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Cavitation corrosion of cylinder liners in heavy duty engines can be one of the significant limits in engine operating time between overhauls. In both laboratory and engine dynamometer studies, engine coolants based on propylene glycol (PG) have performed better than similar formulations based on ethylene glycol with regard to cast iron cavitation corrosion. The performance of PG base coolant in all other aspects of coolant use was equivalent or superior to both industry standards and existing ethylene glycol (EG) products designed for use in heavy duty engines. Additionally, propylene glycol is cost competitive, readily available, and less toxic compared to ethylene glycol. A propylene glycol base engine coolant is described which assists the heavy duty user in solving many current problems related to cooling system servicing and engine life.

A test strip containing three pads for measuring the freezepoint protection, molybdate and nitrite levels in heavy-duty diesel engine cooling systems has been developed for commercial use. The test strip requires no pretreatment or dilution of the sample, other than to allow it to cool to 130 degrees F or lower, and gives results for all three tests within two minutes. The test results are sufficiently accurate, and the strips are stable over extended periods of time, provided the container is kept tightly closed and away from direct sunlight and prolonged elevated temperatures when not in use. The freezepoint test offers an inexpensive alternative to refractometers. Since it can be used with either ethylene or propylene glycol coolants, it is recommended over the use of hydrometers.

Fluid cavitation corrosion can cause severe damage and problems in many practical applications. A collapsing bubble produces pressure and thermal shock waves, and microjets. These intense local forces will erode material in the proximity of the collapsing bubble. The intensity of the collapsing bubble is heavily dependent on the physical and thermodynamic properties of the cavitating fluid medium. An experimental study of the effect of various physical and fluid thermodynamic properties of the fluid has been conducted utilizing an ultrasonic cavitation generator and a real time cavitation intensity measuring method that had been developed earlier by the author and described in reference [1]*. Tests have been conducted at room and elevated temperatures. A test matrix with fluids that have additives to modify certain physical characteristics of the fluid was established. The physical properties were either measured or calculated.

Several ultrasonic bench rigs are widely used in the engine coolant industry for cavitation corrosion tests. These tests are focused on the qualification of coolants formulated to minimize cavitation corrosion. Standardized metal test “buttons” of different materials are used for that purpose. Traditionally these cavitation corrosions tests are run for a specified period of time. At the end of the test the amount of mass removed from coupons due to cavitation is a direct reflection of the cavitation corrosion performance of the additive. However, results can show wide scatter and inconsistencies depending on the ultrasonic probe manufacturer, testing lab, horn type, dial setting level and probe instability. Therefore, a way of quantifying the cavitation intensity of these various designs was clearly called for to establish a standardized test and recommendation to be utilized across the coolant testing community.

Silica gel formation in heavy duty diesel cooling systems has increased with the increased usage of antifreeze with high levels of silicate. Gelation can occur when this type of antifreeze is mixed with supplemental coolant additives which are required to protect heavy duty diesel engine cooling systems, or when the undiluted antifreeze is stored for long periods. Gel in the cooling system can decrease coolant flow and heat transfer causing engine overheating. Gel formation is shown to be a chemical problem, not a problem of newer engine and cooling system design. Recommendations for avoiding the problem are included.

Coolant filters have been used for over 30 years by heavy duty engine builders but little has been published in the technical literature documenting their performance. In heavy duty cooling systems a supplemental additive package is periodically added to the system (usually at the oil drain) to prevent the coolant from becoming corrosive and to stop the build-up of deposits which cut down on heat transfer. Not only is the coolant filter the most convenient and reliable method to deliver the supplemental additive to the cooling system, it removes debris from the coolant which can cause deposits and wear, aggrevate corrosion, and even plug heat exchangers. Additionally, the used coolant filter serves as a diagnostic trouble shooting tool. The results of extensive lab and field evaluations are reported documenting the benefits of coolant filtration.

Approximately 200 to 210 million gallons (or about 2 billion pounds) of antifreeze or engine coolant are produced in North America each year. About 80 percent of this is sold to refill leaking cooling systems. This paper compares the environmental impact of additives in leaking and improperly disposed coolant to other sources of these same chemicals.

Pressure to reduce costs has caused a trend toward extended coolant life in heavy duty applications today. Extended life requires the user to maintain the cooling system within tighter limits over a longer period of time. Ideally, the coolant would be replaced based on need, rather than time or mileage. The introduction of corrosive ions can lead to shortened coolant life and the need to replace the coolant sooner than normal in order to protect the engine. In order to know when to replace the coolant, an understanding of the effects of these corrosive ions in the coolant is necessary. This paper focuses on the effects of chloride and sulfate ions on coolant performance in laboratory tests. Laboratory tests were run on a variety of commercially available heavy duty coolants including organic, inorganic, and treated water systems. The tests consisted of various laboratory procedures used throughout the industry to test the ability of a coolant to protect against corrosion.

A three-pad dip-and-read test strip has been developed for determining whether the pH, chloride and sulfate levels in engine coolant samples lie within or exceed the recommended ranges. The preferred ranges are 7.5 to 11.0 for pH, below 200 ppm for chloride ion, and below 1500 ppm for sulfate ion. Conditions outside of these limits can lead to corrosion of engine cooling system metal surfaces. A quick and convenient test can determine whether the coolant is suitable for continuing use or should be drained from the system. Extensive performance and stability evaluations of the test pads have been carried out, to ensure that the test strip results agree with reference method results and that test strips are stable under normal storage and use conditions. The test strips were evaluated with different glycol levels, with both ethylene and propylene glycol samples, and under different lighting sources.