How to Monitor Grease Degradation

Regular readers of Practicing Oil Analysis magazine will be well-versed in the use of oil analysis to determine thermal and oxidative degradation in used oils. Tests such as acid number (AN), Fourier transform infrared (FTIR), and the rotating pressure vessel oxidation test (RPVOT) should be commonplace in any well-designed oil analysis program, allowing oil analysis practitioners to scientifically determine when a condition-based oil change is warranted.

Conversely, little effort has been made to determine how similar analytical techniques can be applied to lubricating greases. While it is a challenge to obtain a representative sample of in-service greases, simple scientific logic suggests that the rate of oxidation of a grease should be measurable to the oxidation of lubricating oils: after all, a grease has the same or similar additives as those found in conventional lubricating oils, bound up with a soap or other thickener.

The value of being able to scientifically monitor grease degradation is clear. While mechanical methods such as sonic and ultrasonic monitoring, shock pulse analysis and high-frequency vibration analysis have proven to be useful in assessing regreasing intervals, little work has been performed to assess the effects of base oil deterioration in greases. However, with high-performance synthetic-based greases becoming increasingly commonplace and industry-leading companies demanding precision lubrication, being able to determine the optimum regrease interval may require paying closer attention to the oxidative and thermal performance of in-service greases.

Determining Grease Oxidation
To evaluate the effectiveness of oil analysis in monitoring the rate of thermal and oxidative degradation of lubricating greases, researchers at the Fundacion Tekniker in Bilbao, Spain devised a series of simple experiments to try to evaluate the effectiveness of some common and not-so-common oil analysis tests in determining grease degradation.

First, they took a conventional lithium grease formulated with a mineral base oil and typical additives found in most general-purpose greases. They then set about artificially inducing oxidation by stressing the grease over a five-hour period at 125°C. Throughout this time, samples were taken at regular intervals and analyzed using a series of analytical methods. By comparing the test results, the research team drew some general conclusions concerning the effectiveness of the various test methods, which may contribute toward the use of these methods in the evaluation of in-service greases.

Testing Methods
To evaluate the degree to which the grease had oxidized, the team applied several different analytical techniques. First, solvent extraction was used to remove the base oil from the grease samples. After extraction, the following standard oil analysis tests were performed:

• Kinematic viscosity – the viscosity of the base oil was determined at both 40°C and 100°C using ASTM D445.
• Acid number – ASTM D974 was performed on the extracted base oil to determine the acid number (AN) of the oil/grease.
• Infrared – after extracting the base oil using ether, a standard infrared spectrum was recorded. The team was particularly interested in the 1,700 to 1,780 cm-1 region, where infrared bands typically appear due to oil oxidation, as well as the 960 to 1,020 and 650 to 690 cm-1 regions, where absorption due to ZDDP, a common antioxidant and antiwear additive in many oils and greases, may be found.
• Inductive coupled plasma spectroscopy (ASTM D 5185) – ICP is commonly used to determine wear metals contaminants and additive elements in used oil samples. The team focused on two elements, Zn and P, to try to measure the degree to which the ZDDP additive had degraded.

The goal of the team was to try to find the simplest, most cost-effective means of providing the information they were searching for. Therefore, they applied two less common techniques, specifically the RulerTM method and direct scanning calorimetry (DSC) in an attempt to evaluate the degree of oxidation.

• Ruler^TM - The RulerTM instrument, discussed in a previous issue of POA, works on the principle of linear sweep cyclic voltammetry. By applying this test method, in which a variable voltage is applied to the sample while measuring the current flow, the presence and concentration of various antioxidant additives (including but not limited to ZDDP) can be determined based on their unique electrochemical oxidation potential and the magnitude of the induced current. This procedure has recently been developed as a full ASTM test procedure under ASTM D6971. Because of its simplicity, this test was performed on both the extracted base oil and the grease (after suitable dilution).
• Direct Scanning Calorimetry (ASTM D5483) - DSC has been used for several years to determine the degree to which greases have degraded. In this procedure, the grease is placed in a sealed vessel and subjected to heat in an oxygen-rich environment, similar to the more common RPVOT test. By monitoring the temperature of the cell, the onset of oxidation can be determined when a sharp rise in heat generation is noted (commonly referred to as the induction point), due to the exothermic nature of the oxidation reaction.

The Results Are In
A summary of the results of this study are presented in In general, most of the analytical techniques showed a significant change throughout the five-hour period when the grease was stressed, exhibiting excellent correlation between the methods. An exception to this are the viscosity readings at 40°C and 100°C, which are not particularly surprising because viscosity is known to be a lagging indicator of oil oxidation.
Of particular interest was the degree of correlation between data obtained using the RulerTM instrument on both the diluted grease and extracted oil samples, the infrared the AN readings measured in the oil, and the Zn and P concentrations from ICP

confirms that as the oil degraded, a significant drop was observed in the ZDDP concentrations, as measured by the Ruler^TM instrument. At the same time, a reduction in the infrared peaks at 620 to 680 cm^-1 and 970 to 1,080 cm^-1 was also observed, along with a reduction in both Zn and P concentrations as determined by ICP, confirming the depletion of ZDDP.

The AN results were also interesting. The initial AN of the extracted oil was found to be approximately 2.4 mg KOH/g oil. As the oil starts to degrade, the AN dropped, particularly around the 80 to 90 minute mark when the other analytical techniques start to show a decrease

However, after the other techniques indicated that the ZDDP was almost completely depleted (around the 100 to 150 minute mark), a slow but noticeable increase in AN was observed.

Again the conclusions are clear. The initial high AN of 2.4 in the new grease is largely due to the mildly acid nature of ZDDP, as measured by the AN test. As the ZDDP depletes due to thermal stress, the AN shows a corresponding drop consistent with this depletion. However, when the ZDDP, which in this case is serving as an antioxidant additive, is depleted it can no longer protect the base oil from oxidizing. As the base oil begins to oxidize (around the 150 minute mark), the AN begins to rise as weak organic acid by-products of base oil oxidation are formed. A similar effect to this is often seen in ZDDP additized hydraulic fluids and other oils containing mildly acidic additives, and is again consistent with the other findings. Note that no change in viscosity was observed, despite the rise in AN.

The correlation of the DSC results with the other techniques was also apparent. Just like the RulerTM data, a clear drop in the DSC induction point was observed around the 80 to 90 minute mark. It remains that DSC is an excellent technique alongside the other methods used in this study to detect the onset of grease degradation.

Conclusions
Based on the results, the team was able to draw some general conclusions regarding the efficacy of the various techniques in monitoring grease degradation:

1.    The Ruler^TM instrument was able to offer a simple field method, which did not require the oil to be extracted from the grease (a time-consuming and complicated process).

2.    While ICP proved effective at monitoring ZDDP depletion in this case, it may not be possible to use this technique where no organometallic additives are present.

3.    Infrared is an effective technique in determining antioxidant additives, provided the absorption bands lie in a relatively clear area of the spectrum (as in this case), and that a new oil base line is available to quantify the degree of infrared absorption of the new grease and the appropriate resonant frequencies.

4.    AN and particularly viscosity measurements are less effective in determining oxidation potential than other techniques (such as infrared and Ruler^TM) that directly measure additive concentrations.

5.    The correlation between Ruler^TM and DSC methods appears to be excellent though further studies may be necessary to recognize if this is applicable in all cases.

6.    Complete depletion of ZDDP appeared to correlate to an approximate 50 percent reduction in Zn and P concentrations in the extracted oil samples, due to the presence of by-products and ZDDP depletion that remain in the oil and still contain elemental Zn and P.

How to Flush Gearboxes and Bearing Housings

How to Flush Gearboxes and Bearing Housings Noria Corporation

Gearboxes and bearing housings periodically need a thorough flushing rather than a simple drain and fill. Several signs point to this requirement, such as overheating of the sump, gross liquid or solid contamination, and development of a severe wear pattern. Material evidence in the form of sludge, rust, moisture, wear metals, gel or other viscous residue that is present at the beginning of the drain should confirm to the technician that a flush is in order. A thorough flush is also useful for removing construction and assembly contaminants from equipment sumps prior to commissioning.

With these factors in mind, what constitutes a thorough sump flush? Are there any particular problems that the operator should be careful to avoid? What equipment can or should be used for this purpose? Finally, what items should be included in a detailed flushing procedure?

Flushing
Flushing is a clean fluid circulation process designed to remove water, chemical contaminants, air and particulate matter (not fixed to surface) resulting from construction, normal ingression, internal generation or component wear.

Flushing can be useful in many different circumstances, such as the following:

For new or rebuilt machines to remove contamination resulting from manufacture, service or overhaul. The fluid system can be contaminated due to dirty assembling elements, corroded surfaces, water, oxidation products and incompatible elastomers such as seals, sealants and coatings. Also, during the assembly process, dirt is ingested and debris is generated due to threading, joining, welding, etc.

For in-service machinery after an oil change due to heavy fluid contamination, component failure, extremely degraded lubricant (oxidation), or if a system flushing has not been performed in the past three years.

For gearboxes and bearing housings that are not fitted with filtration, flushing is required to remove contamination and sediment. Water, rust, excessive wear debris, sludge, varnish or lacquer, and hard-to-open drain ports suggest system contamination and indicate the need for a thorough flush. Ten percent of the old contaminated or depleted lubricant may be enough to use up most of the additives of the new oil.

What Flushing Removes
Material attached to contact or noncontact surfaces that may be harmful to lubricants or critical working surfaces is generically called soil. Soil may be composed of material that is generated internally, such as varnish, carbon deposits, chemical residues, sludge and rust; or material that is generated externally, such as scale, welding slag, rust, machining swarf and metal debris.

Soils may be mechanically or chemically removed. Flushing is a type of high-pressure, high-flow fluid circulation used to generate physical movement of contaminants. As the pressures/flow is used for flushing, circulating clean fluid in the system cannot clean rust and scale from the piping, deburr machined elements or remove flux or weld slag.

Flushing Methods
Three levels of system flushing are practiced, depending on the machinery internal conditions and type of contaminants compromising the system. Figure 1 provides a summary of different flushing approaches that may be used and various circumstances and criteria associated with each method.

Recirculation cleaning – The recirculation of clean fluid at a high velocity to achieve a turbulent flow helps remove contamination from the fluid system.

Power flushing - A variation of recirculation, where the oil level in the sump is reduced and a high-velocity fluid is applied to mechanically dislodge, lift and entrain particulate debris. Power flushing suspends and transports particles; absorbs air, chemical products and water from the system; and releases the contaminants to a filter.

Wand flushing - A wand attached to one of the cart hoses is used to discharge at high pressure (kicking up adherent debris). The flow is then reversed and the wand vacuums the sediments.

Solvent cleaning – The use of solvents to remove organic deposits that cannot be removed by recirculation. Solvent cleaning may incorporate the use of organic (hydrocarbon-based) halogenated, nonhalogenated and blends solvents (type A-1 cleaners such as kerosene, or A-2 cleaners such as naphtha and Stoddard solvent are common) to dissolve heavily crusted or layered carbon residues.

Organic solvents tend to be blends of aliphatic and aromatic hydrocarbons and dissolve soil as opposed to emulsifying soil. These materials may be warranted if evidence of heavy carbonaceous residue exists.

Chemical cleaning – The use of chemicals that can dissolve inorganic components. Chemical cleaning may incorporate the use of aqueous alkali or acid solutions to accomplish the desired result.

Regardless of the flushing compound/fluid selected, unless it is identical to the lubricant used following the flush, it is important that all of the flushing fluid be removed from the sump prior to final fill. Some petroleum solvents with a concentration of five percent can create an appreciable thinning effect on the lubricant viscosity.

Factors for Effective Flushing
Fluid Properties. Fluid solubility and hygroscopic characteristics influence removal efficiency of water, air and chemical contaminants. Most oil companies supply special flushing fluids (rust-inhibited oils with good solvency power) that demonstrate the following desirable properties:

• compatible with system components and lubricating fluid
• noncorrosive to machine components
• low viscosity (lower than the lubricating oil used in the system)
• high density to suspend particles
• low surface tension to eliminate air
• high solvency
• hygroscopicity (for water removal)
• nonflammable
• economical
• reclaimable

Fluid Turbulence. To remove particles, the flushing process depends on the lift forces, drag forces and the depth of the laminar sublayer in the stagnant fluid next to the conduit wall.

As seen in Figure 1, turbulence can have a significant influence on loosely attached solid debris lingering in crevices or in the sidewall perimeter low-flow area. Turbulence in the system shortens the time and improves the quality of the flushing activity.

To properly achieve particle removal, the fluid must be turbulent. The indexless Reynolds number measures turbulence. In general, a number greater than 4,000 represents turbulent flow, and a number less than 2,000 represents laminar flow. Hydraulic and circulation system designers strive to create laminar flow conditions. For gearbox and bearing housings fed with a central system, turbulence is necessary. For stand-alone housings, the effect of turbulence and the ability to direct the force of the fluid facilitates movement of soil.
The Reynolds number can be calculated by:

Nr = 3160*GPM/CS*D

Where GPM = flushing fluid flow rate in gallons per minute

CS = flushing fluid viscosity – centistokes at 40°C

D = pipe/tube inside diameter – inches

There is some risk associated with the high-velocity flush. Circulation of a fluid at high velocity with particulate contaminants can damage sensitive components (pumps, heat exchangers and valves). Also, such high pressures and flow can affect system filters. It is necessary to bypass flow- or contaminant- sensitive components.

Filter housings can be left in place if filter elements are removed. Components that restrict the flow rate, and thereby increase the pressure drop, should be isolated from the flushing circuit and cleaned individually.

Flushing Equipment
The flushing equipment required depends on the size, location and installed devices on the machinery. A mobile filtration unit is helpful if the pumps are capable of providing a flow rate at least twice that normally used in the fluid system or the flow requirements for the proper Reynolds number. An air breather is required to prevent dirt ingression during flushing.

Use large duplex filters (Beta 3= 200 or higher) with differential pressure indicator to allow filter changing without interrupting flushing. If water removal is desired, include a filter with water-absorbing capabilities.

A heater should be required in case of low ambient temperature to maintain or reduce fluid viscosity and achieve the flow requirements. Permanently installed quick-connectors are beneficial for flushing or filtration if the connector and piping are large enough to facilitate flow. In some cases, a reservoir other than the machinery sump is needed to contain the high volume of fluid required for the appropriate flushing.

A sampling port should be included upstream of the filter to analyze the fluid to establish when system cleanliness is achieved. An in-line, flow decay-type particle counter is the best option. If particle counters are not available, the use of an optical filter patch can help to determine system cleanliness.

Flushing Procedure
The flushing procedure depends on the specifics of machinery, plant conditions and flushing equipment. To obtain the best results, follow these guidelines:

• Drain the used oil while hot, so the viscosity is low and contaminants remain suspended and can be drained within the oil.
• Inspect the drained oil and drain ports for contamination that may indicate the need for power flushing or wand flushing.
• If drain port is not located at the lower point, heavy solid particles, water and/or emulsions will stick to the bottom of the reservoir. Wand flush is required.
• Remove oil filters from system.
• Block or bypass sensitive components.
• Block or bypass components that can reduce fluid velocity.
• If necessary, divide the system in sections.
• Connect the flushing equipment to gear box or bearing housing.
• Install air breather.
• Circulate and heat the fluid if necessary to reduce viscosity and pressure drop.
• Flush at specified Reynolds number to achieve turbulent condition.
• Monitor the contamination level (in-line particle counter readings or sample fluid and optically inspect filter patch).
• Circulate fluid an additional 15 minutes after cleanliness level is achieved.
• Drain and blow the system with dry, filtered air.
• Remove flushing connectors.
• Empty and clean filter housings and install new filter elements.
• Refill the system with filtered specified lubricant.
• Circulate (filter) new oil at least seven times before operating the equipment. Use a filter cart in systems without filtration.
• Label and store flushing fluid.
• Analyze flushing fluid for suitability.

Flushing Cleanliness Targets
For gearboxes and bearings, the target cleanliness level for flushing should be at least one number below the cleanliness level for the operating fluid. A maximum of 16/14/12 (ISO 4406.99) is recommended for critical gearboxes and element bearings.

The flushing process may be perceived to be an expensive, complicated and time-consuming extra task for an oil change. However, some conditions justify the effort. Highly contaminated reservoirs on critical systems warrant additional attention to assure a high state of reliability.

 Flushing is justified for new and rebuilt equipment prior to commissioning to sustain high levels of reliability. A proactive maintenance approach of deploying flushing for in-service bearings and gearboxes helps to increase lubricant life and equipment durability. Generally, the flushing efforts and costs are well compensated with increased reliability related to system cleanliness.

References

1.    E.C. Fitch. Fluid Contamination Control.

2.    A.R. Lansdown. Lubrication and Lubricants Selection.

3.    Specification ES 2184 Cleaning and flushing hydraulic systems/components – Solar Turbines.

4.    Robert Perez. “On-site Portable Filtration - Texas Style.” Practicing Oil Analysis magazine, May 2002.

5.    Tom Odden. “Cleaning and Flushing Basics for Hydraulic Systems and Similar Machines.” - Machinery Lubrication magazine, July 2001.

6.    AISE Lubrication Engineers Manual. Second Edition.

7.    Jim Fitch. “When to Perform a Flush.” Machinery Lubrication magazine, May 2004.

8.    Jim Fitch. “Navigating the Maze of Flushing Tactics.” Machinery Lubrication magazine, July 2004.

9.    Jim Fitch. “Flushing Strategy Rationalization.” Machinery Lubrication magazine, September 2004.

10.   Jim Fitch. “Flushing and the Voice Within Your Oil.” Machinery Lubrication magazine, November 2004.

 

 

كلمات كليدي براي بالابردن بازديد وبلاگ

مشاوره در خصوص فرمولاسيون و توليد  انواع روانکارهای صنعتی موتور 

مشاوره و انجام تست هاي آب

 

 

توليد انواع روان كننده هاي صنعتي معدني (mineral) مصنوعي (Synthetic ) و نيمه مصنوعي (Semi Synthetic)‌

تجهيزات آزمايشگاهي و ماشين  آلات خط توليد

تعيين فرمولاسيون و انجام مراحل آزمايشگاهي و كنترل كيفي محصول

 

 

 تجهيز و راه اندازي آزمايشگاه كنترل كيفيت

 

Estimating Turbine Oil Oxidation

 From steam turbine to gas turbine, from power generation to refining, turbines are pervasive throughout industry. While turbine systems can endure a whole host of different failure modes, studies by major turbine manufacturers such as General Electric have pointed to the lubricant as one cause of poor reliability.

However, other factors such as maintenance and operational practices, electrostatic discharge, contamination, and lubricant chemistry have been identified as root causes. Turbine oils must endure a host of different challenges due to heat from the process itself, compressive heating, aeration, and internal and external contamination, including water and particles.

Perhaps the most misunderstood failure modes are those induced by the turbine oil itself. While turbine oils are naturally pure, well-formulated oils, the long-term stress caused by adverse operating conditions can result in both thermal and oxidative degradation of the oil which can cause problems with the reliability and operability of turbine systems.

Even in the most controlled systems, turbine oils are subjected to a number of stressing factors that can lead to premature degradation of the fluid. These include heat, aeration, water and metal catalysts from the machine itself. While the chemical processes are complex, the end result is the same: the formation of by-products of oxidation such as sludge and varnish.

Sludge and Varnish
Sludge and varnish formation is a sequential process. Initially, heat in combination with aeration causes base oil molecules to chemically react with oxygen. This forms soluble by-products including ketones, hydroperoxides and organic acids. Over time, these by-products can combine either physically - a process referred to as agglomeration - or chemically due to further reaction, eventually becoming large enough that they drop out of suspension in the oil, forming solid or semisolid deposits on oil-wetted machines surfaces.

Compounding their effect, by-products of oil degradation are often sticky or resinous in nature. This can cause a host of problems including servo valve stiction, buildup on spool metering edges, restriction of oil flow, reduced spool-to-bore clearances, thermal insulation of the valve, combination with other particles and the loss of stick-slip control. Recent research findings¹ point to many contributing causes in the oxidation to varnish  process, such as:

• highly localized overheating of the lubricant due to flow restriction or pooling;
• microdieseling which occurs when tiny air bubbles undergo pressure-induced, high-temperature implosions that break down oils;
• static electricity generated by some filter media leading to spark discharges that may subject the oil to localized temperatures above 10,000°C;
• chemical degradation resulting from chemical reactions within a previously used oil which has not been adequately drained/flushed from the system (liquid catalyst);
• chemical degradation from catalyst properties of solid or semisolid varnish or varnish precursors (varnish or precursor sludge catalysts);
• additive chemistries and base oil types used in lubricant formulations that greatly affect the propensity of a finished lubricant to generate varnish.

Because of its significance, researchers in turbine oil analysis are constantly seeking new ways to determine the early onset of lubricant degradation such as oxidation. This article discusses the novel application of a commonly used analytical method to evaluate oxidative turbine oil degradation.

 Ultra-weak Chemiluminescence Method
Within the fields of food sciences, biotechnology research and basic materials characterization, there are several reliable and repeatable methods for determining the level of oxidation within samples. Ultra-weak chemiluminescence (UWCL) analysis is one such method with a proven track record as a versatile, reliable, accurate and repeatable methodology for studying oxidation of liquids, solids and even gases. Materials as diverse as blood fats, food oils², beer, pharmaceutical petroleum oils, polymers^3,4,5 and even ramen noodles have all been intensively studied and characterized using UWCL. Because of its versatility in characterizing oxidation in these materials, this method was applied to determine if it could be used to successfully measure the early onset of turbine oil oxidation.

Let There Be Light
It is well known that low-level luminescence is naturally produced from many kinds of materials. Luminescence simply refers to any process or material that emits light energy. By definition, chemiluminescence refers to luminescence caused by a chemical reaction, such as the glow of a firefly's tail.

Specifically applied to this study of material oxidation, chemiluminescence is induced by heating the sample in question inside a reaction chamber. By heating the sample, unstable molecular species such as hydroperoxides that are intermediates in the oxidative breakdown of organic materials start to decompose. This decomposition liberates an unstable form of oxygen referred to as singlet oxygen or excited carbonyls. As the unstable singlet oxygen or excited carbonyls are liberated, light energy is emitted.

In this study, we tried to estimate the oxidation level of turbine oil by measuring UWCL and measuring the correlation between the UWCL and an established varnish potential indicator test known as quantitative spectrophotometric analysis (QSA®).⁶ Materials and Method

Turbine Oils
In the initial study, seven in-service oil samples with the same fully formulated Group II turbine oil were chosen so that the overall chemistry and additives would be consistent. The samples were chosen so that a broad range of QSA® varnish potential ratings (VPR) range would be represented (Table 1).

Measurement of Turbine Oil UWCL
To measure the UWCL of the turbine oil samples, a chemiluminescence analyzer model CLA-FS3 (Tohoku Electronic Industrial Company, Sendai, Japan) was used. Each oxidized 2-milliliter sample of turbine oil was placed on a stainless-steel dish (50 millimeters in diameter and 10 mm in height) and the UWCL intensity was measured in air at 130°C for 600 seconds.

Result and Discussion
shows the time course change of UWCL of turbine oils at 130°C. There are two peaks at approximately 50 and 150 seconds.

The first peak at approximately 50 seconds of exposure to 130°C is due to weaker oxidation bonds that are more easily broken with heat. The underlying chemistry of that oxidation by-product has not yet been fully studied or identified. Although the peak is not as close to QSA® in correlation, it might later prove to have other relationships to varnish formation.

The second peak around 150 seconds of heating presents chemiluminescence due to oxidation by-products which form as singlet oxygen is liberated or excited carbonyls are generated during decomposition at 130°C.

shows the correlation between the integrated UWCL signal between 150 to 154 seconds and the QSA® results. As can be seen, the UWCL intensity correlated well with the QSA® indicator of varnish potential with a correlation coefficient (R2) of 0.765 (authors' footnote), the correlation coefficient represents the degree to which two parameters correlate. It ranges from zero (no correlation) to one, indicating complete correlation. Values in the range of 0.7 and above indicate a high degree of correlation between two observables.

This result indicates that the UWCL method can possibly be used to estimate propensity to form varnish by measuring specific oxidation compounds of turbine oil.

UWCL assay is important for its ability to measure the oxidation levels of either organic or inorganic materials. Likewise, samples can be in solid, liquid or gas states or a combination of states. Sample sizes are small (approximately 2 mL). Test time is less than 20 minutes. Finally, adding reaction-causing chemicals or time-consuming physical preparations are not required.

Although more data on a variety of different lubricant chemistries needs to be collected and testing procedures perfected specifically for turbine oil, it appears from this study that UWCL may be a promising methodology for the rapid and sensitive measurement of turbine oil varnish potential.

shows how UWCL is generated from the oxidation reaction. The luminescence species are mainly singlet oxygen and excited carbonyl which result from hydroperoxides formed during oxidation.⁷

When an excited carbonyl species or singlet oxygen is released to the ground state, it gives out its energy as a light. Therefore, this UWCL indicates the amount of hydroperoxides or other oxidized products, and it is possible to measure the degree of oxidation.

These oxidation products seem to correlate with the QSA® predictive index.

Chemiluminescence can be induced by many energies, including heat, light, radiation, chemical reaction or pressure. The key in oxidation characterization is "popping" that oxygen singlet off the compound. When it is liberated, there is a photon emission. The more oxygen liberated at the same stress condition means more light; more light means that more of some specific oxygenated compound is present.

Finally, because multiple oxidation compounds can be measured in the same test, the significance of each compound can be mapped with relation to the goal - predicting varnish potential and measuring prevention or remediation effectiveness.

بازار روانكارهاي چين

    در سال2005، گزارشي با عنوان فرصت هاي مناسب در بازار روانكارهاي چين منتشر شد. در اين گزارش آماري، روانكارهاي ويژه خودرو و صنايع هر كدام45 درصد و ساير روانكارها10 درصد كل روانكارهاي توليدشده- كه ميزان تقريبي آن4 ميليون و800 متريك تن و ارزش اقتصادي آن5 ميليارد و980 ميليون دلار در سال است- را تشكيل مي دهند.
    صرف نظر از واحدهاي توليدكننده روانكار چيني، در جهان حدود يكهزار و400 واحد بلندينگ و يكهزار نوع محصول روانكار وجود دارد و اين در حالي است كه كشور چين، به تنهايي داراي4 هزار واحد توليدكننده با ظرفيتي بيش از4 هزار نوع محصول روانكار است.
    بازار روانكارهاي چين تا سال1992 به صورت مركزي توسط سياست گذاران دولتي اداره مي شد. از آن تاريخ به بعد آزاد سازي آن شروع شد. در سال2000 دولت يك خط فرضي در راستاي ديوار بزرگ چين ميان كشور ترسيم كرد و بازار روانكار قسمت هاي شمالي و غربي ديوار چين را به شركت پتروچاينا (PetroChina) و جنوب و شرق آن را به شركت سينوپك (Sinopec) واگذار كرد. اين تقسيم بندي كه به صورت جغرافيايي تعيين شده بود بتدريج جاي خود را به رقابت آزاد در كل كشور داد. امروزه بازار روانكارهاي كشور چين به صورت رقابتي و كاملاً آزاد درآمده و شركتهاي مختلف اين كشور در تلاشند تا سهم بيشتري از بازار را بدست آورند. در طي پنج سال گذشته رشد رقابت در اين بازار منجر به كاربرد روشهاي نوين مديريتي شده است. تا قبل از سال1992 كه مديريت بخش دولتي تعيين كننده خط مشي كلي بازار بود، كارايي پايين، تراكم نيروي انساني، رقابت ضعيف و در نتيجه كيفيت نامناسب محصولات، عدم امكان رقابت با بازار جهاني، بوروكراسي اداري و از جمله موارد بيشماري بود كه امكان رشد در اين بازار را ميسر نمي ساخت و با حذف اين سياست گذاري ها، كاربرد روشهاي نوين علمي و اقتصادي در اكثر زمينه ها شروع شد. مهمترين اقدامات شركت هاي توليدكننده عبارت بود از: حذف بوروكراسي هاي اداري و بخش هاي زيان آور، كوچك سازي، كاربرد نيروهاي متخصص و انتخاب روش هاي اقتصادي كه در كشورهاي پيشرفته اقتصادي مورد استفاده قرار گرفته بود.
    در حال حاضر، دو شركت مهم »پتروچاينا« و سينوپك63 درصد بازار روانكارهاي چين، را در اختيار دارند. شركت »پتروچاينا« بزرگترين توليدكننده روانكار در چين تا5 سال آينده و يكي از عمده ترين توليدكنندگان روانكار در جهان تا سال2015 خواهد بود. اين شركت در حال حاضر داراي11 بلندينگ، دو مركز بزرگ توسعه و تحقيق و يك آزمايشگاه بزرگ تحقيقاتي است. اين شركت با حذف روشهاي گذشته طرحي را در دو بخش به اجرا درآورده است. بخش اول اين طرح داراي5 اصل بود كه شامل تمركز برنامه ريزي و تخصيص منابع، استاندارد ساختن محصولات، افزايش فعاليتهاي تحقيق و توسعه، تدوين روش هاي قيمت گذاري و بازسازي شبكه توزيع مي شود. بخش دوم نيز شامل حذف اسامي مختلف روانكار و عرضه انواع توليدات با استفاده از يك نام ثابت با عنوان Kunlun است. برنامه ريزي و اقدام براي كوچك سازي، مهمترين بخش اجرايي اين طرح بود. بدين ترتيب93 سازمان عرضه محصولات روانكار اين شركت در6 مركز فروش متمركز شدند و   روغن هاي توليد شده از137 نوع به77 نوع كاهش يافت. متمركز ساختن مراكز بسته بندي و ساخت ادتيوها منجر به صرفه جويي قابل توجهي در حدود19 تا25 ميليون دلار در سال شد. با انجام چنين اقداماتي فروش محصولات اين شركت از يك ميليون و210 هزار تن در سال2001 به يك ميليون و830 هزار تن در سال2005 رسيد كه سير صعودي بسيار مطلوبي را نشان مي دهد. 

    در حال حاضر شركت پتروچاينا بزرگترين توليدكننده ادتيو در چين است و مركز تحقيق و توسعه بسيار وسيعي دارد. البته80 درصد توليدات پتروچاينا شامل محصولات صنعتي با كيفيت پايين و تنها20 درصد آنها، روانكارهاي خودرو با كيفيت ممتاز است و به طور كلي مي توان گفت بيشتر محصولات اين شركت از عرضه بسيار خوب و كيفيت پاييني برخوردارند.
    هم اكنون، شركت پتروچانيا36 درصد بازار روانكارهاي چين را در اختيار دارد. پس از سال2001 هدف اصلي شركت برپايه ارايه محصولات تمام بسته بندي شده در ازاي فروش روغن هاي پايه اي با كيفيت پايين و نظاير آن بنانهاده شد.
    دومين شركت توليد كننده بزرگ روانكار در چين سينوپك است. اين شركت داراي سياستي شبيه به سياست شركت پتروچاينا است و مانند شركت پتروچاينا بعد از برداشته شدن كنترلهاي مركزي، سعي در كوچكتر ساختن خود كرد. ادغام سازمانهاي برنامه ريزي، مديريت، تخصيص منابع، بازاريابي، از جمله اقدامات آن بود. اين شركت مانند شركت پتروچاينا در سال2003 عرضه كالاهاي خود را با نامهاي مختلف گذشته متوقف و محصولات توليدي خود را فقط با يك نام تجاري، چانگ چنگ به معني ديوار بزرگ (Great Wall) عرضه كرد. اين عمل براي تمركز بر روي يك نام خاص بود و شناساندن اين نام در سطح بين المللي و صادرات، هدف اصلي اين برنامه بود. نكته بسيار مهم ديگر كاهش هزينه هاي اضافي بود. حذف بخش هاي اضافي و غيراقتصادي و كاربرد روشهاي نوين اقتصادي كمك شاياني به رشد اقتصادي اين شركت كرد. اين شركت در گذشته داراي5 پالايشگاه توليد روغن بود و عرضه محصولات مختلف آن با مشكلات زيادي مواجه مي شد. امروزه هيچ روغن پايه اي به صورت بالك از اين شركت به بازار عرضه نمي شود و تمامي فعاليت آن براي ساخت محصولات خود بكار گرفته مي شود. اين شركت5 مركز فروش و بازاريابي را تاسيس و هدف اصلي را بر پايه كاهش هزينه ها و بالاترين كيفيت محصولات خود بنا نهاده است. سينوپك با انجام تبليغات بسيار در رسانه ها به ويژه تلويزيون سعي در معرفي محصولات خود دارد و هدف نهايي خود را جهاني شدن قرار داده است. صادرات محصولات سينوپك در سال گذشته200 درصد رشد داشته است. هم اكنون سهم شركت سينوپك از كل بازار چين27 درصد است و در حال حاضر از نقطه نظر كيفيت در رتبه نخست روانكارهاي اين كشور قرار دارد. حجم عرضه كالاي آن در سال2002 معادل9 ميليون ليتر و در سال2004 با رشد قابل ملاحظه اي به يك ميليون و300 هزار ليتر به ارزش اقتصادي يك ميليارد دلار ارتقا يافته است. رقابت ميان اين دو شركت براي بدست آوردن سهم بيشتري از بازار ادامه دارد.

 نويسنده: مهندس سعيد صالحي

روانكاري دنده هاي بسته و انتخاب آنها

شرايط استفاده روانكارهاي دنده، بسيار متفاوت است. اين روغن ها بايد بتوانند در حضور مقادير بسيار زيادي آب، در دماهاي عملياتي و محيطي بالا و در شرايط آلوده عمل كرده، و در عين حال از سايش دنده ها بخصوص در بارهاي بالا جلوگيري كنند.  علاوه بر اين ها، دو عامل اصلي، كارآيي روغن هاي دنده را به شدت تحت تاثير قرار مي دهد:
    افزايش توقع مصرف كنندگان براي روانكارهاي با طول عمر بيشتر به منظور كاهش هزينه تعميرات و تخليه.   اصلاح طراحي هاي اعمال شده توسط سازندگان ماشين آلات به منظور بهبود بازدهي گيربكس ها.
    در اين اصلاحات، دنده ها كوچك شده و بايد در سرعت هاي بيشتر كار كنند كه افزايش دماي عملياتي و تنش دنده ها و ياتاقان ها را به همراه دارد. دنده هاي كوچك تر به معني فضاي كمتر براي روغن است. بنابراين مقدار روغن دنده كمتري براي خنك كردن قطعه مورد نظر و معلق كردن آلودگي ها وجود خواهد داشت.
    
 انواع روغن هاي دنده بسته
    اتحاديه سازندگان دنده در آمريكا (AGMA) ، يك بروشور استاندارد تحت عنوان روانكاري دنده هاي صنعتي (AGMA 9005-D94) منتشر مي كند. در اين بروشور طبقه بندي روانكارها، كاربردهاي عمومي و روش سرويس كردن دنده هاي صنعتي كه مطابق با اصول توصيه شده AGMA طراحي شده اند ارائه مي شود. چهار نوع روغن معرفي شده در اين بروشور عبارتند از: روغن هاي دنده ضد زنگ و اكسيداسيون، روغن هاي دنده مركب، روغن هاي دنده EP و روغن هاي دنده سنتتيك.
 روغن هاي دنده ضد زنگ و اكسيداسيون
    اين روغن ها را عموماً به عنوان روغن هاي R&O مي شناسند. اين روغن ها، روغن هايي با پايه معدني و يا داراي مواد سنتتيك هستند كه به منظور محافظت از زنگ زدگي و سايش با مواد افزودني لازم مخلوط مي شوند. علاوه بر اين افزودني ها بعضي از روغن هاي R&O شامل مقدار كمي از افزودني هاي ضد سايش نيز هستند. گريد گرانروي روغن هاي R&O در AGMA با يك عدد تك رقمي از صفر تا شش تعريف مي شود كه معادل گريد گرانروي ISO از32 تا320 است.   روغن هاي دنده R&O براي دنده هايي با اندازه ها و سرعت هاي متنوع در رنج 5F تا 250F (15C تا 121C) داراي كارآيي بسيار خوبي هستند.
    
روغن هاي دنده مركب (Compounded)
    روغن هاي دنده مركب مخلوطي از روغن هاي پايه معدني با افزودني هاي ضد زنگ و اكسيداسيون، افزودني هاي دي مولسيفاير (كه جدايي روغن از آب را افزايش مي دهند) و3 تا10 درصد روغن هاي چرب يا روغن هاي چرب سنتتيك هستند.
    اين روغن ها بيشتر در دنده هاي حلزوني و به منظور روانكاري موثرتر و جلوگيري از سايش لغزشي استفاده مي شود. دماي عملياتي اين روغن ها حداكثر (82C)180F است. اين روغن ها با اعداد تك رقمي AGMA و با پسوند Comp از7 تا8A تعريف مي شوند كه مطابق با گريدهاي ISO 460 تا ISO 1000 مي باشد.
  روغن هاي دنده EP
     اين روغن ها، روغن هاي پايه معدني داراي مواد سنتتيك اند كه شامل افزودني هاي چند منظوره هستند. اين افزودني ها شامل مواد ضد زنگ و اكسيد اسيون، افزودني هاي EP، دي مولسيفايرها، مواد ضد كف و در بعضي موارد روانكارهاي جامد با خاصيت معلق كنندگي كلوئيدها نظير دي سولفيد موليبدن، برات يا گرافيت هستند.
    افزودني هاي EP كه شامل فسفر- گوگرد، برات ها و تركيب گوگرد- فسفر و بُر هستند، يك فيلم محافظ شيميايي ايجاد كرده كه در برابر جوش خوردگي، ساييدگي و خراشيدگي ناشي از شرايط روانكاري مرزي دنده ها كه در هنگام روشن و خاموش كردن و بارهاي ناگهاني به وجود مي آيد، مقاومت مي كند.
    AGMA اين روغن ها را با يك عدد تك رقمي با پسوند EP از 2EP تا 9EP معادل با گريد هاي ISO68 تا ISO1500 مي شناسد. روغن هاي دنده EP براي دنده هاي با اندازه و سرعت هاي متنوع در رنج 5F تا (121C-15C)250F داراي كارآيي مناسبي هستند.
    
 روغن هاي دنده سنتتيك
    روغن هاي دنده سنتتيك با روغن هاي دنده پايه معدني كه با مواد سنتتيك مخلوط مي شوند، متفاوت است. معمول ترين سيالات پايه سنتتيك كه در فرمولاسيون روغن هاي دنده سنتتيك استفاده مي شود عبارتند از پلي آلفا الفنيها (PAO) ، پلي ال استرها، پلي گلايكول ها.

در حالت كلي، روغن هاي دنده سنتتيك در رِنج وسيعي از دماهاي عملياتي پايدار بوده، شاخص گرانروي بالاتري داشته (تغييرات گرانروي كمتر با تغييرات دما)، در برابر اكسيداسيون مقاومت بيشتري مي كند و در بعضي موارد، از قدرت تحمل بار و روانكاري بهتري برخوردار است. هر سيال سنتتيك ويژگي هاي متفاوتي داشته و تعدادي از آنها محدوديت ها و معايبي نظير عدم سازگاري با الاستومرها رنگ ها،backstops و كلاچ ها، واكنش در حضور رطوبت و قيمت بالا دارند.
    روغن هاي دنده سنتتيك مي توانند شامل مواد ضد زنگ و خوردگي، افزودني هاي EP ، دي مولسيفايرها، مواد ضد كف و در بعضي موارد روانكارهاي جامد باشند. اين روغن ها را با اعداد تك رقمي AGMA با پسوند S از 0S تا 9S مشخص مي كنند كه معادل با گريد هاي ISO32 تا ISO1500 مي باشد.
    جدول1، گريدهاي روغن دنده هاي ذكر شده و گريدهاي معادل ISO آنها را نشان مي دهد.
    
 خواص كليدي روغن دنده
    يك روغن براي اين كه نياز روانكاري
    دنده هاي صنعتي مدرن را برآورده كند، لازم است كه داراي ويژگي هاي زير باشد.
    1- پايداري حرارتي و پايداري در برابر اكسيداسيون
    2- سازگاري با آب بندها
    3- محافظت دنده ها و ياتاقان ها در برابر سايش بيش از حد
    4- مقاومت در برابر دما و فشار بالا
    (روغن هاي دنده EP )
    5- پاك كنندگي دنده و ياتاقان
    6- خاصيت دي مولسيبليتي
    7- محافظت در برابر زنگ زدگي و خوردگي، خصوصاً براي فلزات زرد
    8- خواص ضد كف
    بسياري از اين خواص كليدي با بررسي اطلاعات فني توليد كننده روغن و مقايسه آنها با شرايط عملكردي حداقل كه توسط موارد زير تعيين شده، قابل شناسايي است.
    1- مشخصات US-Steel 224 براي روغن هاي دنده صنعتي EP بدون سرب: اين مشخصات پايداري حرارتي و تحمل بار بالا را تعريف مي كنند.
    2- AGMA 9005-DA : اين مشخصات بسيار شبيه US Steel 224 و نيز شامل مشخصات فيزيكي و كارآيي حداقل براي روغن هاي R&O ، مركب و سنتتيك است.
    3- Cincinnati Milacron P-34/P-35/P-59/P-63/P-74/P-76/P-77/P-78 اين مشخصات هم چنين شامل عملكرد حداقل براي پايداري حرارتي و محافظت در برابر زنگ زدگي است.
    4- DIN 51517 Part 3 CLP : توسط انجمن استاندارد آلمان توسعه يافته است. ويژگي هاي روغن دنده پايه معدني شامل افزودني هاي ضد زنگ، افزايش طول عمر و EP را تعريف مي كند.
    علاوه بر اين مشخصات پايه اي، تعدادي آزمايش اضافي نيز براي مواردي كه كارآيي بهينه مورد نياز است قابل انجام مي باشد.
    
پايداري حرارتي و پايداري در برابر اكسيداسيون

تغييراتي كه به منظور افزايش كارآيي گيربكس ها در طراحي صورت گرفته، منجر به توليد دنده هاي كوچكتر كه در سرعت ها، بارها و دماهاي بالاتر كار مي كنند، شده كه اين تنش دنده و ياتاقان را افزايش مي دهد. ماحصل اين تغيير، فضاي كمتر براي روغن بوده و بنابراين روغن كمتري براي خنك كردن دنده ها، ياتاقان ها و معلق كردن آلودگي ها وجود دارد. علاوه بر تغييرات طراحي، دنده ها به دليل ظرفيت تحمل بار نامناسب، تراز نبودن و تميزي ناكافي در معرض دماي بيش از حد هستند. در نتيجه، روغن هاي دنده صنعتي در معرض تنش حرارتي بالا هستند. اين تنش حرارتي مي تواند باعث اكسيداسيون و شكست حرارتي روغن هاي دنده شود.
    اكسيداسيون وشكست حرارتي روغن دنده به نوبه خود باعث افزايش ويسكوزيته روغن، توليد اجزاي اسيدي و تشكيل لجن وارنيش LACQUER و كُك بر روي دنده ها، ياتاقان ها و آب بندها مي شود. تشكيل اين رسوب ها مي تواند منجر به افزايش دراگ اصطكاكي، دماي عملياتي و مصرف انرژي، كاهش راندمان چرخ دنده و سايش زود هنگام و شديد دنده ها و ياتاقان ها شود. تجمع اين مواد همچنين باعث خراشيدگي آب بندها و سخت شدن و شكنندگي زودهنگام آنها شده كه در نهايت عمر آب بند را كاهش و نشتي روغن را افزايش مي دهد.
    به اين دلايل، لازم است كه يك روغن دنده، پايداري حرارتي داشته و در مقابل اكسيداسيون نيز مقاومت كند.   يك روغن دنده پايدار در برابر حرارت، مطابق تعريف، روغني است كه در شرايط دماي بالا، بتواند قطعات حساس را در مقابل رسوب و لجن تميز نگهدارد.

New Lubricant Sam

 The question asked "What tests should be performed on new oil to ensure that you are receiving quality oil? What are the advantages and disadvantages of elemental testing (such as ICP) versus IR spectrum on new lubricant samples?"

In an attempt to adequately answer both questions, each will be addressed separately.

Testing New Lubricants
Testing new lubricants is vital when establishing a condition-based maintenance program. Most incoming lubricants are not necessarily clean lubricants when compared to target cleanliness levels. Unfortunately, lubricants may also be delivered in a drum or other bulk container that is not consistent with the original order.

On-site Testing
Testing new lubricants can take place with on-site screening equipment in addition to running a full commercial lab test slate. Some of the tests that can be performed on-site include viscosity and particle counting.

Because viscosity is the most important property of a lubricant, on-site testing can take place before accepting a delivery. This will allow a general level of confidence because most incorrect deliveries are viscosity-related rather than product-line errors. This, however, is not to say that full commercial quality testing should not take place.

Cleanliness Levels, Commercial Quality Testing
Particle counting indicates the cleanliness level of a new lubricant delivery. This will provide a good idea of the level of filtration that needs to occur prior to putting the oil into service. It is not uncommon for a new oil sample to have an ISO cleanliness level of 22/17 or worse, which is above any target cleanliness level for equipment where reliability is important.

While viscosity and cleanliness levels can be screened on-site, this still does not ensure the correct product is being received. Each new lubricant batch should be sampled and sent for commercial quality testing. For most industrial applications, the following tests should be run on new oil:

• Elemental Analysis - ASTM D5185
• Viscosity at 40°C - ASTM D445
• Viscosity at 100°C - ASTM D445
• ISO Particle Count - ISO 4406:99
• Karl Fischer Moisture - ASTM D1744 or ASTM D6304
• Fourier Transform Infrared (FTIR) Spectroscopy
• Acid Number - ASTM D664

Other tests may be necessary depending on the type of lubricant and associated application; however, the above slate should be considered as a minimum.

Elemental Analysis
Elemental analysis and FTIR are important tests. Elemental analysis measures the actual metallic components in a lubricant. These results have been known to identify delivery truck pump failures as well as additive concentration changes from the oil manufacturer.

While sampling new lubricants, elemental analysis denotes the starting values for additives. When trending used oil, these values help identify cross-contamination during top-ups or the use of an incorrect lubricant during an oil change. Simply stated, elemental analysis helps identify a lubricant.

FTIR
FTIR, on the other hand, indicates the health of a lubricant in addition to identifying various contaminants in used oils. To properly monitor and set alarm values for used oil samples, the current values for new lubricants must be available. Lubricant manufacturers change formulations as product lines are improved. These formulation changes can affect the values derived with FTIR.

To gain the most value from an oil and a condition-based maintenance program, new oil sampling must include the multiple tests that will most appropriately monitor oil conditions. Established alarms and limits of lubricant properties are generally assigned from a baseline sample. The lack of a baseline sample severely limits the accuracy of lubricant health analysis in used samples.

It has been said that "the only downside to oil analysis is finding the time to use it to its fullest potential." New oil sampling is just the beginning of the oil analysis process, and must be utilized to its fullest extent.