George Morrison had some pretty frustrated customers last winter. Morrison's the owner of AV Lubricants, an ExxonMobil distributor in Columbus, Ohio, and he says he worked pretty closely with customers who were having unexpected problems with diesel fuel gelling and plugging filters.
"It was a real head-scratcher," Morrison 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, according to the American Trucking Associations. The problems seem to have been at least partially due – directly or indirectly – to the transition to ultra low sulfur diesel that went into effect last fall.
While winter is over and this year's experience should lead to a smoother time next year, there are other fuel issues that truck owners and fleet maintenance managers need to be aware of. Many believe that ULSD will 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."
And the increasing pressure to use biodiesel could make some of the issues with ULSD look like child's play.
COLD WEATHER ISSUES
There isn't a single culprit to blame for the gelling problems that some people experienced last winter.
"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 what had been, up until then, a fairly mild winter.
In fact, notes Gary Pipenger, president of Amalgamated Inc., a custom manufacturer of fuel additive products, in a March 2007 paper investigating winter operational issues of ULSD, "Many parts of North America encountered the lowest ambient temperatures in the last five years for a period of nearly two weeks while experiencing their initial winter implementation of the new ultra low sulfur diesel fuels."
ATA's 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, 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. The challenge for the additive company is to find the additive that best matches the customer's fuel. In some cases that means optimized performance in a single diesel fuel, and in other cases that means an additive that performs across a broad spectrum of fuels."
Weyenberg says that in many cases, additive makers didn't have a chance to get their cold-flow additives optimized for these many different variations on ULSD before winter hit.
"It's not like the industry had widespread access to ULSD from refineries around the country," he says.
On top of that, some disagree with the EPA's stance, saying there are differences in the chemistry of ULSD that affect how additives work.
"The way the additives normally work is, they affect the formation of wax crystals," explains 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."
Amalgamated's Pipenger says the process that refineries use to remove sulfur from diesel not only raises the fuel cloud point (the temperature at which the paraffin in the fuel changes from a liquid to a solid wax), but also can significantly lower the aromatic content of the fuel. Because of this, he says, when the paraffin changes to solid wax, it is less likely to remain suspended in the fuel. Instead, the wax crystals tend to precipitate faster and accumulate in the bottom of the tank. The solid wax crystals are then drawn into the fuel filter as soon as the pump system is activated, quickly plugging the fuel filter and shutting down the engine.
Another problem was the lack of No. 1 diesel (often referred to as kerosene) available to create cold-weather 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 was priced too high.
"Many of the major oil refiners decided nearly two years ago not to ‘desulfurize' the light distillate (kerosene) stream when the EPA mandate was implemented in June 2006," Pipenger explains. "It is understood that this decision [by refineries] was primarily made in order to preserve the ability of kerosene for substitution into the jet fuel pool during periods of jet fuel shortages."
The result, however, was a shortage of ultra-low-sulfur No.1 available to blend with No. 2 ULSD.
"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."
Some fleets that were able to get the No. 1 fuel still had issues, reports Pipenger. His company received reports from fleet operators who were diluting with kerosene and still experienced severe fuel filter plugging after weekend shutdowns. Some fleets, he says, blended as much as 40 percent kerosene with No. 2 ULSD and still had some problems. On the other hand, he says, some fleets didn't do anything special or different this winter and had no significant problems.
"Odds are that most fleets 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," says Cummins' Clevenger.
Making matters worse, just the process of transitioning to a new fuel could have contributed to filter plugging problems.
"During the transition to ULSD, flushing of lines and tanks may introduce contaminants into the fuel, shortening fuel filter life," says Don DeRoche, manager of heavy-duty technical sales for Fram. "These fuel abnormalities will diminish over the short term."
Another factor in the changeover to ULSD was that ultra low sulfur diesel has a solvent effect. When introduced into an engine for the first time, it will tend to clean out the internal parts. The deposits it has removed from the fuel system get carried along in the fuel until they hit the fuel filter, which catches them, but ends up needing to be replaced sooner than usual.
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."
To help protect yourself, proactively sample and test your fuel supply before winter arrives. Work closely with your fuel and additive suppliers.
"You cannot just additize and hope it's going to provide protection for cold weather," says AV Lubes' Morrison, "You're going to have to test it, and test it often, to make sure you don't get the off load that's going to shut you down on a cold weekend."
Also, if you run in the northern states, consider adding fuel heating equipment to your trucks. "We had an increase in sales of electric and coolant heat exchanger product mid-winter," says Steve Hardison, Racor fuel product manager, "as operators realized that the only way to ensure fuel flow and avoid filter waxing was to raise the fuel temperature."
However, Pipenger says, keeping fuel heated at all times can negatively affect the diesel fuel stability, aggravating effects already seen because of the new engines exposing the fuel to higher heats during operation. When diesel becomes unstable, it creates oxidation particulate materials and causes asphaltenes in the fuel to prematurely plug fuel filters. If fuel heaters are used, he says, you may need to treat the fuel with an anti-oxidation additive.
WATER: THE ENEMY
Most people in the industry agree that water in ULSD is an even bigger potential issue 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 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 ULSD 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.
"A lot of people who have storage tanks have had very poor fuel storage maintenance practices," Clevenger says. "They've been able to get away with it for years because they have had enough sulfur in the fuel to cover up their sins, so to speak. But now, if they practice the same things they've done in the past, they could very easily end up with bug growth in tanks, which will translate to filter plugging and eventually to a fuel storage leak, because bugs, part of their waste stream is an acid that will eat through the tank."
However, Racor's Hardison says "there is no reason to believe that ULSD is more prone to bacterial growth. 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."
If you want to err on the side of caution, it might be a good time to take a look at your storage tank maintenance procedures.
Morrison says in his experience, "a lot of trucking companies with in-house diesel fuel tanks have frankly allowed them to become cesspools. It just makes good business sense, when you're paying $2 and $3 a gallon for diesel fuel, to make sure the place where it's being stored is clean."
If your storage tank maintenance procedures have been a bit lax, consider hiring a company that specializes in cleaning out fuel storage tanks. This involves drawing the diesel fuel out to a very low level, pressure-washing the tank, then filtering the diesel fuel and putting it back into the tank.
"Many cleaning services take a picture of the tank before and after they clean it," Morrison says, "and the before and afters are pretty graphic."
Morrison recommends installing desiccant breathers with one-micron filters on them. Desiccant breathers help prevent moisture and other contaminants from getting into the tank, and also help keep the air above the level of the fuel dry.
In addition, both Morrison and Clevenger recommend monitoring the fuel in your storage tanks regularly for the presence of free water. At the same time, it's a good idea to test it for things such as thermal stability and microbial growth.
These preventive measures are far better than having to resort to chemicals to kill microbial growth in the tank. While biocides can kill the bugs in your fuel tank, they have a couple of big drawbacks. One is that they are highly toxic, presenting risks to employees and the environment (and potential liability on your part). The other is that the dead organisms can still be a problem.
"All those products do is kill the algae," says Vic Brown, national sales manager for Star Brite. "Then what happens is the [microbial growth] settles to the bottom of the tank as a black biomass sludge that slowly turns into an acid that will eat away at the bottom of the tank and get into the fuel and eventually damage fuel system components."
Brown says his company's Star Tron additive works by using enzymes that break the microbial organisms into particles that can be filtered out or burned up in the fuel.
While you're looking at the quality of your in-house fuel, take a look at your dispensing equipment, as well. Make sure it's kept clean. A canopy will help prevent water contamination while fueling in a downpour. Use good filters on those pumps.
"In the past, people have used 50-micron, 90-percent efficiency filters for their fuel islands," Clevenger says. "Now we're recommending they consider 5-micron, 98-percent efficiency. It helps on engine life and filter life and ensures that your injectors are going to perform longer."
On the truck, fuel/water separators may be more important than ever.
"Every diesel unit today would benefit from having a fuel/water 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."
Both fuel gelling and water-related issues are even bigger concerns 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 emissions-compliant 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, it said, the availability of quality fuels from sources accredited by the BQ-9000 certification process developed by the National Biodiesel Board is growing rapidly.
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 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.
Legal standards for biodiesel aren't being enforced very well, says John Hacker, director of global product development for Donaldson. "There's a lot of smaller operations that are able to get into the system, and they're really not regulated. It's not like buying fuel today out of the fuel pump."
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.
"It is not fair to say that 59 percent of the B100 on the market last year failed the spec, but 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 biodiesel to the IRS and the EPA, as well as state agencies. "At least a couple of 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," McCormick says. "Anecdotally, I am not hearing about nearly as many quality issues from biodiesel users this year."
To protect yourself, research your suppliers carefully. Make sure they're BQ-9000 certified by the National Biodiesel Board.
"Fuel quality is the key," says Matt Stein, engineering manager for engine liquids at Donaldson. "Fleets using bulk storage need to get [biodiesel] fuel from a good source and store it properly."
Of course, for a trucker fueling on the road, that's not so easy. In Minnesota, which requires all diesel sold in the state be a 2 percent biodiesel blend, truckers experienced fuel gelling and filter plugging issues the first winter the law went into effect. The main culprit turned out to be off-spec fuel.
"I'd recommend they 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 Donaldson's Hacker.
Even on-spec biodiesel presents some challenges. For one thing, it's even worse than ULSD in terms of water contamination.
"Quality is getting be less of an issue, as long as you get your biodiesel from mainstream, well-trusted sources," says Racor's Hardison. "Quality regulations are 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. You've got to keep water out of biodiesel, or you will have microbes just crawling out of the tank."
So precautions to prevent water contamination – good storage tank maintenance, fuel/water separators on the truck, etc. – are even more important when biodiesel is in the picture.
Other issues with biodiesel is that it can be expected to degrade more quickly than regular diesel and to solidify at a higher temperature in cold weather.
Donaldson, which is based in Minnesota, says don't be surprised if the state decides to go to an even higher mandated biodiesel blend.
"Biodiesel has come a long way in a short period of time," says Fram's DeRoche. "Manufacturing capacity for biodiesel products has grown exponentially over the past few years – from 500,000 gallons in 1999 to 75 million gallons in 2005 – with more capability in the construction and planning stages."