Low sulfur fuel delivery presents challenges

Transporting diesel is about to get a lot more complicated and more expensive for both the vendors and their fleet customers.

There is widespread concern that petroleum vendors may have to run dedicated tanker fleets to prevent contamination of the new ultra low sulfur diesel, which will begin entering the market in significant volumes in less than 18 months. At the very least, existing tank trailers will have to be thoroughly cleaned and purged of residue from higher-sulfur fuels.

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 ultra low sulfur fuel is highly susceptible to sulfur contamination.

2007 engine specs

John Conley of the National Tank Truck Carriers points out that truck fleets know that heavy-duty diesel engines are changing with the 2007 model year, but low sulfur fuel distribution issues aren't even on the radar right now. It will take a strong educational effort to bring all 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 low sulfur fuel quality. In addition, fleets need to consider tank trailers that have the ability to drain product from a previous shipment completely prior to loading low sulfur fuel.

Required by the Environmental Protection Agency under the next round of emission reductions for heavy-duty highway diesel engines, low sulfur fuel must have a sulfur content that does not exceed 15 parts per million. The low sulfur requirement will be phased in between June 2006 for 80% of fuel sold and 2010 when all highway diesel fuel must meet the low sulfur standard. Engines must meet the 15-ppm mandate starting with 2007-model-year trucks.

The EPA's 80/20 rule for highway diesel fuel will allow 20% of the fuel produced in 2006 to have the current allowable 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.

It's important to note that, for the purposes of the EPA rule, biodiesel designated as low sulfur fuel for vehicle use must meet the 15-ppm sulfur content level. The same goes for kerosene blended with low sulfur fuel for winter diesel.

Off-spec fuel

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 low sulfur fuel distribution process.

Out-of-spec fuel is a very real risk. Field tests in the last year demonstrated clearly that low sulfur fuel probably would gain sulfur content at each stage along the distribution process. Low sulfur fuel will leave the refinery at approximately seven parts per million sulfur content. Conservative estimates are that low sulfur fuel will gain one part per million sulfur with each handling during shipment to the fuel 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 final delivery.

Tests conducted by the Association of Oil Pipe Lines' and American Petroleum Institute's ULSD Fuels Team found that a low sulfur fuel 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 fuel terminal. Varying amounts of sulfur would be gained during tank truck transport and at truck stops and other dispensing points.

Further complicating the situation, a wide range of fuels with various sulfur levels are distributed through many fuel 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 fuel 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 diesel tank trailers. As little as two gallons of high-sulfur fuel in 2,000 gallons of low sulfur fuel could push the load over the 15-ppm limit.

“It doesn't take much additional sulfur to put low sulfur fuel out of spec,” says Gregg Scott, Society of Independent Gasoline Marketers of American and the National Association of Convenience Stores.

Fuel testing

Testing will be a big part of the effort to ensure that customers receive low sulfur fuel that is in compliance with EPA requirements. While the burden of compliance rests heavily on fuel 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 these fleets.

“The tank truck carrier is the last link between the refinery and the customer,” Conley says. “We have a concern that tank carriers will be left holding the bag when low sulfur fuel exceeds the 15-ppm limit. Apparently, no field test for low sulfur fuel currently exits, which means sulfur-content tests must be performed in a laboratory. Even with the lab cost, sampling may be the tank 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 low sulfur fuel flows into the market, there are still plenty of questions. Will the loading racks inspect tankers or require additional paperwork prior to loading low sulfur fuel? Will customers require sampling and testing prior to delivery? Who gets fined if the low sulfur fuel in a customer tank exceeds limits?”

Split loads in tank trailers could be another challenge. Multi-compartment petroleum tank trailers are used for these loads, which may include gasoline and high-sulfur diesel in addition to low sulfur 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 low sulfur 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 low sulfur fuel transport tanks rests with the industry. “If the tank truck industry cannot adequately manage segregation of low sulfur fuel from other product, the only option may be to use dedicated tankers for all low sulfur fuel deliveries,” he says.

Older tanks

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 low sulfur 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 low sulfur 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.

Written plan

Petroleum transport fleets need well-thought-out written operating procedures for low sulfur 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 low sulfur fuel prior to loading effectively removed residual sulfur contamination in tankers with either type of floor.

Steps also must be taken at truckstops and other low sulfur fuel customer locations to ensure a smooth transition to 15-ppm diesel. Some customers may add temporary storage for low sulfur 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 low sulfur fuel 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 amount delivered is less than 60% of the final tank inventory.

• Multiple drops into different tanks promote better mixing.