictional heating

Furnaces Sparks from:

Heated dies welding equipment

Exhaust manifolds cutting equipment


Zeeshan Ahmad

9

2.2.3. Fire Resistance and Fire-Resistant Fluids

Almost all organic compounds will ignite and burn if heated to sufficiently high

temperatures in the presence of air or oxygen. Combustion is the reaction of the compound

with oxygen with the release of heat. The ability of a material to withstand high temperatures

without burning is known, rather vaguely, as its fire resistance, and those liquids which ignite

at temperatures higher than does mineral oil are known as ‗less flammable‘ or ‗fire-resistant‘

fluids. The terms, ‗fire resistance‘ and ‗flammability‘ involve several different aspects of fire

behaviour. These include:

(1) Ignitability or the ease of ignition. This will depend not only on the chemical composition

of the fluid and its physical properties, e.g. volatility, but also on the heat emitted by the

source of ignition.

(2) The ability for the flame to be propagated. This is mainly dependent on the heat released

by ignition and whether this is sufficient to volatilise and ignite more fluid (taking into

account the heat lost by conduction convection).

(3) Smoke and gas production: smoke may impede the escape of people caught in a fire, while

toxic gases, such as carbon monoxide, normally represent the most lethal hazard.

2.2.4. Fire-Resistant Hydraulic Fluid Types for Industrial Applications

There are number of different types of fire-resistant hydraulic fluids commercially

available. The current ISO classification (ISO Standard 6743 Part 4) [5]

is given in Table 2,

together with a brief description of the different fluids.

Table 2.2 ISO Classification of fire-resistant hydraulic fluids and their composition

ISO

category

Fluid type Composition

HFAE Oil-in-water

emulsions

(i) Opaque or translucent emulsions containing about

5% oil phase and 95% water with small amounts of

emulsifiers, coupling agents, corrosion inhibitors,

extreme pressure and antiwear additives, antifoamants,

and possibly biocides, to enhance the performance.

(ii) Translucent micro-emulsions containing 2% oil

with a similar range of additives. Some micro

emulsions also contain a polymeric thickener to

increase viscosity

HFAS Chemical solutions

in water

Mixtures of additives dissolved in water combined with

polymeric thickeners to increase fluid viscosity.

Normally the water content is > 85%.

HFB Water-in-oil Emulsions of about 40% water dispersed in mineral oil


Zeeshan Ahmad

10

emulsions (invert

emulsions)

together with a small amount of the additive types used

in HFA fluids. In addition, antioxidants may be

incorporated to reduce oil degradation.

HFC Water polymer

solutions (water-

glycol fluids)

The water content of these fluids varies from -35-50%

with the balance being a glycol, e.g. Ethylene or

propylene glycol, and a polyglycol ether with small

amounts of additives. A typical product might be based

on 40% water, 40% glycol and 20% polyglycol ether.

HFDR Synthetic phosphate

ester fluids

containing no water

Fluids are normally based on triaryl phosphates

although low levels of trialkyl phosphates or alkylaryl

phosphates may be present to improve low temperature

performance. Optionally, small amounts of high

temperature stabilisers, rust inhibitors and an

antifoamant may be present.

HFDS Synthetic chlorinated

hydrocarbons

containing no water

This category has been used for chlorinated aromatic

hydrocarbons. Mainly for ecotoxicological reasons,

fluids in this category have almost disappeared from

general industrial use, and will not be discussed further

in this document.

HFDT Synthetic fluids

consisting of

mixtures of HFD-R

and HFD-S fluids

The same remarks apply as were made for HFDS

fluids. Both these categories are expected to disappear

from the ISO Classification

HFDU Synthetic fluids of

other compositions

and containing no

water

Polyol esters, also known as oleate esters, are organic

esters of ‗polyols‘, e.g. Trimethylolpropane or

neopentyl glycol. These fluids contain a stabiliser

package and, frequently, a polymeric thickener to

improve fire-resistance. The ester content is usually

>98%. Very small amounts of other fluids, e.g.

Chlorofluorocarbons and perfluoroalkyl ethers, are

found in specialist or military applications and are

outside the scope of this comparison.

2.3. Properties of Hydraulic Fluids and Their Effect on System

Performance [6]

While selecting a hydraulic fluid one has to be aware of hydraulic fluid properties and

its effect on hydraulic system. Generally the hydraulic fluids have many properties and some

of the important properties are explained in detail below.


Zeeshan Ahmad

11

2.3.1. Density (ρ)

The density is defined as the mass of a unit volume of material at any given temperature

and pressure.

( ) ( )

( )

In the metric system these units are g/cm3 or kg/m

3. It is frequently more convenient to

express the density as specific gravity, which is defined by

Water has a specific gravity of one, so if a fluid is heavier than water, the specific

gravity value will be more than one. Anything lighter than water will have a value that is less

than one and the fluid will float above the water.

Effect of Density on System Performance

Density is of great importance when calculating flow of hydraulic fluids through

components such as valves, pumps, and motors. The density enters into the flow energy

equations and changes in density will affect the results obtained from the equations. High-

density liquids may generally be eliminated from consideration because of weight limitations

imposed on the hydraulic system, especially in airborne systems.

Many other problems associated with density deviations are given, particularly in

hydraulic systems. These includes

Increased pumping power loss

As systems are designed to pump a fluid of a specific density, increase in density leads

to increase in fluid inertia and hence require more power to operate and hence, the efficiency

of the pump begins to change as well.

Increased stress on pumping elements

As density increase leads to the erosive potential of the fluid. In high turbulence or

high-velocity regions of a system, the fluid can begin to erode piping, valves or any other

surface in its path.

Thus, understanding the importance of density and how it relates to equipment is

essential for the reliability and health of your machines


Zeeshan Ahmad

12

2.3.2. Viscosity

The most important property of the hydraulic fluid to be considered is viscosity of the

fluid. The main selection of fluid for the system depends on the viscosity of fluid. Viscosity is

the measure of resistance of fluid flow that is inverse measure of fluidity. For example honey

is very thick that means it is more viscous than water. Viscosity directly affects the system

(Especially pump and motor) wear, leakage, and most important efficiency thus, overall

performance. It has been well established that viscosity of hydraulic fluid decreases with

increase in the temperature. In general, effect of gamma radiation is not determined for

hydraulic fluids.

Effect of Viscosity on Hydraulic Fluid and System

Various components within a hydraulic system have competing requirements as to high

or low viscosity. High viscosity provides thick lubricating films and reduces internal leakage.

Low viscosity results in less internal friction, smaller pressure losses in pipes and valves, and

an increase in control action and component response. Thus, a compromise in viscosity

requirements must be made. The viscosity of the hydraulic fluid affects the response of

system components, and because its sensitivity to temperature usually imposes limitations on

the upper or lower operating temperature of any hydraulic system. Thus, viscosity must

always be considered in design calculations.

Types of Viscosity

a) Dynamic Viscosity or Absolute Viscosity (η)

Viscosity measured under force induced flow expresses dynamic viscosity. It is a force

per unit area (shear stress) required to move one surface over another separated by unit

distance at a rate of unit distance per second is called dynamic viscosity.

Table 2.3 Units of dynamic viscosity

Unit System Unit Relation

SI Pascal second (Pa s) Pa.s = N/m2.s

CGS Poise (P) Poise (P) = 0.1 Pascal second (Pa s)

ASTM Centipoise (cP) Centipoise (cP) = 10-2

poise (P) = 10-3

Ns/m2


Zeeshan Ahmad

13

b) Kinematic Viscosity ( )

Generally kinematic viscosity is used for measurements. Viscosity measured under

gravity induced is called kinematic viscosity. It is the ratio of dynamic viscosity (η) and

density (ρ).

Table 2.4 Units of kinematic viscosity

Unit System Unit Relation

SI ⁄

CGS stokes (St) stokes (St) = cm2/s = 10

-4 m

2/s

ASTM centistokes (cSt) centistokes (cSt) = mm2/s = 10

-6 m

2/s

2.3.3. Viscosity Index [1]

The Viscosity Index (V.I) of a liquid is a number indicating the effect of a change in

temperature on viscosity. A low V.I signifies a relatively large change of viscosity with

temperature. A high V.I signifies a relatively small change of viscosity with temperature. The

convenience afforded by the use of a single number to express the viscosity-temperature

characteristics of a liquid has resulted in the widespread adoption of the viscosity index

system in the petroleum industry. The V.I is an empirical scale using two series of petroleum

fractions as standards. One fraction which seemed to have minimum viscosity-temperature

sensitivity was arbitrarily assigned a V.I of 100. The other fraction with maximum viscosity

temperature sensitivity was assigned a V.I of zero. At the time the index scale was developed,

all other petroleum fractions were expected to fall within the zero to 100 limits. Subsequently,

however, solvent refining, the use of additives, and synthetics have produced materials that

are outside the V.I scale in both directions. The V.I of a liquid with a given viscosity at 210T

is calculated by relating its viscosity at 100°F to the viscosity at 100T for each of the standard

fractions having a viscosity at 210°F equal to that of the unknown at 210°F. The V.I is

calculated by the following equation.

(

)


Zeeshan Ahmad

14

Where,

L = Viscosity at 100°F of a petroleum fraction

of 0 V.I having the same viscosity at

210°F as the fluid whose V.I is to be

calculated.

H = Viscosity at 100°F of a petroleum fraction

of 100 V.I having the same viscosity at

210°F as the fluid whose V.I is to be

calculated.

U = Viscosity at 100T of the fluid whose V.I is

to be calculated.

2.4. Requirements for Fire-Resistant Hydraulic Fluids [7]

To perform satisfactorily in hydraulic systems the functional fluid shall be fire-resistant

and possess the following properties

The functional fluid shall be fluid enough at all working temperatures to flow readily

through the system and to accommodate rapid changes in velocity and pressure.

At the same time the fluid shall be viscous enough at all working temperatures to prevent

unwanted leakage across working clearances wherever a pressure differential exists across

them.

The fluid shall be of sufficient viscosity and adequate film strength to lubricate working

parts effectively under both hydrodynamic and boundary conditions over the working

temperature range.

The fluid shall be compatible with construction materials used in the system and shall be

non-corrosive.

The fluid shall have thermal stability and be suitable for use at the highest expected

operating temperature.

The fluid shall have chemical stability to give adequate working life.

The fluid shall release entrained air readily and not provide stable foam.

The fluid shall separate readily from contaminants encountered in normal use without

chemical reaction.

The surface tension of the fluid shall below enough to give ―wettability‖ but not low

enough to make sealing difficult.


Zeeshan Ahmad

15

The fluid should preferably be shearing stable, i.e. its viscosity should not permanently

change unduly with applied shear in a system.

Fire-resistant (FR) fluids have been designed for safety reasons to replace conventional

mineral oils in all applications where hydraulic systems are operating in close proximity to

naked flames, molten material or other high-temperature sources, or specifically in hazardous

environments where fire and/or explosion risks have to be reduced to a minimum. It is also

necessary that such fluids shall resist spontaneous combustion if allowed to come into contact

with hot surfaces or absorbent materials into which the fluid may have become impregnated.

Fluids used as fire-resistant hydraulic media obtain their fire resistance by one of two

following means.

Either from the presence of water, or

From their chemical composition.

Water readily available and truly non-flammable fluid, was used in the earliest systems

but water has a very low viscosity and is a poor lubricant. Apart from the obvious temperature

limitation, the use of water also gave rise to problems of corrosion and erosion. For these

reasons, plain water cannot be used in systems the components of which need to be lubricated

by the hydraulic fluid. Even water based fire resistant hydraulic fluids are also not suitable

because of high vapour pressure and the additive oils are not fire resistant. There for keeping

all above difficulties in mind anhydrous FRHF of synthetic type (HFDU) i.e. polyol ester

based has been selected for the utilization in fuelling machine of AHWR as well as other

hydraulic applications of DAE.

2.5. Tribological Properties of Hydraulic Fluids

2.5.1. Lubrication Properties

Varying degrees of lubrication and wear preventing ability are needed for different

systems. The pump design, the system operating temperatures and pressures, component

design, and environmental conditions should all be considered when selecting a hydraulic

fluid. Two fundamental and distinct modes of lubrication are generally recognized-

hydrodynamic and boundary lubrication. When hydrodynamic conditions exist, a liquid film

entirely separates the moving parts. In the boundary condition, contact exists between the

mating surfaces. The difference between hydrodynamic and boundary lubrication is clear;

however, there is no sharp line of demarcation, but rather a gradual transition between the

two.


Zeeshan Ahmad

16

a) Hydrodynamic Lubrication

Hydrodynamic lubrication is "A system of lubrication in which the shape and relative

motion of the sliding surfaces cause the formation of a liquid film having sufficient pressure

to separate the surfaces" [8]

. Under ideal hydrodynamic conditions of lubrication, there is

essentially no wear since the moving parts do not touch each other. Under these conditions,

the parameters of importance are liquid, viscosity, surface speed, and pressure. Most of the

theory of hydrodynamic lubrication is based on the early work of Tower and Reynolds. Full

hydrodynamic lubrication offers the significant advantage of low wear rates and low friction.

Hydraulic systems should be designed to take full advantage of hydrodynamic lubrication.

The coefficient of friction in hydrodynamic lubrication is of the order of 0.001 to 0.010 [9]

.

A hydraulic fluid should be a good lubricant so that friction and wear in a hydraulic

system are reduced to a minimum. The components of a hydraulic system contain many

surfaces which are in close contact and which move in such relation to each other that the

hydraulic fluid must separate and lubricate. The hydraulic fluid must also be a good wear

preventing lubricant. Wear in hydraulic pumps, cylinders, motor controls, valves, and other

components can result in increased leakage, loss of pressure, less accurate control, or failure.

Protection against wear is often a principal reason for selection of a particular hydraulic fluid

since most components of hydraulic systems operate at some time under conditions that can

lead to extreme wear, especially during starting and stopping of the system.

b) Transition From Hydrodynamic To Boundary Lubrication

A given liquid film between moving parts decreases in thickness as the pressure

increases, and/or the liquid viscosity decreases. As the film becomes thinner, a point is

reached where the laws of hydrodynamics no longer fully apply since the effects of surface or

boundary forces are no longer negligible. As the film becomes still thinner, a state is

ultimately reached where metal to metal contact occurs. These transitions influence the

coefficient of friction as shown in Figure 2.1. Here, the coefficient of friction is plotted as a

function of the dimensionless parameter ηV/P where η, N, and P are the fluid viscosity,

relative surface speed, and pressure, respectively.

In the hydrodynamic region, the coefficient of friction is a linear function of ηV/P (see

Fig. 2.1). As ηV/P decreases, the film thickness is reduced and the curve begins to deviate

from linearity. As ηV/P is decreased further, a point is reached where both boundary and

hydrodynamic effects prevail in combination.


Zeeshan Ahmad

17

Figure 2.1 Coefficient of friction Vs. Stribeck parameter

A further decrease in ηV/P will ultimately rupture the film and the curve will show a

sharp break upwards. The minimum point is then regarded as the start of the transition from

hydrodynamic to boundary lubrication. There is no sharp line of demarcation, but an

intermediate zone where hydrodynamic and boundary effects are both present. This zone is

sometimes called the semi-fluid, mixed-film, or quasi-hydrodynamic lubrication zone [9]

. The

condition of full hydrodynamic lubrication is the most desirable; however, all of the factors

that make it possible are not always present. Sometimes speeds are so slow or pressures so

great that even a very b viscous liquid will not prevent metal-to-metal contact. Other cases of

stop-and-start operation, reversals of direction, or sharp pressure increases may cause the

collapse of any liquid film that had been established. These conditions are not conducive to

hydrodynamic lubrication and occur in almost all systems at one time or another.

c) Boundary Lubrication

Boundary lubrication is "A condition of lubrication in which the friction and wear

between two surfaces in relative motion is determined by the properties of the surfaces, and

by the properties of the lubricant other than viscosity" [8]

. When boundary lubrication exists,

the coefficient of friction is independent of both liquid viscosity and sliding velocity. There

are different degrees of severity under which boundary lubrication will prevail. Some are only

moderate and others are extreme. Blok [9]

classifies degrees of boundary lubrication on the

basis of the mechanical conditions. He lists the following degrees:

(1) Low pressure and low temperature, or mild boundary lubrication as found in low speed

sleeve bearings, leaf springs, and hinge joints.


Zeeshan Ahmad

18

(2) High temperature boundary lubrication as found in cylinders of some steam and internal

combustion engines and in certain high speed sleeve bearings.

(3) High pressure boundary lubrication as generally found in cases involving rolling contact at

high pressures but with little frictional or external heat.

(4) High pressure and high temperature, or extreme boundary lubrication, as found in highly

loaded hypoid or other gears having high loads and a high degree of sliding friction.

The temperature and pressure at the region of contact are the factors that determine the

severity of the boundary lubrication. All types of boundary lubrication are characterized by

the rupture of the liquid film and some degree of metal-to-metal contact. The conditions of

boundary lubrication should be avoided where possible because of the resulting increase in

power consumption, and the high friction and wear that occur.

2.5.2. Wear or Surface Damage

According to DIN 50 320, or similarly in other terminology standards, wear is the

progressive removal of material from a surface in sliding or rolling contact against a counter

surface. As described in many textbooks, e.g., Zum Gahr (1987) and Hutchings (1992),

different types of wear may be separated by referring to the basic material removal

mechanisms, the wear mechanisms that cause the wear on a microscopic level. There are

many attempts to classify wear by wear mechanisms, but a commonly accepted first order

classification distinguishes between adhesive wear, abrasive wear, wear caused by surface

fatigue, and wear due to tribochemical reactions. Over a longer sliding distance, either one

mechanism alone, or a combination of several of these wear mechanisms, causes a continuous

removal of material from the mating surfaces, and thereby also adds to the friction force that

opposes the sliding. Such continuous, steady-state wear and friction conditions may be

quantified in terms of wear rates, i.e., removed material mass or volume per sliding distance

or time, or its inverse, the wear resistance, and in terms of friction forces or friction

coefficients.

However, not all types of tribological failures are due to wear in the sense of a

continuous material removal from tribosurfaces, and the tribological properties of the

materials in a component are not always best described by their wear resistances or friction

properties. Instead a broader study of the various types of surface damages that occur may be

more meaningful.


Zeeshan Ahmad

19

2.5.3. Prevention of Wear

The complete elimination of wear is practically impossible. Minimum wear occurs

under conditions of hydrodynamic lubrication and maximum wear occurs under conditions of

boundary lubrication. However, there are several approaches by which the wear rate under

boundary lubrication conditions can be reduced to a satisfactory or controllable level. The

main factors which determine the rate of wear can be classified into two basic types

mechanical and lubrication. Proper consideration of these two factors can produce a wear rate

which is acceptable.

a) Mechanical Factors

The mechanical factors that affect the wear rate are the choice of materials, the surface

finish, and the operating conditions. Wear can often be reduced by a proper choice of

materials for the moving parts. In general, softer materials wear more rapidly than harder

materials. There is, however, no direct relationship between hardness and resistance to wear.

Materials also differ in their ability to resist the various types of wear. For example, materials

selected for their ability to resist abrasion might be more sensitive to corrosion. It is thus

necessary to select materials which would resist the most serious type of wear anticipated.

The combination of metals used can greatly influence the wear. Some metals are very

susceptible to wear when rubbed against them, while others are very susceptible to wear when

rubbed against different types of metals. In practice, the composition chosen for a given part

is influenced by many factors other than wear. Structural strength, weight, cost, and

availability may force a compromise between minimum wear and optimum performance.

Surface finish of the mating parts becomes particularly important during break-in or initial

wear periods. If one of the two mating surfaces has an initial rough finish, considerable wear

may take place. While it is generally desirable to have as smooth a surface as possible, there

are instances where surfaces of controlled roughness are desired so that a "wearing-in" or

mating of parts may occur during the initial run-in or breaking period. Operating conditions

of pressure, temperature, and rubbing speed also affect wear. Increased pressure generally

reduces film thickness and increases the extent of metal-to-metal contact and wear. High

temperature may cause wear due to a decrease in viscosity. Excessive high speeds may result

in overheating at local points. Moderate temperatures and pressures are, therefore, preferred

from a standpoint of wear. However, optimum conditions for wear may not be the optimum

conditions to achieve high efficiency or maximum power from a hydraulic system component.


Zeeshan Ahmad

20

b) Lubrication Factors

Decreases in viscosity of a system operating under hydrodynamic lubrication will

decrease the thickness of the liquid film. If the decrease is sufficient to allow boundary

conditions to be reached, metal-to-metal contact occurs and wear increases. Viscosity,

therefore, would be expected to have an inverse effect on rate of wear-the greater the viscosity

the less would be the expected wear. Since wear is essentially a phenomenon resulting from

friction, it is expected that additives capable of reducing friction under boundary conditions

would simultaneously reduce wear. However, there can be instances where there is little or no

correlation between friction and wear under boundary lubrication conditions [9]

. Some

additives effective in reducing friction have little effect upon wear, while others reduce wear

and have little effect upon friction. Lack of correlation is probably due to the fact that wear

takes place momentarily in isolated spots whereas friction is normally measured as an average

for a larger area and a longer time interval [9]

. Hydraulic components made from iron alloys

other than stainless steel are subject to corrosion unless proper precautions are taken. Most

mineral-oil liquids do not have good antirust properties. Although they do offer protection,

they must be fortified with appropriate additives if any marked degree of rust prevention has

to be achieved [9]

.

2.5.4. Test Methods for Lubricating Properties

Numerous test methods have been proposed and several have been adopted for

evaluating the lubricating and wear reducing properties of fluids. The majority of these tests

have been developed for materials other than hydraulic fluids such as lubricants, greases, and,

in some cases, solid lubricants. However, the basic test procedures are adaptable to the

evaluation of hydraulic fluids, and several Military Specifications for hydraulic fluids call for

these tests or some modification of them. The test methods fall into three general categories

bench-type tests using non-simulating test elements, simulated hydraulic systems, and the

more elaborate load-carrying and scuffing tests. Standard test procedures, either ASTM or

Federal, have been written for some of the test methods. None of the test methods described

in the paragraphs which follow give any indications of the expected "life" of a lubricant or

liquid. The engineer or designer is expected to establish proper lubrication procedures and

lubricant change intervals. The problems become even more complicated in hydraulic systems

because the liquid is both a lubricant and a power transfer fluid. With hydraulic systems

operating with sophisticated hydraulic fluids and/or extreme operating conditions, falling back


Zeeshan Ahmad

21

on "accepted practice" can be expensive, either in terms of wasted hydraulic fluids or

damaged equipment.

Bench-Type Friction and Wear Testers

Several bench tests have been developed to measure the lubricating ability of liquids.

Each test employs a different type of apparatus that utilizes a unique combination of test

elements. The testers are similar in that two well-defined surfaces separated by a liquid film

are in motion with respect to each other. The coefficient of friction is usually determined by

measuring the restraining force on one of the test elements. Wear is determined by the loss in

weight of the parts or by the dimensions of the wear scar. Boundary lubrication characteristics

are determined by increasing the load on the surfaces until seizure occurs. Because of their

differences, the various bench testers do not necessarily rate a given series of liquids in the

same order, and results from a single test procedure can be misleading. Also, the results

obtained do not always correlate well with actual operation. In many instances, the results of

several different bench tests may be taken as a whole in determining the lubricating ability of

a given hydraulic fluid. Experience has shown that application of most of these test

procedures will separate those hydraulic fluids which are extremely poor lubricants from

those which are potentially good lubricants. Five of the more commonly used bench-type

testers and their test methods are described in the paragraphs which follow.

a) Timken Tester

Test Method: Federal Test Method 6505 [10]

In the Timken test, a steel block is pressed

against a rotating, cylindrical steel ring (see Figure 2.2(A)). The test is run for 10 min at a

rubbing speed of 400 Ft./sec. The liquid is allowed to flow over the test pieces. In starting a

test, the motor is brought up to speed and a load is placed on the steel rub shoe block by

means of a weight and lever system. The test can be conducted as a wear test by running at a

set load until failure or as an EP- or load-carrying test by increasing the load until failure.

Federal Test Method 6505 [10]

calls for the test to be conducted as a load-carrying test. Failure

is indicated by scoring on the test block or test ring. The results are reported as the load

(determined from the scar dimensions and. the load) applied just prior to scoring or pickup of

metal.

b) Almen Tester

In the Almen test, a cylindrical rod is rotated in a split bushing which is pressed against

it (see Figure 2.2(B)). Frictional force is measured by a restraining force on the split bushing.


Zeeshan Ahmad

22

Two versions of the Almen test are conducted-the Almen EP test and the Almen wear test. In

the Almen EP test, the machine is run without and applied load for 30 sec as a break-in

period. Weights are added every 10 sec in multiples of 2 lb. until failure occurs as indicated

by seizure or sudden increase in torque. Test results are expressed as the torque and load

which causes seizure. In the Almen wear test, the machine is run without an applied load for

30 sec as a break-in period. Four 2-lb weights are added at 10-sec intervals. Operation is

continued for 20 min. Total weight loss of the journal and the bushings in mg are determined,

and are reported as the wear.

c) Falex Tester

Test Methods: Federal Test Method 3807 [11]


In the Falex

test a cylindrical rod is rotated between two hard V-shaped bearing blocks which are pressed

against the rod (see Figure 2.2(C)). Friction torque is continuously monitored. Both the

journal and the V blocks are submerged in the liquid under test. The two Federal Test

Methods referenced above utilize the Falex Tester in the evaluation of solid film lubricants.

However, the basic procedures of the two tests are adaptable to the evaluation of liquids. The

test can be run in two ways-as a wear test and a load carrying test. For wear testing, the

machine is run at a specified load for a specified time. The amount of wear is determined as

the amount of adjustment that must be made in the loading system to maintain the desired

load. For the EP test, the load is increased continuously until seizure occurs. The test begins

with a break-in period for 3 min at 300 lb. load. The load is then increased to 500 lb. and held

for 1 min and then increased in 250-lb increments with a 1-min run until failure occurs.

Results are expressed in pounds load at seizure.

d) Four-ball Tester

Test Methods: ASTM D-2596-67T [13]


ASTM D-2266-

64T [15]

In the four-ball machine (often called the "Shell" Four-ball Tester) a 1/2-in.-diameter

steel ball is rotated in contact with three stationary similar balls which are clamped in a fixed

position (see Figure 2.2(D)). The rubbing surfaces are submerged in the liquid to be tested.

The test can be operated as a wear test or an EP test. For a wear test, the machine is operated

at a specified temperature, load, and speed, with balls of given material. Federal Test Method

6514 [14]

and ASTM D-2226-64T [15]

are used for determining the wear characteristics of

lubricating greases with the four-ball tester. The general procedures are adaptable to hydraulic

fluids as well as greases. They call for test conditions of 1,200 rpm, a load of 40 kg, a test


Zeeshan Ahmad

23

temperature of 167°F (75°C), and a test time of 60 min. At the end of the test, the scar

diameter on the lower three balls is measured under a microscope. The average diameter in

millimetres is reported and is a measure of wear under the specified conditions. For the EP

test (ASTM D-2596-67T [13]

) there is no provision for temperature control, and the test is

started at room temperature. A test run of 10-sec duration at a given load is usually made.

Scar diameters are measured and the Hertzian contact stresses are calculated. The load is

increased in increments, and the process is repeated until welding occurs. This load is called

the weld point or weld load. Many variations on the four-ball wear and EP tests are used.

Many liquid specifications call for a four-ball test as specified or with certain changes made in

the test time, load, speed, or temperature.

e) SAE Tester

Test Method: Federal Test Method 6501 [16]

In the SAE machine (see Figure 2.2(E)),

two cylinders aligned axially and in contact with each other are driven at different speeds.

One of the cylinders may be driven in either direction. The pieces revolve under a flooded

lubrication condition from the test liquid held in a cup. The load pressing the cylinders

together can be increased until failure occurs. This machine differs from the four-ball tester in

that a combination of rolling and sliding friction is involved. The ratio of sliding to rolling can

be changed by varying the relative speed of the two cylinders. Federal Test Method 6501 [16]

is a test procedure for determining the load-carrying capacity of gear lubricants using the SAE

tester. The same test procedures, however, are adaptable to any liquid lubricant or to hydraulic

fluids. The machine is started and operated at a light load for a 30-sec break-in period. The

automatic loading device then increases the load steadily until scoring occurs. The results are

expressed in terms of the average load needed to cause scoring based on three repeat tests.


Zeeshan Ahmad

24

Figure 2.2 Five bench-type friction and wear testers

2.6. Effect of Gamma Radiation on Properties of Hydraulic Fluid

It has only been since the early 1950's that the radiation resistance of hydraulic fluids

has become important. In the design of modern weapon systems, aircraft, and mechanical

devices, hydraulic systems are frequently expected to be exposed to nuclear radiation. Of all

system components, the hydraulic fluid is the most susceptible to damage by radiation. Since

conventionally used hydraulic fluids and lubricants are especially susceptible, the effects of

radiation on their performance should be considered in the design of almost all systems.

However, there is no general requirement for radiation resistance in most hydraulic fluid

specifications.

Considerable basic work has been done on the radiation of simple organic structures.

With the more complicated molecular structures characteristic of lubricants, both petroleum

and synthetic, it has not been feasible to make studies of the precise reactions that occur. The

empirical observations are:[17]

(a) viscosity may at first be decreased, but eventually increases,

(b) acidity increases, (c) volatility increases, (d) foaming tendencies increase, (e) coking


Zeeshan Ahmad

25

tendencies generally increase but occasionally decrease, (f) flash points decrease, (g)

Autogeneous ignition temperatures decreases, and (h) oxidation stability decreases. In

addition to the listed changes in physical and chemical properties, gas is always liberated [8]

for petroleum liquids the gases are frequently hydrogen and methane. The remaining products

of decomposition are frequently gels that tend to clog hydraulic systems. The formation of the

gases and gels presents a difficult design problem, and provisions must be made in the system

for their presence. Although some changes in lubricants have been found after radiation doses

of 107

(8.77 MRad) roentgens, the major effects are observed between 10

8 (87.7 MRad) and

109

(877 MRad) roentgens [17] [18]

. Beyond 109 roentgens most liquid lubricants have been

damaged to the extent that they are completely unserviceable.

In general, petroleum lubricants are more resistant to radiation damage than other

lubricants. An exception is the polyphenyl ether family which is very resistant to damage.

Currently, the silicone liquids exhibit the poorest radiation resistance of all the high

temperature liquids [19]

. Inclusion of atoms other than carbon, hydrogen, and oxygen in the

molecule generally reduces radiation resistance. Table 2.5 presents data on the relative

radiation resistance of various hydraulic fluids.

Table 2.5 Radiation resistance of hydraulic fluids [20]

Fluid Type Relative Radiation

Resistance

Mineral Oils: MIL-H-5606

MIL-L-25598

Poor

Low

Super-refined Mineral Oils:

Naphthenic and Paraffmic

Poor

Synthetic Hydrocarbons (Average) Poor

Diesters: MIL-L-7808C Poor

Triesters: MIL-L-9236B Poor

Silicate Esters Poor

Disiloxane-diesters: MLO-8515 Poor

Disiloxane: MLO-8200 Poor

Polysiloxanes Poor

Chlorinated Silicones Poor

Silicone Ester Blends: MLO-5998 Poor

Phosphate Esters Poor

Polyphenyl Ethers Excellent

[21][22]Gamma irradiation leads to knocking down of bonding electrons from the

molecules and formation of radicals which leads to polymerization. The extent of effect of

gamma radiation on different types of hydraulic fluids is different. Research carried out by

California Research Corporation dated back in 1950s on hydraulic fluid have demonstrated

that during Gamma irradiation the viscosity of hydraulic fluid initially falls and then


Zeeshan Ahmad

26

increases. Development of nuclear radiation resistant hydraulic fluid had been conducted by

California Research Corporation on silicate based hydraulic fluid particularly ML-0-8200

fluid, after exposure to gamma radiation, they had concluded that the maximum permissible

gamma dose for ML-0-8200 fluid appears to be about 108 roentgens (88 MRad) or slightly

higher. At this level they feel that there is negligible change in viscosity. In addition to lab

testing of silicate fluid, pump testing of the 8200 fluid had been also conducted before and

after expose to 7.85x108 roentgens (688 MRad). In brief it was concluded that irradiation to

this level triples the viscosity but the fluid could still be used as hydraulic systems employing

New York air brake pumps with some reduction in wear to be expected. It was felt that

operation of pumps at temperature much below 0o F would be impaired. They have also

concluded that MIL -0-5606 mineral oil has very poor gamma radiation resistance even at low

doses.

Since the petroleum refining technology is well developed all over the world, there are

countless hydraulic fluid manufacturers dealing in either local or international market. But

these companies mainly focus on markets leading to product suitable for their condition and

industries. It has also been shown that the effect of radiation is different for base fluid

received from different crude reservoirs. So, data on radiation resistance of all the fluids

cannot be expected. Hence, it is necessary to determine the Gamma radiation resistance of the

hydraulic oil which is being used presently or proposed to be used in future in hydraulic

systems of nuclear installations.


Zeeshan Ahmad

27

3. Tribological Evaluation of Hydraulic Fluids

Friction and wear are caused by complicated and multiplex sets of microscopic

interactions between surfaces that are in mechanical contact and slide against each other.

These interactions are the result of the materials, the geometrical and topographical

characteristics of the surfaces, and the overall conditions under which the surfaces are made to

slide against each other, e.g., loading, temperature, atmosphere, type of contact, etc. All

mechanical, physical, chemical, and geometrical aspects of the surface contact and of the

surrounding atmosphere affect the surface interactions and thereby also the tribological

characteristics of the system. Therefore, friction and wear are not simply materials parameters

available in handbooks; they are unique characteristics of the tribological system in which

they are measured.

Reason to Perform a Tribotest?

Ranking of materials for existing equipment

Selection of material for new application

General, application independent, characterization of wear and friction properties of

material

Study of wear mechanism appearing in selected tribological application

It follows from the systems aspect of wear and friction, i.e., the insight that tribological

properties depend on the whole tribosystem and not merely on the materials, that any

tribological testing should be preceded by a thorough evaluation of the characteristics of the

system to be evaluated and the purposes of the test; A tribotest should always be designed to

meet a defined need. One such need to perform a tribotest may be to rank a set of materials in

terms of their friction and wear properties in a certain, well defined system, either with the

purpose of selecting a material for an existing piece of machinery, which the tribotest then

should imitate, or to select a tribological material for a construction under development, for

which field tests or component tests are impossible

3.1. Apparatus and Materials

This experiment has been carried out at Refueling Technology Division (RTD), BARC

Mumbai, under a lubricated medium using reciprocating sliding wear and friction machine.

Bearing steel plate SS-52100 and bearing steel balls SS-52100 of 1/2 inch (12.7 mm)

diameter were used as fixed specimen and moving specimen respectively at the load of 15 N

and 25N with varying the frequency values at 10, 20 and 10 Hz. The sliding speed and total


Zeeshan Ahmad

28

distance is kept constant therefore duration of test at each frequency were 20000s, 10000s,

and 20000s respectively. The coefficients of friction, both, static and dynamic were measured

during the test. The wear for both moving and fixed specimen was measured after each test.

Also after each test the wear scar on specimen was scanned with a Taylor and Hobson make

profilometer and the wear volume was calculated from the 3-D profile of the wear track. The

ball scars were also examined using an optical microscope. The other test conditions are given

in table1.

Table 3.1 Test conditions for Oil-A and Oil-B Oil Name Temperature

(°C)

Load(N) Frequency

(Hz)

Sliding

Distance

(M)

Stroke

Length

(MM)

Time (Sec)

Oil-A

FRHF

POE

65

15 10 400 1 20000

15 20 400 1 10000

25 10 400 1 20000

Oil-B

Mineral

65

15 10 400 1 20000

15 20 400 1 10000

25 10 400 1 20000

Oil-A

FRHF

POE

90

15 10 400 1 20000

15 20 400 1 10000

25 10 400 1 20000

3.2. Experimental Procedure

3.2.1. Standard Testing Method

The tests were carried using ASTM Designation G 133 – 05. The test method used

according to ASTM standards is as follows.

1. This test method involves two specimens – a flat specimen and a spherically ended

specimen (here in called the ―ball ―specimen), which slides against the flat specimen.

These specimen moves relative to one another in a linear, back & forth sliding motion,

under a prescribed set of conditions see fig1.

2. In this test method, the load is applied vertically downward through the ball specimen

against the horizontally mounted flat specimen. The normal load, stroke length, frequency

and type of oscillation, test temperature, lubricant, test duration and atmospheric

environment (including relative humidity range) are selected from one of two procedures.

3. Since this test method involves reciprocating sliding where changes in the sliding velocity

and direction of motion occur during the test, constant velocity conditions are not

maintained. The ball carrier is driven by an electro-magnetic oscillator. The frequency

range is 5 to 100 Hz and stroke range is 0.05 to 1 mm. The type of the motion produced


Zeeshan Ahmad

29

by the drive system is sinusoidal. When the load exceeds the power of oscillator, the

oscillator compensates by reducing amplitude and maintaining the frequency. So

sometimes actual sliding distance varies from the theoretical sliding distance.

4. Dimensional changes for both ball and flat specimens are used to calculate wear volumes

and wear rates.

5. Friction forces are measured during the test and may be used to assess changes in the

contact conditions or the kinetic friction coefficient as a function of time.

1. Test Procedure

The following test procedure was followed as per ASTM standard G133 - 05

1) Specimens on which experiments were carried out (e.g. plate & ball) were cleaned

thoroughly using acetone and ultrasonic cleaning machine. The samples were dried by

using hot air.

2) The sample bath was cleaned using acetone & was dried with hot air.

3) The specimens were cleaned after they were secured in place in the test fixture by wiping

with acetone and then with lint free tissue paper. It is possible that during mounting, some

contamination was inadvertently placed on them, and this final cleaning will alleviate the

problem. The ball tip was inspected with a hand lens after it was mounted to ensure that

there were no defects in the contact area.

4) The ball specimen was gently lowered upon the flat specimen & it was also ensured that

the reciprocating drive shaft motion was horizontal & parallel to the surface of flat

specimen. The test load was applied. It was confirmed that the desired oscillating speed

had been set before starting the test.

5) The tests done for Oil-A and Oil-B are not in full compliance with the provisions of Test

Method G 133, Procedure B, because the normal force in these tests were 15N and 25 N,

instead of 200 N as prescribed by the standard and the stroke length was 1mm instead of

10 mm, therefore test duration was 20000 s and 10000 s for frequency of 10 Hz and 20 Hz

respectively instead of 33min 20s as per standard for same sliding distance of 400 m.

oscillating frequency was 10 Hz and 20 Hz instead of 10 Hz. The temperature was kept

constant at 65 0C & relative humidity was 60 % instead of 150

0C ± 2

0C and 40 to 60 %.

All other provisions of Test Method G133 have been followed.


Zeeshan Ahmad

30

2. Test Parameters

Table 3.2 ASTM std. parameters Vs. parameters used for this test

Sr.

No.

Parameter As per ASTM Standard ( Procedure

B)

Parameters Used For

This Test

1 Applied Normal Force- 200 N 15 N, 25 N

2 Ball Tip Radius 4.76 mm ½ in (12.7 mm)

3 Stroke Length 10 mm 1 mm

4 Test Duration sliding Distance 400 m sliding Distance 400

m

5 Frequency of

oscillation

10 Hz 10,20,10 Hz

6 Type of motion

produced by the

oscillating drive system

Not Specified. It can be Sinusoidal

velocity profile, triangular velocity

profile

Sinusoidal velocity

profile

7 Ambient relative

humidity

40 to 60 % 60%

8 Ambient Temperatures 150 ± 2°C 65°C,90°C

9 Medium Lubrication Lubrication

3.3. Measurement and Calculation of Wear [23] [24]

After the tests the wear scar dimensions of ball were measured under optical microscope

and dimensions of wear scar were noted, which were used to calculate wear volume and wear

rate of ball.

Figure 3.1 Measurement of plate and ball wear scar marks


Zeeshan Ahmad

31

3.3.1. Wear Measurement of Ball Specimen

Owing to the nature of this type of test, the wear on ball specimen may not be circular

or flat always therefore refer the following which applies.

1. If the ball appears flat but not circular, the average of the maximum and minimum

dimensions of the scar is taken as effective ball scar diameter (D).

2. Pin scar measurement may be made by removing the ball specimen holder and placing the

wear scar portion under the microscope. A calibrated ocular or a photo-micrograph of

known magnification may be used to measure scar dimensions.

As per ASTM G99-05(2010) Volume loss of Ball in mm3 is calculated using following

formula

( ) ( )

( )

⁄

Where, Vb = Wear volume for ball scar of diameter D in mm3

D = Ball scar diameter in mm

R = Ball radius in mm

This is an approximate geometric relation that is correct to 1 % for (wear scar

diameter/ball radius) <0.3, and is correct to 5 % for (wear scar diameter/ball radius) <0.7. The

exact equation is as given below

( ) ( ⁄ ) ⁄

Where,

D = Wear scar diameter

R = Radius of Ball

Wear rate of ball is calculated using following formula.

( )⁄

Where, k = Wear rate of ball in mm3/Newton. Meter

Vb = Wear volume for ball scar of diameter D in mm3

P = Load in N

L = Sliding Distance in mm


Zeeshan Ahmad

32

3.3.2. Wear of Flat Specimen

Wear of Flat specimen is calculated using following formula

( ) ( )

Where, w = width of wear scar in mm

d = depth of wear scar in mm

l = length of wear scar in mm

3.3.3. Results and Discussion

The Tribological experiment to compare and qualify the FRHF over mineral oil is

basically based on bench type friction and wear testing machine. The friction and wear

machine available at Fluid Power and Tribology Section, BARC is based on ASTM G 133 –

05. The experiment procedure and standards for this type of test has been explained in

previous sections of this thesis. The data generated and recorded and the results are presented

in tubular form. Based on data generated the friction characteristics and wear characteristics

of hydraulic fluid has been discussed.


Zeeshan Ahmad

33

1. Calculation Table

Table 3.3 Experiment data for hydraulic Oil-A and Oil-B

Experiment data of OIL-A (Fresh)

Oil Name Temperature

(°C) Load(N)

Frequency

(Hz)

Sliding

Distance

mm

Coefficient of friction Std

Deviation

Ball wear (All Dimensions are in mm) Wear

Rate of

Ball

mm³/N.m

Plate wear (All Dimensions are in mm)

Static Dynamic Horiz. Div.

Ver. Div. Scar Dia Wear Vol Length Width Wear Vol Wear Rate

FRHF

27

15 10 406843 0.098 0.079 ± 0.005 10.08 10.13 0.5052 0.000503 8.25E-08 2.03137 0.5455 0.04247493 0.002816001

15 20 796292 0.1 0.095 ± 0.002 11.11 11.22 0.5582 0.000750 6.28E-08 2.18296 0.561 0.046199469 0.003084189

25 10 396894 0.092 0.073 ± 0.004 12.23 12.84 0.6264 0.001190 1.20E-07 2.09879 0.642 0.06923943 0.004788899

65

15 10 404564 0.095 0.089 ± 0.001 9.54 10.91 0.5103 0.000524 8.63E-08 2.1328 0.5065 0.034000613 0.002214819

15 20 821301 0.092 0.095 ± 0.003 10.68 11.04 0.5430 0.000672 5.45E-08 2.35244 0.552 0.044011446 0.002926361

25 10 392425 0.095 0.086 ± 0.001 11.39 11.70 0.5772 0.000858 8.74E-08 2.03012 0.585 0.052386092 0.003534531

90

15 10 402394 0.102 0.081 ± 0.002 7.65 8.63 0.4062 0.000210 3.49E-08 1.88652 0.4315 0.021022812 0.00132268

15 20 809571 0.108 0.096 ± 0.002 9.27 9.91 0.4792 0.000407 3.35E-08 2.12278 0.4955 0.031833133 0.00206324

25 10 394075 0.097 0.073 ± 0.006 12.57 13.10 0.6416 0.001309 1.33E-07 2.11286 0.655 0.07353131 0.005114159

Experiment data of OIL-B (Fresh)


(°C) Load(N) Frequency(Hz)

Sliding

Distance

mm

Coefficient of friction Std

Deviation

Ball wear (All Dimensions are in mm) Wear

Rate of

Ball

mm³/N.m

Plate wear (All Dimensions are in mm)

Static Dynamic Horiz. Dim. Ver. Dim. Scar Dia Wear Vol Length Width Wear Vol Wear Rate

ENKLO

27

15 10 402805 0.092 0.081 ± 0.001 7.67 8.71 0.4087 0.000216 3.57E-08 1.93517 0.4355 0.021612892 0.001362368

15 20 815936 0.1 0.092 ± 0.001 7.85 8.73 0.4140 0.000227 1.85E-08 2.21603 0.4365 0.021762117 0.001372419

25 10 394257 0.082 0.077 ± 0.001 9.22 9.52 0.4683 0.000372 3.77E-08 1.89689 0.476 0.028220796 0.001812786

65

15 10 406606 0.099 0.088 ± 0.001 7.77 6.58 0.3576 0.000126 2.07E-08 2.11317 0.329 0.009318287 0.000557977

15 20 815043 0.115 0.1 ± 0.002 7.37 8.53 0.3964 0.000191 1.56E-08 2.00826 0.4265 0.020300443 0.001274222

25 10 396345 0.105 0.086 ± 0.001 7.49 8.89 0.4080 0.000214 2.16E-08 1.97427 0.4445 0.022980724 0.001454721


Zeeshan Ahmad

34

2. Result Table

Table 3.4 Experiment results of OIL-A and Oil-B

Experiment results of OIL-A (Fresh)


(°C)

Load

N

Speed

Hz

Ball

Radius

mm

Ball Scar

Dia. Mm h

Vol Loss of

Ball mm³

Wear Rate of

Ball mm³/N.m

Vol Loss of

Plate mm³

Wear Rate of

Plate mm³/N.m

FRHF

27

15 10 6.35 0.5052 0.006138002 0.000503 8.25E-08 0.04247493 0.002816001

15 20 6.35 0.5582 0.004180506 0.000750 6.28E-08 0.04619947 0.003084189

25 10 6.35 0.6264 0.007733228 0.001190 1.20E-07 0.06923943 0.004788899

65

15 10 6.35 0.5103 0.005150618 0.000524 8.63E-08 0.03400061 0.002214819

15 20 6.35 0.5430 0.005807625 0.000672 5.45E-08 0.04401145 0.002926361

25 10 6.35 0.5772 0.006562792 0.000858 8.74E-08 0.05238609 0.003534531

90

15 10 6.35 0.4062 0.003261244 0.000210 3.49E-08 0.02102281 0.00132268

15 20 6.35 0.4792 0.004526375 0.000407 3.35E-08 0.03183313 0.00206324

25 10 6.35 0.6416 0.011027409 0.001309 1.33E-07 0.07353131 0.005114159

Experiment results of OIL-B (Fresh)


(°C)

Load

N

Speed

Hz

Ball

Radius

Ball Scar

Dia. Mm h

Vol Loss

mm³

Wear Rate

mm³/N.m

Vol Loss of

Plate mm³

Wear Rate of

Plate mm³/N.m

ENKLO

27

15 10 6.35 0.4087 0.003301686 0.000216 3.57E-08 0.02161289 0.001362368

15 20 6.35 0.4140 0.003384054 0.000227 1.85E-08 0.02176212 0.001372419

25 10 6.35 0.4683 0.004319509 0.000372 3.77E-08 0.0282208 0.001812786

65

15 10 6.35 0.3576 0.002535555 0.000126 2.07E-08 0.00931829 0.000557977

15 20 6.35 0.3964 0.003111278 0.000191 1.56E-08 0.02030044 0.001274222

25 10 6.35 0.4080 0.00330209 0.000214 2.16E-08 0.02298072 0.001454721


Zeeshan Ahmad

35

3. Discussion

The Tribological experiments were performed on sliding friction and wear machine

under lubrication. Bearing steel plate SS-52100 and bearing steel balls SS-52100 of 1/2 inch

(12.7 mm) diameter were used as fixed specimen and moving specimen respectively. The

other experimental conditions are mentioned in above table. The major candidate for

calculation and discussion in this experiment is friction and wear. The calculation were made

and presented in table. The data were recorded and the graphs were plotted based on the data

available.

Friction Characteristics

1. Stribeck Curve

Two types of hydraulic oils were investigated in this experiment. Figures 3.5 to 3.8

show the friction characteristics of the two oils. Figure.3.5 summarizes the effect of load,

temperature, and lubricant on the friction behaviour. The data is presented in a Stribeck type

format. The Stribeck curve is a plot of the friction as it relates to viscosity, speed and load. On

the vertical axis is the friction coefficient and the horizontal axis shows a parameter that

combines the other variables: ηV/P. In this formula, η is the fluid viscosity corresponds to

temperature, V is the relative speed of the surfaces, and P is the load on the interface per unit

width. Basically, as you move to the right on the horizontal axis, the effects of increased

speed or increased viscosity or reduced load are seen. The zero point on the horizontal axis

corresponds to static friction. The stribeck curve shown in figure 3.5 is divided in to three

regimes.

1. Boundary lubrication (Regime 1) – two surfaces mostly are in contact with each other

even though a fluid is present

2. Mixed lubrication (Regime 2) – two surfaces are partly separated, partly in contact

3. Hydrodynamic lubrication (Regime 3) – two surfaces are separated by a fluid film

Boundary Lubrication (Regime 1)

Boundary lubrication occurs when the lubricating film is about same thickness as the

surface roughness such that the high points (asperities) on the solid surfaces contact. This is

generally an undesirable operating regime for a hydrostatic or hydrodynamic bearing, since it

leads to increased friction, energy loss, wear and material damage. In actual stribeck curve the

coefficient of friction in this regime is constant and of very high magnitude because of

starting friction of machine. But in figure 3.5 the coefficient of friction is increasing in this


Zeeshan Ahmad

36

regime because of increase in sliding speed and decrease in load the viscosity is kept constant

in this regime. Both the hydraulic fluids are performing almost equally in this regime and over

the entire curve. The peak in this regime for OIL-B is because of lower viscosity and viscosity

index as compared to OIL-A, the other conditions are same.

Mixed Lubrication (Regime 2)

As the speed and viscosity increase, or the load decreases, the surfaces will begin to

separate, and a fluid film begins to form. The film is still very thin, but acts to support more

and more of the load. Mixed lubrication is the result, and is easily seen on the Stribeck curve

shown in figure 3.5 as a sharp drop in friction coefficient. The friction in this regime is more

in case of OIL-B compared to OIL-A because of lower viscosity. The drop in friction is a

result of decreasing surface contact and more fluid lubrication. The surfaces will continue to

separate as the speed or viscosity increase until there is a full fluid film and no surface

contact. The friction coefficient will reach its minimum and there is a transition to

hydrodynamic lubrication. At this point, the load on the interface is entirely supported by the

fluid film. There is low friction and no wear in hydrodynamic lubrication since there is a full

fluid film and no solid-solid contact.

Hydrodynamic Lubrication (Regime 3)

One might notice that the Stribeck curve in figure 3.5 shows the friction increasing in

the hydrodynamic regime for both the oils, the increase in coefficient of friction for OIL-A is

more in this regime as compared to OIL-B. This is due to fluid drag (friction produced by the

fluid) - higher speed and high Viscosity may result in thicker fluid film, but it also increases

the fluid drag on the moving surfaces. For example, think about how much harder it is to run

in a pool of water than it is to walk. Likewise, a higher viscosity will increase the fluid film

thickness, but it will also increase the drag. Again, think about the difference between walking

in air and walking in a pool of water.

To understand hydrodynamic lubrication, we first should look at the figure 3.2. We

know that a surface will have tiny asperities or peaks that will contact if two plates are placed

together. If one of the plates were to slide over the other, then friction would increase, the

asperities would break and the surfaces would wear. In hydrodynamic lubrication, a fluid film

separates the surfaces, prevents wear and reduces friction. The hydrodynamic film is formed

when the geometry, surface motion and fluid viscosity combine to increase the fluid pressure

enough to support the load. The increased pressure forces the surfaces apart and prevents

surface contact. Therefore, in hydrodynamic lubrication, one surface floats over the other


Zeeshan Ahmad

37

surface. The hydrodynamic lubrication is the desirable condition for operating machines as it

leads to less wear of parts.

(a) (b) (c)

Figure 3.2 Lubrication regimes

2. Effect Of Temperature On Coefficient Of Friction

The effect of temperature on coefficient of friction for both hydraulic oils has been

shown in bar graph from figures 3.6 to 3.8 along with load and speed. The oil-A is tested at

three temperature values viz., 27oC, 65

oC, 90

oC while oil-B is tested at only two temperature

values, because the limiting operating temperature of oil-B is only 65oC. As we see all the

three graphs have similar trend. When the temperature is increasing the coefficient of friction

also increases for both hydraulic fluids because of lower viscosity value. Figures 3.6 to 3.8

corresponds to three different load and speed conditions they are 15N/10Hz, 25N/10Hz and

15N/20Hz respectively. The trend for coefficient of friction in all three graphs is similar. The

coefficient of friction for both hydraulic oil is reducing when we increase the load and

keeping speed constant at all temperature as explained in stribeck curve. But keeping load

constant and increasing speed, the coefficient of friction increases, this is due to fluid drag

(friction produced by the fluid) - higher speed and high Viscosity may result in thicker fluid

film, but it also increases the fluid drag on the moving surfaces and results in higher friction

between the layers of fluid.

Both hydraulic fluids are performing in similar manner when we are talking about

friction characteristics at any conditions, but the desirable condition of operation for both

hydraulic oil is hydrodynamic lubrication. The temperature in this regime is room temperature

with 3 combinations of speed and load. The other test temperature might result in boundary or

mixed lubrication zone that may not be desirable as it may result in more wear.


Zeeshan Ahmad

38

Wear Characteristics

The friction and wear experiment on hydraulic Oil-A and Oil-B has been performed on

reciprocating and sliding friction and wear machine. The standard procedure for this machine

has been discussed in section 3.2.1. The calculations for wear volume and wear rate of both

steel ball and steel plate have been made based on ASTM standard and research papers. The

data generated and the calculations during this experiment have been presented in tabulated

form in table 7 and 8. Based on calculations the have been plotted in figures 3.9 to 3.12.

Figure 3.3 and 3.4 shows the effective wear scar on steel ball and 3d profile of wear scar

on steel plate respectively. The trend found for wear rate for both hydraulic oils at any

condition is almost of similar order. Figure 3.9 to 3.12 shows the change in the volumetric

wear rates with the applied load measured at different temperatures. The wear rates were mild

at all conditions.

The wear rate at load of 15N as well as 25N should be less at room temperature 27C as

compared to 65C because of high viscosity of oil but it is not, the wear rate is more at room

temperature because of oxide layer formation at higher temperature of oil which prevents

wear of ball as well as plate. The effect of load on wear rate is clear in both cases of oils as

well as temperatures; the wear rate is increasing with increase in load. Both hydraulic oils

have similar trend for wear also in case of Oil-A the wear rate is more at all conditions as

compared to Oil-B. But the difference in wear rate of both hydraulic fluids is of order 10-7

it

means it is almost negligible. We can easily conclude that the wear characteristic of both

hydraulic fluids is same in all aspects.

Though the tribological evaluation is important aspect for an oil to be qualified for use

in hydraulic system, but there are other aspects need to be considered if the oil is to be used in

nuclear industry. Among such aspects radiation resistant is a very important criterion for an

oil to be qualified to use in nuclear industry. For initial study of radiation resistant both

hydraulic oils have been gamma irradiated at 50MRad radiation level with dose rate of 0.2

MRad/hr.


Zeeshan Ahmad

39

4. Gamma Irradiation of Hydraulic Fluids

Since based on Tribological result only it is not possible to evaluate a hydraulic fluid for

nuclear industry application, other factors are also need to be studied among all other factors

gamma irradiation is the most severe and hazardous factor for nuclear industry. It has been

cited in literature review that gamma irradiation leads to knocking down of bonding electrons

from the molecules and formation of radicals which leads to polymerization. It has been also

cited in literature that viscosity is most affected property of hydraulic fluid because of gamma

irradiation there for there is real need to study the effect of gamma irradiation on viscosity as

well as other properties of hydraulic fluid. For initial studies two samples (each of 200 ml) of

FRHF synthetic hydraulic fluid and petroleum based mineral hydraulic fluid contained in

glass bottles (67 mm dia) have been irradiated in Gamma Chamber of ISOMED with a dose

rate of 2.0 kGy/hr. (0.2 MRad/hr.). The dose level was 50 MRad. Glass bottles were capped

with glass stoppers. The irradiation was carried out at room temperature.

4.1. Measurement of Properties of Synthetic Fire Resistant Hydraulic Oil

(Oil-A)

The test sample viscosity was adopted as the primary parameter of radiation changes,

since the viscosity is a sensitive index characterizing the chemical structure of oils. Also,

changes in colour, density and Total Acid Number (TAN) are other criteria for study. In this

report TAN and density are not studied. Stabinger viscometer SVM 3000 is capable of

determining and displaying dynamic & kinematic viscosities and density of the fluid at a set

temperature simultaneously. These properties have been measured for fresh as well as 50

MRad oil samples for temperature range of 15 °C (288 K) to 100 °C (373 K).

4.1.1. Effect of Gamma Radiation on Kinematic Viscosity

Table 4.1 Gives the percentage variation of kinematic viscosity for fresh as well as

radiated oil sample with respect to temperature in temperature range of 15-100 °C (288°K to

373°K)

Table 4.1 Percentage change in kinematic viscosity of radiated oil sample from fresh oil

Sr.No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Temp. °C 15 20 25 30 35 40 45 50 55 60 65 72 80 92 100

°K 288 293 298 303 308 313 318 323 328 333 338 345 353 365 373

% change in

viscosity 61.22 59.99 58.17 56.70 55.30 54.03 52.20 50.93 49.61 48.40 49.24 45.39 43.55 41.19 39.82

*Data propriety in nature

[25]


Zeeshan Ahmad

40

The behaviour of the kinematic viscosity for 50 MRad radiation level as compared with

fresh oil is plotted in figure 4.1. It can be observed that the highest viscosity at any

temperature correspond to 50 MRad of oil. It can also be observed that the kinematic viscosity

of the oil for at a given temperature for 50 MRad radiation level has drastically increased. It is

found after the evaluation of figure 4.1 that at the low temperature ranges (below room

temperature) the percentage change in kinematic viscosity is higher as compared to that in

higher temperature range. It is found that the change in kinematic viscosity is approx. 40-60

% as compared to fresh fluid and since only ±10% variation is allowed in ISO standard, 40-60

% change over a 50 MRad dose is significantly high. Hence, it can be concluded that the

kinematic viscosity of this oil is not resistive to radiation levels of 50 MRad or more than that.

4.1.2. Effect Of Gamma Radiation On Viscosity Index

Table 4.2 gives the viscosity index (VI) of Oil-A for fresh oil as well as 50 MRad of

radiation dose oil.

Table 4.2 Viscosity index of Oil-A

It is found that the viscosity index has slightly changed for radiation level. It means that

the viscosity index of Oil-A oil is not affected by radiation dose up to a level of 50 MRad.

4.1.3. Appearance of Oil after Gamma Irradiation

Figure 4.3 gives the effect of radiation on the appearance of the Oil-A. It is clear that

there is no significant change in colour of the oil. The oil has to be further analysed for

presence of oxidation compounds using TAN and oxidation stability testing methods.

4.2. Measurement of Properties of Petroleum Based Hydraulic Fluid (Oil-B)

Similar to FRHF synthetic type of oil, petroleum based oil has also been gamma

irradiated for 50 MRad of radiation and properties has been measured for fresh as well as 50

MRad radiation oil using SVM 3000 Anton Paar Stabinger viscometer.

4.2.1. Effect of Gamma Radiation on Kinematic Viscosity

Table 4.3 Gives the percentage variation of kinematic viscosity for fresh as well as

radiated oil sample with respect to temperature in temperature range of 15-100 °C (288°K to

373°K). The behaviour of the kinematic viscosity for 50 MRad radiation level as compared

Viscosity Index of Oil-A

Radiation dose Fresh Oil 50 MRad

Viscosity Index 143.3 145.8


Zeeshan Ahmad

41

with fresh oil is plotted in figure 4.4. It can be observed that the highest viscosity at any

temperature

Table 4.3 Percentage change in kinematic viscosity of radiated oil sample from fresh oil

Sr.No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Temp. °C 15 20 25 30 35 40 45 50 55 60 65 72 80 92 100

°K 288 293 298 303 308 313 318 323 328 333 338 345 353 365 373

% change in

viscosity 7.93 7.70 7.22 7.12 6.66 6.42 5.93 5.91 5.57 5.54 5.25 4.68 4.42 4.40 4.22

*Data propriety in nature

[25]

correspond to 50 MRad of oil. It can also be observed that the kinematic viscosity of the oil

for at a given temperature for 50 MRad radiation level has slightly increased. It is found after

the evaluation of figure 4.4 that at the low temperature ranges (below room temperature) the

percentage change in kinematic viscosity is higher as compared to that in higher temperature

range. Though it is found that the change in kinematic viscosity is approx. 5-8 % as compared

to fresh fluid and since ±10% variation is allowed in ISO standard, 5-8 % change over a 50

MRad dose is insignificant. Hence, it can be concluded that the kinematic viscosity of this oil

may be resistive to radiation levels up to 50 MRad.

4.2.2. Effect Of Gamma Radiation On Viscosity Index

Table 4.4 gives the viscosity index (VI) of Oil-B for fresh oil as well as 50 MRad of

radiation dose oil.

Table 4.4 Viscosity index of Oil-B

It is found that the viscosity index has not changed for radiation level. It means that the

viscosity index of mineral oil is not affected by radiation dose up to a level of 50 MRad.

4.2.3. Appearance of Oil after Gamma Irradiation

Fig. 4.6 gives the effect of radiation on the appearance of the Oil-B. It is clear that the

oil has under gone significant colour change which may be due to polymerisation as well as

oxidation of the oil. The oil has to be further analysed for presence of oxidation compounds

using TAN and oxidation stability testing methods.

Viscosity Index of Oil-B

Radiation dose Fresh Oil 50 MRad

Viscosity Index 101.7 101.1


Zeeshan Ahmad

42

5. Conclusion and Future Scope

5.1. Conclusion

The oil-a is no doubt a fire resistant hydraulic fluid having very high flash and fire point

of approximately 260oC and 310

oC respectively in comparison with oil-b having same at

210oC and 230

oC respectively, it can be used as hydraulic fluid if there is no issue of

compatibility or degradation because of gamma irradiation. But if such problems are arises

then without experimental evaluation we cannot use this oil in to hydraulic system. Nuclear

industry like DAE is one such industry where these types of problems are very common.

Hence before being put this oil into actual system the oil has been evaluated using two

deferent methodologies and conclusion has been made based on these two methodologies.

Tribological evaluation

a) Tribological Evaluation

The tribological evaluation for qualifying hydraulic Oil-A and Oil-B has been done on

sliding friction and wear machine TE-70. Friction and wear were the major candidate for

qualifying the oils.

As discussed in previous chapter, the friction characteristics of the two oils are almost

same. The stribeck curve shows that both Oil-A and Oil-B have similar operating

conditions in hydrodynamic regime.

The wear characteristics shows that the wear rate of ball and plate under Oil-A lubrication

is high as compared to Oil-B but the order of wear rate is very low for both oils and is of

order 10-7

, which is condition of mild wear. Hence it can be acceptable.

Based on tribological experiment it can be concluded that both hydraulic oils are similar in

tribological behaviour, Oil-A has the advantage of being fire resistant. There for Oil-B can

be replaced by Oil-A if there is chances of fire hazard or the operating temperature is high.

b) Radiation Resistant

Based on only tribological evaluation it is not possible to recommend or replace one

hydraulic fluid over the other if the hydraulic fluids are going to be used in nuclear industry,

there are other factors need to be consider. Among such factors gamma irradiation is the most

severe and hazardous factor which can degrade the hydraulic fluid and it will be hazardous

and dangerous for the entire environment near the nuclear reactor. For the purpose of initial

study of effect of gamma irradiation on hydraulic oils both oils have been gamma irradiated at


Zeeshan Ahmad

43

initial level of only 50 MRad in Gamma Chamber of ISOMED and the properties have been

measured and compared with each other. The conclusion made on this is as follow.

The viscosity of Oil-A has changed tremendously as compared to Oil-B. There is

approximately 40% to 60% change in viscosity over the temperature range of 15oC to

100oC for Oil-A, whereas viscosity of Oil-B changes only 6% to 8% over the same

temperature range.

Hence it is clear that Oil-A is not a radiation resistant whereas Oil-B is radiation resistant

up to 50 MRad level.

It is found after the evaluation that for both oils at low temperature ranges (below room

temperature); the percentage change in viscosity is higher as compared to that in higher

temperature range. This may be advantageous for Oil-A when the operating temperature is

high, because of higher viscosity it can be act as a lubricant for hydraulic system even in

radioactive environment, whereas this may not be possible for Oil-B because of low

viscosity value at high temperature.

The viscosity index of the Oil-A after gamma irradiation has improved whereas viscosity

index of Oil-B remains constant. Due to this variation in viscosity over the temperature

range is reduced for Oil-A compared to Oil-B.

Based on above discussion it is concluded that up to 50 MRad radiation level Oil-A can be

used as hydraulic fluid in replacement of Oil-B in nuclear industry when the operating

temperature is high.

5.2. Future Scope

The test procedure discussed in this report for sliding friction and wear measurement can

be used for general purpose friction and wear test under lubricated or dry condition.

The data available in this report can be used for selection of hydraulic oils for other

applications also.

The properties of hydraulic oils will required to be evaluated at more radiation levels, for

this purpose it is planned to irradiate hydraulic oils at 5, 25, 100, 200, 300, 400 and 600

MRad radiation levels.

The appearance of oil is not a major concern in this report but in future the oil has to be

further analysed for presence of oxidation compounds using TAN and Oxidation Stability

test.


Zeeshan Ahmad

44

Change-over of a system from one hydraulic oil to another can create problems unless

consideration is given to circuit and component design.

For this purpose, a Fire Resistant Hydraulic Fluid Test Facility (FRHTF) will be developed

by RTD at Engineering Hall – 3. In this facility hydraulic performance, compatibility with

existing hydraulic components, and high temperature operability will be tested by

evaluating the changes in properties of the hydraulic oils after being used in this facility

test setups.

The test facility will be designed to be operated without any operator.

A man machine interface (MMI) will be required to design to run this test facility 24x7

without any operator assistance.


Zeeshan Ahmad

45

6. References

[1] ‗Engineering Design Handbook of Hydraulic Fluids, Headquarters‘, U.S. Army Materiel Command, April

1971.

[2] W.D. Phillips, ‗A Comparison of Fire-resistant Hydraulic Fluids for Hazardous Industrial Environments.

Part 1. Fire resistance and lubrication properties‘, FMC Corporation (UK) Ltd.

[3] Sullivan, M.V., Wolfe, J.K., and Zisman, W.A., ‗Flammability of the higher boiling liquids and their

―mists‖‘, Zng. Eng. Chem., 39, 12 (1947), 1607-14.

[4] Murphy, C.M., and Zisman, W.A., ‗Synthetic hydraulic fluids‘, Product Engineering, 21, 9 (1950), 109-13.

[5] ‗Lubricants, Industrial Oils and Related Products – (Class L) – Classification – Part 4: Family H (Hydraulic

Systems)‘, ISO Standard 6743.

[6] Santosh Javalagi and Swaroop Reddy Singireddy, ‗Hydraulic fluid properties and its influence on system

performance‘, Linköping University.

[7] ‗Hydraulic Fluid Power – Fire-Resistant (Fr) Fluids – Guidelines for Use‘, Bureau of Indian Standards,

New Delhi-110002.

[8] ‗Friction, Wear, and Lubrication: Terms and Definitions‘, Research Group on Wear of Engineering

Materials, Organization for Economic Cooperation and Development.

[9] H. H. Zuidema, ‗The Performance of Lubricating Oil‘, Reinhold Publishing Corp., N. Y., 1959.

[10] Federal Test Method Standard No. 791a, Test Method No. 6505.



[13] ASTM Standards 1969, Designation D-2596- 67T, Part 17, p. 970, Philadelphia, American Society for

Testing Materials, 1969.


[15] ASTM Standards 1967, Designation D-2266- 64T, Part 17, p. 799, Philadelphia, American Society for

Testing Materials, 1967.


[17] H. Gisser, ‗The Effects of Nuclear Radiation in Lubricants‘, Conference on Effects of Nuclear Radiation on

Materials, Watertown Arsenal, 1967.

[18] R. C. Gunderson and A. W. Hart, ‗Synthetic Lubricants‘, Reinhold Publishing Corp., N.Y., 1962.

[19] Roger E. Hatton, Introduction to Hydraulic Fluids, Reinhold Publishing Corp., N. Y., 1962.

[20] Charles Spar, Hydraulic Fluids and Their Applications, ASME Publication 64 WA/LUB-14.

[21] R.O .Bolt and J.G. Carrol, ‗Effect of radiation on aircraft lubrications and fuels‘, California Research

Corporation, WADC Technical Report No 56- 646, Part II, ASTIA Document No. AD 151176. April 1958.


Zeeshan Ahmad

46

[22] William L. R. Rice, ‗Nuclear Radiation Resistant Lubricants‘, California Research Corporation, WADC

Technical Report No 57-299, ASTIA Document No. AD 118329 May 1957.

[23] S. Sharma, S. Sangal, K. Mondal, ‘ On the optical microscopic method for the determination of ball-on-flat

surface linearly reciprocating sliding wear volume‘, Wear 300 (2013) 82–89

[24] ASTM G133-05(2010), ‗Standard Test Method for Linearly Reciprocating Ball-on-Flat Sliding Wear‘,

ASTM International, West Conshohocken, PA, 2010, www.astm.org

[25] Zeeshan Ahmad, P.K.Mishra, ‗Determination of Effect of Gamma Radiation on Petroleum based Hydraulic

Fluid - ENKLO-68‘ RTD Report, BARC, Mumbai

[26] Hutchings, I.M. (1992), ‗Tribology — Friction and Wear of Engineering Materials‘, Edward Arnold,

London.

[27] Zum Gahr, K.-H. (1987), ‗Microstructure and Wear of Materials‘, Tribology Series 10, Elsevier,

Amsterdam.

[28] http://www.viscopedia.com/methods/measuring-principles/

http://www.astm.org/


Zeeshan Ahmad

47

Appendix I

Figures and Graphs

TE70 Reciprocating wear & friction machine

Figure 3.3 Reciprocating wear & friction machine PLINT TE 70

Ball SS-52100, 15 N, 10 Hz, 20000 sec

Ball SS-52100, 25 N, 10 Hz, 20000 sec

Figure 3.4 Typical photographs indicating ball wear

Figure 3.5 3D profile of wear scar on SS-52100 steel flat sample


Zeeshan Ahmad

48

Effect of Temperature on Coefficient of Friction

Figure 3.6 Stribeck curve of Oil-A and Oil-B

Figure 3.7 Effect of temperature on coefficient of friction 15 N / 10 Hz

0.05

0.06

0.07

0.08

0.09

0.1

0.11

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35

Co

effi

cien

t o

f Fr

icti

on

η*V/P(Stribeck Parameter)

Stribeck Curve for OIL-A and OIL-B

OIL-A

OIL-B

Regime 1 Regime 2 Regime 3

0.079

0.089

0.081 0.081

0.088

0.05

0.06

0.07

0.08

0.09

27 65 90

Co

effi

cien

t o

f Fr

icti

on

Temperature (ᵒC)

Effect of Temperature on Coefficient of Friction 15 N / 10 Hz

Oil-A

Oil-B


Zeeshan Ahmad

49



0.073

0.086

0.073

0.077

0.086

0.05

0.06

0.07

0.08

0.09

0.1

27 65 90

Co

effi

cien

t o

f Fr

icti

on

Temperature (ᵒC)


Oil-A

Oil-B

0.095 0.095 0.096 0.092

0.1

0.05

0.063

0.076

0.089

0.102

27 65 90

Co

effi

cien

t o

f Fr

icti

on

Temperature (ᵒC)


Oil-A

Oil-B


Zeeshan Ahmad

50

Effect of Load on Wear Rate

1. Ball

Figure 3.10 Load vs. wear rate of ball 27ᵒC /10 Hz

Figure 3.11 Load vs. wear rate of ball 65ᵒC /10 Hz

0.83

1.20

0.36 0.38

0.00

0.30

0.60

0.90

1.20

1.50

15 25

Wea

r R

ate

(mm

³/N

m)

Load (N)

Load Vs. Wear Rate of Ball 27ᵒC /10 Hz

OIL-A

OIL-B

×10-7

0.86 0.87

0.21 0.22

0.00

0.30

0.60

0.90

1.20

1.50

15 25

Wea

r R

ate

(mm

³/N

m)

Load (N)

Load Vs. Wear Rate of Ball 65ᵒC /10 Hz

OIL-A

OIL-B


Zeeshan Ahmad

51

Effect of Load on Wear Rate

2. Plate

Figure 3.12 Load vs. wear rate of plate 27ᵒC /10 Hz

Figure 3.13 Load vs. wear rate of plate 65ᵒC /10 Hz

2.82

4.79

1.36

1.81

0.00

1.00

2.00

3.00

4.00

5.00

6.00

15 25

Wea

r R

ate

(mm

³/N

m)

Load (N)

Load Vs. Wear Rate of Plate 27ᵒC /10 Hz

OIL-A

OIL-B

2.21

3.53

0.56

1.45

0.00

1.00

2.00

3.00

4.00

5.00

15 25

Wea

r R

ate

(mm

³/N

m)

Load (N)

Load Vs. Wear Rate of Plate 65ᵒC /10 Hz

OIL-A

OIL-B

×10-3

×10-3


Zeeshan Ahmad

52

Effect of Radiation on Viscosity of Oil

Oil-A

Figure 4.1 Percentage change in kinematic viscosity of Oil-A

Figure 4.2 Viscosity index vs. gamma radiation dose Figure 4.3 Change of appearance

with gamma radiation dose

-20

0

20

40

60

80

280 300 320 340 360 380

Pe

rcen

tage

Ch

ange

in V

isco

sity

Temperature ( ᵒK)

Percentage Change in Kinematic Viscosity of Oil-A

50 MRad

143.3

145.8

142

143

144

145

146

Fresh (0 MRad) 50 Mrad

Vis

cosi

ty I

nd

ex

Radiation Dose

Viscosity Index

Fresh (0 MRad)

50 Mrad


Zeeshan Ahmad

53

Oil-B

Figure 4.4 Percentage change in kinematic viscosity of Oil-B

Figure 4.5 Viscosity index vs. gamma radiation dose Figure 4.6 Change of

appearance with gamma

radiation dose

-2

0

2

4

6

8

10

280 300 320 340 360 380

Pe

rcen

tage

Ch

ange

In V

isco

sity

Temperature (ᵒK)

Percentage Change In Kinematic Viscosity of Oil-B

50 MRad

100.8

101

101.2

101.4

101.6

101.8

Fresh (0 MRad) 50 Mrad

Vis

cosi

ty In

dex

Radiation Dose

Viscosity Index

Fresh (0 MRad)

50 Mrad

evaluation of fire resistant hydraulic fluid to replace conventional mineral oil in nuclear industry

Documents

university of mumbai

mumbai evaluation

resistant hydraulic

mumbai mr

conventional mineral

zeeshan ahmad rizwan

vjti mumbai

headfluid power