the majority of lubricant R&Ddollars is invested in meetingthe requirements of automo-tive engine oils.Many industrial oil formula-

tions are typically 90 to 99percent base oil (comparedto 75 to 85 percent for auto-motive lubricants), and only 1to 10 percent additives.Because of these low additivetreat rates, the performanceof many of these lubricantsrelies heavily on the physicaland chemical propertiesinherent in the base oil.A major improvement to

base oil quality came in theearly ‘90s when Chevronintroduced and licensedIsodewaxing technology thatenabled cost-effective produc-tion of API Group II andGroup III mineral oil basestocks. Compared to solvent-processed Group I base oils,these base stocks offer excel-lent purity and low-tempera-ture performance.The widespread availability

of Group II and III basestocks led to a step-change invalue/performance for many

Industrial lubricantsencompass a widerange of applications,without an industry-wide definition of

what the category includes.Even if we focus on oils thatlubricate machines that arenot mobile, this is a huge cate-gory that touches practicallyevery person in the world,every day. It includes every-thing from power plants tosewing machines, in operatingenvironments ranging fromhostile to benign. While theapplications for industriallubricants run the gamut, alloperators of this equipmentshare two goals — increasingproductivity and reducingdown time.Despite the broad range of

applications, industrial prod-ucts (not including processoils) account for only abouthalf the volume of automotivelubricants. Industrial lubri-cants are important, butbecause development, licens-ing and certification for auto-motive engine and gear oilsare complicated and costly,

types oflubricantsand, as aresult, originalequipmentmanufacturers (OEMs) andusers were able to expectand/or demand a higher levelof performance from theirlubricants. Higher-perfor-mance machinery was thendeveloped that required lubri-cants to withstand tougheroperations and environments(higher operating tempera-tures, smaller sumps, higherpower densities, longer drainintervals, lighter materials,and more compact designs).In many industrial applica-

tions, premium mineral baseoils can lead to dramatic per-formance improvements withminimal cost increases. Forexample, turbine oils made

28 JULY 2012

with GroupII base stocks can greatlyextend fluid life — up to threeyears in some applications.This article will focus on whyGroup II base oils are ableprovide very good perfor-mance for a broad range ofindustrial applications.

Five FactorsFive base oil attributes arekey to industrial oil perfor-mance: viscosity, oxidationstability, water separability, air

Base Oil Considerations for Industrial Lubes

By John Rosenbaum and Allan Hee

release and low-temperatureproperties.• Viscosity, the single most

important property of an oil,measures the oil’s resistanceto flow under certain condi-tions. While automotivelubricant viscosity is definedby SAE, industrial lubricantviscosity is expressed by ISOvalue, set by theInternational StandardsOrganization. ISO value cor-responds closely to thefluid’s kinematic viscosity at40 degrees C. Industrial oilsare produced in a broaderviscosity range than automo-tive lubricants (see Figure 1,page 30), and run from ISO10 to greater than ISO 3200.However, a large majority ofindustrial oil demand falls inthe ISO 32 to ISO 100 range.

Even thoughGroup I base oils

span a very wide viscosityrange (e.g. from very light oilsto heavy brightstocks andcylinder stocks) and can beused to manufacture a widerange of industrial oils, GroupII base oils provide completecoverage for ISO 32 to ISO100 fluids, the majority of theindustrial oil volume (seeFigure 2, page 30).Additionally, when blended

with Group I brightstock,Group II base oils can com-prise a significant portion ofISO 150 and ISO 320 industri-al fluids as well, improvingtheir performance over an all-Group I formulation. GroupIII oils, by contrast, cover thenarrowest viscosity rangebecause the heaviest GroupIII stocks are only 35 to 45centiStoke at 40 C.

• Oxidation Stability.Oxidation and thermal degrada-tion, the key causes of reducedoil life, occur when high tem-perature, sometimes in addi-tion to oxygen, creates undesir-able compounds through poly-merization and condensationreactions. These compoundsthen react with other com-pounds in the oil to form bothsoluble and insoluble products.Soluble acidic products mayincrease the viscosity of the oiland corrode the system, whileinsoluble products (e.g. gum,sludge, varnish) may increasewear and will eventually pluglines and valves and reduceclearances, which could lead tosystem failure. Group II baseoils have excellent inherent oxi-dation stability, although a smallamount of antioxidant is fre-quently used in almost all lubri-cant applications to greatlyextend oil life.• Water Separability. The

ability of an oil to “shed” or

separatefrom wateris particular-

ly important forindustrial oils used in appli-cations where possible incur-sion of water into the oil sys-tem is very high, such as insteam and hydroelectric tur-bine oils, circulation oils andhydraulic fluids. In these situ-ations the oil must be able toseparate water rapidly andcleanly. By draining separatedwater from the system, opera-tors can extend the life of thelubricant and minimize rustand corrosion formation. Dueto their very high levels of sat-urated hydrocarbons and verylow levels of polar com-pounds, Group IIs will usuallyseparate water from oil morerapidly than Group Is.• Air Release. All oils

absorb air. Air entrainment isa dispersion of tiny air bub-bles throughout the bulkfluid. Hydraulic systemsdepend on the fluid beingincompressible — a propertythat is compromised if air

29LUBES’N’GREASES

In turbines, oil life has beenextended as much as 300percent with Group II for-mulations. (Photo: GE)

have excellent low-tempera-ture properties and, becauseof their extremely low resid-ual normal-paraffin content,respond readily to pour pointdepressants (PPD). As withGroups I and III base stocks,careful selection of the cor-rect PPD is important in opti-mizing the final formulation.Let’s now look at three

industrial oil segments thathave benefitted from the phys-

bubbles are present. In addi-tion to compressibility prob-lems, circulating excessive aircan also cause pump cavita-tion and erratic movement ofmachine parts. High-puritybase oils like Group IIs areless likely to stabilize micro-foams, and tend to have bet-ter air-release times as mea-sured by ASTM D3427.• Low-temperature

Properties. Group II base oils

ical and chemical properties ofGroup II base oil, beginningwith hydraulic oils.

Hydraulic SystemsGroup II base oils are a goodfit for hydraulic oils, especiallysince most of the hydraulic oilvolume falls within the ISO32-68 range. Possible advan-tages of Group II based for-mulations over Group I for-mulations include higher oxi-

dation stability, better ormore rapid water separation,and lower foaming tendency.High oxidation stability sig-

nificantly extends the life ofhydraulic oils. In RotatingPressure Vessel OxidationTests (RPVOT, ASTM D2272),hydraulic oils formulated withGroup II base stocks demon-strated significantly longer oillife than Group I formulations(see table, left).Enhanced water separability

is another factor. Any moisturethat enters the hydraulic sys-tem, whether through contam-ination or condensation, mayemulsify, promoting rust,which will increase friction andwear. Group II based formula-tions can minimize this. In fact,due to their excellent waterseparability and resistance tofoaming, such formulations

30 JULY 2012

Continued on page 32

Comparing Hydraulic Oil Performance (Same additive package and treat rate for all oils)

ISO 32 ISO 46Test Group I Group II Group I Group II

RPVOT (ASTM D2272), 360 449 323 419min to 25 psig drop

TOST (ASTM D943), hrs to 2 TAN 2,520 5,917 2,016 6,460Foaming Sequences* (ASTM D892)Sequence I 10/0 0/0 0/0 0/0Sequence II 30/0 0/0 30/0 0/0Sequence III 50/0 10/0 10/0 0/0

Source: Chevron Base Oils

Industrial oils are produced in a broader viscosity range than automotive lubricants (left). Most of these industrial oil viscosity grades (right) canbe covered using Group II base oil alone (“Fully Capable”), or by blending in an additional volume of another Group (“Partially Capable”).

Figure 1 Figure 2

*Each Sequence conditions the oil differently. The two numberssignify initial foaming tendency/foam stability. Zero is best.

rate rapidly from water or airwith no or minimal assistancefrom demulsifying additives oranti-foaming agents.Turbine OEMs have strin-

gent oxidation-related specifi-cations for turbine oils. Twoof the most common tests arethe RPVOT and the TurbineOil Stability Test (TOST). Bothtests are commonly used inthe industry as measures ofoxidation stability and servicelife. When turbine oils areproperly reformulated fromGroup I to Group II base oils,TOST values can triple.Varnish has become an

issue in some turbine oil systems, where unwanteddeposits can adversely affectthe operation of servo valves,bearings, filters and othercomponents. While somehave blamed varnish on thebase oil used, this is usually a

usually require no or minimalamounts of demulsifiers.

Power Generation TurbinesTurbine oil, in both gas andsteam power generation sys-tems, provides clean and coollubrication to bearings andfrequently acts as the workingfluid in associated hydraulicsystems. Most turbine enginesrequire oils in the ISO 32 or46 viscosity grades. A lower-viscosity fluid may be neededto lubricate high-speed shafts,while an ISO 68 or ISO 100fluid may be needed forgeared-turbine equipment.It is well recognized in the

industry that turbine oils for-mulated with Group II baseoils have much longer life thanthose formulated with GroupI. As with hydraulic oils, GroupII based turbine oils will sepa-

gross oversimplification.Varnish in turbine oils canvary from one application tothe next, and the many caus-es are currently under investi-gation in several labs. Multipleroot causes for varnish forma-tion have been postulated,including microdieseling, cer-tain additive types, electrosta-tic discharge and overextend-ing oil drain intervals.Avoiding varnish formation

requires the development of arobust formulation — both interms of additives and base oil— that properly balances the(sometimes opposing) require-ments for oxidation resistanceand low-varnish tendency.

Natural Gas EnginesNatural gas engines used inindustrial applications operateat high loads, high tempera-tures and for long periods of

time, while exposing the oilto severe oxidation and nitra-tion conditions. The enginesare often in remote locationsand must run with minimaloperator attention, so enginereliability is critical. There areno industrywide tests for eval-uating natural gas engine oilperformance. Instead, OEMapprovals are granted onlyfollowing field trials.Here too, Group II base oils

have proven to be an excel-lent, cost-effective fit. Mostgas engines use an SAE 40 vis-cosity grade oil or, in somecases, an XXW-40 multigrade.As a result, the base oil blendof these lubricants can bemostly or all Group II.Group II base oils also

enable a formulator to main-tain the same additive treatrate as would be used with aGroup I base oil and achieve

32 JULY 2012

Continued from page 30

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higher oxidation stability. Or,a lubricant company maychoose to reduce the additivetreat rate when using a GroupII and offer a product withequivalent stability to a GroupI formula.Gas engine oil formulators

must watch out for sulfatedash. Sulfated ash is combustedresidue (ash) left when a cer-tain quantity of oil is burnedusing the ASTM D874 testmethod. This ash is an inher-ent property of certain addi-tives, some of which are neces-sary to protect exhaust valvesin natural gas engines. Gasengine temperatures are typi-cally high, so deposits are acommon problem if ash levelsare not kept low in the enginelubricant. Piston deposit con-trol is critical to prevent ringand liner wear. If depositsaccumulate in the grooves,

they will push the ring againstthe liner and cause adhesivewear. Also, excessive buildupof deposits on the pistonlands may polish and abradethe liner surface.A key way to improve pis-

ton deposits is through awell-formulated lubricant thattaps into Group II’s strongoxidation and nitration con-trol. One back-to-back fieldtest compared two NGEOs

made with Group II andGroup I, running over 8,000hours each in a natural gaspipeline operation. TheGroup II showed far greateroxidation stability, TBN reten-tion and nitration control,with less than half the pistondeposits. And it did so eventhough the Group II formula-tion’s drain intervals were 50percent longer.To summarize, almost all

industrial oils can benefit fromthe use of Group II base oil intheir formulations. What is crit-ically important is that thelubricant be formulated prop-erly and optimized for theoperating environment inwhich the oil will be used.Every application is different,and additive companies havemany years of experience mak-ing industrial oils with a broadrange of base stock types. ❚

33LUBES’N’GREASES

John Rosenbaum (left) and Allan Hee, bothBerkeley Ph.D.s, are engineers with Chevron BaseOils in Richmond, Calif. Rosenbaum started atChevron in 1981 and spent 16 years in processR&D before moving to Base Oil ProductTechnology. Hee joined Chevron in 2006, andmoved to Base Oil Product Technology after three years in industrial oil R&D. E-mailRosenbaum@chevron.com for more information.

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