Hydraulic fluids treatise fluids...Principles of hydraulic system function — quality and high...

A treatise on formulation for performance and efficiency

Hydraulic fluids

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Hydraulic systems are a series of fluid power components designed to generate, control and transmit power by manipulating large forces over long distances with a high degree of simplicity and flexibility.

While not strictly matching modern definitions of hydraulic systems, the earliest use of fluid power (water systems) can be traced back to the ancient Egyptians in 2000 BC. In this early period, water falling from a higher level to a lower one was used to drive water wheels and rudimentary turbines. In these systems, the work force (referred to as potential energy) is coming from the difference in height between the highest and the lowest level of the water. In other words, the higher the falling water height, the bigger the potential amount of work. Power can be generated in this way from natural sources, such as waterfalls.

Hydraulic systems were widely known and used for centuries; however, one had to wait until 1653 before the fundamental physical and mathematical rules applying in hydraulics were articulated by a brilliant, young French scientist, Blaise Pascal (Figure 1). Known as Pascal’s Law, he stated that “pressure exerted anywhere in a confined incompressible fluid is transmitted equally in all directions throughout the fluid such that the pressure variations (initial differences) remain the same” (Figure 2). In other words, by applying a force at one end of a system through an incompressible fluid, the same force is transmitted to the other end. This finding laid the groundwork for all modern hydraulic concepts.

More than a century later, based on this work, Joseph Bramah from Yorkshire, England, turned the theory into the first real industrial use by inventing a performance gasket, thereby avoiding water leakage and thus allowing the full use of hydraulic systems. In 1795, he patented the first hydraulic press as illustrated in Figure 3. Bramah’s machine had two cylinders and pistons of different cross-sectional areas. The initial force exerted on the smaller piston was amplified into a larger force on the larger piston. The difference in the two forces was proportional to the difference in area of the two pistons. Bramah went on to conceive other ideas for transmitting and using hydraulic power, ranging from beer pumps to a hydro-pneumatic suspension system.

Hydraulic power advanced mightily during the golden-period of the Industrial Revolution, when engineers and industrialists around the world realized they could utilize hydraulic principles on a much larger scale. In the late 19th century, William George Armstrong, looking at a watermill, had a vision for more efficiently harnessing water energy. After several trials of his system concepts, this English engineer pioneered the first piston engine for driving a hydraulic crane.

Over time, hydraulic systems gained in both performance and sophistication, with the addition of seals, control valves and accumulators. These performance-boosting innovations have, in turn, led to an impressive expansion of uses for modern hydraulic power systems. Today, hydraulic power applications range from aerospace to more conventional aviation, to construction and off-highway equipment, automobile, truck and industrial manufacturing, to merchant ships and marine cargo handling as well as power plants.

Introduction — a brief history of hydraulics

Figure 1: Blaise Pascal

Figure 2: Illustration of the Pascal Law Figure 3: Illustration of Joseph Bramah hydraulic machine

A1

A1

A2

A2=F2

F1

F1

PP

P F2

4 5

Hydraulic fluid standards and approvals — quality and high performance warrantyPrinciples of hydraulic system function —

the importance of hydraulic fluid

A typical hydraulic system includes the following components (Figure 4):

1. A fluid flow or force-generating unit that convertsmechanical energy into hydraulic energy, such as a pump.(It is important to note that the pump does not generatepressure; it simply provides fluid flow into a systemunder pressure. The pressure developed in the system isa result of the fluid flow restriction caused by controlvalves or a work load.)

2. A liquid, called the hydraulic fluid, with lowcompressibility capable of operating without degradationunder the conditions of the application temperature,pressure, shear stress and radiation

3. A fluid reservoir that allows for separation of water,foam, entrained air or debris

4. A filter to protect the hydraulic componentsfrom wear particles

5. Pipes and/or hoses for moving the hydraulicfluid through a circuit

6. Control valves that regulate flow, pressure, direction ofmovement and applied forces

7. A relief valve used as a safety device to open and releasepressure above a set limit, thus protecting the pump

8. A unit that converts the hydraulic energy of the fluid intomechanical work, such as an actuator hydraulic motor

Hydraulic fluids are commonly classified by their viscosity grade. The most common classification is ISO 3448 (ASTM D 2422), developed in 1975, that defines viscosity grades for hydraulic oils by their kinematic viscosity nominal value at 40°C. However, the scope of this basic classification is severely limited, since it provides no information on the oil viscosity at higher or lower temperatures.

In the 1990s, other standards were developed that provided information on the fluid viscosity index (VI) and shear stability. VI describes the degree to which the fluid viscosity changes with temperature. Shear stability describes the tendency of the fluid to experience viscosity reduction due to mechanical action. For example, ASTM D 6080 introduced ten low-temperature viscosity grades (Table 1), which are defined by the temperature at which the oil reaches a viscosity of 750 mPa·s measured in the Brookfield viscometer (ASTM D 2983). This value corresponds to the maximum start-up viscosity specified by many OEMs for hydraulic pumps. Moreover, for fluid containing a viscosity index improver (VII), ASTM D 6080 includes information on

The principle of action of a hydraulic system is to convert the mechanical energy from the pump into hydraulic energy in the fluid that is finally converted into mechanical energy at the hydraulic cylinder or hydraulic motor. The conversion efficiency is strongly influenced by the viscosity of the fluid, which also provides protection to the hydraulic system against wear, cavitation and corrosion.

For example, wear and deterioration of the sealing surfaces will promote fluid loss (external leakage) and fluid recycling (internal leakage) from the high-pressure side back to the low-pressure side of the pump. In turn, leakages reduce the pump output, resulting in power loss, and increasing the operating temperature of the fluid. An increase in fluid temperature can cause higher levels of oxidation, and lead to deposits and varnish formation that will clog fine clearances and cause fluid flow and oil starvation problems.

A properly selected fluid with optimal viscosity:

• Helps to maximize energy conversion by lubricatingmetal moving parts, thus reducing friction and increasedoperating temperatures

• Provides adequate seal

• Protects working metal surfaces from wear and corrosion

• Easily separates itself from water (demulsifies) and debriswhile in the reservoir sump tank

• Assures easy air release

• Able to pass through a standard filter without cloggingor plugging

As hydraulic fluids transmit power through pressure and hydrostatics, they need to have low compressibility and must flow readily at all operating temperatures. Thus, hydraulic fluids must be considered as critical as the other hydraulic components and should be carefully selected.

the fluid shear stability (sonic test ASTM D 5621) under the form of the viscosity at 40°C and the VI after shearing. It is interesting to note that three viscosity grades represent over 90% of all fluid consumed. They are ISO VG 32, ISO VG 46 and ISO VG 68.

With the aim of more closely matching real industry operating conditions, several other norms and standards have been created by the international institutes, including the International Standards Organization (ISO), the American Society for Testing and Materials (ASTM) and Association Française de Normalisation (AFNOR), extending the range of requirements for hydraulic fluids.

In 1997, ISO developed the norm ISO 11158 that describes the minimum requirement for new mineral oil hydraulic fluids. It classifies the oils in different categories based on their properties and performances: HH < HL < HM < HV < HG. The standard category, HL, requires fewer performance tests than a more elaborate one, like HV (see Table 2).

Table 2: International Standards Organization (ISO) range of requirements for hydraulic fluids according to ISO 11158

HL HV

Viscosity grade (ISO 3448) ▯ ▯

Flash point (ISO 2592) ▯ ▯

Pour point (ISO 3016) ▯ ▯

Acid number (ISO 6618) ▯ ▯

Water content (ISO 6296) ▯ ▯

Water separation (ISO 6614) ▯ ▯

Elastomer compatibility (ISO 6072) ▯ ▯

Anti-rust (ISO 7120) ▯ ▯

Foaming behavior (ISO 6247) ▯ ▯

Anti-corrosion (ISO 2160) ▯ ▯

Air release capability (ISO 9120) ▯ ▯

Oxidation stability (ISO 4263-1) ▯ ▯

Anti-wear (ISO 20763-A / 14635-1) ▯

Filterability (ISO 13357-1 and -2) ▯

Shear stability (ISO 26422) ▯

Table 1: Low-temperature viscosity grades for hydraulic fluid classifications according to ASTM D 6080

Temperature °C, for Brookfield viscosity of 750 mPa·s*

Viscosity grade min max

L5 -50

L7 -49 -42

L10 -41 -33

L15 -32 -23

L22 -22 -15

L32 -14 -8

L46 -7 -2

L68 -1 4

L100 5 10

L150 11 16

*The temperature range for a given L-grade is approximately equivalent to that for an ISO grade of the same numerical designation and having a viscosity index of 100, that is, the temperature range for the L10 grade is approximately the same as that for an ISO VG 10 grade with a viscosity index of 100.

8 Hydraulic Cylinder

5 Pipes

Relief Valve 7

2 Fluid

3 Reservoir

4 Filter 1 Pump

Control Valve6

Figure 4: Typical hydraulic system

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Pushing standards still further, several fluid suppliers and OEMs have, over time, developed their own approvals in order to consistently meet the increasing specificity of equipment manufacturers, and assure high safety and reliability for their systems to the end users.

Eaton-Vickers E-FDGN-TB002-E Among the most relevant hydraulic fluid performance standards written by an OEM as a requirement to gain approval for hydraulic systems is the Eaton-Vickers E-FDGN-TB002-E for use in pumps and motors. It includes standard bench tests (foaming, filterability, hydrolytic stability, air release, etc.), as well as a pump test using an Eaton-Vickers 35VQ25 vane pump, according to the Eaton ATS 373 test procedure. In this procedure, only the ISO VG 32 is evaluated. The pump is operated at 2400 rpm, with outlet pressure of 207 bar, and with an inlet oil temperature of 95°C for a duration of 50 hours per pump cartridge. Three cartridges out of five need to pass, with a maximum 90 mg weight loss on cam ring and vane.

Parker Denison HF-0 The Parker Denison HF-0 (“zero”) test is based on the approval document. It includes standard bench tests (for foaming, filterability, hydrolytic stability, air release, etc.), as well as pump testing performed using the Parker Denison T6H20C dual pumps (vane and piston). This pump test is conducted with an ISO VG 46 fluid according to the test method TP30533. The approval can be extended to ISO Grades 32 and 68.

The test method TP30533 is divided into four phases, lasting a total of 608 hours. It includes an initial 7-hour “breaking in” phase at 110°C and 2100 rpm at different pressures (ranging

from around 15 bar to either 250 bar for the vane pump or 280 bar for the piston pump). This is followed by a 300-hour dry phase during which pressure is continuously alternated between the two pumps. One pump gets high pressure for two seconds, the second pump is unpressurized.

Then they are switched and the second pump operates two seconds at high pressure (at 280 bar for the piston pump and at 250 bar for the vane pump) in a cycle at 110°C, at 2100 rpm. The third phase consists of a one-hour phase of water injection, during which water equivalent to one percent of total fluid volume is added at 80°C, 2100 rpm and at low pressure (between 10-15 bar). The test is concluded with a fourth phase consisting of a 300-hour wet phase with a four-second pressure cycle at 80°C and at 2100 rpm (same as the dry phase).

Bosch-Rexroth RDE 90245 Hydraulic fluids listed in the Bosch Rexroth Fluid Rating List, RDE 90245, fulfilled the requirements as described in document RE 90235. This document includes standard tests (foaming, filterability, air release…), as well as a test for axial piston pump and axial piston motor. This test is called Rexroth Fluid Test Axial Piston Unit Closed Loop (RFT-APU-CL).

The RFT-APU-CL runs with ISO VG 32 fluid (valid only for ISO Viscosity Grade 32, 46 and 68) and is divided into three testing phases, lasting a total of 510 hours. The first phase includes a “breaking in” cycle of 10 hours at 250 bar, 60°C and 2000 rpm. The second phase consists in a “swivel cycle” of 300 hours, at 450 bar, 100°C and 4000 rpm. And in the last phase, a “corner power test” is conducted during 200 hours at 500 bar, 100°C and 4000 rpm.

Note that some national standards include similar classifications to those described in fluid categories ISO 11158 (Table 3). There are differences between these otherwise similar classifications (Table 4).

Table 3: International and national standards

Standard Country

ISO 11158 International

DIN 51524 Germany

SS 15 54 34 Sweden

AFNOR NF E 48-603 France

ASTM D6158 North America

Table 4: Comparison of ISO 11158 (international) and DIN 51524 (Germany) standards

ISO DIN

Mineral oil without additives HH H

Type HH + oxidation- and corrosion-inhibiting HL HL

Type HL + wear-inhibiting HM HLP

Type HM + viscosity-improving HV HVLP

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The shear stability test ISO 26422 (KRL). In this test, the lubricating fluid is tested at 60°C in a tapered roller bearing situated in a four-ball machine. A constant speed is maintained while a load of 5000 Newtons is applied during a given running time (20 hours). The kinematic viscosity is determined at a temperature of 100°C before and after the test. The percentage viscosity loss is calculated from these two viscosity measurements.

Figure 5: Short description of several tests are common to many hydraulic fluid approvals and norms and have high general relevance.

Fluid filterability is tested using the norm ISO 13357-1 and -2, wet and dry respectively. In ISO 13357-1, the fluid is mixed with a specific quantity of water at high temperature 70°C. After a pass through a membrane with pores of 0.8 µm under defined conditions, the filtration rate is measured and reported. For ISO 13357-2, the same protocol is applied, but no water is mixed with the fluid.

The speed at which the hydraulic fluid will shed entrained air is measured by the air release test ISO 9120. Air is injected under pressure into the hydraulic fluid at different temperatures: 25°C, 50°C or 75°C. The time needed for the fluid to return within 0.2% of its original unblown volume is recorded as the air release time and displayed in a graph.

Foaming behavior is determined using method ISO 6247, which requires testing at both 24°C and 93.5°C. A fixed volume of test hydraulic fluid is blown in standard glassware for five minutes. The decrease of volume of foam is measured and reported. Foaming tendency is given by the foam height immediately after cessation of blowing. Foam stability is given by the foam height remaining 10 minutes later.

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Viscosity impact on hydraulic systems — importance of viscosity indexAs previously mentioned, one of the key components of hydraulic systems is the fluid transmitting the power. Practically speaking, if the fluid does not flow properly, then the hydraulic system will suffer from poor heat transfer, power transmission losses, reduced responsiveness to controls and stress in all other functions.

For example, a fluid in use during cold operating conditions will dramatically increase in viscosity and will experience flow problems during start-up, as well as the following problems during operation:

1. Air entrainment

2. Noisy operation

3. Sluggish response

4. Energy loss

5. In extreme cases, pump breakdown

On the other hand, when the fluid viscosity is too low (during warm operating conditions), other problems will occur:

1. High wear rates due to inadequate oil film thickness

2. Excessive internal and external leakages, leading toa loss of system efficiency

3. Overheating is due to the energy lost from pumpinternal leakage. This heat further increases the oiltemperature leading to further viscosity reduction,increased pump internal leakage and accelerated heatgeneration and fluid degradation.

Therefore, knowledgeable hydraulic equipment owners will work to ensure that the fluid viscosity remains within an optimal range to allow the hydraulic system to work at maximum efficiency. This requires selection of a fluid capable of maintaining an optimal level of viscosity and other key

properties over a wide temperature range. The key benefit of selecting a high-performance fluid is a reduction in the total cost of equipment ownership and avoiding a seasonal change of hydraulic fluids.

To reflect the relationship between fluid performance and fluid viscosity/temperature, the National Fluid Power Association (NFPA) in the USA introduced the concept of temperature operating window (TOW). In practical terms, the operating viscosity for most pumps and motors ranges from 10 to 750 mm²/s (see Graph 1). However, the viscosity range in which hydraulic equipment performs best, that is, at its optimum operating viscosity, is much narrower and ranges from 15 to 50 mm²/s. For example, a Bosch-Rexroth A10 piston pump works optimally with a fluid viscosity between 16 to 36 mm²/s.

As fluid viscosity is a function of temperature, it is essential to make sure that the fluid viscosity stays in the optimal range over the entire TOW. The viscosity index (VI) of a fluid (calculated using ASTM D 2270) can be used to describe, in terms of viscosity change with temperature, this performance. The VI reflects the viscosity-temperature relationship of a hydraulic fluid and its ability to maintain an optimal operating viscosity: the higher the VI, the larger the operating temperature band, or TOW, and thus the larger the optimum operating temperature band. This is illustrated in Graph 2, in which the TOW and the optimum temperature range for the high VI fluid is significantly larger than that of the monograde with a lower VI.

A high VI is a necessary precondition for improving pump efficiency over the hydraulic system’s lifetime and under its severe operating conditions (pressure and temperature). Note that the efficiency boost requires that the high VI of the fluid does not significantly reduce in the high shearing conditions found inside the hydraulic pump. Poor quality high VI fluids will exhibit high temporary and permanent VI loss and no efficiency gain (see the “Shear Stability” phenomenon in the viscosity index improvers section).

To be more precise, the efficiency of pumps in hydraulic systems results from a combination of volumetric and hydromechanical efficiency. Volumetric efficiency is related to flow losses via

external and internal leakages, while mechanical efficiency is dependent on frictional losses and viscous drag. Both components of efficiency are functions of pressure, speed and viscosity. Hence, the overall efficiency shows a strongly non-linear behavior, as shown in Graph 3.

Owners, users and operators of hydraulic equipment increasingly focus on maximizing the efficiency of the hydraulic system. As previously explained, this maximum is reached only in a narrow viscosity range, and high VI fluids widen the corresponding temperature range in which this optimum efficiency is achieved.

Graph 1: Illustration of the viscosity impact on operating conditions

Visc

osity

(mm

2 /s)

10,000

5,000

1,000

500

100

50

10

5

1

Optimum range

Increasing hydrodynamic friction

Overheating

Sluggish operation

Poor flow

Cavitation Equipment failure

High wear Equipment failure

Graph 2: Illustration of the kinematic viscosity as a function of the temperature

-20 0 20 40 70 100Temperature (˚C)

1000

100

20

10

5

3

Kine

mat

ic v

iscos

ity (m

m2 /

s)

High VI oil Standard HM oil

Maximum start-up viscosity

Minimum operating viscosity

Extended TOWStandard TOW

ISO 46

Graph 3: Illustration of overall efficiency of viscosity

Hydromechanical efficiency ɳHM Volumetric efficiency ɳV Overall efficiency ɳOv

Effici

ency

Viscosity

Optimum operating range

Poor volumetric efficiency

High frictional losses

ɳOv = ɳV * ɳHM

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Viscosity index improvers — How to boost the fluid‘s viscosity indexIn the previous section, we have seen that the higher a fluid’s viscosity index (VI), the better its viscometric performance (broader temperature operating window and higher pump efficiency). In order to boost the VI of hydraulic fluids and improve their performances, specially designed polymers called viscosity index improvers (VII) can be added to the formulation.

These copolymers are composed of various types of methacrylic esters with different alcohol chain lengths. The preferred molecular structure greatly depends on the application requirement and can be adjusted to fine-tune oil solubility and low-temperature performance. Polymethacrylates (PMA) are the most widely-used chemistry in hydraulic fluids as they offer the highest VI lift and excellent viscosity-temperature behavior in a variety of base oils and viscosity grades (see Figure 6). This is well illustrated by Graph 4, which shows a comparison of the viscosity performances of PMA VII versus olefin copolymer (OCP) VII in Group II base oil.

In this graph, the relative specific viscosity, e.g. the thickening power of the VII, is reported as a function of the temperature. At similar treat rates (using 100 % active VII), we observe that the viscosity contribution of VIIs based on OCP decreases with increasing operating temperature, whereas the viscosity contribution based on PMA increases. It is particularly relevant as equipment protection during operations at high temperatures is only possible when the viscosity stays high enough to protect the hydraulic system mechanisms. This protection is provided by the PMA VII. In contrast, at low temperatures, hydraulic fluids have high viscosity and do not require additional thickening by additives. In this respect, PMAs show substantial temperature-viscosity benefits over OCPs, and consequently, at similar treat rates, the viscosity indices of the fluids are higher using PMA rather than OCP technology.

To understand the VII mechanism, it is important to know that polymers dissolved in a solvent, such as in hydraulic fluid, adopt nanoscale solvated coil structures, having an ellipsoid or spherical shape, known as hydrodynamic spheres. These spheres increase the fluid resistance to moving (= viscosity) as they increase the friction forces between the internal fluid layers.

Figure 7: Effect of the temperature on the polymer coil structure

Graph 4: Relative specific viscosity as a function of the temperature between PMA and OCP VII in Group II oils (KV40 32 mm2/s)

0 50 100

Temperature (˚C )

1.0

0.8

0.6

0.4

0.2

0.0

PMA (5 wt%) OCP (4 wt%)

Rela

tive

spec

ific

visc

osity

VI 137

VI 171

Figure 6: Typical polyalklymethacrylate structure

CH 3

CO2R CO2R

CH 3

( CH2 - C )x ( CH2 - C )y

The greater the expansion in the size of the coil, the stronger the sum of its intermolecular forces, and the higher the viscosity of the hydraulic fluid. The size of the hydrodynamic spheres depends on many parameters, such as their affinity for the oil matrix, the polymer chain length, structure and composition, the shear rate prevailing in the fluid and the fluid temperature and pressure.

Whereas many of these parameters are fixed by the fluid formulation, temperature is the one dominating parameter affecting the viscosity of the fluid while the hydraulic system is in operation. In many applications, VIIs have to work and perform over a wide range of temperatures, sometimes experiencing conditions ranging from - 40°C to + 100°C. High performance VIIs must be carefully designedto address these extreme conditions.

By fine-tuning the polymer chemistry, VIIs are able to tightly coil at low temperatures, contributing relatively little to the fluid viscosity. At higher temperatures, they occupy a larger hydrodynamic volume, increasing the fluid viscosity to protect equipment’s moving parts. This effect is reflected in the VI number of the fluid. The coil structure of a well-designed VII is strongly dependent on the temperature.

Besides temperature changes, pressure and shear also affect viscosity. Advances in hydraulic system technology have led to an increase in operating pressure and power density. This results in a high fluid pressure gradient across the solvated polymer hydrodynamic volume that can result in “shear” distortion or breakage of the polymer coils.

This “shear” manifests itself as a reduction in the fluid viscosity and can be either temporary or permanent. Distortion of the polymer hydrodynamic volume is reversible and causes a temporary viscosity reduction. When shearing is stopped, the fluid viscosity immediately recovers. However, stronger shearing forces can cause the polymer to be permanently damaged, (chemical bonds are broken) and here the viscosity reduction is permanent.

The bigger the hydrodynamic spheres (high molecular weight), the higher the shear stress experienced by the polymer. This reduction in viscosity due to shear leads to a decreased TOW, an increased likelihood of wear and reduced efficiency.

The impact of shear stress on the hydraulic fluid viscosity is illustrated in Graph 5 and 6. Here, the viscosity of two high VI formulations in a high shear hydraulic system are compared over operating time. The operational viscosity, that is, the viscosity as experienced inside the hydraulic pump, is a combination of both permanent and temporary viscosity losses. The formulation in Graph 5 is made using a highly shear stable VII, whereas the second one uses a low-shear stable VII (Graph 6).

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Typical formulations of hydraulic fluidsTypical hydraulic fluids are composed of base fluid, VI improvers (when required) and specific additives.

The base fluids range from Group I to V as classified by the API (American Petroleum Institute). Groups I, II and III are derived from crude oil and the higher the group, the higher the degree of refinement (quality). Group IV contains polyalphaolefin (PAO) fluids. Group V includes all other base fluid types. Base fluid typically represents 85 to 99 wt% of the composition of hydraulic fluids.

Viscosity index improvers and pour point depressants are polymer-based additives, which together can count for as much as 15 wt% of the formulation. The final hydraulic fluid formulation also includes anti-oxidants, rust- and corrosion inhibitors, anti-wear agents, demulsifiers, yellow metal inhibitors and anti-foam agents. Together, these specific additives account for less than 1 wt% of the final formulation.

Table 5: Typical formulations for hydraulic fluid

Range Example

Viscosity index improver 0.0 - 15.0% 8.0%VISCOPLEX®

Pour point depressant 0.1 - 0.5% 0.3%

Corrosion inhibitor 0.1 - 1.0%

0.9%Anti-wear 0.4 - 2.0%

Antioxidant 0.1 - 0.5%

Antifoam 2-20 ppm 60 ppm VISCOPLEX®

Base fluid 85.0% - 99.0% 90.8%

In both graphs, it can be observed that the viscosity drop, due to permanent shear losses, builds up over time; however, in Graph 5 the permanent shear loss eventually levels out quite rapidly, whereas the less shear stable VII (Graph 6) drops to lower viscosity values.

These two effects combined have been shown to remain constant over the life of the fluid, meaning the detrimental influence of the less shear stable VII on pump operation and efficiency is immediately apparent. The combined permanent and temporary line in Graph 6 shows this.

This is why it is important to use shear stable VIIs in hydraulic oils. Fluids using less shear stable VIIs will have poor performance even when new and before permanent shearing has progressed.

There are three main methods for measuring shear effect.

1. The Bosch Injector Test (DIN 51382) run for 250 cycles at2550 psi. This is considered the least severe shear test appliedto hydraulic fluids.

2. The Sonic Shear Test (ASTM D5621) shears the samplehydraulic fluid for 40 minutes in a sonic oscillator.

3. The KRL Tapered Roller Bearing Test (ISO 26422) requiresthe test oil to run in a fitted tapered roller bearing for 20hours under the design load.

Measuring the tendency of a hydraulic fluid to lose viscosity on shearing is an important indicator of the fluids fit for purpose. Polymer shear stability is indicated by the permanent shear stability index (PSSI). It represents the percentage of viscosity lost by a fresh fluid after shearing. The lower the index, the more shear stable the VII. As the different methods for measuring the shear effect apply different shear force on the polymer, the PSSI varies depending on the used method.

VIIs having a PSSI below 20 using the Sonic test, or below 40 using KRL, are considered to be highly shear-stable. They enable the formulation of lubricants meeting the most severe OEM requirements. High-performance VIIs are optimized to have a good balance between molecular weight (boosting the viscosity) and shear losses.

Units conversion matrix:

• Temperature°F = °C x 1.8 + 32

• Pressure1 psi = 0.069 bar1 psi = 6895 Pa

• Viscosity1 mPa·s = 1 cP1 mm²/s = 1 cSt

Graph 5: Viscosity of high VI HF with high shear stable VII under high shear

Fresh oil viscosity, KV40 (ISO grade)

VII contribution to viscosity

Base oil viscosity

Operating time

Permanent viscosity loss Temporary viscosity loss "used" oil viscosity "in-service" oil viscosity

Visc

osity

Graph 6: Viscosity of high VI HF with low shear stable VII under high shear

Fresh oil viscosity, KV40 (ISO grade)

VII contribution to viscosity

Base oil viscosity

Operating time

Permanent viscosity loss Temporary viscosity loss "used" oil viscosity "in-service" oil viscosity

Visc

osity

14 15

ISO 32, VI 140

Formulations UnitVISCOPLEX® 8-360

VISCOPLEX® 8-400

VISCOPLEX® 8-407

VISCOPLEX® 8-450

VISCOPLEX® 8-610

VII wt% 3.00 3.00 2.80 2.50 2.30

Package wt% 0.85 0.85 0.85 0.85 0.85

PPD VISCOPLEX® 1-254 wt% 0.20

Base Oils

Gr. I 100N wt% 30.00 40.00 41.00 42.00 40.00

Gr. I 150N wt% 65.95 56.15 55.35 54.65 56.85

Gr. I 600N wt%

Data Method Unit Result Result Result Result Result

KV40 ASTM D 445 mm2/s 32.92 32.59 32.20 32.52 32.06

KV100 ASTM D 445 mm2/s 6.2 6.19 6.11 6.16 6.06

VI ASTM D 2270 142 142 140 140 139

Pour Point ASTM D 5949 °C -42 -42 -45 -42 -42

Brookfield (-26°C) ASTM D 2983 mPa·s 4,200 3,900 4,900 3,700 4,900

Shear Stability, Viscosity Loss at 100°C:

Bosch 250 Cycles DIN 51382 % 5 4 3 5 6

Sonic Shear 40 min ASTM D 5621 % 11 10 10 12 13

KRL 20h ISO 26422 % 14 14 14 15 16

PPD = Pour Point Depressant

ISO 46, VI 140


VISCOPLEX® 8-219

VISCOPLEX® 8-300

VISCOPLEX® 8-310

VII wt% 5.60 5.80 4.00 4.00

Package wt% 0.85 0.85 0.85 0.85

PPD VISCOPLEX® 1-254 wt% 0.20 0.20

Base Oils

Gr. I 100N wt% 6.90

Gr. I 150N wt% 86.65 89.00 88.15 86.95

Gr. I 600N wt% 4.15 7.00 8.00

Data Method Unit Result Result Result Result

KV40 ASTM D 445 mm2/s 46.58 46.09 46.33 46.38

KV100 ASTM D 445 mm2/s 7.90 7.88 7.83 7.92

VI ASTM D 2270 140 142 139 142

Pour Point ASTM D 5949 °C -42 -45 -39 -45

Brookfield (-26°C) ASTM D 2983 mPa·s 7,400 9,100 5,300 8,100


Bosch 250 Cycles DIN 51382 % 0 0 2 3

Sonic Shear 40 min ASTM D 5621 % 6 6 9 10

KRL 20h ISO 26422 % 13 13 17 17


ISO 46, VI 140


VISCOPLEX® 8-400

VISCOPLEX® 8-407

VISCOPLEX® 8-450

VISCOPLEX® 8-610

VII wt% 3.30 3.60 3.40 3.10 2.90

Package wt% 0.85 0.85 0.85 0.85 0.85


Base Oils

Gr. I 100N wt%

Gr. I 150N wt% 79.55 84.55 84.00 87.05 82.25

Gr. I 600N wt% 16.10 11.00 11.75 9.00 11.00


KV40 ASTM D 445 mm2/s 46.16 46.64 46.68 46.28 46.09

KV100 ASTM D 445 mm2/s 7.85 7.89 7.89 7.89 7.86

VI ASTM D 2270 141 140 139 141 141




Bosch 250 Cycles DIN 51382 % 5 4 3 6 7


KRL 20h ISO 26422 % 15 16 16 17 19


Examples of formulations meeting DIN 51524-3 (HVLP)

ISO 32, VI 140


VISCOPLEX® 8-219

VISCOPLEX® 8-300

VISCOPLEX® 8-310

VII wt% 4.60 4.70 3.30 3.20

Package wt% 0.85 0.85 0.85 0.85


Base Oils

Gr. I 100N wt% 48.00 52.00 46.00 47.00

Gr. I 150N wt% 46.55 42.25 49.85 48.75

Gr. I 600N wt%


KV40 ASTM D 445 mm2/s 32.46 32.46 32.51 32.03

KV100 ASTM D 445 mm2/s 6.15 6.17 6.14 6.10

VI ASTM D 2270 141 142 140 141


Brookfield (-26°C) ASTM D 2983 mPa·s 3,600 5,300 3,800 4,300


Bosch 250 Cycles DIN 51382 % 0 0 2 2


KRL 20h ISO 26422 % 10 11 15 14


16 17

ISO 68, VI 140


VISCOPLEX® 8-400

VISCOPLEX® 8-407

VISCOPLEX® 8-450

VISCOPLEX® 8-610

VII wt% 4.30 4.50 4.40 3.80 3.60

Package wt% 0.85 0.85 0.85 0.85 0.85


Base Oils

Gr. I 100N wt%

Gr. I 150N wt% 50.65 57.15 54.75 58.35 56.55

Gr. I 600 N wt% 44.00 37.50 38.00 37.00 39.00


KV40 ASTM D 445 mm2/s 68.14 68.52 68.80 68.37 68.01

KV100 ASTM D 445 mm2/s 10.42 10.50 10.48 10.51 10.39

VI ASTM D 2270 140 141 140 142 140




Bosch 250 Cycles DIN 51382 % 5 4 4 6 8


KRL 20h ISO 26422 % 18 19 19 19 21


ISO 32, VI 160


VISCOPLEX® 8-219

VISCOPLEX® 8-310

VISCOPLEX® 8-360

VISCOPLEX® 8-407

VISCOPLEX® 8-610

VII wt% 6.00 6.40 4.30 3.80 3.80 3.00

Package wt% 0.85 0.85 0.85 0.85 0.85 0.85

PPD VISCOPLEX® 1-254 wt% 0.20 0.20 0.20 0.20

Base Oils

Gr. II 4 cSt at 100°C wt% 67.00 68.75 63.50 52.00 60.00 58.45

Gr. II 6 cSt at 100°C wt% 26.15 23.80 31.15 43.15 35.35 37.50

Gr. II 12 cSt at 100°C wt%

Data Method Unit Result Result Result Result Result Result

KV40 ASTM D 445 mm2/s 32.34 32.78 32.40 32.20 32.37 32.25

KV100 ASTM D 445 mm2/s 6.50 6.59 6.525 6.47 6.50 6.48

VI ASTM D 2270 159 161 161 159 159 159

Pour Point ASTM D 5949 °C -42 -51 -54 -48 -54 -54

Brookfield (-26°C) ASTM D 2983 mPa·s 2,400 2,400 2,400 2,600 2,500 2,700


Bosch 250 Cycles DIN 51382 % 0 0 2 3 3 6

Sonic Shear 40 min ASTM D 5621 % 6 5 9 10 10 14

KRL 20h ISO 26422 % 12 12 15 15 16 18


ISO 46, VI 160


VISCOPLEX® 8-219

VISCOPLEX® 8-310

VISCOPLEX® 8-360

VISCOPLEX® 8-407

VISCOPLEX® 8-610

VII wt% 7.60 8.00 5.50 5.00 4.80 3.90

Package wt% 0.85 0.85 0.85 0.85 0.85 0.85

PPD VISCOPLEX® 1-254 wt% 0.20 0.20 0.20 0.20

Base Oils

Gr. II 4 cSt at 100°C wt% 29.00 31.30 25.50 10.75 19.50 17.00

Gr. II 6 cSt at 100°C wt% 62.55 59.65 67.95 83.20 74.85 78.05


Data Method Unit Result Result Result Result Result ResultKV40 ASTM D 445 mm2/s 46.32 46.82 46.06 46.24 46.44 46.48

KV100 ASTM D 445 mm2/s 8.44 8.52 8.43 8.45 8.43 8.45

VI ASTM D 2270 161 161 161 161 160 160




Bosch 250 Cycles DIN 51382 % 0 0 3 4 3 7


KRL 20h ISO 26422 % 15 14 18 18 19 21


ISO 68, VI 140


VISCOPLEX® 8-219

VISCOPLEX® 8-300

VISCOPLEX® 8-310

VII wt% 7.00 7.20 4.90 5.00

Package wt% 0.85 0.85 0.85 0.85


Base Oils

Gr. I 100N wt%

Gr. I 150N wt% 57.65 61.75 58.65 59.30

Gr. I 600 N wt% 34.50 30.00 35.60 34.65


KV40 ASTM D 445 mm2/s 68.37 68.10 68.61 68.20

KV100 ASTM D 445 mm2/s 10.35 10.39 10.42 10.43

VI ASTM D 2270 138 139 139 140


Brookfield (-26°C) ASTM D 2983 mPa.s 13,800 23,000 14,600 21,000


Bosch 250 Cycles DIN 51382 % 0 0 2 3


KRL 20h ISO 26422 % 12 14 18 18


18 19

Feel the power with DYNAVIS® technology — Let it flow.DYNAVIS® technology from Evonik’s Oil Additives team contributes to fuel and energy savings in industrial and off-highway equipment. In carefully designed and monitored field tests, hydraulic fluids formulated with DYNAVIS® technology have achieved up to double-digit percentage improvements in fuel savings, reducing operating costs as well as CO2 emissions.

Hydraulic equipment operating with DYNAVIS® formulated fluids have credibly demonstrated their potential to achieve the following:

• Up to 30% more hydraulic power under full-load conditions

• Up to 30% lower energy consumption to complete the same amount of work

• Faster response to operator control

• More stable oil temperature

ISO 32 / 46 / 68, VI 180

Gr. I / III Gr. III

Formulations Unit ISO VG 32 ISO VG 46 ISO VG 68 ISO VG 32 ISO VG 46 ISO VG 68

VISCOPLEX® 8-200 wt% 8.30 10.50 13.90

VISCOPLEX® 8-219 wt% 7.50 10.00 13.20

Package wt% 0.85 0.85 0.85 0.85 0.85 0.85

Base Oils

Gr. I 100N wt% 44.40

Gr. I 150N wt% 1.50 44.65 40.00

Gr. I 600N wt% 2.25

Gr. III 4 cSt wt% 45.45 37.00 70.50 23.00

Gr. III 6 cSt wt% 7.00 42.75 21.15 66.15 62.00

Gr. III 8 cSt wt% 23.95


KV40 ASTM D 445 mm2/s 32.37 46.14 68.91 32.22 46.42 68.23

KV100 ASTM D 445 mm2/s 6.890 8.99 12.33 6.86 9.01 12.28

VI ASTM D 2270 181 180 179 181 180 180




Bosch 250 Cycles DIN 51382 % 0 0 0 0 0 0


KRL 20h ISO 26422 % 16 19 22 12 14 18

ISO 68, VI 160


VISCOPLEX® 8-219

VISCOPLEX® 8-310

VISCOPLEX® 8-360

VISCOPLEX® 8-407

VISCOPLEX® 8-610

VII wt% 10.10 10.70 7.40 6.60 6.30 5.10

Package wt% 0.85 0.85 0.85 0.85 0.85 0.85

PPD VISCOPLEX® 1-254 wt% 0.20 0.20 0.20 0.20

Base Oils


Gr. II 6 cSt at 100°C wt% 85.05 86.95 83.00 66.80 76.45 74.35

Gr. II 12 cSt at 100°C wt% 4.00 1.30 8.55 25.55 16.40 19.50


KV40 ASTM D 445 mm2/s 68.34 69.48 67.99 68.25 68.86 68.25

KV100 ASTM D 445 mm2/s 11.33 11.48 11.37 11.32 11.34 11.32

VI ASTM D 2270 160 160 161 160 159 160




Bosch 250 Cycles DIN 51382 % 0 0 3 4 3 8


KRL 20h ISO 26422 % 18 17 20 20 22 25


This information and all further technical advice is based on our present knowledge and experience. However, it implies no liability or other legal responsibility on our part, including with regard to existing third party intellectual property rights, especially patent rights. In particular, no warranty, whether express or implied, or guarantee of product properties in the legal sense is intended or implied. We reserve the right to make any changes according to technological progress or further developments. The customer is not released from the obligation to conduct careful inspection and testing of incoming goods. Performance of the product described herein should be verified by testing, which should be carried out only by qualified experts and is the sole responsibility of the customer. Reference to trade names used by other companies is neither a recommendation, nor does it imply that similar products could not be used.

VISCOPLEX® and DYNAVIS® are registered trademarks of Evonik Oil Additives GmbH.©08/2016 Evonik Industries AG - v10

Asia Pacific Evonik Oil Additives Asia Pacific Pte. Ltd. 3 International Business Park 07-18 Nordic European Centre Singapore 609927phone +65 6809-6571 fax +65 6809-6707

Americas Evonik Oil Additives USA, Inc. 723 Electronic Drive Horsham, PA 19044-4050 USAphone +1 215 706-5800 fax +1 215 706-5801Toll-free +1 888 876-4629

Europe, Africa, Mideast Evonik Resource Efficiency GmbH Kirschenallee 64293 Darmstadt Germanyphone +49 6151 1809 fax +49 6151 18-4100

[email protected]/oil-additives

Hydraulic fluids treatise fluids...Principles of hydraulic system function — quality and high...

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