Hydraulic Fluid And Temperature Recommendations For Mobile Hydraulic Systems

The oil in a hydraulic system serves as the power transmission medium. It is also the system’s lubricant and coolant. The selection of proper oil is a requirement for satisfactory system performance and life.

In most cases, use of these recommendations will lead to selection of a suitable oil. However, due to the complex nature of oil formulation, the variety of oils available and peculiarities of individual hydraulic applications, there will be rare instances where an oil selected on the basis of these recommendations may yield unsatisfactory results. Vickers cannot be responsible for such exceptions. In this respect, the customer is encouraged to consult his Vickers representative or a reputable oil company when selecting an oil.

Important Factors In Selecting An Oil
Additives
Hydraulic fluids contain a number of additive agents which materially improve various characteristics of oil for hydraulic systems. These additives are selected to reduce wear, increase chemical stability, inhibit corrosion and depress the pour point.

Antiwear
Pump performance and reliability are directly affected by the antiwear additive formulation contained in the oil. Oils providing a high level of antiwear protection are recommended for optimum performance and long life.

Viscosity
Viscosity is the measure of the fluid’s resistance to flow. The oil selected must have proper viscosity to maintain an adequate lubricating film at system operating temperature.

In addition to dynamic lubricating properties, oil must have sufficient body to provide an adequate sealing effect between working parts of pumps, valves,clylinders and motors, but not enough to cause pump cavitation or sluggish valve action. Optimum operating viscosity of the oil should be between 16 cSt (80 SUS) and 40 cSt (180 SUS).

“Viscosity Index” reflects the way viscosity changes with temperature. The smaller the viscosity change, the higher the viscosity index. The viscosity index of hydraulic system oil should not be less than 90. Multiple viscosity oils, such as SAE 10W-30, incorporate additives to improve viscosity index (polymer thickened). These oils should have a minimum viscosity index of 120. Oils of this type generally exhibit both a temporary and permanent decrease in viscosity due to oil shear encountered in the operating hydraulic system. The actual viscosity can, therefore, be far less in the operating hydraulic system than what is shown in normal oil data. Accordingly, when such oils are selected, it is necessary to use those with high shear stability to insure that viscosity remains within recommended limits while in service.

Chemical Stability
Oxidation and thermal stability are essential characteristics of oils for mobile hydraulic systems. The combination of base stocks and additives should be stable during the expected lifetime of the oil when exposed to the environment of these systems.

Suitable Types Of Oil
Crankcase Oil
Oil having an API letter designation SE, SF, SG or SH per SAE J183. Note that one oil may meet one or more of these designations.

Antiwear Hydraulic Oil
These oils are produced by all major oil suppliers and should consist of good quality base stocks compounded with antiwear, antioxidation, antifoam and antirust additives. These may be petroleum, vegetable or synthetic base oil.

Due to the large number of different antiwear hydraulic oils, it is impossible for Vickers to test its products with all of the available fluids. Because of this, an evaluation procedure was developed for fluid suppliers to establish the suitability of their products for use in Vickers components. Refer to “Pump Test Procedure For Evaluation Of Antiwear Hydraulic Fluids For Mobile Systems”, for details of the 35VQ25 test procedure. It is the responsibility of your oil supplier to assure that their fluids meet Vickers requirements.

Environmental Hydraulic Oil
If you have equipment that operates in environmentally sensitive areas, you may consider use of more envionmentally aware fluids. These fluids perform well in our hydraulic systems but may require extra caution in order not to exceed their performance capabilities. For further clarification, refer to Vickers Guide to Alternative Fluids, Bulletin 579.

Other Oils
Certain other types of petroleum oil are suitable if they meet the following provisions:

1. Contain the type and content of antiwear additives found in the above designated crankcase and antiwear hydraulic oils, and have passed the pump tests.

2. Have sufficient chemical stability for mobile hydraulic system service.

3. Meet the viscosity requirements in the Oil Viscosity Recommendations tables.

Hydraulic Fluid and Temperature Recommendations for Industrial Machinery Part 2

General Data

Oil in hydraulic systems performs the dual function of lubrication and transmission of power. It constitutes a vital factor in a hydraulic system, and careful selection should be made with the assistance of a reputable supplier. Proper selection of oil assures satisfactory life and operation of the system components with particular emphasis on hydraulic pumps and motors. Generally, oil selected for use with pumps and motors are acceptable for use with valves. Critical servo valves may need special consideration. Some of the factors especially important in the selection of oil for use in an industrial hydraulic system are:

1. The oil must contain the necessary additives to ensure high antiwear characteristics. Not all hydraulic oils contain these in sufficient amounts.

2. The oil must have proper viscosity to maintain adequate sealing and lubricating quality at the expected operating temperature of the hydraulic system.

3. The oil must have rust and oxidation inhibitors for satisfactory system operation.

Two specific types of oil meet the requirements of modern industrial hydraulic systems:

1. Antiwear type industrial hydraulic oils.  A new generation of industrial hydraulic oils containing adequate quantities of antiwear compound is recommended by VIckers for general hydraulic service.

These oils are generally developed and evaluated on the basis of pump wear tests such as the Vickers 35VQ25A and ASTM D-2882. These oils offer superior protection against pump and motor wear and the advantage of long service life. In addition, they provide good demulsibility as well as protection against rust.

2. Automotive type crankcase oils having API letter designation “SE”, “SF”, “SG”, “SH”, per SAE J183.

The above classes of oils in the 10W and 20-20W SAE viscosity ranges are for severe hydraulic service where there is little or no water present. The only adverse effect is that the “detergent” additive tends to hold water in a tight emulsion and prevents separation of water, even on long time standing.

Automotive type crankcase oils generally exhibit poorer shear stability which could result in some loss of viscosity during their service life. More shear stable multiple viscosity industrial grade hydraulic fluids will provide improved viscosity control.

Over the years, Vickers hydraulic oil recommendations have been based on oils that: (1) provide adequate wear protection, (2) have proper viscosity, and (3) are sufficiently stable to withstand the chemical, thermal and mechanical stresses of severe hydraulic service. There are automotive crankcase oils that are outside of the API SE, SF, SG and SH classes that meet the above basis of recommendation.

With these oils, it is highly desirable to have acceptable data from pump wear tests (35VQ25A and ASTM-D-2882). In exceptional cases where the requirements of speed, pressure, temperature and ambient conditions exceed the recommendations for industrial machinery, please refer to the oil recommendations. These fluids must also pass the Vickers 35VQ25 pump test.

Viscosity

Viscosity is the measure of the fluid’s resistance to flow. The selection of a hydraulic oil of specific viscosity range must be based on the needs of the system, limitations of critical components, or proper performance of specific types of units. Vickers recommends that certain maximum and minimum viscosity ranges of the oil at start-up and during running be maintained. (See chart) Very high viscosities at start-up temperatures can cause noise and cavitational damage to pumps. Continuous operation at moderately high viscosities will tend to hold air in suspension in the oil as well as generate higher operating temperatures. This can cause noise and early failure of pumps, motors and erosion of valves. Low viscosities result in decreased system efficiency and impairment of dynamic lubrication which causes wear.

Choose the proper oil viscosity for your particular system so that over the entire temperature range encountered, the start-up viscosity and the running viscosity range shown in the chart is met. This is important, and assurance should be obtained from your oil supplier that the viscosity of the oil being used will not be less than the minimum recommended at maximum oil temperature encountered.

A number of antiwear hydraulic oils containing polymeric thickeners (V.I. improvers) are available and are used for low temperature application. The temporary and permanent viscosity loss of some of these oils at operating temperature may adversely affect the life and performance of components. Be certain you know the extent of loss of viscosity (shear stability) of polymer containing oils under hydraulic service before using them so that you do not operate below the recommended minimum viscosity. The selection of an oil with good shear stability, is recommended for low temperature applications.

Temperature

To obtain optimum service life from both the oil and the hydraulic system, operate between 49degC (120degF) and 54degC (130degF). The maximum oil temperature normally recommended is 66degC (150degF).

MHT motors are permitted to operate at higher temperatures, but this is permissible by meeting special application requirements. For this service, oils should have antiwear characteristics required to pass pump test on page 20. Pumps can be approved to operate MHT motors at these higher temperatures. Contact your Vickers representative for recommendations.

Cleanliness

Thorough precautions should always be observed to ensure that the hydraulic system is clean.

1. Clean (flush) entire system to remove paint, metal chips, welding shot, lint, etc.

2. Filter each change of oil to prevent introduction of contaminant into the system.

3. Provide continuous oil filtration to remove sludge and products of wear and corrosion generated during the life of the system.

4. Provide continuous protection of system from entry of airborne contamination by proper filtration of air through breathers.

5. During usage, proper oil filling of reservoir and servicing of filters, breathers, reservoirs, etc. cannot be over emphasized.

Sound Level

Noise can be an indication of system problems. Fluid selection and the condition of that fluid in service will affect the noise levels of your systems. Some of the major factors affecting the fluid conditions that cause the loudest noises in a hydraulic system are:

1. Very high viscosities at start-up temperatures can cause pump noises due to cavitation.

2. Running with moderately high viscosity fluid will impede the release of entrained air. The fluid will not be completely purged of such air in the time it remains in the reservoir before recycling through the system.

3. Aerated fluid can be caused by ingestion of air through the pipe joints of inlet lines, high velocity discharge lines, cylinder rod packings, or by fluid discharging above the fluid level in the reservoir. Air in the fluid will cause abnormal noise and wear in your system.

4. Contamination fluids can cause excessive wear of internal pump parts which may result in increased sound levels.

5. Systems using water based fluids are susceptible to noise created by vaporization of the fluid if excessive vacuums and temperatures are encountered.

Fire Resistant Fluids

Hydraulic systems using fire resistant fluids require special engineering considerations. For applications using fire resistant fluids, consult Vickers Guide to Alternative Fluids, Bulletin 579, for the specific component being used or contact your local Vickers representative for assistance.

Proper design, operation and maintenance of fluid power systems is of paramount importance to obtain the optimum performance of fire resistant fluids such as synthetics, water glycol and water-in-oil emulsion types.

Additionally, you should consult your fluid supplier for specific fluid maintenance and application data on their fluid.

Water Based Fluids

General Data

To assure an effective emulsion or solution, the water should not have excessive hardness or have an acid nature, and it should be distilled or deionized with less than 300 parts per million hardness.

Hard water containing excessive mineral content, such as calcium and iron, may cause deposits in the hydraulic system or result in additive separation or emulsion breaking.

Proper maintenance of water containing fluids requires periodic testing for pH, oil and water concentrations. The pH should be maintained at 8.0-9.5 in accordance with the supplier’s recommendation. If the pH number exceeds these limits, discard the fluid. Always use a premixed fluid to replenish the system. The recommended storage or operating temperature range of water containing fluids is 4degC (39degF) to 49degC (120degF), unless otherwise specified by the fluid supplier.

Types Of Water Based Fluids

Invert Emulsions

Invert emulsions are inverted water-in-oil emulsions consisting of a continuous oil phase surrounding finely divided water droplets that are uniformly dispersed throughout the mixture.

Water-Glycol Fluids

Water-glycol fire-resistant fluids are typically water and diethylene glycol mixtures. They have approximately 40% water content.

Oil-In-Water Fluids

Oil-in-water fluids are emulsions of oil and water. When preparing these mixtures, the soluble oil should always be added to the water while maintaining good fluid agitation. The water should never be added to the soluble oil. Do not mix soluble oil brands.

Filters

Many Vickers standard indicating type inlet filters and return line filters are approved with water-based fluid types.

A reduction of predicted life of hydraulic components should be expected when using water-based fluid types.

Synthetic Fluid Type

Phosphate Ester

Phosphate ester type fluids are manufactured from chemically produced esters. These types of fluids require fluorocarbon seals. Consult your fluid supplier for the types of seals which are compatible.

Environmental Hydraulic Oil

If you have equipment that operates in environmentally sensitive areas, you may consider use of more environmentally aware fluids. These fluids perform well in our hydraulic systems but may require extra caution in order not to exceed their performance capabilities.

Hydraulic Fluid and Temperature Recommendations for Industrial Machinery Part 1

Unit Type	Viscosity	Anti-wear Characteristicts
Inline Piston (Pumps & Motors)	lViscosity Grades: 32-68 cSt (150-315 SUS) @ 40degC. (104_F) Running: 13-54 cSt (70-250 SUS) At Start Up: 220 cSt (1000 SUS) Max.	Antiwear type hydraulic oils such as: automotive crankcase oils having API letter designations “SE”, “SF”, “SG”, or “SH” per SAE J183
Angle Piston Vane (Except MHT) Gear (Pumps & Motors)	l Viscosity Grades: 32-68 cSt (150-315 SUS) @ 40degC. (104degF) Running: 13-54 cSt (70-250 SUS) At Start Up: 860 cSt (4000 SUS) Max.
u MHT (High Torque/ Low Speed Vane Motors	l Viscosity Grades: 32-68 cSt (150-315 SUS) @ 40degC. (104degF) Running: 13-54 cSt (70-250 SUS) At Start Up: 110 cSt (500 SUS) Max.

cSt: Centistokes
SUS:Saybolt Universal Seconds
u Adhere to the oil recommendations for MHT units rather than the pumps involved.
l Viscosity Grades are the standard viscosity grades listed in ASTM D-2422 titled “Viscosity System for Industrial Fluid Lubricants”, but any intermediate viscosity is acceptable.

Selection Of Viscosity Grades
Use the following tabulation to determine the temperature extremes between which the viscosity grades can be used to remain within Vickers start–up and running viscosity range recommendations.

The SAE 10W grades fall between the 32 cSt (150 SUS) and 46 cSt (215 SUS) grades and the SAE 20–20W approximates the 68 cSt (315 SUS) grade.

Viscosity Grade 40oC (104oF)	Start Up 860 cSt (4000 SUS)	Start Up 220 cSt (1000 SUS)	Start Up 110 cSt (500 SUS)	Running 54 cSt (250 SUS) Max.	Running 13 cSt (70 SUS) Min.
32 cSt (150 SUS) 46 cSt (215 SUS) 68 cSt (315 SUS)	–12oC (11oF) –6oC (22oF) 0oC (32oF)	6oC (42oF) 12oC (54oF) 19oC (66oF)	14oC (58oF) 22oC (72oF) 29oC (84oF)	27oC (80oF) 34oC (94oF) 42oC (108oF)	62oC (143oF) 71oC (159oF) 81oC (177oF)