TRANSPORTING diesel is about to get a lot more complicated for petroleum fleets. Diesel hauling also is likely to become a more expensive operation — for both the transporters and their customers.
There is widespread concern that petroleum haulers may have to run dedicated tanker fleets to prevent contamination of the new ultra low sulfur diesel (ULSD), which will begin entering the market in significant volumes in less than 18 months. At the very least, existing petroleum trailers will have to be thoroughly cleaned and purged of residue from higher-sulfur fuels. New loading charts will be needed from the petroleum terminals.
Changes also will be required at customer facilities. Diesel storage tanks, piping, and fuel dispensing systems at truck stops and fleet terminals must be purged. Aggressive action will be needed because field tests over the past year showed that ULSD fuel is highly susceptible to sulfur contamination.
2007 engine specs
John Conley, National Tank Truck Carriers, points out that truck fleets know that heavy-duty diesel engines are changing with the 2007 model year, but ULSD distribution issues aren't even on the radar right now. It will take a strong educational effort to bring the fleets up to speed, and there isn't a lot of time left.
Tracie McCall, Marathon Ashland Petroleum, says diesel haulers will need to develop and adopt new handling procedures to protect ULSD quality. In addition, fleets need to consider tank trailers that have the ability to completely drain product from a previous shipment prior to loading ULSD fuel.
Required by the Environmental Protection Agency under the next round of emission reductions for on-road heavy-duty diesel engines, ULSD fuel must have a sulfur content that does not exceed 15 parts per million. The ULSD requirement will be phased in between June 2006 (80% of fuel sold) and 2010 (100%). Engines must meet the 15-ppm mandate starting with 2007-model-year trucks.
The EPA's 80/20 rule for on-road diesel fuel will allow 20% of the diesel produced in 2006 to have the current sulfur content of 500 parts per million, as long as 80% meets the 15-ppm level. The 500-ppm fuel will remain available in diminishing quantities until 2010.
Sulfur content in off-road diesel also will be ratcheted down over several years. Sulfur levels in off-road diesel will have to fall to 500 parts per million in 2007, from the currently allowed 3,000 parts per million. Off-road diesel with 15-ppm sulfur content becomes mandatory in 2010.
It's important to note that, for the purposes of the EPA rule, biodiesel designated as ULSD fuel for vehicle use must meet the 15-ppm sulfur content level. The same goes for kerosene that will be blended with ULSD fuel for winter diesel.
Use of fuel that is out of spec could damage truck emission control systems and void warranties. It's also very likely to bring stiff fines from EPA, which has made clear that it will keep a close watch over the ULSD fuel distribution process.
Out-of-spec fuel is a very real risk. Field tests in the last year demonstrated clearly that ULSD fuel probably would gain sulfur content at each stage along the distribution process. ULSD fuel will leave the refinery at approximately seven parts per million sulfur content. Conservative estimates are that ULSD fuel will gain one part per million sulfur with each transition during shipment to the terminal. As a result, it could be at or near the 15-ppm maximum sulfur level by the time it is loaded into a tank trailer for delivery to the consumer.
Tests conducted by the Association of Oil Pipe Lines' and American Petroleum Institute's ULSD Fuels Team found that a ULSD shipment would gain slightly under one part per million sulfur on each pipeline leg. It will pick up one to five parts per million at each terminal. Varying amounts of sulfur would be gained during tank truck transport and at truck stops and other retail outlets.
Further complicating the situation, a wide range of fuels with various sulfur levels are distributed through many terminals. The overall range of fuels includes jet/kerosene (up to 3,000 ppm), 500-ppm diesel, high-sulfur diesel for locomotive and marine use, heating oil (up to 5,000 ppm), and all of the gasoline grades (up to 300 ppm).
Operational testing has highlighted a number of problems at terminals and loading racks, especially with piping that can retain product with a higher sulfur level. Piping and manifolds also can be a problem on petroleum transports. As little as two gallons of high-sulfur fuel in 2,000 gallons of ULSD fuel could push the load over the 15-ppm limit.
“It doesn't take much additional sulfur to put ULSD fuel out of spec,” says Gregg Scott, Society of Independent Gasoline Marketers of American and the National Association of Convenience Stores. “To avoid liability, you'll have to prove that you didn't cause the contamination.”
Testing will be a big part of the effort to ensure that customers receive ULSD fuel that is in compliance with EPA requirements. While the burden of compliance rests heavily on terminals, tank truck fleets will want to protect themselves with their own testing program. Third-party testing may be the most cost-effective choice for the fleets.
“The tank truck carrier is the last link between the refinery and the customer,” Conley says. “We have a concern that carriers will be left holding the bag when ULSD fuel exceeds the 15-ppm limit. Apparently, no field test for ULSD currently exits, which means sulfur-content tests must be performed in a laboratory. Even with the lab cost, sampling may be the carrier's only defense.
“It's possible that several carriers could have delivered fuel to a customer tank that later was found to have out-of-spec diesel. Or product in a storage tank might have come from several sources.
“As ULSD fuel flows into the market, there are still plenty of questions. Will the loading racks inspect tankers or require additional paperwork prior to loading ULSD? Will customers require sampling and testing prior to delivery? Who gets fined if the ULSD fuel in a customer tank exceeds limits?”
New loading charts will be needed to provide further protection against contamination. “Clearly worded product loading sequence charts need to be posted at the loading racks where they can be seen easily,” Conley says.
The charts show how to avoid contamination when a petroleum hauler follows a switch-loading program in which a tanker is used to transport various fuels. The chart shows which fuels are compatible and what steps must be taken to prepare the tanker before loading less compatible products. Conley called for an industry standard on switch loading because many carriers haul for a variety of customers.
Split loads could be another challenge. Multi-compartment petroleum trailers are used for these loads, which may include gasoline and high-sulfur diesel in addition to ULSD fuel. Under National Fire Protection Association guidelines, a double bulkhead could be required between the compartments. Fleet managers also have to be aware that some product may go up through the common vapor recovery manifold, possibly contaminating fuel in other compartments. Delivery hoses must be drained well because multiple products are being delivered through each hose.
The jury is still out on whether dedicated equipment will be needed to transport ULSD fuels. However, the hope is that this can be avoided. “Dedicated tank trailers will cost our customers more,” Conley says. “It's less efficient use of equipment and drivers.”
Al Mosser, ChevronTexaco, told tank fleet maintenance managers during the NTTC's annual Cargo Tank Maintenance Seminar in October 2004 that the burden for avoiding dedicated ULSD tanks rests with the industry. “If the tank truck industry cannot adequately manage segregation of ULSD from other product, the only option may be to use dedicated tankers for all ULSD deliveries,” he says.
Whether dedicated or not, many of the tankers used for 15-ppm diesel will be among the oldest petroleum transport equipment on the road. General practice has been to “retire” gasoline tankers into diesel service. Average age of cargo tanks in the US petroleum fleet is in excess of 15 years, and diesel tanks are the oldest, according to NTTC.
What's the best cargo tank design for hauling ULSD fuel? Tests conducted by Marathon Ashland Petroleum determined that tanks with a sloped floor performed best. Cargo tanks need to be designed for drain-dry operation, according to Mosser. “It's crucial to absolutely minimize the amount of prior cargo residue so that it won't impact the integrity of the next load of ULSD fuel,” he says.
Tanks must have enough floor slope to always drain completely regardless of the delivery site conditions. Piping systems should be configured to avoid or minimize low spots that might retain product. Sight glasses are needed to verify that there is no retained product in the piping.
Steps need to be taken to guard against static electricity incidents at the loading rack. The refining process lowers the conductivity of ULSD fuel, which increases the potential for static build-up during loading. It's important to ensure that the cargo tank has adequate bonding and grounding systems and that there are no loose conductive objects or spark promoters inside the tank.
The American Petroleum Institute's recommended practice, titled “Protection against ignitions arising out of Static, Lightning and Stray Currents,” recommends avoiding splash filling at the loading rack until the inlet nozzle of the loading arm is submerged. Loading flow rates also may need to be reduced. Once the tank is loaded, it should be allowed to sit for at least a minute before the lading is gauged or sampled.
Petroleum fleets need well-thought-out written operating procedures for ULSD fuels. Even flat-floor tanks can perform reliably if they are accounted for in the program and drivers follow the procedures.
In the tests done by Marathon Ashland Petroleum, draining the tank compartments at the loading rack reduced product retention in the flat-floor trailers. Flushing compartments with ULSD prior to loading effectively removed residual sulfur contamination in tankers with either type of floor.
Steps also must be taken at truckstops and other ULSD customer locations to ensure a smooth transition to 15-ppm diesel. Some customers may add temporary storage for ULSD fuel due to limited initial demand, while others will opt to convert existing storage tanks to the new fuel.
McCall says high-volume customers should have the least difficulty making the switch. Smaller-volume operations will have a tougher time.
Regardless of facility size, customers should minimize inventory levels in storage tanks before receiving the first ULSD loads to limit stratification. The number of loads necessary to convert a facility can be estimated using historical sulfur content, tank inventories, and the amount of fuel dispensed at the site.
The Marathon Ashland Petroleum tests found the following:
Mixing does occur across manifolded tanks.
Stratification in underground storage tanks can occur if the drop volume is less than 60% of the final tank inventory.
Multiple drops into different tanks promote better mixing.