Both cavitation and corrosion can result in shorter engine life if the SCA level of your coolant is not monitored and maintained. The proper level of a chemical concentration of 1. You can use the utility below to determine how much SCA to add to your system for the proper level of protection. The recommended level of SCA is 1. If you do not check the level frequently you should aim for a higher level such as 2. Concentrations above 3. This buildup can become loose or flake off the water jacket walls, and because it can be abrasive, it will cause damage to your water pump or even clog certain parts of the cooling system like the heater core.
The pistons in your engine move up and down about 2, times a minute. While they move vertically, the crankshaft is performing a completely different movement by rotating horizontally. These contradictory movements will cause your engine's liners to vibrate a lot.
Although the outer wall of the liner is surrounded by cooling fluid, its inertia creates tiny vacuum pockets, causing bubbles of vapor to form on the liner wall. When the liner vibrates back, these bubbles collapse under an enormous pressure and take small chunks out of the liner. Eventually you will have block failure. To prevent this, a supplemental coolant additive needs to be added to the cooling system and monitored regularly. The truck coolant side claimed that there was a problem with phosphate and silicate, something about inhibitor fallout, overheating, pump failures and green goo.
D15 eventually constructed standards for these truck folk and established new definitions, such as, Heavy Duty and Light Duty. Both sides learned to reach across the line, embrace each other and work together to establish D15 standards. Thank goodness for recyclers! OK, I could live with Heavy Duty standards, but I did not see the tempest of new standards to come in the following years. Little did D15 know that events in CT and TX were going to result in numerous new standards, definitions and debates. The Lime, CT area was host to 2 historical events.
The first was the disease traced back to a tick bite, hence the name Lymes disease. The second occurred at the same race track where Paul Neuman was known to race. A race team in Lime Rock was experimenting with reversing the coolant flow in an engine and using concentrated propylene glycol. Claims of better heat transfer, better gas mileage, better corrosion control and lower toxicity soon surfaced. Over a number of years and much debate, D15 established standards and definitions for propylene glycol based coolants.
At about the same time down in TX, a man with a star was promoting engine coolants based on an additive that is used to make monofilament fishing line. It was claimed that this new longer, life fluid could last 30, 50 maybe even , miles. This sebacic acid additive, long life concept grew in popularity, caught root, and landed in D Long Life standards and definitions were established and continue to be established today and include the Organic Acid Technology or OAT fluids.
By the mids recycling engine coolants became a major issue in D Both OEM and the States were demanding performance and chemical standards for recycled coolants. Recycling technology at that time ran the gamut from passing used coolant through a machine with gauges and blinking lights coming out the other end virtually unchanged, to add packs that raised the pH, to reverse osmosis, to distilling and then adding inhibitors and buffers.
Along the development of OAT and long life fluids, not to be confused with extended service fluids, it was found that blending traditional coolant technology with OAT fluids could improve performance. This was the start of Hybrid fluids. I have heard the term HOAT to describe these hybrid organic acid technology fluids. New research is now investigating developmental organic acid nitate technology, or DONT. More standards, more research, more definitions, more challenges. Compatibility issues, oxidation stability issues, new technology issues. But being a new member of the Old Guard at D15 I am entitled to long for days past, meetings with no cell phones or lap tops and breaks with long lines at the pay phone.
Days when blackberry was a fruit, blue tooth meant a trip to the dentist and yahoo meant you were really excited. AND P. YANG, F. YANG, P. YANG, A. MORI, M. CHEN, R. The advances in coolant system components and construction continue to impact the modern automotive, heavy-duty, locomotive and free standing engine design and performance.
The expanding use of lighter metals, advances in non-metallics, changes in fluid control technologies and coolant filtration in todays engines, plus advancing discoveries in EGR and fuel cell technologies in engines of the future are a few of the challenges facing the experts in engine coolant formulating. Challenges of today include extended service life, liner pitting, the impact of EGR, advances in turbo charging and component compatibility.
Research areas must consider state and local regulatory requirements for increasing the use of recycled fluids and efforts for global standardization of test methods. The symposium presented an open forum for the presentation of new research in modern engine coolant formulating addressing the complex issues mentioned above.
The symposium was well attended by international technical representatives from OEM and engine coolant producers. The presentations were followed by open comments and questions from the attendees resulting in a robust, professional exchange of ideas. These papers include current overviews of heavy duty coolant technology and coolant development in Asia, new testing methods, both in field and at the bench, designed to help determine localized corrosion by electrochemistry, erosion corrosion, degradation of coolant components at elevated temperatures and under accelerated oxidation, and depletion of corrosion inhibitor additives.
Compatibility issues are also presented addressing both multi-fluids mixing and affects of fluid composition on engine components. I want to thank the reviewers that volunteered their valuable time to complete the critique of the papers presented. William N. Matulewicz Wincom, Inc. In the early days of ethylene glycol based engine coolants, simple inhibitor systems based on borates, phosphates, etc. With the advent of aluminum engines and their rapid usage growth throughout the s and s, engine manufacturers of the regions began to place more stringent requirements on the anticorrosion performance of the OEM coolants.
Based on the specific strategies utilized by the cooling system component manufacturers, divergent requirements began to be placed upon the coolant makeup. This paper will speak generally to the regional history of coolant trends and specifically on the activity for coolant development in Asia. Development of organic acid Manuscript received January 27, ; accepted for publication November 7, ; published online July Matulewicz, Guest Editor. Box , Lemont, IL However, the recent automotive industry growth in China is rapid and well documented and it will be interesting to see what the technological growth pattern will eventually be.
However, it does not contain sections on cavitation durability performance and compatibility with nonmetallic parts, thus these issues will be future topics. The addition of phosphate and organic acid salt inhibitors as main components allowed for the increased durability of nonamine coolants. On the other hand, in Japan, P-OAT and LP-OAT which contain organic acids and phosphate but do not contain borate and silicate are typically used, as it is a characteristic for coolants in Japan to contain phosphate.
Therefore, LP-OAT that was developed utilizing the latest Japanese coolant technology is a global coolant that is being used, without reservation, all over the world. As a result, automotive manufacturers will bring new technology vehicles for the new world and new long-life coolant must be developed with new technology. Duffey, F. Shiotani, E. Kawamoto, S. Kiryu, K. Hercamp, R. Kikuchi, M. Hara, H.
Tange, K. Osawa, M. Nishii, M. DeBaun1 and Fred C. The cooling systems contained in these vehicles are similarly being impacted by smaller designs, new cooling system configurations, and increased usage of lighter, softer metals. This paper reviews the changes in heavy duty diesel engine technology and provides information on coolant performance in emission compliant engines. Predictions are also made on future engine technology and next generation engine coolants. KEYWORDS: heavy duty engine coolants, cooling system trends, oxidation stability, erosion corrosion, cavitation, elastomer compatibility, traditional fully-formulated coolants, extended service coolants, extended life coolants, supplemental coolant additives Introduction Diesel engines continue to be the work horse engines of industry.
Advances in diesel engine technology are being driven by needs for increased power, emission reductions, improved fuel economy, and longer reliability. Recent advances in engine cooling and the cooling system have not been as significant. This paper will review some of the changes in heavy duty diesel engine technology and the impacts on the cooling system and coolant along with future trends in the cooling system and coolant technology.
The exhaust gas is cooled and the turbocharger boost pressures must increase to increase the air into the cylinder. In meeting the lower NOx requirements, the recirculated exhaust gas is cooled. Stainless steel EGR coolers are used to cool the exhaust gas with engine coolant. The addition of the exhaust gas lowers the oxygen content and lowers the combustion temperature which reduces the high temperature formation of NOx. In some cases, bulk coolant temperatures increase if radiator size cannot be increased in order to make up for increased coolant heat rejection.
The high temperatures in the EGR cooler led to localized boiling, increased degradation of the coolant, and reduced coolant life. The use of the lighter, softer metals often have maximum flow rate limitations which must be considered during system design. In some of these regions, heat transfer is accomplished by nucleate boiling which places additional stress and demands on the coolant. Residual air bubbles in the cooling FIG. Vehicle and engine deaeration systems and characteristics must also be taken into consideration during cooling system design.
The use of a turbocharger allows more air to be forced into the engine which allows more fuel to be burned resulting in increased power. To achieve even more power, the air may be cooled through an air-to-air or air-to-liquid charge air intercooler which increases the density and makes more oxygen available for combustion. For air-to-liquid charge air intercoolers, the intercooler adds an additional thermal load on the coolant.
Supplemental Coolant Additives (SCA)
The ECM communicates with an elaborate array of sensors placed at strategic locations to monitor engine speed to coolant and oil temperatures. With regards to engine cooling, the increase in power output for given cylinder volume during combustion results in increased heat rejection to the coolant. The air conditioning compressor adds an additional thermal load on engine cooling, particularly under heavy load and idle conditions. Transmissions are operating at higher temperatures resulting in additional heat rejection to the coolant through the transmission fluid cooler.
In addition, these vehicles may operate with numerous starts and stops, often resulting in hot soaking of the coolant which raises the coolant temperature and can cause boiling. In some cases, engine coolant service intervals for extended life and extended service coolants used in these vehicles are being lowered to automotive service intervals.
Elastomers, Seals, and Hoses Elastomers, seals, and hoses are extremely important since they are widely used throughout the engine and cooling system. There also have been some problems in the field with certain engines containing silicone seals in high temperature regions using OAT-based coolants which resulted in loss of compression set and leakage. Additional cooperative work is required between the OEM, elastomer supplier, and coolant supplier to extend the temperature limitations of elastomers and to improve coolant and elastomer compatibility. Impacts on the Engine Coolant The more severe operating conditions and environments in which heavy duty diesel engines operate have an impact on coolant formulations and performance.
Ethylene glycol-based engine coolants are still the predominantly used heat transfer fluid for heavy duty applications. Several different types of engine coolants are used in heavy duty applications, which may be classified by the type of corrosion inhibitors contained in the formulation. In Europe, Asia Pacific, and other parts of the world, conventional, hybrid, and extended life coolants are used in heavy duty applications.
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However, there is less distinction between light duty and heavy duty coolants and less usage of SCAs outside the United States. In Europe, phosphate is generally not used due to potential hard water compatibility problems. In Asia, silicates are generally not used due to gel and water pump seal abrasion concerns. An engine coolant containing OAT providing long service life. An engine coolant also providing extended service life. An engine coolant containing a combination of inorganic and organic corrosion inhibitors.
Europe hybrids are phosphate free. Asia hybrids are silicate free. Any group of carboxylic acids including aliphatic mono and diacids and aromatic acids applicable as corrosion inhibitors in coolants. A chemical additive that is periodically added to the coolant to maintain protection against general corrosion, cylinder liner pitting, and scaling in heavy duty engines. A conventional coolant containing an initial dosage of SCA. As discussed in the preceding paragraphs, the advances in heavy duty engine technology are placing greater demands on the coolant in all of these performance areas.
The overall test results indicate that traditional fully formulated, extended service interval and extended life coolants overall are performing satisfactorily with only minimal impacts on oxidation and coolant life. With regards to oxidation stability, there also have been some sporadic incidents in the field involving black coolant and engine failures. Used coolant and failure analyses have often indicated that the failure mechanism includes severe thermal stressing and oxidation of the coolant. Liner pitting is the result of cavitation and erosion processes that occur on the coolant side of the cylinder liner.
Cylinder liners vibrate from the motion of the piston within the cylinder which can cause low pressure regions of the fluid causing vapor bubbles to form and collapse on the surface of the liner. A heavy duty engine cavitation test based upon an internal John Deere cavitation test is being considered for adoption as a standard ASTM engine coolant cavitation test.
The test has been shown to discriminate between satisfactory and unsatisfactory coolants with regard to cavitation erosion-corrosion protection. In view of the more severe operating conditions which can contribute to more rapid nitrite depletion, it is anticipated that extended life or extended service nitrite free coolants, or both, will be used to a greater extent in diesel engines.
Anti-scaling Performance Scale resulting from the use of hard water, cooling system contaminants, and corrosion inhibiting film agents can block the ability to transfer heat resulting in overheating and metal fatigue failures. Previous studies reported that scale layers in the range of 0. Scale tends to form in specific areas of the hot side of the engine resulting in localized hot spots, which also accelerate oxidation degradation of the coolant.
The use of good quality water and properly inhibited coolants minimizes these deposits. Erosion-corrosion is typically caused or accelerated by excessive flow conditions which generate shear forces sufficient to remove corrosion passivating films or naturally protective oxides, or both. Erosion-corrosion problems have been observed in the field with brass fuel injector cups, aluminum alloy oil coolers, and aluminum heater cores with several different types of coolants.
The problems have been resolved by changes in metallurgy, addition of flow restrictors, or cooling system design changes, or a combination thereof. Engine coolant chemistry can also influence erosion-corrosion protection. The engine manufacturers anticipate meeting these limits through a combination of changes in engine technology and additional emission reduction equipment, particularly heavy EGR to reduce NOx and diesel particulate filters to reduce PM.
The emissions regulations will require the use of lower sulfur fuels which may require OEMs to utilize more sophisticated fuel systems. Some engines will be utilizing dual turbochargers for better efficiencies. All of these will increase the stress on the coolant and decrease the life of the coolant. Diesel particulate filters will be used to lower the PM emissions. The filter itself will not impact the coolant, but may cause additional stress by modifying the way the engine runs.
If the burning of the soot from the diesel particulate filter is through the cylinder post injection of fuel, cylinder temperatures will increase and coolant stresses will increase. The use of selective catalytic reduction technology to reduce NOx emissions may reduce the load on EGR which will lessen the thermal load to the coolant. The emission reduction technologies will impact coolants and cooling systems. Larger water pumps will be used to supply higher coolant flow due to higher power requirements.
Larger radiators will be used to reject higher heat loads. Crankcase water jackets may be changed to handle higher pressures. Lighter, softer metals are being used in cooling systems, and specifically, aluminum is being used more widely for cooling systems. The use of electric water pumps in place of conventional pumps will provide benefits in delivering the correct amount of coolant from cold start-up to high operating temperatures. The electric pump will also eliminate hot soak after shutdown by circulating coolant through the engine.
Electric valves may be used to provide more precise temperature control of coolant and engine temperatures than conventional thermostats. The use of a single electrical fan may not currently be practical due to the high power consumption required for operation. However, small auxiliary electric fans may be added to the cooling system to achieve more efficient cooling over a single mechanical fan.
The cooling system will also include computer controls to accurately control the temperatures for the primary engine cooling, emission equipment, transmission, engine oil, and charge air cooler. Laboratory and field data indicate that extended life coolants or extended service interval coolants, or both, provide performance benefits in terms of oxidation-thermal stability which translates to longer coolant and reduced usage of SCAs. It is anticipated that the usage of extended life and extended service interval coolants will displace conventional and traditional fully-formulated coolants.
In addition, coolant suppliers will develop truly next generation coolant technology that provides greater high temperature capabilities, is effective under high flow conditions, and possesses improved compatibility with elastomers. Engine coolants in the far future are expected to provide significantly greater heat transfer properties.
Ionic fluids are a new class of fluids that are emerging to replace organic solvents commonly used in chemical processing, cleaning, electrolyte, and heat transfer fluid applications. Ionic fluids may be used to reduce or replace glycol, or both, which would also improve heat transfer properties.
The use of nanotechnology or ionic fluids, or both, may require or allow significant changes in cooling system design, components, and materials. Acknowledgments The authors wish to thank Mr. Stede Granger and Mr. Joseph Hill and Ms. McGeehan, J. Olson, G. Challen, B. Bussem, H. Beal, Ed. Greaney, J. Chen, Y. Technology Transfer Systems, Inc. Pellet,1 Leonard S. Bartley, Jr. The test strategy of these methods depends on the known alkyl carboxylate ability to protect cooling system metals such as aluminum by forming insoluble metal soaps. Various test configurations make this test strategy suitable for the rapid analysis of used coolants in the field.
This paper will document the initial test strategies and the development efforts that led to the first field test for alkyl carboxylate-based coolants. Test kit performance with laboratory and field samples is also discussed. KEYWORDS: coolant, field test, organic additive technology, carboxylate, inhibitor Introduction In typical operation, a heavy duty diesel engine can generate sufficient heat to warm five single family homes in winter. In addition to removing heat generated by fuel combustion, the cooling system must also remove heat generated by other components such as the transmission and turbo charger.
Because of the severity of diesel engine operation and the stress that it places on the cooling system, it is especially important that coolant properties are routinely monitored to assure proper protection of cooling system components and the engine itself. Moreover, rapid testing in the field is essential if needed corrections are to be made before damage occurs. In addition there are tests to detect thermal degradation and contamination with aggressive agents.
Freeze point is easily measured using a refractometer. Coolant degradation can be followed to some extent by monitoring the coolant pH. If the coolant is allowed to become acidic, inhibition becomes ineffective and corrosion damage will occur. Monitoring coolant pH is a quick way to detect the possibility of thermal degradation in the field. A rapid pH drop may also be caused by exhaust gas entry into the cooling system. Exhaust gas can enter the cooling system through leaking head gaskets, for example. In addition to a rapid pH drop, exhaust gas in the coolant may also be indicated by the presence of elevated levels of sulfate.
There are test Manuscript received February 24, ; accepted for publication December 13, ; published online February The test method uses a test pad, impregnated with a soluble barium salt and colored chelating agent. Sulfates in the coolant solutions will react with barium irreversibly, removing it from the chelating agent and changing the pad color. Tests for corrosion inhibition focus on coolant nitrite or molybdate levels, or both. Pad color is related to nitrite level. OAT corrosion inhibition, provided by alkyl carboxylate salts, depletes quite slowly and so does not require frequent refortification by SCAs to assure on-going corrosion protection.
Unlike conventional coolant technology, frequent testing, performed in the field is not necessary in order to determine compliance with an SCA refortification regimen. As discussed above, conventional coolant technologies rely on nitrite and molybdate test strips to determine if the coolant is providing adequate cylinder liner protection.
Nitrite test strips can also be used with OAT coolants. However, options were limited if rapid field testing for carboxylates were required.
Engine cooling - design & function | BEHR HELLA
Shortly after the introduction of OAT coolants, a wet chemistry test method was developed to determine the level of carboxylate inhibition remaining in used coolants. The test was highly accurate with field samples, indicating a pass or fail condition based on carboxylate level. While the test was intended for rapid analysis in the field, the initial configuration did involve several steps and coolant manipulation. It has subsequently been replaced with a test strip method that employed the same test strategy but greatly simplified analysis.
The following sections document the initial test strategies and the development effort for the early field test. Experimental Details The organic additive coolants used in this study for the development of a carboxylate field test were based on the alkyl carboxylate, ethylhexanoate. These coolants were available commercially from Texaco, Inc. The mixtures were further diluted to obtain a constant volume of 50 mL for each resulting solution using deionized water. A precipitate was observed in all mixtures to which coolant was added.
Solutions were filtered to remove the aluminumethylhexanoate reaction product and then analyzed by ICP to determine the amount of aluminum cation remaining and by ion chromatography to determine the amount of ethylhexanoate remaining after reaction. Colorimetric EHA Test Development The following experiments were conducted to demonstrate the feasibility of an EHA test method based on reactions with aluminum cation and aluminum detection using hematoxylin.
The solutions were prepared to yield EHA to Al molar ratios of 0, 1. Total mixture weight was brought to 50 g by adding additional deionized water to keep the total reaction volume constant. In all but the 0 ratio mixture, an aluminum-EHA soap was formed. Field Coolant Evaluation Prototype kit performance was evaluated using coolant samples from an over-the-road, heavy duty diesel fleet.
Vehicles in this fleet had been converted to TELC by flush-and-fill procedures, which involved draining of conventional coolant, flushing with water and then filling with TELC. The super-concentrate was, on occasion, used to convert a vehicle to extended life technology by addition to the conventional coolant already in place in the engine without recourse to the drain, flush, and fill procedure.
Because of the high EHA content of the superconcentrate as well as variability of diesel engine cooling system volumes, EHA levels significantly above those found in fresh TELC were possible. For the purposes of test kit evaluation, 39 samples were obtained and tested by laboratory methods. Coolant samples were also evaluated using two different prototype versions of the field test.
At the time of its introduction, there were no rapid and accurate tests for carboxylate ion concentration in coolants. Consistent with these observations was the fact that aluminum ion was almost never detected in used coolant samples, even applications where significant aluminum componentry was present throughout the cooling system.
This can be seen in solubility data presented in Fig. The figure presents the amount of soluble metal cation in the presence of various alkyl carboxylate anions. Data are presented for aluminum, copper, and iron ions. The effect is least pronounced for copper cation which remains partially soluble in the presence of carboxylates up to ten carbons in length. It is interesting to speculate that the effective corrosion protection, observed with this coolant, may be provided by this insoluble soap formation at the sight of incipient corrosion; soap formation would terminate the corrosion process before damage was done while consuming a minimal amount of inhibitor.
From the graph, it can be seen that there is a linear, inverse relation between the amount of aluminum remaining in solution and the amount of ethylhexanoate added to the mixture. From the graph, all aluminum is removed from the stock solution when sufficient ethylhexanoate is added to achieve a ratio of EHA to Al of approximately 1.
Importantly, the fact that the graph of aluminum remaining versus ethylhexanoate added is a straight line suggests that this stoichiometry remains constant over the range of aluminum and EHA concentrations examined. This may be more apparent from the data in Table 1. Here, the amounts of aluminum and ethylhexanoate ion present in the initial solutions are compared with the amount of ions present after reaction and filtration.
Diesel Engine Coolant Maintenance
The ratio of EHA and aluminum disappearing from solution remains constant over the concentrations studied. Initial Al 0. To render this method useful for rapid field analysis, a method of soluble aluminum detection in required. The coolant sample contains an unknown amount of EHA inhibitor. The two solutions are mixed; a colorimetric aluminum indicator is added to the solution portion of the mixture.
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The presence of aluminum in the mixture indicates there is insufficient EHA to precipitate all the aluminum and thus there is insufficient EHA inhibition. The colorimetric detection of aluminum indicates a failing coolant that would need to be refortified to provide adequate corrosion protection. There are several colorimetric tests for aluminum reported in the literature; a sampling of possible techniques is provided in Table 2. All of these tests permit the visual detection of aluminum at ppm levels by the formation of colored complexes. Conceptually all could be used in the test described above.
However, testing is complicated by the fact that all heavy duty coolants are dyed to help to distinguish them from other engine fluids. Initially heavy duty extended life coolants were dyed red to distinguish them from conventional coolants which were purple or blue. Because of coolant color, aluminum indicators that turn red in the presence of aluminum may be of limited use. From Table 2, it can be seen that tests based on hematoxylin should not suffer from this limitation as it develops a violet color in the presence of aluminum.
Initial efforts to develop a field test for EHA focused on the use of hematoxylin test which was first reported in According to the hematoxylin procedure, a test solution containing aluminum must be buffered to within a pH range of 6. The purple colored complex will not form at pH values below 6. Above 8. At the pH of solutions made alkaline with ammonium carbonate, uncomplexed hematoxylin is red or purple, masking the violet color produced by the aluminum complex.
Thus, lowering the mixture pH after forming the aluminum complex removes the interference and allows aluminum detection if present. To demonstrate feasibility of this test method, solutions were prepared mixing aqueous aluminum stock solution with an EHA containing coolant to yield EHA to Al ratios ranging from 0 to 3. The resultant mixtures were filtered and then tested for the presence of aluminum by raising the pH with saturated ammonium carbonate buffer, adding hematoxylin indicator and then lowering the pH with acetic acid solution.
The dramatic color change can be seen in Fig. Note that the color change occurs precisely and sharply at the end-point previously determined using laboratory methods of ion chromatography and ion-coupled plasma. Thus a potential field test should be in excellent agreement with the more time consuming laboratory analysis requiring ion chromatography. Again, by selecting the amount of aluminum added to the field coolant, it is possible to determine if adequate corrosion inhibition is present as indicated by the coolants ability to precipitate all added aluminum.
It is also important to note that the dramatic color change is obvious even in black and white photography and so utility of this colorimetric test would not be limited for a color blind observer. Obviously, despite its potential accuracy, this multistep test would be too cumbersome for field use unless carefully designed to minimize coolant and solutions handling and manipulation.
With simplification as a goal, a commercial field test kit was designed and ultimately made commercially available. The contents of the commercial kit are shown in Fig. The initial commercial kit consisted of three components: a white-capped test tube contains a premeasured amount of aluminum stock solution.
A measured amount of coolant was added to this tube and an aluminum EHA precipitate was formed. The resulting mixture was filtered using the filter syringe provided and the filtered solution was added to the red-capped plastic test tube. There were three ampoules in this tube containing ammonium carbonate, hematoxylin indicator, and acetic acid. The ammonium carbonate ampoule was broken first releasing the buffer and raising the mixture pH to 8; the second ampoule was FIG. The third ampoule was broken lowering the pH, removing uncomplexed hematoxylin interference.
The resultant color would be purple or violet if there was insufficient EHA to completely remove the soluble aluminum that was initially present. As initially configured, the test took less than five minutes to complete and exhibited high accuracy with laboratory samples. However, a more important indicator was performance with real world, used coolant samples from the field. To this end, prototype test kits were used to evaluate 39 coolants obtained from the field.
The results of laboratory analysis of these field samples are provided in Table 3. These conventional corrosion inhibitors were absent in fresh TELC. Analysis also revealed varying degrees of dilution with water. In the table, coolants are arranged in order of increasing EHA content which is expressed as a percent EHA relative to fresh coolant. It can be seen that in real world use, coolant contamination with conventional inhibitors is quite common. Water contents and coolant pH values also vary significantly. All coolants were tested using the prototype test kit described above.
The results of this evaluation are presented graphically in Fig. A number of observations can be made. This high end-point and the several false fails observed needed to be corrected. Based on these results and a close examination of the chemical analysis of the coolant samples, it was discovered that molybdate interfered with the test by yielding a near black complex with hematoxylin. Its presence in many of the samples with high EHA, resulted in the false fails observed. In addition, an ampoule was added to the white tube containing a lead acetate; lead acetate will precipitate molybdate, allowing it to be removed upon filtration and prior to hematoxylin addition in the red tube.
The modified prototype was used to evaluate the same 39 coolant samples from the original test. Results of that evaluation are presented in Fig. Furthermore, FIG. Conclusions The first kit for EHA field analysis was commercially introduced in and exhibited excellent performance in evaluating extended life, alkyl carboxylate coolants even with highly contaminated samples. This test strategy, relying on aluminum solubility should work with any alkyl-based carboxylate coolant. However, aluminum cation is significantly more soluble in the presence of some aromatic carboxylates and so this strategy may not be effective for coolants based on these inhibitors.
Ultimately, the hematoxylin method for detecting soluble aluminum was replaced with a two strip test kits. The new kit still relies on the reaction of EHA in carboxylate base coolants with a stock aluminum solution but has been significantly simplified by replacing the hematoxylin wet chemistry test with a test strip method for aluminum detection. Accuracy for the test strip method has remained high while the test procedure takes about a minute to execute. Kreiser, T. Kolthoff, I. Hemmes, P. Pellet, R. Hattfield, W.
Mowlem, J. Liang, P. Kdriss, K. Yl, Abdel-Aziz, M. Bertsch, P. Hudgens,1 E. Schmidt,2 and M. Williams2 A Comparison of Membrane Technologies for Engine Coolant Recycling ABSTRACT: Recycling of used engine coolants containing ethylene glycol and other glycols would appear to be well established, particularly for reverse osmosis and nanofiltration membrane, electrodialysis, and distillation-based processes. Both literature and recycling facilities indicate success in employing these techniques. In addition, some recycling facilities have produced and marketed product that led to coolant system damage and engine failure, either as a result of not sufficiently removing contaminants or inadequately reformulating with corrosion inhibitors and other additives.
However, no study to date has focused on a fundamental assessment of the separation characteristics and interactions of the various classes of coolant technologies with the commercially available reverse osmosis, nanofiltration, and electrodialysis ion exchange membranes typically seen in recycling operations.
This study presents results of a comprehensive evaluation of the separation characteristics of a wide range of these membranes with a wide range of coolant types. In particular, the study examined production rate characteristics, inhibitor and other additive separation, and contaminant removal for reverse osmosis, nanofiltration, and electrodialysis. Residual inhibitors remaining in the recycled coolant are examined, with guidance provided on how these residuals might affect coolant reformulation and performance. KEYWORDS: used engine coolant, used antifreeze, recycling, electrodialysis, reverse osmosis, nanofilteration Introduction Engine coolants are used to protect internal combustion engines from temperature extremes.
The amount of coolant changed-out in the past has traditionally been discharged to the sanitary sewer. However, as a result of restrictive legislation on disposal and increasing raw materials cost, recycling engine coolant has and continues to become increasingly desirable. While the idea of designing products for recycling is superior to simple disposal, the public perception of recycling is typically that the recycled product is less in quality. Some antifreeze recycling methods do indeed result in downcycled product compared to virgin coolants; however, other technologies have been successfully employed to yield upManuscript received April 21, ; accepted for publication February 12, ; published online April There are considerable separation efficiency differences between these various processes.
Consequently, the desalting technology unit operations required to remove TDS and produce on-specification products at high recoveries are the most essential part of any recycling process. In all these technologies, separating a large portion of TDS from the coolant in the recycling process is key. The desalting technologies are essential unit operations required to produce an on-specification concentrate or prediluted recycled product and include any one or a combination of vacuum distillation, membrane separation, or ion exchange. The thermal and membrane-based desalting devices essentially separate a saline solution into two streams: one with a low concentration of dissolved salts and the other containing the remaining dissolved salts often referred to as the concentrate or brine stream.
While many early antifreeze studies and recyclers touted each of the recycling technologies as suitable for producing acceptable product, practical experiences have shown that a commercially successful recycling operation will use multi-stage processes in order to produce recycled coolant meeting OEM requirements.
A primary cause of these failures and of critical importance in any recycling process, but unfortunately one in which many recyclers fall short, is removal of corrosive inorganic ions. These include chloride and glycol degradation products that can cause coolant system failure.
Also unfortunately, these failures have also caused many to skeptically view antifreeze recyclers out of concern that the technologies used cannot consistently produce a product as good as virgin coolant. As shown in Fig. Studies were done with a wide variety of virgin coolants to identify problems that the two unit operations could potentially encounter with the various coolant additives.
Finally, studies with actual used coolants were performed to determine if these technologies could produce a product equivalent to virgin coolant, individually or in combination. As the equation indicates, higher pressures across the membrane serve to increase flux, while higher osmotic pressure differences across the membrane decrease flux. Finally, recovery is defined as the ratio of final product volume to feed volume. It is important to note the subtle but important difference between RO and NF.
Traditional RO membranes typically have high salt rejection for both monovalent and multivalent ions as well as many organics and are typically capable of producing high purity water in a single pass. While antifreeze recycling with RO is many times claimed by commercial recyclers, further investigation reveals their actual use of NF membranes. It is important to note the distinction to avoid misperceptions concerning the separation characteristics that can be achieved with NF as opposed to traditional, high rejection RO.
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- Supplemental Coolant Additives.
A flow diagram identifying the streams of the ED process is shown in Fig. Table 2 lists virgin and recycled coolant ASTM specifications, as well as military recycled coolant standards. This system had an effective membrane area of cm2. Integrity of the membranes before coolant studies were verified with standard salt solution. Table 4 lists properties of the four ion exchange membrane sets studied. Separation characteristics with each membrane were verified with standard salt solutions prior to coolant studies. Table 5 lists properties of the coolants. The used coolant was pretreated using filtration and activated carbon.
Ethylene glycol content was determined by diffraction. Results and Discussion The production rate and separation efficiency of RO, NF, and ED processes were found to be dependent both on membrane characteristics and coolant chemistry. Coolant No. In fact, all the RO membrane flux rates are too low to be considered practical.
Also, coolant chemistry had very little impact on productivity of the traditional RO membranes: production rates of both conventional and hybrid coolants were similar. In contrast, the NF membranes exhibited much better productivities. These are compared to those of the RO membranes in Fig. As would be expected, the more open, lower salt rejecting NF membranes generally had higher production rates. Figure 5 summarizes conductivity rejection with a hybrid coolant. While conductivity alone does not indicate coolant quality or correlate well with TDS content, it does provide an indication of the membrane separation efficiency.
Figure 6 summarizes average production rate and production rate ranges encompassing all eight coolants for the four NF membranes determined in the initial screening to be practical. Conductivity rejections for these are given in Fig. This indicates the importance of considering not only standard salt rejection and water flux, but also the differences in interaction of the ethylene glycol and other constituents of the coolant with the specific membrane used. In this study, thin-film composite NF membranes based on aromatic polyamide with a more open pore structure performed better overall when considering both flux and removal on all types of coolants compared to both thin-film composite aromatic polyamide membranes with a tighter pore structure and asymmetric cellulose acetate NF membranes.
This is in part the result of the higher viscosity of EG compared to water: the higher viscosity EG would be less efficiently transported through the membrane than water at the same pressure. In addition, it is expected that EG would be less absorbed by the membrane than water. Figure 8 better illustrates the effect of coolant type on nanofiltration flux.
The flux for each membrane was better with the conventional coolant and less productive with the hybrid or OAT-based coolants. Rejection, shown in Fig. These figures also show the substantial flux and conductivity rejection variability of each membrane with the different types of coolants. This trend was generally followed for all eight of the coolants studied for each FIG.
These figures also show the flux and conductivity rejection of a typical pretreated used coolant; flux generally falls below that of the spiked coolants, while rejection is higher. Based on ion chromatograph and HPLC analyses, it was determined that the used coolant contained additives typical of a mix of conventional, hybrid, and OAT-based coolants; Table 8 compares the species in the virgin coolants to those in used coolant. It is informative to examine the individual species rejection, as shown in Figs. As would be expected, multivalent species such as sulfate, phosphate, and molybdate were rejected well by the membranes, while monovalent species such as chloride, nitrite, and nitrate were poorly removed.
Glycol degradation acids, which would consist of primarily glycolic and formic acids, were marginally rejected. It is expected the larger, more polar glycolic acid would be better removed than the smaller formic acid. The lower rejection of these would be expected since both are relatively small molecular weight compounds and so separation would be based primarily on charge; both nonionized species passed through the membrane. In particular, chloride and glycol degradation acids were too high in the permeate products, even at the low recoveries studied.
Higher recoveries would result in even lower removal rates for these. For the typical coolant FIG. All of these species would be present predominately in the ionic form and so were rejected well by the charged NF membranes. Conversely, removal of tolytriazole was poor, possibly because of its expected monovalent charge at the feed pH. Examination of Figs. In general, the conventional coolants contain substantial amounts of silicate, tetraborate, nitrites and nitrates, and phosphates.
While the phosphate is well removed, removal of the other species is only marginal and so overall conductivity rejection is low. As a result, flux with the conventional coolants is high. Hybrid and OAT coolants contain substantial amounts of organic acids that are very well rejected by the membranes. However, since these are rejected, there is a substantial osmotic pressure drop across the membrane and corresponding drop in pressure driving force according to Eq 1 and decreases in flux relative to those of the conventional coolants.
The lowering of pressure driving force due to high osmotic pressure difference across the membrane also accounts for the low fluxes of traditional RO membranes: these tight membranes reject most species, resulting in a relatively high osmotic pressure difference across the membrane and correspondingly low flux. Figure 14 summarizes average production rate and ranges for the four different ion exchange membranes studied with the eight spiked coolant solutions.
Conductivity removal is summarized in Fig. Conductivity removals were substantially higher than those of the NF membranes since batchwise ED operation allows the feed solution to be processed until either the target conductivity is achieved or no further reductions in conductivity are possible.
In general, productivity was higher with the conventional coolants, followed by the hybrid and the OAT coolants. Conductivity removal was essentially the same for each coolant type and for each membrane. However, these had no clear impact on the hybrid and OAT-based coolants productivity. Production rate was similar to that of the OAT coolant, with excellent final conductivity removal.
Glycol degradation acids, chloride, sulfate, nitrite, nitrate, phosphate, and molybdate were essentially completely removed over the course of the run. Tolyltriazole, sebacic acid, and benzoic acid, all FIG. Removal of 2-ethylhexanoic acid was less than the other organic acids, possibly due to the side chain branching of the compound, resulting in a lower transport number in the IX membrane compared to the divalent sebacic acid and the smaller tolyltriazole and benzoic acid.
Comparison of Figs. However, the ED product does have a slight color, usually a visible yellow tint. While many of the dyes are ionic, these tend not to be completely transported across the IX membranes. Also, as with the NF studies, ED removals of individual inorganic and organic species in virgin spiked coolants followed the same trends as the individual species removals in the pretreated used coolant.
As discussed above, a single process usually falls short of producing an acceptable recycled product, particularly if the goal is to produce coolant meeting virgin specifications. While the ED process alone can nearly meet all requirements, the product does contain a slight color.
Conversely, the NF process is better at removing color. Permeate from the NF process is water white, while monovalent species removal is usually unacceptable. However, an integrated approach combining these two processes utilizes the advantages of each. In addition, ED process production rate also increases since part of the species of concern has been removed by NF. The NF subprocess partially reduced the multivalent species and a fraction of the organic acids, and the ED subprocess removed the remaining species to near virgin ethylene glycol specifications.
Figures 12, 13, 20, and 21 and Table 9 show the individual contaminant and additive species removal efficiencies of NF, RO, and an integrated process with the used coolant; as indicated above, the used coolant represents a mix of conventional, OAT, and hybrid coolants. In general, NF removals of chlorides and conventional additive species were low. However, if the chloride levels met specifications, the presence of the conventional additives would not be a great issue if the recycled coolant reinhibition package consisted of compatible conventional additives.
Similarly, the presence of residual organic inhibitors in the NF or ED recycled product would not have a great impact on a recycled product reformulated with compatible OAT-based additives. However, some incompatibilities might exist between some conventional and OAT-based additives. Ideally, each coolant could be characterized and processed to remove corrosive species and degradation acids to meet corrosive species specifications, with further processing limited only to the extent necessary to reduce species incompatible with the planned reformulation additives.
Fluxes of traditional, high salt rejection RO membranes have been verified to be impractical, despite claims by many recyclers that they use RO. NF membrane productivities are acceptable, but conductivity and contaminant removal range from only marginal to good, with none of the studied NF membranes capable alone of producing recycled coolant meeting virgin coolant specifications. While the removals of most organic acids and divalent species were excellent, removal of monovalent species such as chlorides and nonionized species such as silicates were poor.
The ED process was capable of reducing conductivity to very low levels and well as removing individual contaminants and other ionic components, although some slight color remained. The productivity of the ED was greatly improved and the product solution was water white when it was combined with an NF process, with ED treating the NF permeate. Ideally, the degree of removal of the residual inhibitors could be customized for each individual batch of used coolant based on the planned reinhibition additive and laboratory analyses for each species present in the coolant.
Practically, the robustness of the type of reinhibition additive to be used and conductivity can serve to guide the extent of deionization required. Frye, D. Haddock, M. Kugn, W. Kurio, N. Jehle, W. Richardson, R. McCosh, D. Gavaskar, A. Penray Technical Bulletin Ho, W. Strathmann, H. Marinho,1 and Aleksei V. New engine coolants are often required to meet many of these new developments and the associated changes in cooling system requirements. Since corrosion protection is one of the key performance parameters for engine coolants, new and more effective corrosion measurement methods are useful for evaluating old and developing new coolants to meet the needs of new cooling systems or having improved corrosion protection performance, or both.
Existing ASTM test methods for engine coolants either rely on inspection of the sample after a relatively long exposure period to determine the extent of localized attack or do not yield results directly related to localized corrosion. In this paper, coupled multi-electrode sensors test and simulated localized corrosion cell technique are compared and discussed to gain new insight for facilitating the development of more effective inhibited coolants.
Extensive efforts are being devoted to research to develop new and more environmentally friendly propulsion technologies, such as fuel cell and petroleum-hybrid electric power, and new material technologies, and to explore methods to increase the use of lighter metals or materials, or both. Since corrosion protection is one of the key performance parameters for engine coolants, new and more effective corrosion measurement methods are useful for developing new coolants to satisfy the needs of the new cooling systems or to improve corrosion protection performance, or both.
However, this method is conducted at room temperature and does not provide a quantitative localized corrosion rate. Since the s, significant advancements have been made in developing more effective, reliable and Manuscript received February 22, ; accepted for publication October 4, ; published online November The surface of one end of the wire electrodes is exposed to the test solution.
The other end of the wire electrodes are coupled electrically via zero-resistance ammeters or an equivalent sensing instrument. Localized corrosion can be estimated by measuring the coupling current flowing into or out of the selected wire electrode. However, the localized corrosion rates determined by the coupled multi-electrode sensor probes have not been verified by independent reliable measurements on the same electrodes. The anodes and the cathode of the cell are normally coupled electrically via the ZRA to simulate the localized corrosion conditions. The ZRA measurements are used to provide the component of the localized corrosion current that results from the galvanic cell interaction between the large cathode and the small anodes.
The cell used in this method simulates faithfully the localized corrosion conditions under the studied conditions. It has been used extensively in laboratory studies and field applications.