By – Gary Pipenger President, AMALGAMATED, INC.
This article is the second of two articles drafted to define what chemistries are needed in petroleum diesel fuel additives in order to create the best possible additive products to insure optimum winter time operability. The first article, Part 1 titled “The ‘Right Way’ and the ‘Wrong Way’ to Build a Good Diesel Fuel Performance Additive” detailed the required chemical additives and test methods for achieving ideal engine performance and fuel economy.
The following pages outline the chemical additive enhancements and testing methods required in order to effectively eliminate operational issues experienced during cold weather operations. While some fuel producers, fuel suppliers and fuel users may argue that it is impossible to eradicate all of the potential winter operability issues, this author disagrees based on his more than 43 years of fuel additive formulation experience, independent laboratory analyses and actual field results.
When the fuel additive supplier does his job correctly and the winter diesel fuel additive is properly compounded with the ‘right’ chemistries in the correct amounts AND the diesel fuel is accurately treated, operational issues can be eliminated. This is a must for the new common rail fuel injection engines.
Unfortunately there are many diesel fuel additive companies marketing products in North America (and other countries around the world) who cut corners and do not formulate the winter additive products they market with the required amount of proper chemistries. These cost cutting decisions are made in an effort to keep the end product additive price low and maximize profits for the additive vendor.
Some diesel fuel additive marketers may compound the correct amounts of chemistries but offer these additive products for sale with unrealistically reduced treat rates. This decision again is made in order to maximize profits with the “hope” that the properly formulated additive will work for the fuel user “in most cases” at the lower dosage rate. They also hope for mild winter temperatures or they just tell the additive buyers to “double the treat rate and blend kerosene” – both will immensely increase costs.
This marketing method is simply wrong and does not do justice to the additive buyer because it leads to various winter operability issues which culminate in increased downtime and severely decreased fuel efficiency. The net effect is much higher operational costs for the diesel fuel consumer and an incorrect belief that diesel fuel additives do not work. This does not help the additive buyer or the industry.
The following article is directed to the diesel fuels marketed in North America with reference to the ASTM D-975 Specifications For Diesel Fuels(1), but it is wholly applicable to all other marketing areas of the world. While the required specification may be different, the testing methods suggested herein to insure winter operability performance are valid regardless of the diesel fuel used.
Discussion
As indicated in the previous article, the proof of any diesel fuel additive’s performance is the sole responsibility of the purchaser of the additive product. However, unlike some of the suggested summer ‘performance additive’ testing detailed in Part 1, there are precise laboratory test methods to evaluate winter diesel fuels and additives. Like for summer additives, the winter diesel fuel additive buyer should diligently ‘test the prospective product’ BEFORE the purchase is made because there is no guarantee that the particular diesel winterization additive product chosen will achieve any of the benefits claimed.
Winter diesel fuel additive testing begins with choosing a reputable ASTM(2) qualified laboratory with established experience in testing winter diesel fuel additives. This can be a bit of a challenge for the winter diesel fuel additive buyer but if the right questions are asked, a good laboratory can be found.
The laboratory search should begin with reviewing winterization requirements for diesel fuels listed in the current ASTM D-975 Specification for Diesel Fuels(1). This document lists the basic physical parameters that must be met for all winter diesel fuels whether in an on-highway or off-road application.
The ASTM D-975 Specification for Diesel Fuels(1) provides the recommended physical fuel property boundaries; however, it does not specifically address all winterization operability improvements achievable with diesel fuel additives. The laboratory tests described in ASTM D-975(1) should be done to determine the improvements wanted and accomplished with a prospective winter diesel fuel additive.
CLOUD POINT is the laboratory measurement of the fuel temperature at which the inherent paraffin content in a diesel fuel first begins changing from a liquid to a solid state. The fuel’s liquid paraffin content changes to solid wax crystals as the fuel temperature drops. This causes the diesel fuel to appear to be ‘cloudy’ (i.e., Cloud Point).
The fuel Cloud Point is a common temperature used by individual fuel refiners to describe their winter diesel fuel productions and fuel suppliers to sell their products. But this laboratory test parameter result is a very conservative temperature when used as an indication of potential vehicle operability if diesel fuel cold flow improvers have been treated in the diesel fuel. This is because the ‘right’ cold flow improver additives can lower the actual vehicle operability well below the Cloud Point temperature.
The ASTM D-975 Specification for Diesel Fuels(1) lists the expected 10th percentile minimum ambient air temperatures for the United States. These expected ambient temperatures are often used by fuel producers, fuel suppliers and fuel users as a means to gauge when a diesel fuel will fail if the fuel has not been treated with cold flow improver additives. A vehicle engine with unadditized diesel fuel will likely fail at or near these ambient air temperatures.
There are Cloud Point Depressant Additives marketed in North America, but it should be noted that there is no chemistry available today that will lower a diesel fuel Cloud Point by more than a few degrees F. Cloud Point Depressants can be effective to achieve a fuel marketing specification when only a few degrees F (typically 2 to 4 degree F) reduction is required.
As previously stated, the fuel Cloud Point temperature is routinely used by petroleum refiners and fuel suppliers to define winter diesel fuels for sale. This is relevant only when the diesel fuel does not contain any chemistries to effectively modify the wax crystal formations and suspend them in the fuel at fuel temperatures below the Cloud Point.
It should be noted that the ‘belief’ that diesel engines cannot adequately operate with fuel temperatures exceeding a delta of 10 degrees C below the Cloud Point is a total myth. When the diesel fuel is properly treated with a combination of the ‘right’ chemical cold flow improvers, wax crystal size and shape modifiers plus effective wax crystal suspension agents in the correct dosages, diesel vehicles can successfully operate at more than 10 degrees C below the fuel Cloud Point temperature.
Over the past 43+ years, this author’s own field experience has proven successful diesel equipment operability with fuel temperatures of more than 25 degrees C below the fuel Cloud Point when the correct chemicals in the recommended amounts are treated in the diesel fuel.
Laboratory testing of the diesel fuel Cloud Point (and the following parameters herein) without and with the recommended chemical treatment(s) is the key to proving diesel vehicle operability. It is also critical that the testing be done with the diesel fuel expected to be used BEFORE the additive purchase is made.
POUR POINT is a laboratory test determination of the fuel temperature at which all of the liquid paraffin content in a diesel fuel is completely changed to solid wax (also called the solidification point temperature). A diesel fuel at its Pour Point temperature will not flow and cannot be poured out of the container storing it.
While there are several Pour Point Depressant Additives sold, the diesel fuel Pour Point test result is not relevant for diesel powered vehicle operability because the diesel engine will usually have failed long before the fuel Pour Point temperature is reached. The ASTM D-975 Specification for Diesel Fuels(1) does not contain a requirement or make mention of a diesel fuel Pour Point recommendation.
The Pour Point temperature is applicable only for defining diesel fuel cold weather handling properties where pumping of the diesel fuel from one point to another is necessary. Most of the pipelines in North America have a Pour Point requirement of less than 15 degrees F (-26 degrees C) during the winter months and many utilize Pour Point Depressant Additives to achieve this pipeline requirement.
It should be noted that most quality diesel fuel cold flow improver additives will adequately lower the Pour Point temperature several degrees when used even at very low treat rates.
LTFT – Low Temperature Flow Test – ASTM D-4539(5) is a laboratory measurement of ‘estimated’ filterability of a diesel fuel at cold temperatures. This laboratory test method is extremely difficult to conduct because of its requirement to ‘predict the failure point’ of the fuel before lowering the temperature at a prescribed cooling rate in a series of test specimens of the subject fuel.
The test procedure also requires a large amount of fuel to be sampled (200ml samples for each 1 degree C test temperature point starting at 5 degrees C above the fuel Cloud Point temperature. The fuel samples all must be cooled in the same bath at a rate of 1 degree C per hour.
The large number of test samples require an extensive amount of time to run the test (a single sample is tested at each 1 degree C of temperature drop from the starting point and each 200ml sample is only used for one test). If the fuel Cloud Point is +3 degrees C and the predicted fuel failure point is -12 degrees C, then 20 separate 200ml samples of the fuel will be needed for the test (i.e. 5 samples to be tested above the fuel Cloud Point and 15 samples to be tested at each 1 degree C drop in temperature from the fuel Cloud Point to the expected -12 degree C failure point temperature).
If the predicted LTFT failure point temperature is not reached using all of the specimen samples, the test must be started over with a new series of specimen samples.
The LTFT test generally yields results at or slightly below the fuel Cloud Point in diesel fuels. There are LTFT Reducing Additives marketed, but these additives can only lower the LTFT of a diesel fuel a few degrees (typically 2 to 3 degrees C) below the diesel fuel Cloud Point temperature. Therefore, the LTFT test data achieved in diesel fuels treated with LTFT Reducing Additives is extremely conservative for predicting diesel engine winter operability.
The ‘true’ operability temperature achievable when the ‘right’ cold flow improver chemistries are properly added to a diesel fuel allow the equipment to operate several degrees below the LTFT result.
CFPP (Cold Filter Plugging Point) is a laboratory test measurement of a diesel fuel’s temperature that simulates the expected fuel filter failure point resulting from the ‘caking’ or collecting of paraffin wax crystals on the fuel filter media. Some fuel producers argue the CFPP result does not accurately represent the expected fuel filter failure point, but the CFPP temperature historically is the most widely used test in many countries around the world for all types of diesel fuels to define expected vehicle operability.
While the current ASTM D-975(1) specification does not include a specific CFPP recommendation for diesel fuels sold in North America, most fuel users utilize CFPP test results to summarily predict vehicle operability. CFPP test results from a quality laboratory with proper equipment and experience in CFPP testing using the ASTM D-6371(6) test procedures can be used much more reliably than Cloud Point, Pour Point or LTFT for vehicle operability without and with diesel fuel additives.
The CFPP test result will typically be at or slightly below (1 to 2 degrees F) the diesel fuel Cloud Point temperature when quality diesel fuel Cold Flow Improver Additives have not been treated in the fuel. The ‘right’ multi-component Cold Flow Improver Additives (if compounded correctly with the ‘right’ kinds and amounts of chemistries) can significantly lower the fuel CFPP temperature and permit acceptable diesel powered vehicle operation well below the fuel Cloud Point temperature.
Laboratory testing without and with the prospective Cold Flow Improver Additives treated in the user’s diesel fuel will verify the CFPP reduction capabilities of any additive product. Automatic ASTM D-6371(6) CFPP test equipment results have been correlated to actual field operability in various diesel engines and vehicle types over the past fifty years in Europe and other parts of the industrialized world.
Proper CFPP testing is also very important for todays ‘common-rail’ fuel injected diesel engines with fuel pumps typically operating at 25,000 to 35,000 psi of pressure. Any fuel flow reduction to the injectors due to restricted fuel flow through the fuel filters will cause a lack of adequate pump and fuel injector lubrication which will culminate in catastrophic engine failure and excessive repair costs.
WAX DISPERSANCY is a newer term used to describe the ability of a diesel fuel additive to ‘fully suspend’ the paraffin wax crystals up in the fuel at fuel temperatures below the Cloud Point. This fuel parameter is extremely important because the individual solid paraffin wax crystals themselves are heavier than the liquid fuel components and they tend to settle in the low points of the fuel system.
The paraffin wax crystals also tend to agglomerate together to form even larger and heavier wax crystals which accumulate in the bottom of the fuel lines and in tanks where the engine fuel draw lines are located. When a vehicle is parked in a cold ambient temperature overnight, these paraffin wax crystals settle in the bottom of the vehicle fuel tank and will be the first thing pulled into the engine when engine start is initiated. This will immediately plug the fuel filters and the engine will not start.
The same thing can happen to above ground fuel storage tanks during cold weather causing the island pump filters to plug up with excessive paraffin wax crystals and stop fuel flow.
Research Laboratories, Inc in Fort Wayne, Indiana(7) has developed a proprietary laboratory test for evaluating the tendency of the paraffin content in a diesel fuel to settle out of solution at cold temperatures. This WDFT – Wax Dispersancy Filterability Test(8) can be conducted on a diesel fuel to effectively determine and document the suspension capabilities of the diesel fuel treated with a Wax Dispersing Additive. NOTE: Many of these additives being marketed do not work as advertised.
COLD ROOM TESTING
The only real means of testing diesel fuel winter operability (with or without an additive) is to use the diesel fuel in the diesel engine(s) during the winter season. Unfortunately, this testing method can lead to catastrophic fuel failures and excessive equipment downtime during the worst possible moments for all of the equipment using a particular diesel fuel.
It is possible however to ‘simulate’ the actual cold weather operability of a diesel fuel (without or with
Cold Flow Improver Additives) by using a unique Cold Room Testing Program(8) developed exclusively by Research Laboratories, Inc (7). This testing procedure uses OEM diesel engine fuel pumps to flow diesel fuel through OEM diesel engine fuel filters placed in a computer controlled cold room at fuel temperatures down to -28 degrees F.
The Cold Room Test(8) procedure yields the best possible ‘real world’ performance results for diesel fuels tested without and with Cold Flow Improver Additives. The diesel fuel Cold Room test results represent the most accurate possible ‘simulation testing’ of diesel fuel cold flow capabilities which has been directly correlated to actual diesel engine and vehicle cold weather operability in the field.
This unique testing is the ultimate method available to diesel fuel producers, suppliers and fuel users for verifying winter/cold weather diesel fuel suitability before placing the fuel in operation and the testing does not require an actual vehicle for testing purposes. Additionally, this testing method is a ‘must’ for diesel fuel additive manufactures and suppliers who want to verify their products and provide the best winterization treatments for their customers’ fuels.
Other Factors Affecting Diesel Fuel Winterization
WATER (moisture content) is inherent in all diesel fuel as a contaminant. Water weighs 8 pounds per gallon and diesel fuel weighs slightly more than 7 pounds per gallon. Accordingly, the water content in diesel fuels will sink to the lowest levels of the fuel delivery system (i.e., tank bottoms, lines and sumps).
Water corrodes metal (causes rust) and acts like a sponge picking up dirt, debris and other small contaminants commonly found in fuel storage tanks, fuel delivery lines, vehicle fuel tanks and vehicle fuel lines. It can be delivered along with the diesel fuel from pipelines, delivery trucks or railcars.
The diesel fuel water content (both visible so-called ‘free’ water and non-visible so-called dissolved water) and the small size contaminants will not always be taken out of the fuel by the fuel delivery system filters or vehicle fuel filters. When the water and these contaminants enter the diesel fuel pumps and injectors (especially in today’s very fine tolerance high pressure common-rail injected engines), the damage will be extensive and costly for the equipment operator.
Equipment manufacturers have advocated installing reduced micron sized fuel filters (2µm or less) on their engines in order to help minimize the damage from inherent diesel fuel water and contaminants. This tactic only increases filter costs and maintenance expenses for the diesel equipment operator over time due to frequent filter changes and added lost hours of operation from equipment downtime.
The water content in diesel fuel will change to ice crystals at fuel temperatures below 32 degrees F. These ice crystals can collect in low areas of the fuel delivery system and plug fuel lines or be drawn into fuel filters causing fuel flow restriction which reduces engine power or stops the engine entirely.
It is not realistically possible to completely eliminate all moisture and all contaminants in today’s diesel fuels. However, as detailed in this author’s Part 1 article (The ‘Right Way’ and the ‘Wrong Way’ to Build a Good Diesel Fuel Performance Additive), if the ‘right’ chemical additives are treated in the right amounts in diesel fuels, the negative maintenance and operational effects of inherent moisture and contamination in diesel fuels can be dramatically minimized or eliminated.
De-Icer Additives (glycol ethers) can be added to diesel fuels at a rate of 1 pint per 100 gallons of fuel to lower the moisture freeze point temperature and prevent fuel system icing. A laboratory can run a Gas Chromatograph ‘fingerprint’ test in order to determine the amount of De-Icer Additive compound present in a diesel fuel additive if the de-icer component used is identified to the laboratory. To the author’s knowledge, there is no ASTM method for testing or analyzing diesel fuel De-Icer Additives.
Other Factors Affecting Diesel Fuel Winterization
CRUDE OIL SOURCING for the diesel fuels produced today should play a significant part in selecting the ‘right’ diesel fuel winterization additive. Many of the crude oils used to manufacture diesel fuels in North America today are derived from the Canadian Tar Sands and Bakken Basin areas of the USA. These crude oils produce diesel fuels with higher than typical Cloud Point temperatures and higher water contents. These diesel fuels are extremely difficult to treat effectively with winterization chemistries.
The Cold Flow Improver Additives required to properly treat diesel fuels refined from these crude oil sources must be compounded with multi-component chemistries including CFPP Reduction Additives,
Wax Crystal Modifiers, Wax Suspension Additives and De-Icer Additives all specifically formulated for such crude oil derived diesel fuels.
These ‘multi-component’ Cold Flow Improver Additives will also need to be dosed at substantially higher treat rates in order to achieve acceptable diesel engine operability performance targeted to the expected cold weather temperature points.
Again, a Cold Room Testing Program(8) undertaken BEFORE the diesel fuel is placed into service is the best means to verify the operability temperature failure point without and with any prospective winterization additive.
KEROSENE BLENDING has been the main method of diesel fuel winterization used by petroleum refiners, fuel suppliers and fuel users for many decades in the past. Adding (blending) 10 to 30 percent of light distillate (kerosene) into diesel fuels in past years often substantially lowered the fuel Cloud Point, Pour Point and CFPP temperatures to improve the fuel mixture’s cold weather operability.
However, as the test data below shows, kerosene blending in today’s diesel fuels does not significantly change the cold weather properties of the base (unblended) diesel fuels.
As previously indicated, the Research Laboratories, Inc Cold Room Testing Program provides the best possible ‘real world’ indication of how good or how poor a prospective diesel fuel winterization additive will protect the fuel and equipment. The same is true for kerosene blended diesel fuels without the use of a winterization additive.
The lab tested the above four diesel fuels (blended with 30 percent kerosene) in the Cold Room and compared them to the same four diesel fuels (without kerosene) but treated with a well-formulated ‘good’ quality winterization additive (see below).
Blending kerosene is used by many diesel fuel suppliers and distributors as a means to allegedly ‘winterize’ diesel fuels for today’s fuel users. As demonstrated in the data above, this practice cannot compete with a properly compounded and proven diesel fuel winterization additive.
It should also be pointed out that kerosene blending of diesel fuel reduces the BTU Content (heat energy) of the diesel fuel which will decrease engine power productions. This will increase driver complaints and significantly reduce fuel economy (typically a 30 percent kerosene blend will reduce fuel economy by 25 percent or more in most diesel engines).
Kerosene blending also decreases the fuel lubricity value which can cause increased wear in the entire fuel delivery system (this is a particular problem for today’s high pressure common-rail fuel injection systems because of the extremely close tolerances in the systems).
Finally, since kerosene can cost substantially more per gallon ($0.50 cents to $1.00 in most winters) than No. 2-D ULSD fuels, kerosene blending will greatly increase the operational fuel cost.
Summary
There is a ‘right’ way and a ‘wrong’ way to make a good diesel fuel winterization additive and it is the responsibility of the diesel fuel additive buyer to sort out the differences between products. This article lists the many different chemistry types, test parameters, test methods and other associated considerations for determining which winterization additives fall into which category.
While the task of determining the differences can seem monumental given all of the additive vendor ‘marketing fluff’ floating around the market place, the benefits and rewards realized from selecting the best possible and ‘right’ diesel fuel additive product will be well worth the effort. The diesel fuel producer, fuel supplier and diesel powered equipment operator must all be diligent and must test the prospective diesel fuel additive BEFORE any additive is selected. Only then will the additive buyer reap the best performance at the least possible cost for the optimal winter operability results desired of the product purchased.
References
Note: The data and statistics in this article are only a representative sample of the multitude of laboratory and field testing Amalgamated, Inc has undertaken over the past 43+ years to document and verify the validity and performance of the diesel fuel additive products it sells. Amalgamated, Inc encourages all fleet owners and diesel fuel users to test using an ASTM quality petroleum laboratory and verify available performance and compare the cost effectiveness of diesel fuel additive products BEFORE they purchase any additive.