زيوت الهيدروليك (انواعها/مواصفاتها/كيفية اعادة تدويرها واستخدامها مرة اخرى)

زيوت أنظمة الهيدروليك

مجموعة تكنولاب البهاء جروب

عميد دكتور

بهاء بدر الدين محمود

استشارى كيميائى

01229834104

وتحتوي هذه الزيوت على مواد تحمي من التآكل والأكسدة والصدأ ، تتميز باستقرارية عالية بسبب تصنيعها من زيوت ذات أساس بارافيني ، موصى بها لمحركات الحركة الذاتية والمكونات الصناعية كما يوصى بها بشكل خاص للتطبيقات الصناعية وتشمل المكائن الانشائية الثقيلة،الكابسات ، والمكائن الانشائية المتحركة ، كذلك مكائن حقن البلاستك ، مكائن السحب ، ضاغطات الهواء

شهادات الهيدروليك هي دن 51524 الثالث وعلى آيزو 6743 / 4 ،أن أف إي 48ـ 603 و 60ـ 203 ، أج في ومطابق لمواصفات محركات فايكر موبيل معهد الطاقة الامريكي

يوصى بزيت الهيدروليك الممتاز في عمليات تغير درجات الحرارة ضمن معدلات واسعة ، وبسبب خاصيته العالية للأنتشار فأنه يوفر تنظيم النظام وهو يحمي من التآكل والصدأ

هيدروليك؟

الهيدروليك ده هو عمليه نقل القدره او الحركه والتوجيه.

الزيوت الهيدروليكيه من اهم خواصها انها بتتحمل ضغوط ودرجات حراره عاليه جدا يعنى ضغط الزيت بيحرك اجسام وبيدى قوه وعزم اقوى من قوى الانسان بكتير .

نص ليتر من الزيت ده بيرفع احمال بتوصل اوزانها للأطنان وبيحرك الاجسام الساكنه لان ضغطه ممكن يوصل لـ 100:200 bar .

- يعنى ايه bar ؟

البار وحده قياس للضغط

طبعا مش اى زيت هيستحمل درجات الحراره العاليه ولا الضغوط العاليه جدا دى عشان كده فى المنظومات الهيدروليكيه بيستخدم زيت خاص للعمليات دى .

الزيوت الهيدروليكيه؟

الزيوت الهيدروليكيه دى نوع من انواع الزيوت المعدنيه وليها خصائص ومواصفات.

-خواص الزيوت الهيدروليكيه:

1-سلوك لزوجى حرارى جيد.......يعنى يقدر يتماسك ويحافظ على لزوجته فى درجات الحراره العاليه.

2- ثبوت ضد قدم الزيت........يعنى حتى لما يقدم الزيت يكون قادر على الشغل لفتره.

3- وقايه جيده من الصدأ...... لازم كمان يكون ليه القدره على مقاومه الصدأبدرجه كبيره.

4- قابليه تحمل الضغوط العاليه.......زى ماقلنا انه بيرفع احمال كبيره وبيتعرض لضغوط عايه جدا لازم يكون جزيئات الزيت قادره على الصمود ومقاومه الانهيار عند الضغوط العاليه دى.

5- تكوين رغوى قليل......الزيوت دى بتبقى رايحه جايه فى الخراطيم والخزان لأنها دايره مغلقه ومع الحركه دى بتكون رغوه فى الزيت ودى ممكن تتسبب فى مشاكل كبيره جدا فى الدائره الهيدروليكيه.

6- امكانيه الانفصال عن الماء....... لأن دى بتسبب حاجه اسمها الاستحلاب ودى ليها مشاكل كتير فى الدائره.

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Hydraulic oils

Hydraulic oil is a fluid lubricant used in hydraulic systems for transmitting power.

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Common hydraulic system consists of:

Oil tank;

Hydraulic pump;

Oil filter;

Control valves;

Pistons;

Pipes.

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The following characteristics and properties are important for hydraulic oils:

Low temperature sensitivity of viscosity;

Thermal and chemical stability;
Low compressibility;

Good lubrication (anti-wear and anti-stick properties, low coefficient of friction);

Hydrolitic stability (ability to retain properties in the high humidity environment);

Low pour point (the lowest temperature, at which the oil may flow);

Water emulsifying ability;

Filterability;

Rust and oxidation protection properties;

Low flash point(the lowest temperature, at which the oil vapors are ignitable);

Resistance to cavitation;

Low foaming;

Compatibility with sealant materials.

Hydraulic systems are widely used in industrial machinery, construction equipment, automotive, aircraft and marine applications.

Types of hydraulic fluids

Viscosity of hydraulic oils

SAE Designation of hydraulic oils by viscosity

ISO Designation of hydraulic oils

Properties of some hydraulic oils

Types of hydraulic fluids

Optimal properties of hydraulic oils are achieved by a combination of a base oil and additives (anti-wear additives, detergents, Anti-oxidants, anti-foaming agents, Corrosion inhibitors etc.).
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Mineral hydraulic oil (petroleum base).

Mineral based oils are the most common and low cost hydraulic fluids.

They possess most of the characteristics important for hydraulic oils.

The disadvantages of mineral (petroleum) based oils are their low fire resistance (low flash point), toxicity and very low biodegradability.

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Phosphate ester based synthetic hydraulic fluids.

Phosphate esters are produced by the reaction of phosphoric acid with aromatic alcohols.

Phosphate esters based hydraulic fluids possess excellent fire resistance, however they are not compatible with paints, adhesives, some polymers and sealant materials.

They are also toxic.

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Polyol ester based synthetic hydraulic fluids.

Polyol esters are produced by the reaction of long-chain fatty acids and synthesized alcohols.

Polyol ester based hydraulic fluids are fire resistant and possess very good lubrication properties.

They are environmentally friendly but their use is limited by high cost.
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Water glycol synthetic hydraulic fluids.

Water glycol based fluids contain 35-60% of water in form of solution (not emulsion) and additives (anti-foam, anti-freeze, rust and corrosion inhibitors, anti-wear etc.).

Water glycol based hydraulic fluids possess excellent fire resistance, they are non-toxic and biodegradable.

However their temperature range is relatively low: 32°F - 120°F (0°C - 49°C).

Water evaporation causes deterioration of the hydraulic fluids properties.

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Vegetable hydraulic oils.

Vegetable hydraulic oils are produced mainly from Canola oil.

Their chemical structure is similar to that of polyol esters.

Vegetable hydraulic oils possess very good lubrication properties and high viscosity index (low temperature sensitivity of viscosity).

They are non-toxic and biodegradable.

The main disadvantage of vegetable hydraulic oils is their relatively low oxidation resistance.

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Viscosity of hydraulic oils

Viscosity of a hydraulic fluid depends on its composition and the temperature.

Low viscosity limit is determined by the lubrication properties of the oil and its resistance to cavitation.

Upper viscosity value is limited by the ability of the oil to be pumped.

Common viscosity of hydraulic oils is in the range 16 - 100 centistokes.

Optimum viscosity value is 16 - 36 centistokes.

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SAE Designation of hydraulic oils by viscosity

The Society of Automotive Engineers (SAE) established a viscosity grading system for oils.

According to the SAE viscosity grading system all oils are divided into two classes:

monograde and multigrade:

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Monograde hydraulic oils

Monograde hydraulic oils are designated by one number (10, 20, 30, 40, etc.).

The number indicates a level of the oil viscosity at a particular temperature.

The higher the grade number, the higher the oil viscosity.

Viscosity of hydraulic oils designated with a number only without the letter “W” (SAE 10, SAE 20, SAE 30 etc.) was specified at the temperature 212°F (100°C).

These oils are suitable for use at high ambient temperatures.

Viscosity of hydraulic oils designated with a number followed by the letter “W” (SAE 10W, SAE 20W, SAE 30W etc.) was specified at the temperature 0°F (-18°C).

The letter “W” means winter.

These grades are used at low ambient temperatures.
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Multigrade hydraulic oils

Viscosity of hydraulic oils may be stabilized by polymeric additives (viscosity index improvers). Viscosity of such oils is specified at both high and low temperature.

These oils are called multigrades and they are designated by two numbers and the letter “W” (SAE 5W30, SAE 10W20, SAE 10W30 etc.).

The first number of the designation specify the oil viscosity at cold temperature, the second number specifies the oil viscosity at high temperature.

For example:

SAE 10W30 oil has a low temperature viscosity similar to that of SAE 10W, but it has a high temperature viscosity similar to that of SAE 30.

Multigrade hydraulic oils are used in a wide temperature range.

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ISO Designation of hydraulic oils

International Standardization Organization (ISO) established a viscosity grading (VG) system for industrial hydraulic oils.

According to the system hydraulic oils are designated by the letters ISO followed by a number equal to the oil viscosity measured in centistokes at 40°C (104°F):

ISO VG 32, ISO VG 46 et
c.

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زيوت الهيدروليك (انواعها/مواصفاتها/كيفية اعادة تدويرها واستخدامها مرة اخرى) Tm-9-410

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موضوع: the Right Hydraulic Fluid الأحد فبراير 10, 2013 4:33 am

the Right Hydraulic Fluid

Most hydraulic systems will operate satisfactorily using a variety of fluids.

These include multigrade engine oil, automatic transmission fluid and more conventional antiwear hydraulic oil.

But which type of fluid is best for a particular application?

While it is not possible to make one definitive recommendation that covers all types of hydraulic equipment in all applications, the following are some of the factors to consider when selecting a hydraulic fluid.

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Multigrade or Monograde

Viscosity is the single most important factor when selecting a hydraulic fluid.

It doesn’t matter how good the other properties of the oil are if the viscosity grade is not correctly matched to the operating temperature range of the hydraulic system.

In this situation, maximum component life will not be achieved.

Defining the correct fluid viscosity grade for a particular hydraulic system involves consideration of several interdependent variables.

These include:

starting viscosity at minimum ambient temperature

maximum expected operating temperature, which is influenced by maximum ambient temperature

permissible and optimum viscosity range for the system’s components

If the hydraulic system is required to operate in freezing temperatures in winter and tropical conditions in summer, then it’s likely that multigrade oil will be required to maintain viscosity within permissible limits across a wide operating temperature range.

If fluid viscosity can be maintained in the optimum range, typically 25 to 36 centistokes, the overall efficiency of the hydraulic system is maximized (less input power is given up to heat).

This means that under certain conditions, the use of a multigrade can reduce the power consumption of the hydraulic system.

For mobile hydraulic equipment users this translates to reduced fuel consumption.

There are some concerns when using multigrade fluids in hydraulic systems.

The viscosity index (VI) improvers used to make multigrade oils can have a negative effect on the air separation properties of the oil.

1 This is not ideal, particularly in mobile hydraulic systems which typically have a relatively small reservoir with correspondingly poor deaeration characteristics.

The high shear rates and turbulent flow conditions often present in hydraulic systems destroy the molecular bonds of the VI improvers over time resulting in loss of viscosity.

When selecting a high VI or multigrade fluid, it is recommended that the hydraulic component manufacturers’ minimum permissible viscosity values be increased by 30 percent to compensate for VI improver sheardown.

This adjustment reduces the maximum permissible operating temperature that would otherwise be allowable with the selected oil and thereby provides a margin of safety for viscosity loss through VI improver shearing.

If the hydraulic system has a narrow operating temperature range and it is possible to maintain optimum fluid viscosity using a monograde oil, it is recommended not to use a multigrade for the reasons stated above.

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Detergent or No Detergent

DIN 51524;

HLP-D fluids are a class of antiwear hydraulic fluids that contain detergents and dispersants.

The use of these fluids is approved by most major hydraulic component manufacturers.

Detergent oils have the ability to emulsify water, and disperse and suspend other contaminants such as varnish and sludge.

This keeps components free from deposits, however, it also means that contaminants do not settle out - they must be filtered out.

These can be desirable properties in mobile hydraulic systems, which unlike industrial systems, have little opportunity for the settling and precipitation of contaminants at the reservoir, due to its relatively small volume.

The main concern with these fluids is that they have excellent water emulsifying ability, which means that if present, water is not separated out of the fluid.

Water accelerates the aging of the oil, reduces lubricity and filterability, reduces seal life and leads to corrosion and cavitation.

Emulsified water can be turned into steam at highly loaded parts of the system.

These problems can be avoided by maintaining water content below the oil’s saturation point at operating temperature.
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Antiwear or No Antiwear

The purpose of antiwear additives is to maintain lubrication under boundary conditions.

The most common antiwear additive used in engine and hydraulic oil is zinc dialkyl dithiophosphate (ZDDP).

The presence of ZDDP is not always seen as a positive, due to the fact that it can chemically break down and attack some metals, and reduce filterability.

Stabilized ZDDP chemistry has largely overcome these shortcomings, making it an essential additive to the fluid used in any high-pressure, high-performance hydraulic system, such as those fitted with piston pumps and motors.

A ZDDP concentration of at least 900 parts per million can be beneficial in mobile applications.

As far as hydraulic oil recommendations go, for commercial reasons relating to warranty, it is wise to follow the equipment manufacturer’s recommendations.

However in some applications, the use of a different type of fluid to that originally specified by the equipment manufacturer may increase hydraulic system performance and reliability.

Always discuss the application with a technical specialist from your oil supplier and the equipment manufacturer before switching to a different type of fluid.

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زيوت الهيدروليك (انواعها/مواصفاتها/كيفية اعادة تدويرها واستخدامها مرة اخرى) Backup10

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Understanding Hydraulic Oil Compatibility

We will soon need to choose a new oil for one of our hydraulic systems but are concerned about the mixing of hydraulic oils.

Do we have reason for concern?

There are dozens of additives available for use when blending hydraulic oils.

Some anti-foam additives, for example, may prevent the buildup of foam on the oil's surface, but at the same time may actually retard the release of air trapped in the bulk oil.

As a result, the mixing of hydraulic oils with different anti‑foam agents may actually increase the foaming of the oil.

Some hydraulic oils may be blended to allow water to mix or emulsify with the oil.

On the other hand, some oils are formulated to ensure that the water separates from the oil.

Therefore, the mixing of hydraulic oils with differing water separation characteristics may cause a reduction in emulsification characteristics or eliminate these characteristics altogether, thereby causing undesirable operating conditions.

Hydraulic oils should be chosen based upon the equipment manufacturer's specifications, keeping in mind the temperature range in which the equipment is to be operated.

Occasionally, the manufacturer's specifications may recommend an oil that may not provide the necessary protection due to unique or unusual operation conditions.

If these situations occur, detailed consultations with the equipment manufacturer and oil supplier, in cooperation with an independent oil analysis laboratory, are recommended.

Generally speaking, however, it is suggested that top-quality hydraulic lubricants should meet the following requirements.

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Oxidation and thermal stability

Hydrolytic stability (which is the ability to resist chemical reactions with any water present)

Anti-rust capability

Demulsibility (the ability to separate water so that excess water can be drained off)

Anti-wear capability (which is critical in today's high-pressure systems)

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Corrosion control

Filterability (should be at least 5 microns to control contamination, particularly for high-pressure systems)

Anti-foam and air-release capability

The oil must be shear stable and must be compatible with seal and hose materials
In addition, hydraulic fluids must be maintained in order to ensure their long life and reliability.

Some recommendations include:

Keep hydraulic fluids cool.

The bulk oil temperature at the exterior of the reservoir should never exceed 60 degrees C (140 degrees F).

Keep hydraulic fluid clean.

There is general agreement among hydraulic experts that 75 to 80 percent of hydraulic system failures are caused by fluid contaminated with dirt, wear particles and other foreign material.

In today's high-pressure systems, clearances between wear surfaces are very small, making contamination control critical.

Keep hydraulic fluid dry.

Water and condensation content should never exceed a maximum of 1,000 ppm, depending on the systems design.

Immediately repair fluid leaks. If oil can escape, dirt and dust can re-enter the system.

Also, a fluid leak of one drop per second is equal to 400 gallons in a 12-month period.

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زيوت الهيدروليك (انواعها/مواصفاتها/كيفية اعادة تدويرها واستخدامها مرة اخرى) 2de56e10

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Contamination of Biobased Hydraulic Oils with Mineral Oil

Tags: contamination control, bio-based lubricants, hydraulics

During the last decade, demand for biobased hydraulic fluids has increased, especially for applications in mobile equipment and in close-to-water stationary installations like movable bridges.

Motivation for the change comes both from users being more conscious about environmental risks and from government policies to create new markets for agricultural products.

One of the major obstacles in this market conversion is the sensitivity of biobased ester fluids or biodegradable fluids (bio-oils) to contamination with traditional mineral hydraulic oils.

Typical situations involve either incomplete flushing during conversion from mineral oil to bio-oil or lack of attention during maintenance and refilling.

This has been motivation to analyze the contamination effects in more detail.

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Effects of Contamination

With mineral oil contamination levels reaching several percent, problems like excess foam generation, poor air release or filter clogging have been reported during conversions.

As a consequence, malfunction or even severe damage to the equipment may occur.

For example, in a movable bridge that had been converted, frequent filter changes were necessary during several months following the conversion, returning to normal intervals after that period.

There have been numerous reports about unsuccessful conversions of hydraulic equipment to bio-oil, yet these reports were mostly undocumented and imprecise.

There is hardly any literature available about this problem.

The experience of hydraulic equipment manufacturers and their fear of expensive warranty claims have resulted in a very cautious and restrictive attitude toward the use of bio-oil.

Biodegradable hydraulic fluids were first standardized by recommendations from the German Machine Manufacturers Association (VDMA), which eventually led to the issue of the international standard ISO 15380.

The ISO 15380 standard requires contamination of bio-oil not to exceed 2 percent in the case of the contaminant being common hydraulic fluid and 1 percent in the case of HLPD or engine oils.

Discussions with fluid manufacturers have suggested that the main deteriorating effects may not even be caused by the mineral oil itself, but by metal containing additives that attack the fatty acids in the ester molecules and eventually lead to the formation of soap-like reaction products.
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Market Situation and Conversion Practices

Biodegradable and biobased hydraulic fluids have been increasing their market share during the last decade.

Despite some progress in the market, the majority of existing mobile equipment still have mineral oil in their hydraulic systems.

Companies that decide to order new machines with bio-oil also want to convert their existing machines, reducing the number of different lubricants in their stock.

Therefore, conversion of used machines from mineral oil to bio-oil has a larger volume presently than the acquisition of new equipment factory-filled with bio-oil.

Mobile hydraulic systems only have little more than half of their fluid volume in the reservoir.

A very large part of the fluid is distributed in piping, cylinders and other hydraulic components.

It is difficult to drain 80 or 90 percent of the fluid without opening connections.

As a consequence, reaching a 98-percent drain result of the old fluid in order to obtain a less than 2-percent contamination level for the new fluid is impossible, unless a major maintenance job requiring complete disassembly is scheduled.

To convert to bio-oil and avoid mixing old and new fluids, hydraulic systems need to be flushed, often several times.

It should be clear that this is an expensive, time-consuming procedure. Furthermore, several disadvantages are associated with the 2-percent rule:

Every bio-oil product is different. Some are more tolerant than others.

Every mineral oil product is different. Some are more aggressive than others.

Every hydraulic system is different. Some by design have more tolerance to contamination than others.

It is difficult to measure the mineral oil content in bio-oil after finishing the flushing procedure.

In addition to these problems, even after successful flushing, contamination risks are also present at later stages, including refilling leakage losses, wrong maintenance instructions, attachment of external equipment and many more.

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Experimental Setup

Experiments at the Institute for Fluid Power Drives and Controls (IFAS) investigated relevant properties of biobased oils contaminated with mineral oils.

The goal was to obtain an insight of how severe the problem is and to gather information about which effects occur at various concentrations and combinations.

For this purpose, 10 different bio hydraulic products of the HETG and HEES types from different manufacturers were selected.

These bio-oils were combined with seven mineral oil products, including a common HLP46 as well as HLPD, HVLP, zinc-free HLP, engine oil SAE 15W-40 and one fossil-based synthetic ester.

Engine oil was added to the choice of mineral contaminants because it is sometimes used as a hydraulic fluid.

It is also mentioned in the conversion guidelines in ISO 15380 (Appendix A) with an even lower limit of 1-percent contamination.

These contaminant fluids were applied in a concentration range between 0.1 and 20 percent, depending on the degree of effects observed during the experiments.

While properties like viscosity, density and the effects on elastic materials used in seals and hoses did not show unexpected changes, it was found that foam generation and filter clogging were the most critical aspects requiring closer investigation.

There was also some effect on air-release properties.

It was clear from a previous test sequence that the reactions would take several hours or days to develop, depending on the temperature.

At a storage temperature of 60 degrees C, most of the reactions were complete within eight hours.

Therefore, all test samples for the following experiments were first submitted to a 20-hour heat treatment at 60 degrees C.

The foam experiments were carried out according to the ASTM D 892 standard, where foam is generated by blowing air into the fluid.

The volume of foam was measured twice, immediately after shutting off the foam generation and again 10 minutes later.

Having the previous heat treatment performed on all samples, only one foam sequence at 24 degrees C was found to be necessary instead of the three sequences at different temperatures as recommended in the standard test procedure.

Filtration experiments were conducted at 25 degrees C with a paper filter having a 1.2-micron pore size and a 47-millimeter diameter.

The pore size was chosen because a growing number of mobile hydraulic systems are equipped with bypass filtering systems with very fine filters.

Flow was forced by a constant vacuum on the downstream side of the filter.

For the experiment, three samples of 60 milliliters each were poured through the same filter, recording the time required for each step.

Obstructions developing in the filter during the process became apparent by increasing throughput times.

Air release was tested according to DIN 51381, which is almost equivalent to ISO 9120.

Air was blown into the fluid under determined conditions.

The test requires the measurement of the time until the air content of the fluid is reduced back to a value of 0.2 percent.

From all bio-oils that were tested, two (numbers 1 and 7) were found to be more sensitive to contamination with mineral oil and were investigated in more detail.

Both were synthetic esters from different manufacturers with 50 percent or more biobased content and good acceptance in the market.
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Visual Inspection

In most cases, visual inspection could provide an early indication of how severe the changes of the properties would be.

Results of the chemical reactions typically appeared as cloudiness, often at the bottom of the container if left still, or as larger particles floating in or on top of the fluid.

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Foam Generation

The foam volume is indicated twice per sample, immediately after the foaming (upper value) and then after a 10-minute settling time (lower value).

In the ISO 15380 standard for bio-oils, the tolerated levels for both are 150 ml and 0 ml, respectively.

The column at the far left is the pure bio-oil, which demonstrates a good value well below the allowed maximum.

Contaminations with hydraulic oils A, B and D show higher but still acceptable results at 2 percent, yet are beyond the allowed maximum at concentrations of 5 percent or higher.

The higher the contaminant concentration, the more foam is present even after 10 minutes.

In the case of engine oil C, even a 0.5-percent contamination (half of that permitted in the ISO standard) results in unacceptable performance.

Interestingly, the last column (zinc-free mineral fluid F) shows that even a contamination as high as 10 percent does not cause any problems in this test.

While bio-oil 1 had good values for foaming in pure condition and was seriously affected by contaminants, bio-oil 7 is average when not contaminated but shows almost unchanged behavior with all contaminants except engine oil C.

In the case of engine oil, a content of only 0.5 percent causes problems.

Since zinc-free mineral oil F seemed not to cause any problems, it was interesting to check the influence of zinc and other metals.

For an overview, both values of each foam test were combined and the sum plotted over the total metal content of the mixtures.

For bio-oil 1, there was an almost linear functional relationship between metal content and foaming problems.

At and beyond 20 micrograms/gram (20 ppm), foaming reached unacceptable levels.

Engine oil has a high calcium content, while many hydraulic oil additives are zinc-based substances.

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Filtration

As described previously, filter experiments resulted in three consecutive throughput times through the same filter.

The bio-oils were first tested in pure condition and then with various contaminants.

Pure bio-oil is easy to filter, and all three passes took the same amount of time.

For bio-oil 1, contaminations with mineral oils A and B showed a light increase and filter clogging tendency at 5 percent, as well as complete clogging at 10 percent.

A clear clogging tendency could be seen with engine oil C at all concentrations from 0.5 percent upward.

Adding zinc-free mineral oil F did not cause any changes with respect to the pure bio-oil even at a 10-percent level.

Bio-oil 7, which was more stable than bio-oil 1 in the foam test, was much more sensitive to mineral oil in the filter test.

A 2-percent contamination with common hydraulic fluid A resulted in progressive filter clogging. In this case, even the zinc-free mineral oil F caused minor problems at 5 percent (half of the concentration used for bio-oil 1).

Filtering became easier again after passing the 10-percent concentration of oil B, which was a detergent HLPD, where at 20 percent there was less filter clogging than with 5 or 10 percent.
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Air Release

Air-release time in the ISO 15380 standard is limited to 10 minutes, a value that is maintained by both bio-oils in pure condition.

Adding mineral oils increases the time measured but only in concentrations beyond 2 percent (beyond 1 percent for engine oil C), which is acceptable.

Like in the foam test, bio-oil 1 initially was better than bio-oil 2 in pure condition but was more sensitive to contamination.

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Conclusion

Some biobased hydraulic fluids sold in the market are sensitive to contamination with common hydraulic fluids.

Problems that occur at higher contamination levels reaching several percent include the formation of reaction products that lead to poor filtering, foaming and air-release properties of the mixture.

It is obvious that the degree of deterioration does not correlate to the amount of mineral oil added but to the amount of metals introduced through the additives present in some of the mineral oil products.

Therefore, the mineral fluids were analyzed for their content of metals: zinc, calcium and magnesium.

The observed effects were specific for different bio-oil products and for different mineral oils.

The effects took several hours or days to develop.
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This has several practical consequences:

The reactions between bio-oils and mineral oils vary in a wide range, depending on the combination of products used.

A 2-percent tolerance level for contamination is a very coarse measure.

Metal-free or zinc-free mineral oil seems not to cause major problems.

The observed delay effect increases the breakdown risk for users, as qualified maintenance personnel may no longer be available when problems appear several hours or days after the conversion of equipment from mineral oil to bio-oil.

As a quality check after conversion, the remaining metal content in the mixture would be much easier to analyze in standard lab procedures than the amount of mineral oil.

A specific metal tolerance index likely could be defined for each bio-oil product, also as a performance indicator for product development, eventually replacing the inflexible 2-percent rule in the ISO 15380 standard.

Table 1. Mineral oils used for contamination experiments

The mineral oils used for contamination experiments will be referenced in the results with letters as shown in Table 1.

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Visual Inspection

Figure 4. Cloudy reaction products (right)

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Figure 5. Floating particles

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موضوع: What are hydraulic fluids الأحد فبراير 10, 2013 5:25 am

What are hydraulic fluids?

Hydraulic fluids are a large group of liquids made of many
kinds of chemicals.

They are used in automobile automatic
transmissions, brakes, and power steering;

fork lift trucks; trac
tors; bulldozers; industrial machinery; and airplanes.

The three
most common types of hydraulic fluids are mineral oil, organo
phosphate ester, and polyalphaolefin.

. (Use of trade names is for identification only

and does not imply endorsement by the Agency for Toxic Sub
stances and Disease Registry, the Public Health Service, or the
U.S. Department of Health and Human Services.)

Some hydraulic fluids have a bland, oily smell and others
have no smell; some will burn and some will not burn.

Certain
hydraulic fluids are produced from crude oil and others are
manufactured.

What happens to hydraulic fluids when they
enter the environment?

� Hydraulic fluids can enter the environment from spills,
leaks in machines that use them, or from storage areas and
waste sites.

If spilled on soil, some of the ingredients in hydraulic
fluids will stay on top and others will sink into the
groundwater.

� In water, some hydraulic fluids' ingredients will transfer
to the bottom and can stay there for more than a year.

� Certain chemicals in hydraulic fluids may break down in
air, soil, or water, but how much breaks down isn’t
known.

� Fish may contain some hydraulic fluids if they live in
contaminated water.

How might I be exposed to hydraulic fluids?

� Touching or swallowing hydraulic fluids.

� Breathing hydraulic fluids in the air near machines where
hydraulic fluids are used.

� Touching contaminated water or soil near hazardous
waste sites or industrial manufacturing facilities that use
or make hydraulic fluids.

How can hydraulic fluids affect my health?

Little is known about how hydraulic fluids can affect
your health.

Since hydraulic fluids are actually mixtures of
chemicals, some of the effects seen may be caused by addi
tives in the hydraulic fluids.

In people, the effects of breathing air with high levels of
hydraulic fluids are not known.

Drinking large amounts of
some types of hydraulic fluids can cause pneumonia, intestinal
bleeding, or death in humans.

Weakness of the hands was seen
in a worker who touched a lot of hydraulic fluids.

Rabbits that inhaled very high levels of one type of hy
draulic fluid had trouble breathing, congested lungs, and
became drowsy.

The nervous systems of animals that swal
lowed or inhaled other hydraulic fluids were affected immedi
ately with tremors, diarrhea, sweating, breathing difficulty,
and sometimes several weeks later with weakness of the limbs,
or paralysis.

The immediate effects are caused because hy
draulic fluids stop the action of certain enzymes, called cho
linesterases, in the body.

There are no reports of people swal
lowing or breathing the types of hydraulic fluids that cause
these effects.

When certain types of hydraulic fluids were put
into the eyes of animals or allowed to touch the skin of
people or animals for short periods of time, redness and swell
ing occurred.

It is not known whether hydraulic fluids can
cause birth defects or reproductive effects.

How likely are hydraulic fluids to cause cancer?

The Department of Health and Human Services (DHHS),
the International Agency for Research on Cancer (IARC), and
the EPA have not classified hydraulic fluids as to their carcino
genicity.

Is there a medical test to show whether I’ve been
exposed to hydraulic fluids?

Hydraulic fluids can’t be measured in blood, urine, or feces,
but certain chemicals in the hydraulic fluids can be measured.

Some of the hydraulic fluids stop the activity of certain en
zymes, called cholinesterases, in blood and this activity can be
measured.

However, many other chemicals also cause this effect.

This test isn’t available at most doctors’ offices, but can be done
at special laboratories that have the right equipment.

Characteristics of a Good Hydraulic Fluid

Viscosity

Viscosity is a measure of a hydraulic fluid's resistance to flow.

It is a hydraulic fluid's most important characteristic and has a significant impact on the operation of the system.

When a hydraulic oil is too thin (low viscosity), it does not seal sufficiently.

This leads to leakage and wear of parts. When a hydraulic oil is too thick (high viscosity), the fluid will be more difficult to pump through the system and may reduce operating efficiency.

All hydraulic fluids must be able to retain optimum viscosity during operation in cold or hot temperatures, in order to consistently and effectively transmit power.

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Compressibility

Compressibility is a measure of the amount of volume reduction due to pressure.

Although hydraulic oils are basically incompressible, slight volume reductions can occur under certain pressure ranges.

Compressibility increases with pressure and temperature and has significant effects on high-pressure fluid systems.

It causes servo failure, efficiency loss, and cavitation; therefore, it is important for a hydraulic oil to have low compressibility.

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Wear Resistance

Wear resistance is a hydraulic fluid's ability to reduce the wear rate in frictional boundary contacts.

Antiwear hydraulic fluids contain antiwear components that can form a protective film on metal surfaces to prevent abrasion, scuffing, and contact fatigue.

Antiwear additives enhance lubricant performance and extend equipment life.

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Oxidation Stability

Oxidation stability is a hydraulic oil's resistance to heat-induced degradation caused by a chemical reaction with oxygen.

Hydraulic oils must contain additives that counteract the process of oxidation, improve the stability and extend the life of the fluid.

Without these additives, the quality of the hydraulic oil will deteriorate quickly.

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Thermal Stability

Thermal stability is the ability to resist breakdown at elevated temperatures.

Antiwear additives naturally degrade over time and this process can be accelerated at higher temperatures.

The result of poor thermal stability is the formation of sludge and varnish which can clog filters, minimize flow and increase downtime.

In addition, as these antiwear agents decompose at high temperatures, acids are formed which attack bronze and yellow metals in piston pumps and other hydraulic system components.

Hydraulic oils can be formulated with very high levels of thermal stability to minimize these issues and help extend the life of the hydraulic fluid and the components of the hydraulic system.

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Filterability

Water can react with additives in hydraulic fluids forming oil insoluble material.

These contaminants can precipitate from the lubricant and block filters, valves and other components resulting in decreased oil flow or the system going on bypass.

Blockage can eventually result in unplanned downtime.

Hydraulic fluids are designed to be filtered with modern filtration systems without fear of the additive being depleted or removed from the system.

This enables systems to stay clean without sacrificing critical performance requirements such as antiwear, rust protection or foam inhibition.

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Rust and Corrosion Protection

In many systems, water can enter as condensation or contamination, and mix with the hydraulic oil. Water can cause rusting of hydraulic components.

In addition, water can react with some additives to form chemical species which can be aggressive to yellow metals.

Hydraulic oil formulations contain rust and corrosion inhibitors which prevent the interaction of water or other chemical species from attacking metal surfaces.

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Foam Resistance

Foam results from air or other gases becoming entrained in the hydraulic fluid.

Air enters a hydraulic system through the reservoir or through air leaks within the system.

A hydraulic fluid under high pressure can contain a large volume of dissolved or dispersed air bubbles.

When this fluid is depressurized, the air bubbles expand and produce foam. Because of its compressibility and poor lubricating properties, foam can seriously affect the operation and lubrication of machinery.

Proper foam inhibitors modify the surface tension on air bubbles so they more easily break up.
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Demulsibility

Water that enters a hydraulic system can mix or emulsify with the hydraulic oil.

If this 'wet' fluid is circulated through the system, it can promote rust and corrosion.

Highly refined mineral oils permit water to separate or demulsify quickly. However, some of the additives used in hydraulic oils promote emulsion formation, preventing the water from separating and settling out of the fluid.

Demulsifier additives are incorporated to promote water separation from hydraulic fluids.

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Hydrolytic Stability

When hydraulic fluids come into contact with water, the water can interact with the additive system of the hydraulic oil resulting in the formation of acids.

Hydraulic fluids that lack hydrolytic stability hydrolyze in the presence of water to form oil insoluble inorganic salts that can block filters and valves inhibiting oil flow.

This can result in hydraulic system failure.

Properly formulated hydraulic fluids are designed to contain additives that are resistant to interactions with water, helping to extend the life of the equipment.

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Seal Compatibility

Leaking hydraulic fluids can cause many issues from simple housekeeping problems to more serious safety concerns and lubrication failures.

Most hydraulics systems utilize rubber seals and other elastomers to minimize or prevent hydraulic oil leakage.

Exposure of the elastomer to the lubricant under high temperature conditions can cause the rubber seals to harden, crack and eventually leak.

On the other hand, hydraulic oil exposure can seals to swell excessively preventing hydraulic valves and pistons from moving freely.

Hydraulic oils are tested against a variety of seal materials to ensure that the hydraulic fluid will be compatible with seals under various conditions.

Hydraulic Oil Properties

Hydraulic systems can be subject to tens of thousands of pounds of pressure under extremely hot or cold conditions.

Choosing the right hydraulic fluid for your application is crucial for system longevity and performance after thousands of work and heat cycles.

There are a number of options when it comes to fluid, and each offers advantages and disadvantages.

What Is Hydraulic Fluid?

Compressibility

Also known as bulk modulus, "compressibility" refers to a fluid's tendency to change volume or density in response to pressure.

Although it may seem strange to think of any fluid compressing, the additives, impurities and microscopic air bubbles in the oil will regularly do so.

In short, a perfect hydraulic fluid would have zero compressibility, but this isn't usually possible because it requires a very thin fluid with almost no additives.

Air Release

Air release is a factor in the fluid's compressibility and heat transfer characteristics.

A very thick hydraulic oil will tend to keep air bubbles trapped inside well after they've been introduced, which is never good.

Detergent Content

Most types of oil contain some sort of detergent that is used to emulsify water and to suspend contaminants that can cause sludge build-up in the system.

This keeps contaminants from turning into deposits and keeps water from causing system damage.

When using a detergent oil, bear in mind that you'll need to filter your oil and keep a close eye on its condition.

Emulsified water can turn into steam under high temperature, which will wreak havoc on your hydraulic system.

Viscosity

Viscosity refers to how well a fluid holds together when allowed to free-flow.

Water has very low viscosity, and maple syrup has high viscosity.

Viscosity almost always diminishes with increased heat, as the molecules of the hydraulic fluid move farther apart.

A delicate balance must be struck in viscosity, as a higher-viscosity fluid makes the system more efficient, but a thinner fluid has better air release and performs better in cold weather.

Although multi-viscosity oils would seem to be the magic bullet answer to this problem, bear in mind that the additives used in them tend to reduce its air-release characteristics.

Multi-viscosity oils are good for high-capacity systems with large reservoirs and good air-release characteristics but should be avoided on smaller systems unless they're needed.

Lubricity

Like most oils, hydraulic oil is also used as a system lubricant where applied.

The base stock of oil itself does not provide very good lubrication, which is why manufacturers use a Zinc dialkyl dithiophosphate (ZnDTP) to increase its lubricity.

Fluids with high levels of ZnDTP (sold commercially as "anti-wear" oil) should only be used in systems that are designed for them, as this chemical can be highly corrosive to some metals.

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