Análises de óleos para leigos

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Se você quer entender o básico de análise de óleo lubrificante e compreender um assunto que nos afeta o dia a dia da manutenção de equipamentos mecânicos, então acabou de encontrar o que precisa no Analises de Óleo para Leigos. Este guia de fácil compreensão te leva através do mundo da Analises de Óleo, dos conhecimentos sobre aditivação e contaminantes e a desmistificação de tópicos complexos de como criar um programa para analise óleo.

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Análises de óleos para leigos

  1. 1. sier! " C ¡fl/ Aisen w179’ MÏW ‘IIILÍII I, YA .1 ‘¿<4 Ilïïllflïfïf‘ iïfliïïílfiïïlï; ¿Fijate ‘¿IDIIÏÏIÏEÏIBI by Michael Barrett Insight Services Learn to: - Understand performance and wear ‘ J 4 Karrie - Choose the right oil analysis test y f» ‘s’ ‘r l " l; Insig ht Services slate for your equipment - Create a world-class oil analysis program Complimenrs of Y)“ _ . I Ar r; . I r Ir‘. s: R VI ¿‘:3 @ WILEY Michael Barrett John Wiley & Sons, Inc. Karrie Williams
  2. 2. Oil Analysis For Dummies; Insight services Special Edition Published by John Wiley & Sons, Inc. III River St. Hoboken, NJ 07030-5774 wwvnwlley. com Copyright (c) 2012 by John wiley er sons, inc, Hoboken, New Jersey Published by John Wiley s sons. lnc. . Hobuken. New Jersey No part oi this publication may he reproduced, stored in a retrievai system or transmitted in any Iorm or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, except as permitted under sections 107 or 108 ot the 197o‘ united states Copyright Act, without the prior written permission oi the Puhiisher. Requests to the Publisher lor permission should he addressed to the Permissions Department, John wiiey a. sons, lnc. , iii River street, Hohnken, NJ 07030, (201) 742.601 l, [ax (201) v4ssms, or online at nt- z/ lwww. wiley. cum/ go / p2nn; ss1uns. Trademarks: wiley, the wiley logo, For Dummies. the Dummies Man logo, A Reierence for the Rest oi Usl, The Dummies way, Dummiescom, Making Everything Easter, and related trade dress are trade- marks Or registered trademarks oi John Wi| ey&SOns, Inc. and/ Or its alliliates in the United States and other countries, and may not he used without written permission, Insight Services and the Insight Services logo are trademarls or registered trademarks oi Insight services, lnc. and may not he used without written permission. All other tradeinarls are the property oI their respective owners. John wiley sr sons, inc, is not associated with any product or vendor mentioned in this book. : THE PUBLISHER AND THE AUTHOR MAKE N0 REPRESENTATIONS OR WARRANTIES WITH RESPECT TO THE ACCURACV OR COMFLETENESS OF THE CONTENTS OF THIS WORK AND SPECIFICALLY DISCLAIM ALL WARRANTIES, INCLUDING WITHOUT LIMITATION WARRANTIES OF FITNESS FOR A PARTICULAR PURPOSE. NO WARRANTY MAY BE CREATED OR EXTENDED BY SALES OR FROMOTIONAL MATERIALS. THE ADVICE AND STRATEGIES CONTAINED HERElN MAY NOT BE SUITABLE FOR EVERY SITUATION. THIS WORK IS SOLD WITH THE UNDERSTANDING THAT THE FUBLISHER IS NOT ENGAGED IN RENDERING LEGAL. ACCOUNTING, OR OTHER PROFESSIONAL SERVICES. IF PROFESSIONAL ASSISTANCE IS REQUIRED, THE SERVICES OF A COMPETENT PROFESSIONAL FERSON SHOULD BE SOUGHT. NEITHER THE FUBLISHER NOR THE AUTHOR SHALL BE LIABLE FOR DAMAGES ARISING HEREFROM. THE FACT THAT AN ORGANIZATION OR WEBSITE IS REFERRED T0 IN THIS WORK AS A CITATION AND/ OR A FOTENTIAL SOURCE OF FURTHER INFORMATION DOES NOT MEAN THAT THE AUTHOR OR THE PUBLISHER ENDORSES THE INFORMATION THE ORGANIZATION OR WEBSITE MAY FROVIDE OR RECOMMENDATIONS IT MAY MAKE. FURTHER, READERS SHOULD BE AWARE THAT INTERNET WEBSITES LISTED IN THIS WORK MAY HAVE CHANGED OR DISAPFEARED BETWEEN WHEN THIS WORK WAS WRHTEN AND WHEN IT lS READ. For general iniormatron on our other products and services, please contact our Business Development Department in the u. s. at 317-5723205. Far details on how to create a custom For Dummies bOOk lor your husiness or Organization, contact rnroddumroes . b1z. For iniormation about licensing the Fnr Dummies brand ior products or services. contact Etoindedkígtitssdaicensesíilrhlev. com. ISBN 97m4 “LEOMEN (phk) Manutactured in the united states OI America lO 9 s 7 e 5 4 3 2 i ruhiisherls Acknnwledgmenu some oi the people who helped bring this hoolt to market include the following: Acquisilions, Editorial, and Media Camposifion Services ”"""°”'"°"' senior Project Coordinator‘. Kristie Rees Development Editor. Chad sievers Layout and Graphics: Julie Trippetti Pruject Eflilnl‘. JenniIer Bingham Fmofreaders: Melanie Hoffman Editorial Manager: Rev Mengle Business Development Representan e: B""'""‘ ”“’°’°"”'°’" Klmberley Schumacket Director, New Market and Brand custom Publishing Rmiect Specialist: Development: Lisa Coleman Michael Sullivan @ witzv Table of Contents Introductían. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 1 About This Book . . Icons Used in This Book. Chapter1: Grasping the Basics oí Luhrication andflilïesting Knowing What Lubricants Are . Identifying What Lubricants DO In a Machine Eyeing the Types OI Lubricating Oils Seeing Why Oil Analysis ls Important . 3 4 4 6 7 9 Chapter 2: Understanding Performance anti Wear. . . .. Comprehending Lubrication Modes. .. Taking a Look inside the Machin What Causes Wear? ... .. 14 Examining the Ins and Outs of Particles. Adding Additives: How They Can Protect against Wear Recognizing What Viscosity ls Chapter 3: Getting Luhrication to ltsProperDestination 27 33 37 43 Grasping the Different Lubrication Systems . . Recognizing Lubricant-Related Failure Knowing What Alarm Levels Mean ÍOr Machine Wear Chapter 4: Oil Testing 101: Getting into the Lab. .. Ensuring People Are Trained tO Correctly Take Samples. .. 44 Knowing How to Correctly Read Your Oil Analysis Report. .. 46 Measuring Metals: Elemental Spectroscopym . . 49 Checking Resistance: Viscosity” 51 Screening for Moisture: Crackle Test 52 Quantiíying the Amount OI Water: Karl Fischer Water Test. “ Looking at Chemical Composl ion: ITF-IR Gauging Acidity: Acid Number. a. 55 56 57
  3. 3. Oil Testing For Dummies, Insight Services Special Edition Testing the Reserve Alkali ty ase Number . 57 Gauging Particle Count. . 58 Ferreting Out Ferrous Wear Concentration . 59 Examining Wear Particles: Analytical Ferrography. . 60 Chapter 5: Oil Testing 201: More Intense Lah Work . ..71 Checking Oil’s Ability to Separate from Water: Demulsibility . ... .. Determining Oxidation Stabili Checking for Rust Preventing Characteristic .71 .72 The Rust Test . ... ... ... ... .. . . . 73 Analyzing Foaming Tendenc Foam Test . . 73 Detecting Varnishing Problems: Varnishing Potential . 75 Checking for Advanced Wear: Filter Debris Analysi . 77 Chapter 6: Ten Ways to Create a World-Class Oi Testing Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79 ldentifying Critical Equipment 79 Knowing What Tests to Choose . 80 .81 .81 .82 .83 .84 .84 .85 .86 Ensuring Everyone Has the Proper Training Storing and Handling Lubricants . Considering Your Testing Options Choosing the Correct Oil Analysis Provider . lnterpreting an Oil Analysis Repor Justiiying Your Program . . Establishing and Maintaining Your Credi ility. ... . Using Web-Based Tools to Manage Your Program Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .89 Introduction gil analysis can uncover, isolate, and offer solutions for abnormal lubricant and machine conditions when used as a predictive maintenance tool. These abnormalities can result in expensive, sometimes catastrophic, damage causing lost production, extensive repair costs, and even operator accidents. The goal oí an effective oil analysis program is to increase the reliability and availability oí machinery while minimizing maintenance costs associated with oil changeouts, labor, repairs, and downtime. Accomplishing this goal takes time, training, and patience. l-iowever, the results are dramatic and the documented savings and cost avoidance are significant. Many organizations throughout the world have implemented oil analysis programs to manage their equipment. Some have experienced substantial savings, cost reductíons, and increased productivity, while others have received only mar- ginal benefits. A successful oil analysis program requires a dedicated commitment to understand the equipment, the lubricant, the operating environment, and the relationship between the test results and the actions to be performed. About This Boo/ c This book provides plenty of current and practical informa- tion and advice that you can immediately apply to your com- pany. It can help you understand the benefits that oil analysis can ofler your company. Furthermore, we hope this book helps clear up any coníu- sion you may have about oil analysis and gives you practical advice about how to ensure your machinery is protected and running smoothly. If we can help you avoid any lubrication problems or machinery problems, this book will have done its job. This book was created with Insight Services.
  4. 4. 2 Oil Testing For Dummies, Insight Services Special Edition Icons Used in This Boo/ c “sin o? In this book we use little round pictures, called icons, in the margins. They mark certain types of information. The Remember icon points out text we suggest you keep in mind, because we expect these tidbits to be useful to you in the future. This icon gives you plenty of hands-on information and advice that you can use. Chapter 1 Grasping the Basics of Lubrication and Oil Testing In This Chapter Defining lubricants Understanding the functions of lubricants Naming the different types of lubricating oils Recognizing the importance of oil testing gil testing, also called oil analysis, involves systematically sampling and checking oil for various properties and materials to monitor wear and contamination in the internal components of a machine, including a turbine, gearbox, com- pressor, pump, and so on. Having oil testing done on a regular basis establishes a baseline of normal wear and can help indi- cate when abnormal wear or contamination is occurring. A detailed analysis of a sample of lubricant is a valuable preven- tive maintenance tool. In many cases, it enables identification of potential problems before a major repair is necessary, has the potential to reduce the frequencies of oil changes, and increases the resale value of used equipment. This chapter provides a starting point for you to understand how lubricants work and why testing those lubricants on a regular basis is important. Consider this chapter your jump- ing-off point into everything you need to know about lubri- cants and oil testing.
  5. 5. 2 Oil Testing For Dummies, Insight Services Special Edition ¡(nou/ ing What Luhricants Are You may already have a firm grasp of what lubricants are, but this section gives you a quick reminder. Industrial lubricants, sometimes referred to as oils, are specifically designed fluids composed of two aspects: Al Base oil: The base oil performs several functions includ- ing forming a fluid film between moving parts in order to reduce friction and wear, carrying away contaminants to the filter, and removing heat generated within the machine. l/ Additive packages: Additives are chemical components added to the base oil to significantly enhance the per- formance characteristics of the lubricating oil. Additive enhanced properties include oxidation stability, wear protection, and corrosion inhibition. Chapter 2 identifies common additives and their roles. Identifyina What Lubricants Do in a Machine Lubricants do more than just lubricate. They actually perform several important roles inside a working machine. The follow- ing sections explain the six primary functions that a lubricant provides. lubricate As you might expect, the most critical function provided by lubricants is to lubricate and minimize friction and wear, which can extend equipment service life. Essentially, the pres- ence of a lubricating film minimizes metal-to-metal contact and reduces the force necessary to move one surface against the other, thereby reducing wear and saving energy. By introducing a film between moving parts, opposing friction surfaces are separated and allowed to move freely without any interlocking of the asperities at the metal surface. By physically separating the moving parts, friction is greatly reduced. The result is less wear generated and less energy required to perform the work. T Chapter 1: Grasping the Basics oI Lubrication and Oil Testing 3 Cool The second function lubricants provide in a working machine is to cool it. Lubricants absorb the heat generated at the friction surface and carry it away to a reservoir where it is allowed to cool before returning for service. Oil coolers and heat exchang- ers are sometimes used to efficiently disperse heat. Clean You may consider lubricants as your own cleaning service for your machines. Lubricants pick up solid contaminants and move them away from the contact zone (the metal-to-metal contact area). The contaminants can then be removed by filtration or by settling in the reservoir. Many oils have deter- gent characteristics to hold tiny dirt and soot particles in sus- pension and help prevent sludge and varnish in a system. Protect Lubricants also have a protective aspect. They coat a compo- nent suríace, which provides a barrier against moisture. The presence of moisture in the air eventually leads to corrosion. Rust occurs when steel surfaces are attacked by moisture, and corrosion occurs when a metal surface is attacked by acids or water. Oils can be fortified with alkaline reserves to counter the corrosive contaminants. Seal Many lubricants form a viscous seal to keep contaminants out of a component. Greases form physical barriers to protect against dirt and water ingress. Transmi t power Lubricants also can transmit power in some machines. For example, hydraulic systems use lubricants as a source of fluid power. Fluid under pressure actuates moving parts.
  6. 6. h Oil Testing For Dummies. Insight Services Special Edition Eyeiny the Types of lubricating Oils As we discuss in the “Knowing What Lubricants Are” section earlier in this chapter, a base oil and an additive package for- mulated to enhance the oil‘s performance compose lubricat- ing oils. The additive package can constitute 2 to 30 percent of the oil, depending on the oil type. Many specialty oils, such as Automatic Transmission Fluid (ATF), are designed for a very specific use. Most lubricating oils, however, can fall into one of the four following types: i/ Engine oils: These oils contain anti-wear agents and detergents, and are designed to work in a wide tempera- ture range. This category includes heavy duty motor oils (HDMO) designed to lubricate diesel engines, and pas- senger car motor oils (PCMO) formulated for gasoline engines. M Anti-wear (AW) oils: These oils are formulated with anti- wear additives to aid in preventing wear iri static loading situations. This category includes AW hydraulic fluids and light gear oils. 1/ Extreme pressure (EP) oils: EP oils are designed for applications where heavy loading and shock loading are expected. They’re usually heavy gear oils designed for use in slow moving and reversing gear cases. They’re also used in heavily loaded antifriction bearings, i/ Rust and oxidation inhibiting (RSzO) oils: These oils are designed for long life applications where light loads and high speerls are generally expected, which includes many turbine oils and hydraulic fluids. R&O oils are formulated with additives to inhibit the oxidation process. The formulation of the various types of lubricating oils varies significantly depending on their application. Due to the wide variety of applications in which oils are used, many different formulatíons for oils exist. Machine manufacturers generally designate the oil iormulations that are suitable for their equipment. T Chapter 1: Grasping the Basics of Lubrication and Oil Testing Taking a look back: The history of oil analysis The first used oil analysis dates hack to the early 19403 by the railway companies in the western United States. Technicians used simple spectrographic equipment and physical tests to monitor Iocomotive engines. By the l980s, oil analysis formed the basis of condition-based maintenance in most railways in North America. Bythe mid-l950s the U. S. Navy began tu use spectrometric techniques to monitor ¡et engines on their aircraft. Around this time Rolls-Royce was also experimenting with oil analysis fortheirjetturbines. Throughoutthe 19505 and early l960s oil analysis programs were developed hy other U. S. militaryforces, but it wasn't until the early 1950s that commercial oil analysis Iahoratories first appeared. 5 Seeiny Why Oil Analysis Is Important ¡para A‘ Maintaining a lubricant means ensuring that it has the correct uiscosiry (a measure of a lubricants resistance to flow; see Chapter 2) and has the necessary additives for the applica- tion. You must take steps to keep the lubricant clean and ser- víceable. Oil analysis is the most effective way to prolong the useful life of lubricants, while maintaining maximum protec- tion of equipment. Lubricant that has been inside any moving mechanical apparatus for a period of time reflects the condition of that assembly. Lubricant is in contact with the engine or mechani- cal components as trace metallic wear particles enter the oil. These particles are so small they remain in suspension. In the specific case of engines, many products of the combustion process also become trapped in the circulating oil, So the oil becomes a working history of the machine, Particles caused by normal wear and operation will mix witli the oil. By identifying and measiiring these impiirities through
  7. 7. Oil Testing For Dummies, Insight Services Special Edition oil analysis, you get an indication of the rate of wear and of any excessive contamination. Report recommendations may also suggest methods to reduce accelerated wear and contamination, Oil analysis has three aspects, which we discuss in the follow- ing list: l/ Lubricant condition assessment: The assessment of lubricant condition reveals whether the system fluid is healthy and fit for further service, or is ready for a change. i/ Contaminant monitoring: increased contaminants from the surrounding environment in the form of air, dirt. water, and process contamination are the leading cause of machine degradation and failure. increased contamina- tion alerts you to take action in order to save the oil and avoid unnecessary machine wear. i/ Machine wear monitoring: An unhealthy machine gener- ates wear particles at an exponential rate, The detection and analysis of these particles assist in making critical maintenance decisions. You can avoid machine failure due to worn-out components. Healthy, clean oil mini- mizes machine wear, Chapters 4 and 5 discuss several different tests that may be worthwhile for your organization, The different tests in Chapter 4 check on the most basic functions of your machines and the lubrication to ensure everything is running smoothly, Chapter 5 focuses on some more advanced tests you and your company may want to consider. ChapterZ Understanding Performance and líilear In This Chapter Grasping the different lubrication modes Knowing what causes wear in a machine Seeing how additives protect against wear Eyeing viscosity our company has many working machines that it relies k on to keep it in business every day. As a result, you want your machines working efficiently with as few problems as possible. Unfortunately, machines can face a slew of problems —- from inefficiency to breaking down. That‘s where lubricants come into play. Your machines‘ lubricants can greatly affect their performance and wear. A well-oiled machine can operate smoothly with few issues. This chapter examines how lubrication can enhance perfor- mance in your machines and reduce the amount of wear, thus giving your machines a longer running time. Comprehendina Lubrication Modes By identifying and defining different lubrication modes, you can begin to consider how various operating conditions can
  8. 8. lo Oil Analysis For Dummies, Insight Services Special Edition Chapter 2: Understanding Performance and Wear 1 I affect lubricant performance and how proper lubricant selec- 4 4 tion is beneficia]. The following sections identify the different Iubrlcatlon lubrication modes. When reading the following sections, keep surface roughness in mind. Although metal surfaces may feel smooth to the touch, none are perfectly smooth at the microscopic level. Friction surfaces are riddled with peaks called asperities (see Figure 2-1), Friction is the result of the asperities of opposing friction surfaces coming in contact with each other. Additives can help reduce this friction (refer to the later section, “Adding Additives: How They Can Protect against Wear” for more information). When the oil film is squeezed to the point where the oil film thickness is equal to the average asperity height, it’s called boundary lubrication, When this mode occurs, severe wear happens as a result of asperities coming in contact with each other (refer to Figure 2-3). This mode is commonly encoun- tered during times of start-up and shut-down, when running speeds are slower than normal. Other common causes are overloading, shock loading, and insufficient lubrication. ln cases where boundary lubrication is the norm, such as slow- moving, heavily loaded equipment or reversing equipment, ASPEÍÍÚES lubricants must be fortified with extreme pressure additives to reduce friction and combat wear. gí/ fl _ Friction surface Figure 2 o metal surface is completely smooth. Figure 2-3: ln boundary lubrication a full-fluid lubricating film ' ' ' ' d d | b bb" rf . Fu” ¡‘(md fflm [ubncatwn Full fluid film lubrication means a sufficient oil film thickness to completely separate the opposing friction surfaces and ' f‘ ' ' asperities, in this perfect-world scenario, no metal-to-metal Mlxed ‘Im Iubrlcatlon contact occurs; therefore, little-to-no wear occurs. The reduc- some Components operate on a ¿ombtnatton ot ¡n11 thnd film tion of friction is the result of the base oil forming a physical and boundary lubrication known a5 mixed m, " [nbr¡¿-a¡¡on_ barrier to separate the friction surfaces, as in Figure 2-2, in ThE mode happens when the on film reduces ¿nd some aspet. applications with this constant mode of lubrication, anti-wear ¡nes come ¡nto contact wnh each other ¿S ¡n Figure 2_4_ At ¿md extïeme Pressflfe addlïlVes ¿tren t needed HOWEVBY, When this point, anti-wear and extreme pressure additives become 0311i Speedv Oïnlubïlciïnt PWPQYÜES ¿“e a le? ?? a danger OÏ active and reduce friction and wear. This mode of lubrication seVeïe Wei" 9x15“ due t” the absence Oi addltweï is common in moderate speed and load applications, where variances in speed and load are expected. m. Wfim“ Figure 2-2: In this mode, an oil film creates a barrier Figure 2-4: With mixed film lubrication, some asperities between two metallic surfaces. rub against each mhen
  9. 9. 12 Oil Analysis For Dummies, Insight Services Special Edition Hydrodynamic lubrication Hydrodynamic lubrication controls friction in journal bear- ings. Hydrodynamic lubrication is a system of lubrication in which the shape and relative motion of the sliding surfaces cause the formation of a fluid film with sufficient pressure to separate the surfaces. As a journal starts to turn in a bearing, the shaffs rotation pulls the oil into the load zone (refer to Figure 2-5a). The oil wedge lifts the journal from the bearing, allowing it to ride on top of the oil much in the same way that a log spins in water, as in Figure 2-5b. When the proper lubricant is used, the machine runs at normal load and speed, the friction surfaces are completely separated, and no wear occurs. Juurnal Bearing at rest Ü” Wedge A B Figure 2-5: The oil creates a barrierwhere the bearing can restwíthuutrubbín . The whole of the lubrication and friction reduction rests on the base oil. Due to the high speed application, you must take great care to properly maintain the lubricant to prevent a breakdown in the oil wedge. Should the lubricant fail, cata- strophic bearing damage would take place very rapidly. Hydrastatic lubrication During times ol start-up and shut-down when shaft speed is insufficient to fully form the oil wedge, fluid, in the form of hydrostalic lubrication, can be pumped into the bearing under pressure. This added pressure aids in lifting the journal off Chapter 2: Understanding Performance and Wear the bearing to avoid severe wear to the bearing (check out Figure 2-6). Hydrostatic lubrication is also common in vari- able speed equipment, or equipment that often experiences changes in load. When extra loading is applied to the bearing, pressure from the hydrostatic system compensates for the squeezed oil film. T Oil flow Figure 2-6: Hydrostatic lubrication preve nts severe wear. Elastohydrodynamíc (BHD) lubrication When opposing surfaces are nonconforming (a mismatch exists between opposing surfaces), such as in roller bearings, the contact area is much smaller. With the total load concen- trated on a much smaller area, pressures are obviously much higher. Pressures in the load zone of a roller bearing can com- monly exceed 200,000 psi. With this much pressure, the roller element actually deforms, much in the same way that a car tire deforms where it meets the road. When this much pressure is applied to the oil film, a dramatic rise in the oil’s viscosity occurs. At the peak of the load, the lubricant can achieve a near solid state. This tendency, called elastohydrodynamic (EHD) lubrication, maintains lubrication under these extreme circumstances. The oil film thickness varies based on a number of operating factors such as load, Velocity, and the oil’s original viscosity as in Figure 2-7. The average EHD film thickness falls below 1.25 microns, which brings two important considerations into light:
  10. 10. 16 Oil Analysis For Dummies, Insight Services Special Edition i/ Oil contamination: With such tight clearances in roller element bearings, oil cleanliness is crucial. Although large particles may not pose a serious threat, small abra- sive solids particles, such as silt and dust, accelerate wear and significantly reduce bearing life. Maintaining clean and healthy lubricants greatly enhances the life of roller element bearings. 1/ Oil selection: When the oil film is as thin as 1.25 microns, boundary lubrication is occurring (check out the ear- lier section on boundary lubrication in this chapter). Asperities are coming into contact with each other, causing wear. Lubricants should contain the appropriate additives to combat wear under these circumstances. _____ __ Hollerelement 0¡| fi|m Innerrace Elastíc defermation Rullerbearing Figure 2-7: The oil lubricates under extreme conditions. Taking a Look inside the Machine: What Causes Wear? In order to fully understand how proper lubrication affects machine life, you need to examine the mechanisms and scenar- ios that generate wear. Ask yourself these questions. In simple terms, how does equipment wear? What causes actual material loss at the friction surface? The following sections help answer these questions and explain the four wear mechanisms. Adhesion Metal surfaces are never perfectly smooth. Contact between asperities causes friction (as in Figure 2-8a). Although these asperities would be completely separated under full-fluid film lubrication during boundary and mixed lubrication, in most circumstances they tend to come in contact with each other, Chapter 2: Understanding Performance and Wear causing wear called adhesion. This contact leads to high tem- peratures producing a welding or bonding effect. This bond can be stronger than the metal itself, and the result is a particle that is sheared from the friction surface (refer to Figure 2-8b). Adhesion can take place under normal circumstances, such as break-in or normal rubbing. ln cases of overloading, or in the absence of the appropriate additives, adhesion can be very destructive and lead to premature failure and wearout as in Figure 2-8c, a. i; Q .1.. - / / Asperities Bond (weldíng) Wear particles A B C Figure 2-8: Contact between asperities causes friction, which can lead tu adhesions and ultimately result in causing wear particles to shearfrom the surface. The typical causes for adhesion include high loads, speeds, or temperatures; insulficient lubrication; lack of anti-wear addi- tives; and break-in wear. susceptible components for adhe- sion include piston rings and cylinders, rolling and slíding bearings, gears, and cutting tools. Ahrasian Abrasion, which is the most common industrial wear mecha- nism, can occur in all moving surfaces. Abrasion basically is the cutting and deformation of materials in a machine. Two types of abrasion can occur: ¡I Three-bodied: When oil becomes contaminated with abrasive particles such as dirt, these particles become lodged into the softer of two opposing wear surfaces.
  11. 11. 16 Oil Analysis For Dummies, Insight Services Special Edition The particles can then cut into the metal surface in a lathing effect, generating excessive wear and material loss. These particles then also lodge themselves into softer metals causing a snowball effect. Refer to Figure 2-9 for an example, i/ Two-bodled: When components aren’t properly aligned, the harder of two opposing wear surfaces can penetrate the softer metal surface. This results in a cutting away of the component and results in excessive, rapid wear, as in Figure 2-10. Abrasive particle Wear particle Figure 2-9: Particles can get stuck between two pieces of metal, causing wear. Wear particle Fi ure 2-10: Misali ned arts can also cause wearfati ue. Over time, metal wear surfaces can become brittle. Stressing or repeated concussion can lead to micro-cracks in the wear surface. These cracks progress until a spall (flake of a mate- rial) is formed like in Figure 2-11, This fatigue is very common in roller element bearing races and gears. Additional causes for fatigue include a water dint in the oil and particles with sharp edges causing wear. Chapter 2: Understanding Performance and Wear 1 7 Wear particle Micro-cracks Spelling Figure 2-11: Fatigue can cause micro-cracks to progress into more si nificantwear. Corrosion When oils degrade, the acid levels increase, making the oil corrosive. Carrosion is another common cause for wear in machinery. In corrosion, a chemical reaction causes the for- mation of an oxide layer on the metal surfaces. Surface motion then rubs the oxide layer, generatlng oxide particles into the oil. When these oxides are harder than the component materi- als and if loose particles are formed, a corrosive wear occurs (check out Figure 2-12). Components susceptible to corrosion include all bearings, cylinder walls, and the valve train. Üxide layer Figure 2-12: A corrosive layer can wear machinery. Examininq the Ins and Outs of Particles Particles play a significant role in the performance and wear of your machinery. These particles can be either large, such a piece of metal, or small, such as dirt or dust. No matter the size of the particles though, you need to know what causes particles and how they sometimes disappear. Additives in your oil can also help break down and eliminate them. (See the next section for more information on additives. ) The
  12. 12. 18 ar Oil Analysis For Dummies, Insight Services Special Edition following sections explain how particles are generated and lost and how the generation and loss of particles reaches a balance. Particles are generated Particles in the oil can be very destructive. They can also be accurate indicators of problems in a machine. The following are some sources of particles in a lubricating system: V Wear: As wear occurs, potentially abrasive particles are generated into the oil. V Corrosion: Corrosion generates oxides that travel in the oil. V External contamination: Dust, dirt, and other airborne contaminants can enter a system through breathers, open ports, and hatches. V Scale and rust in reservoirs: Large reservoirs and piping can rust and corrode, generating debris. V Lubricant degradation: As the base stock of the oil degrades, solid by-products are produced. Consider which of these problems your system(s) may be sus- ceptible to and examine ways that you can control them. Particles are natural/ g fast Just as particles are generated during routine operation, particles are also lost. Particle densities in oil don’t just keep rising over time and this is a good thing. Filtration is prob- ably the number one contributor to particle loss. Here are some examples of how particles are removed through natural occurrences: V Filtration: Particles are removed by in-line iiltration systems, V settling: Particles will settle out of the oil in the reservoir or sump. V Grinding: Particles will be “ground up" as they pass through friction points. Chapter 2: Understanding Performance and Wear V oxidation (chemical breakdown): Some particles will oxidize and break down naturally over time, V Dissolution: Some particles will dissolve in the oil, Particles reach equilibrium The balance between particle generation and loss results in what’s called the particle equilibrium, Monitoring and control- ling this equilibrium can have a significant impact on equip- ment reliability and longevity. Higher amounts of particles are prevalent when a new machine is broken in. ln midlife, par- ticle levels should even out and decrease. increases from this point may indicate machine health issues. Figure 2-13 shows an example of particle equilibrium. Particle population Break-in Normal operation Abnormai lima Figure 2-13: Sometimes particles reach a balance between generation and loss. Adding Additives: How They Can Protect against Wear You can include different additives in your lubrications to help improve your machine and lubricant performance and protect against wear. These additives include elements such as calcium, zinc, and phosphorus. Some of the most common additives in oil include: V Anti-wear (AW) V Extreme pressure (EP)
  13. 13. 20 Oil Analysis For Dummies, Insight Services Special Edition V Oxidation inhibitors V Rust inhibitors V Detergents V Corrosive inhibitors V Foam inhibitors V Demulsifiers The following sections take a closer look at these common additives and their properties and functions, Table 2-1 dis- plays levels of common additives that you may expect to see in various types of oils, These levels are listed in parts per million. Table 2-1 Typical Additive Packages üil Type Calcíum Zinc Fhosplrorus HDMÜldieseH 2300 i050 1180 EP gear 0 (l 220 AW hydra 4D 32D 450 Turbíne oil i) i] Ü Comoressor i) 0 Ü Table 2-2 shows some formulations for different types of oils, Table 2-2: How Different Oils Are Formulated Industrial Anrioxidant Foam Demulsifier Antí- EP üils & Rust Inhibitnr Wear Additive Inhihílar A ddítive Ci rc u | ati n g X X X oils H yd ra u | i c X X X X oils G e a r o i I s X X X X X Compressor X X X X oils Grease X X X Chapter 2: Understanding Performance and Wear 2 I Anti-wear (AW) Anti-wear additives provide protection against friction and wear under moderate boundary film conditions. They form a chemical film on the metal surface to form a protective coat- ing that allows moving parts to slide across each other with low friction and minimal loss of metal. The following materials are used as anti-wear additives: V Zinc dithiophosphate (ZDP) V Zinc dialkyldithiophosphate (ZDDP) V Tricresylphosphate (TCP) Extreme pressure (EP) Extreme pressure additives reduce friction, control wear, and prevent severe surface damage at high temperatures or under heavy loads, Under high loads, scoring and piiting of metal surfaces is a major problem. Frequently, welding of mating sur- faces occurs at very high local temperatures developed when opposing bodies are rubbed together under sufficient load. The excessive temperature initiates a chemical reaction between the metal surface and the EP additive to resist welding. The following materials are used as extreme pressure (EP) additives: V Chlorinated parafiins V Sulphurized fats V Esters V Zinc dialkyldithiophosphate (ZDDP) V Molybdenum disulfide Oxidation inhibitors Oxidation inhibitors slow down the rate of oxidation and pre- vent premature thickening of the lubricant. When oil is heated in the presence of air. oxidation occurs. The effects result in the formation of acid, sludge, and varnish and oil thickening.
  14. 14. 22 Oil Analysis For Dummies, Insight Services Special Edition Oxidation inhibitors can react with the peroxides to form inactive compounds or they can decompose these materials to form less reactive compounds. The most common oxidation inhibitors are: V Zinc dithiophosphate (ZDP) V Alkyl sulfides V Aromatic sulfides V Aromatic amines V Hindered phenols Rust inhibitors Rust inhibitors prevent water from reaching the metal sur- face. Rust is surface damage that results from the attack of water and oxygen on iron and its alloys. Rust inhibitors have a high polar attraction to the metal surface. Through chemical interaction, they form a protective layer on the metal surface and prevent rusting. The most common rust inhibitors are: V Alkaline compounds V Organic acids V Esters V Amino-acid derivatives Detergents Detergent additives, sometimes referred to as dispersants, attach dirt and solid contaminants to break them up and pre- vent sludge and varnishing, These additives then attach them- selves to the contaminants to hold them in suspension in the oil so that they can be filtered out. Phenolates, sulphonates, and phosphonates of alkaline and alkaline-earth elements, such as calcium (Ca), magnesium (Mg), sodium (Na) or Ba (barium), are used as detergents in lubricants. Chapter 2: Understanding Performance and Wear Corrosive inhibitors Corrosion inhibiting additives have an alkaline property to neutralize acids formed through oxidation, or from combus- tion in engine applications. Calcium-based additives are a commonly used corrosion inhibitor. Corrosive inhibitors are the same as rust inhibitors Foam inhihitors Foam inhibitors are a type of additive that causes foam to dis- sipate more rapidly, They promote the combination of small bubbles into large bubbles that can then burst more easily. Dimethyl silicone (dimethylsiloxane) is commonly used as an anti-foaming agent in lubricants, Demulsifiers Highly refined straight mineral oils have inherently good demulsibifity, which is a measure of a lubricating oil’s ability to separate from water. This characteristic is important in the maintenance of many circulating oil systems that must read- ily separate from water. Even after violently shaking an oil/ water mixture, the oil separates and rises rapidly to the top of the water, which is true also of other oils formulated for good demulsibility. Most demulsifiers are proprietary blends using trade names only, Recagnizing What Viscositg Is The single most important property of a lubricant is its vis- cosity. Viscosily is the measure of the oil‘s resistance to flow (shear stress) under certain conditions. To simplify, the oil‘s viscosity represents the measure for which the oil wants to stay put when pushed (sheared) by moving mechanical components. The viscosity of any fluid changes inversely with temperature. As temperature increases, viscosity decreases and as temper- ature decreases, viscosity increases. Understanding an oil‘s viscosity is important because in a given machine, the thin
  15. 15. 24 Oil Analysis For Dummies, Insight Services Special Edition film separating the moving surfaces can be maintained only if the operational viscosity range is correct. Viscosity is an important criterion in the selection of a fluid. At low temperature, excessive viscosity may result in poor mechanical efficiency, dífliculty in starting, and wear, As oil temperature increases, viscosity decreases, restilting in lower volumetric efficiency, overheating, and wear. Selection of the optimum fluid viscosity grade will provide the most efficient machine performance at standard operating temperatures, therefore minimizing lost time and energy and fuel costs for the operator. These sections explain the different ways viscosity is mea- sured so when you’re ready to select an oil based on viscos- ity, you know what you're looking for. ln general, a high-speed, low-load machine will require a lower viscosity lubricant, whereas a low-speed, high-load machine will require a higher viscosity lubricant. What to loa/ z for when sefecting aif viscosity An oil‘s viscosity affects its ability to perform all its functions. A lower viscosity oil that is efficient at removing heat and con- taminants can effectiveiy reduce the amount of energy used and accommodate higher running speeds. On the other hand, a higher viscosity oil can handle heavier loads and can maintain fluid film thickness at slower speeds. When you‘re selecting lubricant viscosity, keep the following considerations in mind: V Load: The lighter the load, the lighter the oil. The heavier the load, the heavier the oil. V Temperature: The lower the temperature, the thinner the oil. The higher the temperature, the thicker the oil. V Running speed: The faster the speed, the thinner the oil. The slower the speed, the thicker the oil. Viscosity index The viscosity index (VI) is an arbitrary numbering scale that indi- cates the changes in oil viscosity with changes in temperature, Chapter 2: Understanding Performance and Wear Knowing the viscosity index of an oil is crucial when selecting a lubricant for an application and is especially critical in extremely hot or cold climates, The viscosity index can be classified as follows: V Low VI: Below 35 V Medium VI: 35 to 80 V High VI: 80 to 110 V Very high VI: above 110 A high viscosity index indicates small oil viscosity changes with temperature. A low viscosity index indicates high viscos- ity changes with temperature. Therefore, a fluid that has a high viscosity index can be expected to undergo very little change in viscosity with temperature extremes and is consid- ered to have a stable viscosity. A fluid with a low viscosity index can be expected to undergo a significant change in viscosity as the temperature fluctuates, For a given temperature range, say —l8° to 370°C (0 — l00°F'), the viscosity of one oil may change considerably more than another. An oil with a VI of 95 to 100 would change less than one with a VI of 80, Failure to use an oil with the proper viscosity index when tem- perature extremes are expected may result in poor lubrica- tion and equipment failure. Typically, paraffinic oils are rated at 38°C (l00°F') and naphthenic oils are rated at —18°C (0°F'). Proper selection of petroleum stocks and additives can pro- duce oils with a very good Vl. Understanding Viscosity Grades There are a number of ways to designate viscosity grades of the lubricants used in manufacturing. There are SAE (Society of Automotive Engineers) grades for gear oils and crankcases (engines), AGMA (American Gear Manufacturers Association) grades for gear oils, SUS (Saybolt Universal Seconds), ISO Viscosity grades for industrial oils (reported in Centistokes cSt), and absolute viscosity. There are also two measures of temperature (Fahrenheit and Celsius) that can be applied to most of these. Confused yet?
  16. 16. 26 Oil Analysis For Dummies, Insight Services Special Edition the prominent viscosity systems isn’t listed on the lubricant's product label. To remedy the problem, the International Standards Organization Viscosity Grade, ISO VG tor short, was created as a universally accepted Viscosity designation. G b Table 2-3 pulls together some popular viscosity measurement methods into one table. You can use the table to see the cor- p, ‘ ¡ ' relating viscosity range in another measurement. Just choose p er n a o n a viscosity type and see its correlation within the other types of measures. The number of options can be confusing, particularly if one of 3 Use this table as an approximate reference; it assumes that all I" rms chapter oils have a viscosity index of 95. Checking out lubrication systems _ _ _ _ _ identifying when lubrication failure happens Table 2-3 Viscosity Classlflcatlons [80 ¿‘ST SAE AGMA SUS Knowing what alarms signily Grade 40°C 100M Gear Auto Lube 100°F 210‘F —. 4 Grade Grade No. v . . hen you lubricate your machinery, you want to make 1“ "J 2-5 5° 33 sure it gets to where it’s supposed to go and that your 15 15 31 79 37 machinery efficiently uses the lubrication. If it's not going 22 22 4 3 ¡o 1o. , 41 where it’s supposed to, you're wasting money and could poten- ' tially lose more money from damaged or shut-down machinery. 32 32 5-4 ‘Ü 150 44 That’s where this chapter comes into play, so you know the oil 45 45 s5 2g 1 233 4g systems and can then match the proper oil with it. 68 68 83 2D 2 355 54 If for some reason, your machinery and lubrication have a 100 100 11.0 30 3 500 54 problem, you need to be able to quickly identify it before the 15g 150 147 90 4g 4 770 75 issute]: ezcalatesdinto ahcatasïtlrlophliïc error lsuch a4 a pernlmla- nen y amage mac me. ls c ap er a so exp alns w en 220 22° 13's 90 5D 5 “a0 97 lubrication failure happens and what it looks like — including 320 320 24.0 90 6 1706 118 what types of alarms indicate a problem exists. 460 460 30.0 140 7 2438 147 68D 68D 38.0 140 8 3628 189 BA Grasrvínq the Different Lubrication Systems Proper lubrication is making sure the right amount of the right lubricant gets where it's supposed to go in the right amount of time. Lubrication systems are the way that you get the lubricant to the proper place at the proper time, A lubricating system
  17. 17. 28 Oil Analysis For Dummies, Insight Services Special Edition Chapter 3: Getting Lubrication to Its Proper Destination RW can be as simple as a sump and a drain plug, or can involve thousands of feet of piping and dozens of pumps. Although Keep these factors in mind when maintaining equipment using an oil level system: many types of lubricating systems are in use in the industry, most of them can be assigned to one of the following types. 0¡f fer/ ef systems/ splash system The simplest type of oil system is the oil level system. In an oil level system, the component to be lubricated is partially submerged in the lubricant sump as Figure 3-1 shows. A5 the component turns, it picks up the lubricant. Controlling the amount of lubricant that reaches the friction surface is very difficult; the use of splashing devices such as slinger rings can enhance lubrication. Because the oil basically stays static in the sump, this type of system provides very limited opportu- nities for removal of heat and contamination. Most oil level systems are unfiltered, and condensation is common due to the amount of air in the component and cycling between run- ning and not running. leen. l! Breathers: Because there is generally not an effective filter in oil level systems, steps should be taken to keep external contaminants out of the lubricant. Desiccant breathers are ideal. They use desiccating material to draw moisture from the inhaled or exhaled air, plus some contain a microglass pleated filter to remove particles down to l micron. They let only clean, dry air into the lubrication system to prevent contamination. l! Oil level: You need to check the oil level frequently, because a low oil level can directly impact the amount of lubricant being applied to the friction surfaces. l! 0ll selection: The proper oil selection is crucial in an oil level system. A thin oil runs off the component too rapidly causing oil slaruation (a severe deficiency of oil), while a thick oil doesn't penetrate the friction surfaces rapidly enough and wastes energy. l/ Oil condition: You want to regularly monitor the oil con- dition in an oil level system. If the oil becomes contami- nated or is no longer serviceable, you need to have an oil change performed. With no iiltration or settling tank, a contaminated lubricant can cause severe damage very quickly. Farced-feed systems Forced feed systems (as in Figure 3-2) deliver the lubricant directly to the friction surface. A circulating system typically supplies the lubricant and provides the following advantages over an oil level system: / : s, s». Fi ure 3-1: In this s stem, the com nnent is submer ed in the lubricant. Oil level systems are effective for smaller components running at low to moderate speeds. Larger components, especially those that run very slowly, should use oil fortified with a tackifier to ensure that the lubricant sticks to the friction sur- face. Some examples of components with oil level systems are small- to medium-sized gearboxes, small pedestal bearings, and small pumps and motors. Tackifiers are chemical com- pounds used in formulating adhesives to increase the sticki- ness of the surface of the adhesive. l/ The quantity of lubricant delivered to the component can be regulated to provide optimum performance. l/ Filtration can be added to the system to aid in keeping the oil clean. l/ Cooling is enhanced as the oil carries heat away from the component. l/ Heat exchangers can be used to maintain a consistent oil temperature, which ensures accurate viscosity and helps prevent condensation in the system.
  18. 18. 30 Oil Analysis For Dummies, Insight Services Special Edition l/ The reservoir serves as a settling tank to allow contami- nants to separate and heat to dissipate. m a . _ cool, clean un from reservoir —> Heat and contaminants carried awayfrvm component Figure 3-2: Forced feed system. With a circulating system, monitoring and maintaining the oil quality becomes increasingly important. Just one system can be responsible for lubricating numerous components, so con- taminated or unhealthy oil has a much larger impact on pro- duction. Conversely, a clean and healthy lubricant can extend the life of every component on the system. Additionally, most circulating systems have large capacities, making oil changes very expensive, Basic maintenance practices such as keeping filters clean and regularly draining water and sediment from low points in the system go a long way toward reaching maxi- mum component life. The most common types of automated systems are grease, circulating oil (refer to Figure 3-3), oil mist, air/ oil, and the high-pressure compressor systems. Floating oil pick-up I Y‘ Water sediment drains Z7 Fi ure3-3:At icalcirculatin s stem. Chapter 3: Getting Lubrication to Its Proper Destination 3 I Air/0¡f and 0¡f mist systems As a rule, automated lubrication systems have established their value to the industry. Although some areas of overlap do exist, one type of system generally can't be used in place of another. The exception to this rule is the air/ oil system com- monly used in place of a grease system. By combining oil with compressed air, very fine particles of oil can be delivered to a friction surface. This system provides an even distribution of lubrication directly to the point where it's needed. Some advantages of the air/ oil system include the following: l/ It ensures that lubrication is maintained with the minimal use of lubricant. l/ The oil delivered to the friction point is clean and cool with very low particulate contamination. ll The positive air pressure inside the component helps to keep moisture and contaminants out of the component, l/ These types of systems often create significant oil con- sumption savings. On the other hand, some disadvantages for this system you have to consider are: l/ Leaks in the system can create environmental concerns. l/ Workers can inhale the oil mist, and oil can settle on sur- rounding surfaces. ll Nozzles can become clogged, causing lubricant starvation. ll The compressed air source is critical to the lubrication system. l/ The Cooling effect of oil flow is greatly reduced using air- oil systems. In general, there are two types of pure oil-mist lubrication systems: open (one-way) systems and closed systems. The open system has a distribution header with its corresponding drainpipe, but it doesn't have a method for the recovery and return of the Condensed mist. l-lowever, closed systems have two headers, one as in the open system and a second for the return of the residual mist.
  19. 19. 32 Oil Analysis For Dummies, Insight Services Special Edition Although most commonly used to lubricate bearings, you can use these systems in gear applications as well. Various types of nozzles are used for various applications. Some examples are spray fittings, condensing fittings, and mist fittings. Grease lubrication systems Grease lubrication systems are automated systems generally comprised of a controller or timer, a pump and reservoir, metering valves and fittings, and supply and feed lines, From a central location and at specified times, they deliver a con- trolled amount of grease to multiple, specific locations on a machine while the machine is operating. Grease lubrication systems are designed principally to make the work environment safer for maintenance personnel by simplilying the process of accessing remote grease points, especially in confined spaces, when equipment is in opera- tion. However, the primary benefit of the continuous applica- tion of small amounts of grease is in improved equipment lite, due to the uniiorm supply ot grease. These automated systems allow greater control of the amount of lubricant being applied. However, many grease systems have long lines, precise metering valves, fittings, and numer- ous connections that can malfunction due to vibration, air entrainment, and other environmental impacts. So remember, carefully monitoring and maintaining the systems on a con- sistent basis is critical. You should periodically purge grease- lubricated components to remove contaminants and replace degraded lubricant as Figure 34 demonstrates. Grease lubrication systems do seem low maintenance because they're a tairly simple solution. The component is packed with grease, and the grease is replenished un a regular basis. Grease can also be applied manually using grease guns, but many technicians improperly lubricate components more often than not by overgreasing them. When a component is overgreased, the moving parts must plow through the excess grease resulting in high temperatures and excess load. The grease has to travel somewhere, often damaging seais by pushing through to the outside of the component. Chapter 3: Getting Lubrication to Its Proper Destination ¿Z Purge with ‘e fresh grease Purge with fresh grease Allow old grease to flow cut of the component Figure 3-4: As soon as fresh grease begins to appear, operate the nom nnentbefure re Iacin the drain lu . «W So how do you know when to grease and when not to grease? Keep these pointers in mind and grease under these circumstances: 1/ To decrease dripping and splattering of lubricant 1/ To decrease frequency of lubrication 1/ To seal out contaminants l/ To deal with intermittent operation 1/ To suspend solid additives 1/ To be prepared for when extreme operating conditions exist, such as o High temperature/ pressure - Shock loading 1/ To stay in compliance with manufacturing specs Recagnízínq Lubricant-Related Failure Lubrication-related failure accounts for more than 50 percent of all machine failures. This type of failure, also referred to as premature failure, is the least understood and/ or largely ignored type of failure. Lubricant-related equipment failures come in all shapes and sizes. The following sections examine
  20. 20. 34 Oil Analysis For Dummies, Insight Services Special Edition the common lubricant problems that often lead to lubrication- related failure, Eyeínq genera! lubricant proálems When determining machine and lubricant condition, you want to observe the oil's appearance. The appearance often indi- cates an abnormal condition and/ or suggests what tests may or may not be required. The following problems and symp- toms are examples of the kind of information that you may determine from a quick look at an oil sample. il Changes in oil color: An oil color changing from normal generally indicates that the oil has undergone a chemical change, been contaminated, or been replaced by a differ- ent lubricant blend. il Visible contaminants in the oil: Any contamination that is visible in the sample bottle indicates that a serious problem is in progress or the sample has been inadver- tently contaminated when taken. V Changes in oil odor: An abnormal odor is also an indica- tion that the sample is contaminated or has undergone a chemical change. Strong or burnt odors usually indicate the oil has been subjected to excessive temperatures. You should investigate any change in oil odor from the new smell. V Changes in oil consistency: Any change in the expected consistency of used oil may be an indication ol a lubri- cant problem or trouble in the machine. il incorrect oil: One of the most critical and overlooked problems in used-oil analysis is the mistaken use of an incorrect oil type or grade for a given machinery applica- tion. Although incorrect oil isn't an equipment or lubri- cant failure mode per se, it is sometimes the root cause of real lubricant problems. seeing how lubricants are contaminated Many equipment types use multiple pressurized fluid systems (fuel, coolant, hydraulic, and lubricant) in close proximity. Chapter 3: Getting Lubrication to Its Proper Destination As a result, a leak in the high pressure side of one system can transfer fluid into the other system and contaminate the oil, Oil contamination is the single most important cause of oil- related machinery damage. The most common oil contaminants can be broadly catego- rized as particulate or chemical and are usually associated with ingress from the environment or other machine systems. These contaminants promote degradatíon, consume addi- tives, impair lubricant properties, and cause component wear of machines, The following is a summary of the leading con- taminants that may be indentified during routine oil analysis: i! Water contamination: Water is easily the most common contaminant found in machinery lubrication systems, Water usually enters an oil system as a consequence of condensation, the introduction of a coolant leak or free water during equipment cleaning, or environmental exposure. i! Foreign material contamination: Foreign materials in oils (such as particles) very seldom affect the lubrication oils but greatly decrease the life of the equipment com- ponents, Foreign materials in the particle form are prob- ably the easiest to eliminate and remove, but doing so takes training and equipment, from the lubricants coming into the plant all the way through the lubricants in the equipment during operation. The foreign materials need to be removed from the lubricants and eliminated from entry into the equipment. AI Fuel dilution: This indicates the amount of raw, unburned fuel that ends up in the crankcase of an engine, The fuel contaminates the oil and lowers its viscosity and flash point, creating friction-related wear almost immediately by reducing film strength. Fuel dilution is the second most important lubricant failure mode in internal combustion engínes and is usu- ally the result of overfueling, broken or detective fuel injectors, leaking fuel/ oil heat exchangers, and so on, Fuel dilution reduces the oil’s viscosity and flash point temperatures and diminishes its load-carrying ability. A high fuel dilution over a short period of time or a mod- erate fuel dilution over an extended period of time can severely damage oil wetted components (bearings, gears,
  21. 21. 36 Oil Analysis For Dummies, Insight Services Special Edition pistons, and so on). ln addition, fuel dilution promotes other failure mechanisms, including: o increased wear of oil wetted parts t Lubricant breakdown and component seizure 0 increased oil oxidation, sludge, and deposits 0 An increase in the potential for fire or explosion due to volatile light ends Breaking clown: Lubrication alegradation Machines such as industrial gear boxes. steam turbines, and gas operate at lower nominal temperatures and are generally less stressful on a lubricant. However, these applications have much longer drain intervals and as a consequence, suffer from a longer-term oxidative degradation. This problem occurs when the lubricant is broken down and needs to be replaced. As with petroleum engine oils, the oxidation of industrial min- eral oils increases the oil's viscosity and acidity. Even though you can usually control the problem by periodically adding more oil, you still need to monitor the oil to assess the need and indicate whether remedial action is required and to what degree. Understanding machine failure The two most common types of machine failure are catastrophic and functional. When referring to a catastrophic failure, we are usu- ally talking about a sudden failure to a machine that causes it to cease operation. Catastrophic failures can cause damage not iust to the specific component in question but also collateral damage. The second category to consider is functional failure —the machine is still operat- ing, but can't function according to the required design Specifications and likely needs to be shut down to correctthe problem. Chapter 3: Getting Lubrication to Its Proper Destination 3 7 ¡(nou/ ing What Alarm Let/ els Mean for Machine Wear Although maintaining a healthy, clean lubricant can minimize machine wear, many wear modes can still arise in spite of these eflorts. Misalignment, imbalance, overloading, improper installation. fatigue — the list goes on, Abnormal wear, for whatever reason, happens more often than you want to think about, Therefore, having a strategy in place to monitor machine wear is essential, Oil analysis remains the best tool in your predictive mainte- nance toolbox for the early detection ol wear problems. Wear metal levels detected using spectroscopy begin to rise well before the machine exhibits symptoms in the form of vibra- tion, temperature, or noise (refer to Chapter 4 for the low- down on spectroscopy), As you see increasing levels, how do you determine an alarm level to alert you ol a potential prob- lem? Determining what alarms to set for wear metal levels isn’t easy, particularly in industrial applications where equip- ment categories, such as gearboxes, are so general. For example, you may wonder how much iron is too much in a gearbox, Now consider how many different sizes, types, loads, environments, and applications can be included in that ques- tion, Then add the many lubrication systems and lubricant types in use, This simple question becomes much more com- plicated, Does it seem realistic that a good answer to such a question could exist? Probably not, Yet in most cases, this type of question is exactly what you should be asking each time you take an oil sample. lf you expect your oil analysis programs to detect machine wear problems effectiveiy, you need to ask better questions. When you take a sample what you really want to know is what is normal, which means defining normal. Normal typically means something that is conlorming to a usual or typical pat- tern. That is a start, With that definition, how can you identify a pattern in a broad category such as a gearbox? The answer is really lairly simple — by evaluating as much data as you possibly can, The following sections outline the different ways to evaluate wear metals,
  22. 22. 38 Oil Analysis For Dummies, Insight Services Special Edition Giving a pass or fail grade: Fixed limits Fixed limits, sometimes referred to as alarms, are devices created to assist in interpreting oil analysis reports. Even ii they‘re not lormally defined, they’re still used as a type of mental “limit" review process in examining the numbers. Many programs have used fixed limits, which give a simple pass or fail criteria lor each wear metal. Table 3-1 shows what fixed limits might look like. The table represents very basic wear metal limits ior different types of machines. Sort oi a starting point il you're looking at a first time sample. Table 3-1 Grading Wear Metal with Fixed Limits Metal Hydraulic Geerimx Diesel Trans- Diflerenríul Engine mission Iron 75 300 150 300 1000 Chrumium 5 N/ A 25 10 N/ A Le ad 2D N/ A 50 5G N/ A Copper 75 250 50 400 25D Ti n l ll 250 25 20 250 Aluminum 25 250 30 50 250 Nickel 5 N/ A lO 20 N/ A This type of alarming technique doesn't account for dilíerent contributing factors. It you‘re testing gearboxes, many sizes and shapes exist. Some gearboxes are lightly loaded and con- stant speed, which lend to a low wear rate. Such a gearbox may be in serious trouble ii the iron level were to reach 200 ppm (parts per million). On the other side oi the spectrum, you may have a low speed, reversing, heavily loaded gearbox that hasn’t had less than 500 ppm ot iron in its oil since it was tested at the assembly plant. The lubrication method can have a large impact on wear metal levels as well. Many gearboxes are splash-lubricated with a small oil level system, and wear metals build in the Chapter 3: Getting Lubrication to Its Proper Destination lubricant over time. This situation reveals a steadily increas- ing wear metal level and may cause a false positive reading when the level broaches the iixed alarm. Other gearboxes may be lubricated by a filtered circulating system, where wear particles are removed by iiltration as rapidly as they’re gener- ated. In this case, the wear metal trend would be tlat, and a significant change could occur without surpassing the fixed alarm. Such an exception would likely be missed by a fixed limit system. Trend analysis Another way to evaluate wear and look for potential alarms is the trend analysis method. Trend analysis allows the devel» opment of a pattern oí behavior for a particular unit. Il the sampling technique and interval are consistent, regular moni- toring oi the wear metal levels can eltectively monitor lor changes in the wear rate. This helps to account tor many of the variables within the equipment group. An uncharacteristic increase in iron, tor example, would indicate a change in the wear rate. Many techniques can be applied to evaluating trend data, such as averages, standard deviations, and linear regression. All are intended to identity a condition that isn't normal in relation to the machines past behavior. What this method fails to do, though, is identify what is normal lor that machine type. Is it normal for a gearbox like this to generate this level of iron? Family analysis Another way to look tor potential alarms is with family analy- sis. The family analysis method allows you to answer the question that the trend analysis can’t: What is normal for that machine type? This technique compares the wear metal levels of groups ol similar or identical equipment to identify what is a usual or typical pattern.
  23. 23. 40 Oil Analysis For Dummies, Insight Services Special Edition 97% Equipment is grouped together by family. A family may con- sist of identical equipment located in many plants, such as the GE Frame 7 turbines in many power plants across the country. You may also group equipment together based on load, size, lubrication type, and operating parameters, such as a group of agitators at a chemical plant. The wear metal data is then evaluated as a whole. The data for each machine is then com- pared to the family to evaluate its wear rate. For example, say that a family of 50 motor bearings is at a steel mill. The average tin reading is 7 ppm with 90 percent of the bearings reading less than 10 ppm. You could safely assume that it’s “normal” for these bearings to have less than 10 ppm of tin in their oil. If one of the bearings were found to have 35 ppm of tin, you could safely say that its wear rate is abnormal. An effort could then be initiated to determine the cause of the higher wear rate and correct the problem. The problem can be detected, identified, and resolved before the damage occurs, saving a premature bearing failure and replacement costs. Family analysis techniques can have a significant impact on both large and small companies’ programs. A large company can use such a program to monitor large fleets of similar equip- ment among their plants, as well as to benchmark performance of individual plants. Companies with less equipment can com- pare their wear rates to equipment in many other plants and take advantage of the lab‘s vast database of equipment data. Blemliny the techniques Realistically, the ideal analysis program blends the three alarming techniques that we discuss in the preceding sec- tions. However you can see how cumbersome applying the data evaluation process to every wear metal lor every machine tested in a program could be. With computers, you can automate this process so that each parameter is evalu- ated using numerous techniques, and the best possible analy- sis is obtained. Computers are now capable of using statistical calculations, database mining, and a rule-based knowledge hierarchy to compare the test data to fixed limits, trend analysis, and Chapter 3: Getting Lubrication to Its Proper Destination 4 I family analysis, and select the most appropriate evaluation for each application. Figure 3-5 shows an illustration of how com- puters can blend these three methods into one. lt is possible that for one specific sample, the limit schemes can vary depending on information available. For example, there may be a customer limit on water content, family limit (machine) for iron, family limit (fluid) for R oxidation, individ- ual machine limit for copper, and empirical limit on particle counts. In other words, different parameters may be alarmed with different techniques. Are customer Yes . . . . . . Customer s ecfc specific limits e Hmíts used " available? N0 Are family . . . . Sample family Y slatmlmal "m5 ¿»es statistical limits available and used valid? N0 Are individual statistical machine limits available? No Equipment/ fluid YES Individual specific limits statistical machine used limits used Figure 3-5: An alarming selection decision tree.
  24. 24. 46 Oil Analysis For Dummies, Insight Services Special Edition Chapter4 Ensuriny People Are Trained to Correctly Take Samples I I I | 0 | | 1 ¡ G When taking samples for used oil analysis, the primary objec- tives are data validity and data repeatability. To accomplish ' these obiectives, you want to have trained people in-house H t e a who know what they‘re doing. Your goal in training is to obtain a sample in a manner that is easily repeatable and that effectiveiy represents the actual condition of the machine. Good sampling requires the following two important aspects I" TMS Chapter to have repeatable (and reliable) data that actually represents the machine s condition: Understanding the importance of training Reading oil analysis reports i! Consistency: The samples need to come from the same location via the same pathway and with a consistent pro- cedure every time. Having the best sample point in the world will yield unreliable data if samples are taken in an inconsistent manner. . 4 . 4 _ . . , , Handling: The integrity of the sample must be protected hen undergoing any oil analysis, knowing what you re t, . . Wgelting into is important. Your company and staff from me amblem envlroïfmen" a reáult’ the Way lb? need to be prepared before, during, and alter the testing to samplfis are léasdléd ltshvnéll’ Haïlng Sunalïtbïclg? “ f“ m ensure it’s accurate and reliable. Many tests are available with a mac me ye avmg e 01 ana ys” res” s m ¡Ca e a“ any oil analysis provider, so being knowledgeable about them Éïnormal Condltio" ¡s 995mm due lo poor sample ha” is important. ing or extraction practices. Grasping the wide array of basic oil analysis available The following sections outline important aspects of training This Chapter explaíns the importance of your team being your staff on taking samples to ensure they‘re accurate. trained and ready so they know how to correctly take samples and make the testing worthwhile. After the testing, your team also needs to know how to read and use the reports. Finally, this chapter walks you through the basic repertoire of tests and where that are typically available. Chapter 5 discusses some more f ‘ advanced testing you may consider. o taklnq samples Train your staff so they know when and where to sample in A“ tesis diswssed ¡”e Sublect 1° ‘he need f0’ a representa‘ order to get reliable test results. You want to sample at these tive and uncontaminated sample. as well as calibrated test ¡“(msnm instruments. In short, always double check with another sample before taking any invasive maintenance action. Never y While the eqmpment ¡S at ¡un operanng ¡emperamre rely on just one piece of data when making a maintenance decision. i/ During operation, if possible i/ Directly after shutdown
  25. 25. Chapter ll: Oil Testing 101: Getting into the Lab Meanwhile, making sure everyone knows where to sample is equally important so the samples are reliable. When sampling, keep these pointers in mind about where to sample: i/ The test should be a good representation of oil in the system. ¡I The location and method should be consistent. l/ Don’t test on a dead zone. Fluids in dead-zones (gauge- line extensions, regenerative loops, standpipe, and so on) are stagnant and typically possess properties difier- ent from working fluids. l/ Test should be safely and readily accessible when the equipment is running. ¡I Make sure you're getting a clean sample. identifying the different sampling methods Getting your staff trained also includes ensuring they know how to actually take the samples and understanding which method is the best for the most reliable data, The following list identifies three ways to take samples: AI Pressurized valves: Install valves upstream of any filter in order to capture wear particles generated by the machine. Make sure the valve is clean and adequately flushed. ¡I Nonpressurized valves: Use a vacuum pump with appro- priate tubing. Make sure to use new tubing for each sample in order to avoid cross contamination. Cut the tubing to the same length each time you sample. Try to avoid scraping the tubing along the sides or bottom of the tank or reservoir. ¡I Ball valves: Make sure you drain plenty of oil before you collect your sample. This is the least desired method of sample acquisition because the sludge. particles, and water that settle to the bottom of a tank or resewoir pro- vide poor results. 46 Oil Analysis For Dummies, Insight Services Special Edition ¡(nou/ ing How to Correctly Read your Oil Analysis Report Understanding your oil analysis reports allows you to get the most out ol your oil analysis program. Having detailed knowl- edge of the analysis report (see Figure 4-1) can help you pin- point problem areas. As you gain experience in interpreting the reports, you’ll become an expert in the corrective actions needed on your equipment. Many times, catching lubricant issues can save time and money in equipment repairs and downtime. TESTOIL SÉ ¿gamma-m rNDi/ srmat ANALYSIS u 2227.. h. .. mi" 1., “ 3.7L? __. .. m. h. .. mu». .. . ... v.. . mas. ..“ u. .. un h-vIwII-enuul Figure 4-1: An example oíl analysis report.
  26. 26. o? Chapter 4: Oil Testing 101: Getting into the Lab 6 7 When all else fails, if you’re not sure where to begin decipher- ing the results, read the instructions. The oil analysis reports are the instructions for smooth running equipment. Oil analy- sis reports begin with problem summaries and red-letter criti- cal alerts to help you follow along. You can quickly glance to the top right-hand box for lubricant and machine condition on oil analysis reports. Then you can grab what you can from the graphs of individual elemental tests, The oil analysis report, however, has much more to say than a quick scan of the condition of machine and lubricant status. Reading an oil analysis report can be daunting and dull unless you know what you’re reading, You must analyze the oil anal- ysis report, know your equipment, and correctly interpret the results. These sections oiier some checkpoints when you're reading an oil analysis report. Focus on the basic details When you open your reports, make sure they're just that, your reports. Read the name and equipment details to ensure that the report is yours. Mistakes can be made; be certain the oil analysis report includes your name, the company name, the unit ID. the manufacturer, the model. and the unit type or component. Look for the lubricant manufacturer and type and viscosity grade of the oil in the unit, and note the time the unit was serviced and whether the oil was changed or makeup oil added. Examine the analysis summary and review the data Look for a quick summary of your oi| ’s condition with a cur- sory glance at your oil analysis report. You should be able to identify the problem area in your unit, gauge the criticality of the problem, and obtain a suggested course of action from the summary information provided in your oil analysis report. Take a closer look at your oil analysis report. Understand that the lab analyst is looking at hundreds of samples every day and may misinterpret some details of your unit and its particulars. 48 Oil Analysis For Dummies, Insight Services Special Edition ar Analyzing the oil analysis report involves understanding the concentration oi expected and unexpected elements in your oil. You can read the viscosity level, the water content, and the acid number (AN) in your oil analysis report. (Refer to later sec- tions in this chapter ior information ahout these tests. ) Understand the elemental spectroscopy A wealth of information is available on your oil analysis report about wear behavior, contaminants entering the system, and the service needed. As you read your oil analysis report, ask yourself what all the data means. Ask yourself other questions like: Where is contaminant debris coming from in this unit‘! What am I looking for that will help me see what is happening inside my machine? Am I looking at elemental levels that are from the additives, particles being picked up as the oil circulates, or from external contaminant ingression? These elements — iron, chromium. aluminum, copper, lead, tin, nickel, antimony, silver, titanium, and manganese — com- monly indicate component wear. On your oil analysis report, some elements are singled out such as copper or iron and given special attention. The remaining information in this chapter explains the basic tests that appear on your oil analysis test report. These tests focus on detecting the particles suspended in your oil and verifying that your machinery is running efficiently. ¿cuan? Elements found in your oil sample are measured in parts per million (ppm), a very small amount. A single ppm is equiva- lent to 0.0001 percent. To put that in perspective, it takes 10,000 ppm to equate to 1.0 percent. Concentrations seen in oil analysis reports will be from one to several thousand ppm.
  27. 27. Chapter ll: Oil Testing 101: Getting into the Lab 6 9 Measuring Metals: Elemental spectroscopy Elemental spectroscopy determines the concentration of wear metals, contaminant metals, and additive metals in a lubricant. With this test, an energy source excites atoms in a sample, causing them to release energy in the form of light. A spectrum is created with different wavelengths for each ele- ment. The instrument then quantifies the amount of energy emitted and determines the concentration in parts per million (ppm) of 20 to 30 elements present in the sample, Two types of elemental spectrometers are commonly used ln oll analysis: ¡I Arc emlssion spectrometers: They apply energy in the form of an electric arc to the sample, As the atoms are excited, each element emits light at a characteristic wavelength. The íntensity of light at each wavelength is measured and quantified. ¡I Inductively coupled plasma (ICP) spectrometers: They operate on a similar principle, except that the energy is applied to the sample by an argon flame rather than an electric arc. On the downside, spectroscopy can’t measure particles larger than roughly 7 microns, which leaves this test blind to larger solid particles. These sections provide a bit more information about spec- troscopy, As with any type of testing, spectroscopy is subject to inheren! variante (natural inconsistency). Setting a trend for detection To take full advantage of monitoring wear metals, a trend should be established to provide an operational baseline of data. A trend can be created by collecting information and attempting to spot a pattern. Analyzing the trend can help you effectiveiy monitor changes and ensure detection of abnormal wear rates as they develop, 50 Oil Analysis For Dummies, Insight Services Special Edition Typical levels of wear metal elements can vary greatly depending on the type of equipment being sampled. For exam- ple, a gearbox normally has much higher levels of iron than a hydraulic system, Levels of wear metals can vary in different units of the same type depending on oil hours, operating con- ditions, loading levels, or other conditions. For this reason, establishing firm limits for any piece of equipment based solely on the equipment type is impossible, Keeping an eye on additives Monitoring the additive levels provides information to ensure that the proper lubricant is being used for the application and for topping off. Generally, four types of lubricants are used in most industrial applications, and each has different additive levels. Note that an oil's level of additives measured by spec- troscopy isn't necessarily an indication of the oil's quality, because the pressure of the element doesn't indicate the func- tionality of the additive. i/ Engine oils: They typically contain antiwear additives composed of zinc and phosphorus. Expect to see these elements present in about 1,000 ppm (plus or minus 200 ppm). A detergent package should also be present, com- posed of some configuration of barium, magnesium, and calcium. These levels vary depending on the oil, but are usually above 1,000 ppm. i/ Extreme pressure (EP) oils: EP oils are typically for gear applications. You commonly see significant amounts of phosphorus. i/ Anti-wear (AW) oils: AW oils include many bearing oils, some gear oils, and hydraulic fluids. These oils contain both zinc and phosphorus from 200 to 600 ppm, They may also have low levels of detergent (magnesium or cal- cium) present. il Rust and oxidation inhibiting (R&0) oils: R8r0 oils are the easiest to identify. They include turbine oils, compres sor oils, and some bearing and hydraulic oils. These oils have no additives that spectroscopy can measure, so they should have extremely low numbers for all additive metals. Seeing low levels (less than 20 ppm) of some additives metals where they aren't expected is uncommon. These amounts are
  28. 28. Chapter ll: 0ilTesting 101: Getting into the Lab usually the result of residual contamination in the equipment or storage tanks, Some oils don't fit into these descriptions. Many oils are for- mulated for specific applications, and alternative additives must be used; for example, oils formulated for some station- ary and EMD engines, ln many cases, operating conditions or emission concerns call for a less traditional additive package. Cheo/ ring Resistance: Viscosity This test measures a lubricants viscosity (resistance to flow at a specific temperature), Check out Chapter 2 for more specif- ics about viscosity. An oil's viscosity is considered its most important property. This test can quickly detect the addition of a wrong oil. ln fact, it's the best standard for measuring oil serviceability. The most common method for measuring an oil's viscosity is ASTM D-445 using a viscometer. A small sample of the oil is drawn into a calibrated capillary tube in a constant tempera- ture bath. The oil is warmed to a desired temperature of 40°C or 100°C and allowed to flow via gravity through the tube. The viscometer measures the time the oil takes to flow through the calibrated region. The viscosity is the product of the flow time and tube calibration factor. The results are reported as the oil's kinematic viscosity in centistokes (cSt), Industrial oils are identified by their ISO viscosity grade O/ G). The ISO VG refers to the oil's kinematic viscosity at 40°C. To be categorized at a certain ISO grade, an oil’s (either new or used) viscosity must fall within plus or minus 10 percent of the grade. So for an oil to be classified as ISO 100, the viscos- ity must fall within 90 to 110 cSt, If an oil's viscosity is within plus or minus 10 percent of its ISO grade, it's considered normal. If the oil's viscosity is greater than plus or minus 10 percent and less than plus or minus 20 percent, then it's considered marginal. Viscosity greater than plus or minus 20 percent from grade is critical, An increase in viscosity may indicate: V increasing suspended solid material such as wear par- ticles, contamination, or soot 52 Oil Analysis For Dummies, Insight Services Special Edition V Additions of a higher viscosity oil V Lubricant oxidation V Water contamination A decrease in viscosity may indicate: V Contamination from fuels or process fluid V Additions of a lower viscosity oil V Additive shear lf a lubricant doesn’t have the proper viscosity, it can't perform its functions properly, lf the viscosity isn’t correct for the load, the oil film can't be established at the friction point, Heat and contamination aren't carried away at the proper rates, and the oil can't adequately protect the component. A lubricant with the improper viscosity can lead to overheating, accelerated wear, and, ultimately, the failure of the component. Screening for Moisture: Crac/ ele Test One of the easiest ways to measure the presence of free and emulsified water in oil is with the hot-plate crackle test. An emul- sion is the stable state of physical coexistence of chemically insoluble substances, like oil and water. Additives and impuri- ties that lower the oil's surface tension can serve as agents to strengthen the emulsion, Water is in a free state when undis- solved globules of water are physically suspended in the oil. For years, oil analysis laboratories have screened samples with the crackle test, performing more detailed analysis, such as the mrl Fischer test (see the next section for more infor- mation), only when the crackle test is positive. Under care- fully controlled lab conditions, the crackle test is sensitive to around 500 ppm (0.05 percent) of water-in-oil depending on the type of oil. ln the crackle test, a drop of oil is placed on a hotplate that has been heated to approximately 400°F. The sample then
  29. 29. ar Chapter ll: Oil Testing 101: Getting into the Lab bubbles, spits, crackles, or pops when moisture is present. If the crackle test is negative, it simply means that the level of water present in the sample is below the detection limit; it doesn’t necessarily mean the sample is void of water. Sometimes the crackle test may not be appropriate and you would need a Karl Fischer test done on all samples from that machine. The crackle is not a scientific test but an estimate that is affected by oil type. Here are some questions to think about to help you decide: V What is the detection limit for the test? V Does the detection limit change depending on the lubri- cant type? V Do you know what your limits for water should be? V How important is it to know any water contamination? V Are detection limits above my condemnation limits? The following sections explain the side effects of water in your lubrication and describe a sample test that shows you the effectiveness of the crackle test. Not a friendly relationship: Water and oil Moisture in hydraulic fluids and lubricating oils has a degrading effect on both the lubricant and the machine. Although some additives cling to the water and are removed when the water separates from the oil (known as water washíng), others are destroyed by water-induced chemical reactions (oxidation and hydrolysis). Water promotes oxidation of the oil's base stock, increasing the risk of sludge and varnish formation. Water also causes rust and corrosion of machine surfaces and reduces critical, load-bearing film strength. Water represents a real risk to equipment and should be aggressively controlled. Water coexists with oil in a dissolved, emulsified, or free state. Free and emulsified water pose the greatest risk to the machine and the lubricant, and they should be carefully moni- tored and controlled. 56 Oil Analysis For Dummies, Insight Services Special Edition Looking at results from an example test ln an effort to communicate the limitations of the crackle test in detecting water contamination, Insight Services embarked on a lab study to uncover crackle detection limits. A total of 493 samples comprised of a variety of lubricant types were run on a 400°F hot plate. The samples were assessed for a positive or negative crackle. These same samples were then analyzed for water contamination using a Karl Fischer titra- tion (ASTM D6304-C). The water results were recorded in parts per million (ppm). Table 4-1 summarizes the results of the study, The table lists oil type, the number of samples in the study, the detection limit range, the lowest negative crackle value, and the highest positive crackle value, Tahle 4-1 Checking Out the Limitations of the crackle Test Oil Type Samples Detection Lowest Highesr Tester! Limit (ppm) Positive Negative (rpm) Ipnm) Turbine 111 110-BIO 110 S10 Mineral 62 240-1190 240 1190 gear Synth etic 8B 110-460 10D 460 gear AW 8B 320-750 32D 750 hydraulic Polyol 37 34lFlS30 340 1830 ester Phosphate 37 45lkl 140 450 1140 ester Engine 40 320-580 320 580 Wind 35 780-1070 780 1070 turbine (Optigearl Combined 493 1013-1830 10D 1830
  30. 30. Chapter 4: Oil Testing 101: Getting into the Lab The lowest positive values represent those samples that exhibited a positive crackle and the associated Karl Fischer result while the highest negative values represent those samples that clearly had water present according to the Karl Fischer results, yet didn’t crackle. Clearly, the study demon- strates that quite a bit of variance exists in the water detec- tion limit of the crackle test. You really need to know your lubricant type before making assumptions on what the crackle can detect. ln some cases, your water limits may fall below crackle detection and running the Karl Fischer test on every sample may be worth the cost. Just make sure you under- stand the detection limits for the crackle test and know your lubricant’s tolerance for water. Quantifyinq the Amount of Water: Kar! Fischer Water Test If a crackle test (see the preceding section) is positive, further testing is needed in the form of the Karl Fischer Water Test. The Karl Fischer coulometric moisture test is a series of chemi- cal reactions discovered in 1935 by the German chemist Karl Fischer. This method analyzes water in the microgram or part- per-million range. This test is very accurate, to .001 percent. Water determination by Karl Fischer is defined in ASTM D 6304. For this test, a sample of oil is introduced into a titration vessel in known mass or volume. Any water present in the sample will react with iodine in the titration vessel. The amount of iodine required to react with the water and the known mass or volume of the sample are used to calculate the amount of water present in the sample. Results can be clearly expressed in percent or parts per million. An electric current passes through a generator contain- ing a Karl Fischer solution. Iodine is produced at the anode that consumes the water in the introduced sample. When an excess of iodine is detected, the analysis is complete. In choosing this method, make sure that test specimens are compatible with the chosen reagent and that no side reac- tions occur. This method is typically used to analyze hydro- carbons, alcohols, and ethers. Note: Analysis ot ketones must employ a Karl Fischer solution that is specifically formulated for ketone analysis. 56 Oil Analysis For Dummies, Insight Services Special Edition Low levels of water (less than 2 percent) are typically the result ot condensation. Higher levels can indicate a source ol water ingress. Water can enter a system through seals, breath- ers, hatches, and lill caps. Internal leaks from heat exchangers and water jackets are other potential sources. ¿»un When free water is present in oil, it poses a serious threat to the equipment. Water is a very poor lubricant and promotes rust and corrosion to the components. Dissolved water in an oil promotes oil oxidation and reduces the load handling ability oi the oil. Water contamination can also cause the oil's additive package to precipitate, Water in any form causes accelerated wear, increased friction, and high operating temperatures. li left unchecked, water can lead to premature component failure. ln most systems, water should not exceed 500 ppm. Looking at Chemical Composition: FT JR Every compound has a unique infrared signature. A Fourier Trans/ crm infrared (FF-IR) Spechometer monitors key signa- ture points of a specific lubricant in the spectrum. These sig- natures are usually common contaminants and degradation byproducts unique for a particular lubricant. Molecular analysis of lubricants and hydraulic fluids by l-T-IR spectroscopy produces direct information on molecular species of interest, including additives, fluid breakdown products, and external contamination. lt compares infrared spectra of used oil to a baseline spectrum. The differences in IR spectra are quanti- fied. Levels of the following oil degradation are reported: ¡I Oxidation: At elevated temperatures, oil exposed to oxygen from the air oxidizes to form a variety of com- pounds. The majority of these are carbonyl-containing compounds, such as carboxylic acid. l/ Nitration: This level shows the reaction of oil compo- nents with nitrogen oxides. ¡I Soot: This measurement is the level ol partially burned fuel in oil; it’s relevant for diesel engines. 1/ Glycol: This measures coolant leak.
  31. 31. Chapter 4: Oil Testing 101: Getting into the Lab Gauging Acialitg: Acid Number N’ Acid number (AN) is an indicator of oil serviceability. It is useful in monitoring acid buildup in oils due to depletion of antioxidants. Oil oxidation causes acidic byproducts to form. High acid levels can indicate excessive oil oxidation or deple- tion of the oil additives and can lead to corrosion of the inter- nal components. By monitoring the acid level, the oil can be changed before any damage occurs. An oil analyst is looking for a sudden increase. When your oil is flagged for high acid levels, it indicates accelerated oil oxidation, and you should change the oil a5 soon as possible. If any of the remaining highly acidic oil is left, it will quickly deplete the antioxidants in the new oil. AN is measured by titration using ASTM D-664 or D-974. Both methods involve diluting the oil sample and adding incremen- tal amounts of an alkaline solution until a neutral endpoint is achieved. The AN of a new oil will vary based on the base oil additive package. An R&O oil will usually have a very low AN, around 0.03. An AW or EP oil will have a slightly higher value, typi- cally around 0.5. Engine oils commonly have a higher AN, in the neighborhood of 1.5. Testing the Reserve Alhalinitg: Base Number Base number (BN) testing is very similar to AN testing, except that the properties are reversed, The sample is titrated with an acidic solution to measure the oil's alkaline reserve. ASTM test methods D-2896 or D-4739 are most commonly used to measure BN. Measuring the BN can help ensure that the oil is able to protect the component from corrosion due to acid, Many oils (especially motor oils) are fortified with alkaline additives to neutralize acids that are formed as a result of oil oxidation. ln diesel engine applications, acid is formed in the combustion chamber when moisture combines with sulfur under pressure. 58 Oil Analysis For Dummies, Insight Services Special Edition The BN of an oil is highest when the oil is new and decreases with use. Once again, condemning limits (limit where the oil is condemned for use and should be replaced) are based on the application. As a rule, the BN should not drop below 25 percent of its original value, BN values for new engine oils run from 4 to 30 depending on the application, Gauging ¡’article Count The particle count test measures the size and quantity of par- ticles in the oil sample with a result given in particles per milliliter. Particulate contamination has negative effects on all types of equipment. Particle counting is a way to monitor the level of solid contamination in an oil. Two types of automatic particle counters test oil cleanliness: l/ Light blockage: The light blockage method involves pass- ing this sample through a small orifice that has a laser light source on one side and an optical sensor on the other side. Particles interrupting the light beam are counted; the degree of light blockage determines their size. This method is generally considered more accurate; however, it involves careful sample and instrument preparation. Light blockage particle counting isn’t effective when an oil is contaminated with water, or when air is entrained in the oil. ln these circumstances, water or air bubbles will be counted as particles causing erroneous results. I/ Pore blockage: The pore blockage method, also referred to as flow decay, passes the sample through a mesh filter. As a filter clogs, the flow of the sample is digitally recorded, The amount of flow decay is calculated, and the particle count can then be extrapolated. Water droplets and entrained air don’t interfere and restrict the fluid flow. Results are reported as particles per milliliter in six size ranges: greater than 4, greater than 6, greater than 14, greater than 25, greater than 50, and greater than 100. ISO cleanliness codes are then assigned for particles in 4, 6, and 14 micron ranges. The result is reported by three numbers with a slash between them, the first number referring to particles in the