Lubrication Fundamentals 2011 Part 4 pps

soluble polyglycols are also used in the preparation of water-diluted lubricants for rubberbearings and joints.Water-insoluble polyglycols are used as heat transfer fluids and as the bas

Figure 5.8 Glycols Ethylene glycol is the simplest glycol; when polymerized, the oxygen bond

is formed and it becomes a polyglycol ether

for the bulk of the materials used in lubricants Small quantities of simple glycols, such

as ethylene and polyethylene glycol, are also used as hydraulic brake fluids Typicalstructures for the two types are shown in Figure 5.8

Polyglycols are polymers made from ethylene oxide (EO), propylene oxide (PO),

or their derivatives The primary raw materials are ethylene or propylene, oxidized to formcyclic ethers (alkylene oxides) Combining ethers derived from ethylene oxide (EO) topropylene oxide (PO) has a profound effect on the solubility of the product in other fluids:

EO:PO ⴔ 4⬊1 Water-soluble, not soluble in hydrocarbons EO:PO ⴔ 1⬊1 Soluble in cold water, soluble in alcohol and glycol ethers, not

soluble in hydrocarbons

EO:PO ⴔ 0⬊1 Not soluble in water, conditionally soluble in hydrocarbons

These comparisons help explain the differences between the various types of, anduses for, polyglycol: automotive antifreeze, brake fluid, water-based hydraulic fluids, hy-drocarbon gas compressors, and high temperature bearing lubricants In addition to ethyl-ene and propylene oxides, butylene oxide is used to provide some polyglycols with specificproperties and is oil soluble Polyglycols made with butylene oxide are more expensiveand do not exhibit traction coefficients equal to combinations of EO and PO

One of the major advantages of polyglycols is that they decompose completely tovolatile compounds under high temperature oxidizing conditions This results in low sludgebuildup under moderate to high operating temperatures, or complete decomposition with-out leaving deposits in certain extremely hot applications Polyglycols have good viscos-ity–temperature characteristics, although at low temperatures they tend to become some-what more viscous than some of the other synthesized bases Pour points are relativelylow High temperature stability ranges from fair to good and may be improved withadditives Thermal conductivity is high Not generally compatible with mineral oils oradditives developed for use in mineral oils, polyglycols may have considerable effect onpaints and finishes They have low solubility for hydrocarbon gases and some refrigerants.Seal swelling is low, but with the water-soluble types some care must be exercised in sealselection to be sure that the seals are compatible with water Even if the glycol fluid doesnot initially contain any water, it has a tendency to absorb moisture from the atmosphere.The applications for the polyglycols are divided into those for the water-solubletypes and those for the water-insoluble types

The largest volume application of water-soluble polyglycols is in hydraulic brakefluids Other major applications are in metalworking lubricants, where they can be removed

by water flushing or being burned off, and in fire-resistant hydraulic fluids In the latterapplication, the polyglycol is mixed with water, which provides the fire resistance Water-

soluble polyglycols are also used in the preparation of water-diluted lubricants for rubberbearings and joints.

Water-insoluble polyglycols are used as heat transfer fluids and as the base fluid inindustrial hydraulic fluids of certain types, as well as high temperature gear and bearingoils They are also finding application as lubricants for screw-type refrigeration compres-sors operating on R12 and hydrocarbon gases, and compressors handling hydrocarbongases (The use of R12, a potential ozone layer depleting substance, is being phased out;seeChapter 17for additional information on refrigeration compressors and refrigerants.)

In these latter applications, the low solubility of the gases in the polyglycol minimizesthe dilution effect, contributing to better high temperature lubrication

Phosphate esters are one of the other commonly used classes of synthetic base fluids Atypical phosphate ester structure is shown in Figure 5.9

One of the major features of the phosphate esters is their fire resistance, which issuperior to mineral oils Their lubricating properties are also generally good The hightemperature stability of phosphate esters is only fair, and the decomposition products can

be corrosive Generally, they have poor viscosity–temperature characteristics (low VI),although pour points are reasonably low and volatility is quite low Phosphate esters haveconsiderable effect on paints and finishes, and they may cause swelling of many sealmaterials Their compatibility with mineral oils ranges from poor to good, depending onthe ester Their hydrolytic stability is only fair They have specific gravities greater than

1, which means that water contamination tends to float rather than settle to the bottom,and pumping losses are higher than is the case with products lower in specific gravity.Their costs are generally high, and they are limited in viscosity

The major application of phosphate esters is in fire-resistant fluids of various types.Hydraulic fluids for commercial aircraft are phosphate ester based, as are many industrialfire-resistant hydraulic fluids These latter fluids are used in applications such as theelectrohydraulic control systems of steam turbines and industrial hydraulic systems, wherehydraulic fluid leakage might contact a source of ignition In some cases they may also

be used in the turbine bearing lubrication system

Phosphate esters are also used as lubricants for compressors where discharge atures are high, to prevent receiver fires and explosions that might occur with conventionallubricants Some quantities of phosphate esters are also used in greases and mineral oilblends as wear and friction reducing additives

temper-Figure 5.9 Phosphate ester The R group can be either an aryl or an alkyl type If, for example,the methyl group (CH3) is used, the ester is tricresyl phosphate

V OTHER SYNTHETIC LUBRICATING FLUIDS

Brief descriptions and principal applications of some of the other synthetic base fluids aregiven in Sections V.A–V.D

A Silicones

Silicones are among the older types of synthetic fluid As shown in Figure 5.10, theirstructure is a polymer type with the carbons in the backbone replaced by silicon.Silicones have high viscosity indexes, some on the order of 300 or more Their pourpoints are low and their low temperature fluidity is good They are chemically inert,nontoxic, fire resistant, and water repellent, and they have low volatility Seal swelling islow Compressibility is considerably higher than for mineral oils Thermal and oxidationstability of silicones are good up to quite high temperatures If oxidation does occur,oxidation products include silicon oxides, which can be abrasive A major disadvantage

of the common silicones is that their low surface tension permits extensive spreading onmetal surfaces, especially steel As a result, effective adherent lubricating films are notformed Unfortunately, the silicones that exhibit this characteristic also show poor response

to additives aimed at reducing wear and friction Some newer silicones show promise ofovercoming these deficiencies

Silicones are used as the base fluid in both wide temperature range and high ture greases They are also used in specialty greases designed to lubricate elastomericmaterials that would be adversely affected by lubricants of other types Silicones are alsoused in specialty hydraulic fluids for such applications as liquid springs and torsion dam-pers, where their high compressibility and minimal change in viscosity with temperatureare beneficial They are also being used as hydraulic brake fluids and as antifoam agents

tempera-in lubricants Some newer silicones are also offered as compressor lubricants

B Silicate Esters

Silicate esters have excellent thermal stability and, with proper inhibitors, show goodoxidation stability (see Figure 5.11 for their chemical structure) They have excellentviscosity–temperature characteristics, and their pour points are low Their volatility islow, and they have fair lubricating properties A major factor for their limited use is theirpoor resistance to hydrolysis

Small quantities of silicate esters are used as heat transfer fluids and dielectriccoolants Some specialty hydraulic fluids are formulated with silicate esters

Of primary interest in selection and use of this class of EA lubricants is definingand measuring the product attributes that could affect the environment In addition, thelubricants must provide performance in key areas such as oxidation stability, viscos-ity–temperature properties, wear protection, friction reduction, rust and corrosion protec-tion, and hydrolytic stability where water or moisture may be present In other words, the

EA products must perform at levels equivalent to those achieved by conventional

mineral-or synthetic-based lubricants in the equipment, while providing characteristics that reducethe negative impact in the event of inadvertent introduction into the environment

Environmental acceptability of lubricants is not well defined and can encompass a broadrange of potential environmental benefits: use of renewable resources, resource conserva-tion, pollutant source reduction, recycling, reclamation, disposability, degradability, and so

on Therefore, any claim of environmental acceptability must be supported by appropriatetechnical documentation Most petroleum-based lubricants can be considered to be envi-ronmentally acceptable by various standards For example, long-life synthetics (discussed

in Chapter 5) and other lubricants that provide extended oil drain capability might be

classed as EA materials because they conserve resources and aid in potential pollutantsource reduction (since quantities for disposal will be lower) Many oils can be reclaimed,recycled, or burned for their heat energy value, again resulting in conservation of resources.All these efforts to help reduce the environmental impact of lubricants have positive effectsand should be an integral part of the planning to establish an environmental program Theremainder of this chapter is devoted to discussions of a class of lubricants exhibitingspecific characteristics such as biodegradability and low toxicity.

II DEFINITIONS AND TEST PROCEDURES

The two environmental characteristics most desirable in EA lubricants are speed at whichthe products will biodegrade if introduced into nature and toxicity characteristics thatmight affect bacteria or aquatic life Most lubricants are inherently biodegradable, whichmeans that given enough time, they will biodegrade by natural processes They will notpersist in nature In certain applications, however, much faster rates of biodegradation are

desired These are referred to as readily biodegradable products All lubricants range in

toxicity from low (sometimes called nontoxic) to relatively high Toxicity has a directeffect on naturally occurring bacteria and aquatic life and therefore needs to be an importantpart of the development of EA lubricants

Unlike traditional lubricant development, where the predominant focus is on productperformance in equipment, a major part of developing EA lubricants involves understand-ing and defining environmental test criteria and developing ways to assess the effects ofnew and used lubricants in actual applications where environmental sensitivity is an issue.Since both base fluids and additive systems impact the environmental characteristics, thesetests must evaluate the ecotoxicity of base fluids, additives, and finished lubricants

A Toxicity

The impact of lubricants on the aquatic environment is evaluated by conducting acuteaquatic toxicity studies with rainbow trout (a freshwater fish that is sensitive to environ-mental changes) or other aquatic life-forms that are sensitive to changes in their environ-ment Since oil is insoluble in water, the aquatic specimens are exposed under oil–waterdispersion (mechanical dispersion) conditions to increasing concentrations of test materials

up to a maximum concentration of 5000 ppm This oil–water dispersion technique follows

a modification of the procedure used by the British Ministry of Agriculture, Fisheries andFood (MAFF) In the oil–water dispersion procedure, the test materials are added toaquaria equipped with a central cylinder-housed propeller system that provides mechanicalagitation to continuously disperse the test material as fine droplets in the water column.The propeller is rotated to produce flow in the cylinder by drawing small quantities ofwater and test material from the surface into the top of the cylinder and expelling asuspension of oil droplets in water through apertures near the bottom of the cylinder Thisprocedure, which simulates physical dispersion by wave and current action, is used toevaluate the relative toxicity of lighter-than-water materials The aquatic specimens areexposed to five concentrations of test material and a control (without test material) duringeach study Toxicity is expressed as the concentration of test material in parts per million(wt/vol) required to kill 50% of the aquatic specimens after 96 hours of exposure (LC50)

B Biodegradability

Two tests are most commonly used to assess the biodegradability of lubricants The shakeflask test* is used to determine ultimate biodegradability (conversion to CO2) of the testmaterial The second, the CEC (Coordinating European Council) test, is not as discriminat-ing but is widely used in Europe for assessing the biodegradability of lubricants and was,

in fact, specifically designed to evaluate the aerobic aquatic biodegradation potential oftwo-stroke-cycle engine oils Both tests use a mineral salts mix for the growth medium,with the carbon substrate being supplied only by the test material Both the shake flaskand CEC tests use unacclimated sewage inoculum, which is typically obtained from amunicipal wastewater treatment plant that has no industrial inputs The shake flask test,

in addition, utilizes a soil inoculum

The shake test flasks, closed with neoprene stoppers from which are suspended alkalitraps, are placed on a rotary shaker and heavily shaken at 25⬚C Periodically, over a 28-day period, the flasks are removed and titrated to quantify the trapped CO2 The medium

is then sparged with air to maintain aerobic conditions, and the fresh traps are placed back

in the flasks Blank controls, which are run alongside the flasks containing the test material,have all components present in the test flasks except the test material At each time point,the quantity of CO2 evolved from the blanks is subtracted from CO2 values in the testmaterial flasks A positive control containing a readily biodegradable material is also run

to ensure inoculum viability

ASTM has issued a test for biodegradability to standardize testing for ity of environmental type products This test (ASTM D 5846) is a modified Sturm testand very similar to the shake flask test just described It also measures CO2evolution asthe bacteria metabolizes the test material

biodegradabil-The CEC test utilizes cotton-stoppered flasks and, as with the shake flask test, theflasks are placed on a rotary shaker table and heavily shaken at 25⬚C At 0, 7, and 21days, flasks are extracted with Freon 113 and the quantity of test material in each of theextracts is determined by infrared (IR) analysis at 2930 cmⴚ1(C—H stretch) The percent

of material biodegraded after 7 and 21 days is determined by comparing the intensity ofthe IR absorbance in the test flask extracts, after each period of time, against zero timevalues and against values in the abiotic controls (HgCl2-poisoned)

C Environmental Criteria

At the present time, there are no generally accepted worldwide regulations to define criteriafor lubricants used in environmentally sensitive areas There are products with limitedapplications such as those receiving the German Blue Angel Label for lubricants A lubri-cant can carry a Blue Angel label if all major components meet OECD ready biodegradabil-ity criteria and all minor components are inherently biodegradable Secondary criteriainclude a ban on specific hazardous materials, and lubricants must meet aquatic toxicitylimits Based on an evaluation of current legislation for new product registration by theEuropean Inventory of Existing Commercial Chemical Substances (EINECS) and on ma-rine transport requirements by Marpol, the International Maritime Organization (IMO),

as well as a review of proposed labeling schemes, there is some consensus in industry for

* ‘‘Shake flask test’’ refers to either the U.S Environmental Protection Agency test described in EPA 82-003 or the Organization for Economic Development and Co-operation tests described in OECD 301.

560/6-biodegradation and aquatic toxicity criteria for lubricants that will be used in tally sensitive areas A product may be considered acceptable if it meets the followingcriteria:

environmen-Aquatic toxicity⬎1000 ppm (50% min survival of rainbow trout)Ready biodegradability ⬎ 60% conversion of test material carbon to CO2 in 28days, using unacclimated inoculum in the shake flask or ASTM D 5846 testAquatic toxicity and ready biodegradation studies were conducted on products formulatedwith mineral oils and non–mineral oil base stocks (Table 6.1) In general, the base stocksthat comprise the major component of most lubricant formulations are nontoxic Theaquatic toxicity observed following exposure to the formulated products inFigure 6.1iscaused by one or more of the additives

Vegetable oils, such as Mobil EAL 224H, and a number of synthetic esters easilymet the ready biodegradation criterion (⬎ 60% conversion to CO2in 28 days) and alwayshad CEC test results exceeding 90% conversion after 21 days None of the formulationstested containing mineral oil base stocks were able to meet the ready biodegradationcriterion, although 42–49% of these materials were converted to CO2in 28 days (Figure6.1) This does not appear to be a significant difference from the 60% criterion, but inactual field conditions, it is a major difference

The polyglycol-based materials, although soluble in water, failed to meet the readybiodegradability criterion, with only 6–38% of the test material converted to CO2 in 28days The biodegradation of polyglycols is determined by the ratio of propylene oxide toethylene oxide, with polyethylene glycols being more biodegradable The average molecu-lar weight of the material is also critical, with material under a molecular weight of

1000 being rapidly biodegraded The rate and extent of biodegradation diminishes withincreasing molecular weight Some additional studies of the polyglycol materials is needed

to further quantify biodegradation rates of these materials

Evaluations of the impact of base stocks used to formulate hydraulic oils, formulatedconventional hydraulic oils and EA hydraulic fluids have been conducted to determinethe various levels of aquatic toxicity that these materials may exhibit The toxicity testingwas done using the EPA 560/7-82-002 (for all intents and purposes, this is the same test

as the OECD 203⬊1–12) The results of this study of base stocks and fully formulatedhydraulic fluids, given inFigure 6.2,indicate that the toxicity of most lubricants is due

to one or more of the additives in the formulation

Table 6.1 Ecotoxicology Data for Select Hydraulic Fluids

Biodegradability (%)

Sources: Shake Flask Test Measures Carbon Dioxide Evolution, EPA Method 560/6-82-003; CEC

Method-CEC-L-33-T-82.

III BASE MATERIALS

One of the primary choices of base oils for EA lubricants today is vegetable oils This isdue to their good natural biodegradability and very low toxicity in combination with verygood lubricity characteristics These renewable resources also provide a cost advantageover other EA base materials such as synthetic base stocks But, there are some performancelimitations of the vegetable-based lubricants that have been and continue to be addressed.These characteristics are mainly high temperature oxidation stability, low temperatureperformance, viscosity limitations, and cost Although less expensive than synthetic alter-natives, vegetable-based products can cost several times as much as conventional mineral-based lubricants Genetic engineering will provide improved performance in the future inareas of oxidation stability and low temperature performance by increasing the high oleicacid content as well as other by means of genetic alterations (branching) In most applica-tions, the vegetable-based EA lubricants can be formulated to perform in all but the mostsevere equipment It is important to note that not all vegetable-based EA lubricants willprovide the same levels of performance Vegetable-based oils derived from rapeseed plants,cotton seeds, soybean oil, sunflower seed oil, corn oil, palm oil, and peanut oils arefrequently used materials, with rapeseed being the most common

Synthetic-based materials such as polyglycols (discussed earlier), polyol esters, taerithritol esters, and certain PAOs (seeChapter 5)are used to formulate the synthetic

pen-EA lubricants Their advantages over vegetable-based pen-EA lubricants are wider temperaturerange application, longer drain capability (oxidation stability), and excellent performance

in systems with close-tolerance servo valves

Some of the more general performance characteristics of the various base materialscan be discussed in the following categories

1 Vegetable oils The choices of correct processes to refine, bleach, and deodorize

vegetable-based oils can yield very satisfactory base materials for the formulation of ished lubricants This renewable resource provides excellent natural lubricity, low volatil-ity, and good environmental characteristics Weaknesses are in low temperature perfor-mance, hydrolytic stability, and oxidation stability in high temperature applications Theseproducts are also currently limited to low viscosity (ISO 32–68) materials Properly manu-factured and formulated vegetable-based lubricants can equal conventional mineral oilbased lubricants in performance in all but the most severe applications

fin-2 Polyalphaolefins (PAOs) As discussed in Chapter 5, PAOs provide a good

option for formulating environmental lubricants Their ready biodegradability in the lowerviscosity range is good They also provide excellent low and high temperature (oxidationstability) performance, good hydrolytic stability, and low volatility Their disadvantagesare in costs and lower rates of biodegradability rates as viscosities increase To achievethe good characteristics of the PAOs in finished products, they are often blended withbiodegradable synthetic esters to get both the performance and environmental characteris-tics desired

3 Synthetic esters Several materials based on synthetic esters exhibit good

biode-gradability as well as high levels of oxidation stability, low and high temperature mance, and good hydrolytic stability and seal swell performance The synthetic esters willallow formulation of higher viscosity lubricants typically used in circulating systems andsome gear oils

perfor-Table 6.2 Comparison of Fully Formulated EA Lubricants with Various Bases

characteristics

a These ratings are generalizations Specific manufacturers of products should be consulted for current data Exc, excellent; VG, very good.

Table 6.2 shows a general comparison, against mineral oils, of some of the morecommon performance characteristics of fully formulated EA lubricants using the variousbase materials Actual finished product performance could vary from these ratings as aresult of technological advancements in such areas as additive technology, use of blends

of base materials, and manufacturing processes

As a result of the higher costs, EA lubricants will typically be used in areas whereenvironmental sensitivity is an issue In many instances of spillage or leakage that arereportable to governmental agencies such as the U.S National Response Center, the addedcosts of EA lubricants may be offset by the potential for lower fines and remediationcosts

EA lubricants are not meant for use in all applications but only when their use can

be economically justified or the environmental sensitivity issues are of prime importance

In many cases, economic justification of the EA lubricants based solely on equipmentperformance is not sufficient to merit their use The economics must be derived fromreducing costs of remediation in the event of spills or leakage Also, in some localities,limited legislation or regulations promote or require the use of such products Environmen-tal sensitivity issues prevail in the following specific areas

Dredging operations for waterwaysOperation of equipment for dams and locksOffshore drilling

Marine equipmentRecreation and parksConstruction sites on or near water or groundwater systemsAgricultural operations

Forestry and loggingMining

Automotive service liftsHydraulic elevators

A Product Availability and Performance

Because of the large volumes of hydraulic fluids used around the world and the tendency

of these products to leak under conditions of relatively high pressures and severity ofsome applications, the first category of EA fluids to be developed and widely marketedwere hydraulic oils Once readily biodegradable base oils and low toxicity additive systemshad been identified, the next hurdle was to provide fully formulated oils that exhibitedrequired equipment performance as established by the builders of equipment as well asthe users Equipment builders have received many requests to approve the use of EAlubricants by their customers and need to be assured that the EA products will performsatisfactorily in their equipment and meet the service life requirements of the customers.Certain EA lubricants are formulated not only to meet the environmental criteriabut also to provide performance equal to that of conventional mineral based lubricants.Much of the performance in hydraulic systems is determined by industry standard pumptests We list three common tests

1 Vickers V-104C Pump Test (ASTM D 2882) A rapeseed-based EA antiwear

hydraulic fluid provided little or no pump wear in the ASTM D 2882 pump test In addition

to the standard 100 h dry test, a more severe 200 h test was undertaken in which 1% waterwas added at 0 and 100 hs Because water contamination affects some EA fluids withpoor hydrolytic stability, this 200 h test simulates wet systems and evaluates the oil as itdegrades at accelerated rates or loses pump wear protection in the presence of water Testresults (Table 6.3) indicate low cumulative wear as well as good viscosity control andlow total acid number (TAN) increase Fluid characteristics did not change appreciablyand wear protection was excellent, even in the presence of high moisture levels

2 Vickers 35VQ pump test This severe industry-accepted antiwear vane pump

test is based on the Vickers 35VQ25 vane pump run at 3000 psi and 200⬚F Standardprocedures require that the same fluid be subjected to three successive 50 h test runs, andtotal ring and vane wear be less than 90 mg for each run The tests (Table 6.4)showedlow wear and good pump component appearance at the end of five successive 50 h pumptest inspections While fluid color darkened rapidly, increases in viscosity and TAN weresmall

Table 6.3 Extended ‘‘Wet’’ Vickers 104C Vane Pump Test Results with Mobil EAL 224HVegetable-Based Oil

wear measured at 100 and 200 h

Table 6.5 EA Lubricants and Application Data

Vegetable-based An ISO viscosity grade Primary application is for Provides good systemhydraulic and 32/46 vegetable oil- industrial and mobile equipment performance whilecirculating oil based antiwear hydraulic systems operating at substantially reducing

hydraulic oil that is temperatures of 0⬚F to 180⬚F the negative impact onreadily biodegradable Meets requirements of major the environment whenand virtually hydraulic pump manufacturers inadvertently leaked or

Synthetic-based Ester-based, readily Primary application is for Provides excellenthydraulic and biodegradable, and hydraulic and circulation performance over acirculating oil virtually nontoxic systems operating in moderate wide temperature range

antiwear hydraulic to severe applications such as while demonstratingand circulating oil mobile equipment hydraulic excellent biodegradationProduct available in systems where low and high and virtual nontoxicity.four ISO viscosity temperatures exceed the If inadvertently spilledgrades: 32, 46, 68, limitations of vegetable-based or leaked, theyand 100, all with EA oils Recommended for a significantly reduce theexcellent oxidation temperature range fromⳮ20⬚ environmental impactstability and wide to 200⬚F Owing to their high relative to mineral oilstemperature range degree of antiwear and high and can help reduce orapplication capability FZG (12Ⳮ stages), they can elimiante fines and the

also be used in gear units not costs of remediation.requiring EP additives

Multipurpose Synthetic-based EP Designed for multipurpose Provides excellentgrease NLGI #1 and #2 outdoor applications where lubrication

grade greases grease leakage or run out could characteristics over a

contaminate soil, groundwater, wide temperature range

or surface water systems They while reducing thecan be used for indoor potential for negativeapplications where grease impact on theleakage could enter plant water environment They aresystems They are compatible with mostrecommended for plain and other greases

rolling element bearings andcouplings that operate attemperatures fromⳮ15⬚ to

refined mineral oil based products with higher levels of oxidation inhibitors but overalllow levels of other additives that could interfere with achieving high RBOT and TOSTresults For example, there is poor correlation between high RBOT and TOST values andlong-term performance of antiwear mineral oil based hydraulic oils In fact, some premiumquality hydraulic oils with lower RBOT and TOST values perform much better and providelonger service life than those with higher values It is well recognized that vegetable oilbase stocks do exhibit poorer oxidation stability With proper processing and use of correctadditives, however, the finished formulation can provide satisfactory performance in themajority of applications Most manufacturers and suppliers of EA lubricants will provideapplication guidelines for application such as those shown inTable 6.5.

2 Low Temperature Performance

The low temperature performance of vegetable oil based products will naturally be poorerthan those that of lubricants based on highly refined mineral oil based products Withoutthe use of VI improvers and pour point depressants, paraffinic mineral oil based productsalso exhibit poor low temperature performance Vegetable oils respond to VI improversand pour point depressants by exhibiting substantially lower finished product pour pointsand low temperature fluidity Pour points are less meaningful for vegetable oil basedproducts than for lubricants based on mineral oils and should not be used as an indication

of the lower use temperature for application A more meaningful indication of low ture performance of EA lubricants consists of the solidification point and low temperaturepumpability These better represent how the product performs under longer cold soakconditions This information is important for outdoor applications such as mobile equip-ment, where fluids may be subjected to subzero temperatures for extended periods of time

tempera-If the application involves low temperatures, data on low temperature performance should

be obtained from the supplier

3 Hydrolytic Stability

It is almost impossible to keep moisture out of most lubrication systems, and water can

be detrimental to lubricant performance regardless of the base material used to formulatethe lubricant Vegetable oils, as well as all natural and synthetic esters, have poorer hy-drolytic stability than comparable mineral oil based products The proper formulation of

EA products is the key to minimizing the potential for negative hydrolysis effects Currentstudies of a specific EA fluid indicate that only severe water contamination (⬎ 0.1%allowable limit for both conventional and EA fluids in critical systems) will adverselyaffect a lubricant’s performance because of hydrolysis or additive depletion

Because of the many choices of available EA lubricants and the lack of clear and sally accepted guidelines to define environmental criteria, the selection process is moredifficult than that used for selecting conventional non-EA products Even so, many of theproduct performance aspects in actual equipment applications are essentially the same.The selection process needs to include the following aspects of product performance:Environmental acceptability

univer-Product physical specificationsEquipment builder approvalsEvidence of proven field performance

Credibility of the supplierOperating and maintenance considerationsThe major difference lies in the first and last items in this list: environmental accept-ability and operating and maintenance considerations.

A Environmental Acceptability

The area of environmental acceptability itself encompasses the greatest difference in ing EA lubricants versus selecting conventional mineral-based lubricants Although most

select-conventional lubricants are inherently biodegradable and can be low in toxicity, EA

prod-ucts need to meet more stringent requirements, as was discussed earlier in this chapter(see Section II: Definitions and Test Procedures) Again, some industry consensus hasbeen established for environmental acceptability, but at present there are no universalindustry/regulatory agency agreements on definitions and test procedures This should not

be a deterrent to the use of EA products, particularly in areas that are sensitive to spills

or leakage of conventional lubricants Where such spills have inadvertently occurred, EAlubricants have clearly demonstrated much less negative impact on the environment thanwould have been expected from the older formulations Environmental performance re-quirements also must include the specification that a product not lose its environmentalcharacteristics during its projected service life

B Specifications

A product that is going to be relied on in a given piece of equipment must exhibit certainphysical and chemical characteristics that have been shown to be important to the perfor-mance of that equipment The primary concern is to have adequate viscosity characteristics.Too low a viscosity could result in metal-to-metal contact and consequent wear Too high

a viscosity can result in improper flow or excessive internal shear, resulting in excessiveheating and energy losses Other characteristics would include compatibility, antiwear,oxidation stability (long life), rust and corrosion protection, filterability, and demulsibility

C Equipment Builder Approvals

Much of the initial thrust to develop an EA class of lubricants came from equipmentbuilders whose customers were requesting guidance on such products Chances are that

if the equipment builders have approved the use of these products, they have satisfactorilytested the products or have test data showing that desired performance requirements aremet Also, builders have followed field applications to assure that the product not onlymeets laboratory test requirements but works in the equipment in question under fieldservice conditions In some cases, builders will grant conditional approvals only if theycan limit temperatures and pressures and may in some cases derate equipment for which

EA products must be used This generally means lower service pressures, speeds, and/ortemperatures If the equipment is under warranty, the builders should be consulted beforeits use to ensure that the requirements of the warranty are met

D Proven Field Performance

Similar to selecting conventional lubricants, testimonials of customers who have used theproducts in equipment that represents a certain application, indicate that the products