DIESEL FUEL GELLING: IT S A COLD FACT

Transcription

1 DIESEL FUEL GELLING: IT S A COLD FACT DAVE VORNBERGER 12 RoadStar July 2007

2 George Morrison had some pretty frustrated customers last winter. The owner of AV Lubricants, an ExxonMobil distributor in Columbus, Ohio, Morrison worked closely with customers who were having unexpected problems with diesel fuel gelling and plugging filters. It was a real head-scratcher, he says, because the normal additives that would lower the cold filter plug points were simply not working. Fuel that had been treated with additives that should have lowered the filter plug point to 20 or 30 degrees below zero were found in lab tests to have a plug point of 5 to 10 above. Morrison s customers were not the only ones. Widespread diesel fuel gelling problems stranded trucks throughout Illinois, Indiana, Iowa, Minnesota, New York, Pennsylvania and Wisconsin in late January and early February, reported the American Trucking Associations. The problems seem to have been at least partially due to the transition to ultra low sulfur diesel that went into effect last fall. While this year s experience should lead to a smoother time next winter, there are other fuel issues facing truck owners. ULSD is widely expected to be more likely to have water issues, which is a greater danger than ever with today s engines and also could mean increased microbial growth. Ultra low sulfur diesel is definitely a horse of a different color, says David Forester, director of technical services at Power Service Products, and it has created some unique challenges on both the cold flow side and the maintenance side as it relates to the ability to handle water and contamination. The new engines and fuels mean you really have to start paying attention to your fuel quality and filters. BY DEBORAH LOCKRIDGE Senior Editor And the increasing pressure to use biodiesel could make some of the issues with ULSD look like child s play. Cold Weather Issues The problems that were experienced this year were mostly a result of colder than expected conditions, says Rich Moskowitz, regulatory affairs counsel with ATA, noting that the rash of cold weather problems occurred at the end of January and into February, when much of the country experienced extremely cold temperatures following a fairly mild winter. Moskowitz says that fuel terminals had not properly additized the fuel to perform in that severe weather. Once the terminals recognized what they were dealing with and used the appropriate additive package, those problems seemed to dissipate. The U.S. Environmental Protection Agency told ATA the gelling problems were not directly related to the chemistry of ULSD, but admitted that some batches of ULSD may be difficult to winterize with existing cold-flow additives. We tend to think that ultra low sulfur diesel is all the same, says Tom Weyenberg, business manager for diesel fuel additives at Lubrizol, which makes additives used by fuel refiners. Actually, Fuel Filtration each refinery s ULSD is a little different. It all depends on the crude oil that they may be starting with, and on the processing, how they actually get down to ultra low sulfur. Some are very easy to treat; some are much more severe. In many cases, additive makers had not had a chance to get their cold-flow additives optimized for these many different variations on ULSD before winter hit. In addition, some people in the industry disagree with the EPA s stance and say that in addition to the issue with different fuel performance from different refineries, that there are differences in the chemistry of ULSD that affect how additives work. The way [cold-flow] additives normally work is they affect the formation of wax crystals, says John Clevenger, director of global products for Cummins Filtration. When you change the fuel, you change the chemical process of how wax crystals form. So it stands to reason, and we ve definitely seen it, the previous additives don t work exactly the same. Another problem was the lack of No. 1 diesel (often referred to as kerosene) available to create coldweather blends, which has been a standard procedure for trucks operating in northern states in the winter. In order to legally produce such a blend with ULSD, however, the No. 1 now has to be ultra low sulfur as well. And ultra-low sulfur No. 1 diesel was either not available at all, or priced too high. When ultra-low-sulfur kerosene was available, it was at least 20 cents a gallon more, says Power Service s Forester. In many markets we heard 50 cents to a dollar higher. So people tried to do without it. July 2007 RoadStar 13

3 Some fleets that were able to get the No. 1 fuel still had issues. On the other hand, some fleets didn t do anything special or different this winter and had no significant problems. Odds are that most [truck operators] are going to have to look, at least in the near term, at using their own additives versus getting a blended fuel to cover them in the winter, Clevenger says. Many of these issues will likely have improved by next winter. With a winter season under our belt, we re all looking at the chemistry, at the additives themselves, and how they can be optimized for the ULSD we ve seen in distribution, says Lubrizol s Weyenberg. Refineries may be making some changes at the refinery level, and we re going to see more availability of the ultra low sulfur kerosene. Water: The Enemy Water in ULSD may be an even bigger potential problem than cold-weather performance. While water has always been a common component of diesel fuel, it acts differently in ULSD, in ways that can cause greater problems in the engine and increased free water Water in ULSD may be an even bigger potential problem than cold-weather performance. DEB WHISTLER in storage tanks. There have been people who got a truckload transport full of No. 2 ULSD and had 6 inches of water in the bottom of their fuel tank after the delivery, Morrison says. Water is an issue for two reasons: It s hell on injectors, and it harbors microbes. Looking at 2007 engines and forward, everybody s pretty much going to high-pressure common rail engines, explains Cummins Clevenger. Pressures have gone up substantially, he says, and tolerances are tighter than ever. The small moving parts within an injector nozzle used to have clearances in the thousandths of an inch, he says. Now we re talking 3 to 5 microns. If you ve got very small clearances, you cannot afford to have water get through to the injectors. The second issue with water is microbe growth. A number of industry experts contacted for this article felt that USLD would be more likely to grow microbes in storage. Any time you have clear water in the bottom of [a storage] tank, that barrier where the water and fuel meet, you ve just presented a steak dinner to the microbes that live in the water, Morrison explains. Most of those microbes love diesel, and they proliferate immediately. Making matters worse is that sulfur, a natural biocide, is no longer present in enough quantity to perform that function. However, there is no reason to believe that ULSD is more prone to bacterial growth, says Steve Hardison, Racor fuel product manager. Some additive makers claim ULSD holds more dissolved water and is therefore more likely to support microbe growth, but that s not our current experience. Biodiesel Blues Both fuel gelling and waterrelated issues are even bigger issues when you look at biodiesel. Cummins recently announced the approval of blends of up to 20 percent biodiesel, or B20, for use in its 2002 and later emissionscompliant ISX, ISM, ISL, ISC and ISB engines. The company notes that the American Society of Testing Materials specification ASTM D6751 now includes an important stability specification for biodiesel. In addition, pointed out that there s a growing supply of biodiesel from sources accredited through the BQ-9000 certification process developed by the National Biodiesel Board. But there are still plenty of concerns out there about biodiesel quality. We are very concerned with the off-spec fuel, particularly biodiesel, that has entered the marketplace, says ATA s Moskowitz. While high-quality biodiesel used in small blends is a reasonable way to extend the fuel supply, there is no place in the marketplace for off-spec biodiesel. So we believe, since the government has taken on the endeavor of promoting biodiesel s use, they should bear the responsibility to ensure 14 RoadStar July 2007

4 biodiesel s quality. Part of the problem, critics say, is that there are many small producers getting into the biodiesel business that don t have the necessary quality standards in place. There s a lot of back-garage brewing going on, Morrison says. The National Renewable Energy Laboratory did a survey of biodiesel quality last year, collecting about 35 samples of 100-percent biodiesel nationwide from terminals and bulk plants. It found that 59 percent of those samples failed to meet the requirements of ASTM D6751. Clearly a large and unacceptable fraction of the B100 on the market was failing, says Robert L. McCormick, principal engineer with NREL. The biodiesel industry, McCormick says, took the study very seriously, with the National Biodiesel Board amending its bylaws to allow them to report members producing off-spec Cold weather problems occurred at the end of January and into February, biodiesel to when much of the the IRS and the EPA, as country experienced well as state extremely cold agencies. temperatures after a At least a couple of fairly mild winter. biodiesel plants have been shut down by state agencies for failing to produce quality fuel, he says. Because of the industry focus on quality and quality enforcement over the past year, I am optimistic that our 2007 B100 quality survey, ongoing right now, will find an improved situation. Even on-spec biodiesel can cause trouble. For one thing, it s even worse than ULSD about water contamination. Just as in ULSD, water can damage injectors and lead to microbial growth. Quality is getting be less of an issue, as long as you get your biodiesel from mainstream, welltrusted sources, says Racor s Hardison. Quality regulations are BETTE GARBER in place, but they don t address interfacial tension, or the propensity for water to dissolve into the biodiesel blend. It is now well known that biodiesel can hold many times more dissolved water than pure diesel. Making matters worse, he says, is that free water is very difficult to remove from biodiesel using normal filtration means. It s important for truck owners using biodiesel to invest in an oversized fuel filter/water separator or coalescer to increase the amount of water that is removed. Forester says at Power Service, they do a lot of testing in their laboratory of biodiesel, especially blends between 2 and 20 percent What we find is that biodiesel suffers from the fact that it attracts a lot more water, and it s not quite as soluble in ultra low sulfur diesel because of the makeup of the fuel, so at lower temperatures it tends to separate. Morrison, who also does a lot of fuel testing at AV Lubricants, explains that biodiesel is a naturally occurring ester, and esters attract water. We have an ester compressor oil for use in refrigeration systems. It loves water so much, if you pour it more than twice, it will have picked up enough moisture from the air to make it unusable, he says. That s what esters are like. That s what biodiesel is. Other issues with biodiesel is that it can be expected to degrade more quickly than regu- 16 RoadStar July 2007

5 lar diesel and to solidify at a higher temperature in cold weather. What You Can Do To help protect yourself this winter, do your homework. Talk to cold-flow fuel additive suppliers about whether their additive is optimized for ULSD in the areas where you regularly run. Also, if you run in the northern states, consider adding fuel heating equipment to your truck. To avoid injector damage from water in the fuel, fuel/water separators may be more important than ever. Every diesel unit today would benefit from having a fuel/water WATER IS AN ISSUE FOR TWO REASONS: IT S HELL ON INJECTORS AND IT HARBORS MICROBES. Circle 116 on Reader Action Card separator on there, says Paul Bandoly, manager of technical services and customer training at Wix Filters. If it doesn t have one on, it s worth the investment. But then you ve got to service it, too. Too often people neglect to drain the water out and don t get the value of their investment. Carry fuel filters with you in case of plugging problems, whether from fuel waxing in cold weather or microbial contamination in warmer temperatures. As for biodiesel, you might think you can protect yourself by simply not buying it, but Minnesota requires all diesel sold in the state be a 2 percent biodiesel blend. Other states are considering similar regulations. I d recommend [truckers] keep good records of their fuel purchases to monitor where they re having a problem, and let that place know they had a problem and maybe even avoid it, says John Hacker, director of global product development for Donaldson. 18 RoadStar July 2007