91��Ƶ

March 19, 2012 8:00 AM, EDT

By Seth Clevenger, Staff Reporter

This story appears in the March/April 2012 issue of Equipment & Maintenance Update, a supplement to the March 19 print edition of Transport Topics.

Fleets that have embraced nitrogen tire inflation said the practice extends service life and improves fuel efficiency, but tire makers stop short of endorsing use of the gas in their products.

“Nitrogen has proven a valuable maintenance tool for us — both in cost and, we believe, in safety,” said Pete Larsen, president of Larsen Trucking Inc., a longhaul truckload carrier based in Greenville, Mich. “We’re convinced of it.

“Casing-recap life has gone up tremendously,” Larsen said, resulting in “huge savings in the overall tire budget.” The company’s fleetwide miles-per-gallon fuel use improved by about 3%, he said, from 2008 to 2010, the first year after fully implementing nitrogen inflation throughout the fleet.

During the same time frame, the company also was working on other fuel-efficiency initiatives, including driver training efforts, Larsen said, so it’s impossible to pinpoint precisely how much of that improvement is attributable to nitrogen.

And that is exactly one of the points tire manufacturers make when discussing nitrogen.

“There has not been any data presented to Bridgestone that there is a payback for the use of nitrogen instead of air for commercial tires,” said Guy Walenga, director of engineering for commercial products and technologies at Bridgestone Commercial Solutions, a unit of Bridgestone Americas, Nashville, Tenn.

And while some manufacturers acknowledged at least some benefit from nitrogen inflation, all stopped short of recommending it for trucking fleets.

Walenga said in a statement that the only proven, direct benefit for the use of nitrogen over dry air is better retention of inflation.

However, he added, “The use of nitrogen for the sole reason of better inflation retention is not significant enough for a fleet operation, and the use of nitrogen should not be considered the equivalent of a proper inflation-pressure maintenance program.

“We do not recommend that truck fleets switch over to nitrogen from air,” Walenga said. “The costs involved are not offset by the performance of nitrogen-filled tires.”

Nitrogen isn’t a rare gas. In fact, it makes up most of the atmosphere. The air we breathe consists of 78% nitrogen, 21% oxygen, 0.9% argon and trace amounts of other gases, including carbon dioxide.

So the value of nitrogen tire inflation isn’t the nitrogen itself. Instead, it’s what’s not inside that’s important.

“It’s not about the nitrogen; it’s about getting rid of water vapor and getting the oxygen out,” said Brian Brasch, president of Branick Industries, Fargo, N.D., which sells generators that fill tires with high-purity nitrogen.

Moisture and oxygen, he said, cause greater fluctuations in tire pressure and speed up the deterioration of tire quality.

Inflating tires with high-purity nitrogen, instead of regular air, removes the majority of the air’s detrimental contents, he said.

Nitrogen generators run off of shop-compressed air and filter out oxygen and water vapor — leaving about 95% to 99% pure nitrogen.

Dan Guiney, director of technical service at Yokohama Tire Corp., Fullerton, Calif., said in a statement that it is “OK” to use nitrogen, but it “does not change the requirement for regular tire-inflation pressure maintenance.”

“Our tires are designed to complete their full service life with normal atmospheric air inflation and regular maintenance of proper tire-inflation pressure,” he said.

In a position statement, Michelin North America Inc., Greenville, S.C., said nitrogen is “strongly recommended” for tires used in a high-risk environment or for use in some aircraft and in racing. . . . For all other tires in normal use, nitrogen inflation is not required and does not necessarily bring the expected benefit.”

It’s true that nitrogen reduces pressure loss from the natural permeability of the tire, and “the broad use of nitrogen will, in general, assist motorists with pressure maintenance,” Michelin said, but other possible sources of leaks, such as at the tire-rim interface, prevent the guarantee of better pressure maintenance for those using nitrogen inflation.

Goodyear Tire & Rubber Co., Akron, Ohio, endorses nitrogen inflation for “certain sizes of earthmover tires used in particular applications” but said the issue of nitrogen inflation for over-the-road truck tires is “not quite so clear,” according to language from Goodyear’s radial truck tire and retread service manual provided by the company.

The manual concludes that “nitrogen inflation appears to have quite small, perhaps insignificant, advantages for over-the-road truck tires.”

Nonetheless, most fleet managers interviewed for this story said they see advantages in nitrogen-inflated tires.

The Larsen Trucking president said he became interested in nitrogen tire inflation when an announcer mentioned it during a NASCAR race. While listening to the announcer explain that racing teams inflate their stock cars’ tires with nitrogen to improve performance, Pete Larsen asked himself if it also could produce results for his trucking fleet.

“I wondered, ‘What’s that about?’ ” he said.

After exploring the issue, Larsen invested about $25,000 in a nitrogen generator to convert his company’s truck fleet to nitrogen, which proponents say helps maintain ideal tire pressure and prolong tire life by removing moisture and oxygen.

Four years later, Larsen said, he’s still using the generator and his company has benefited from fuel savings, more “recaps” per tire and fewer calls for tire failures.

Larsen said his fleet’s nitrogen generator is still in use almost every day, four years after purchase. The unit, a membrane filtration nitrogen generator from Branick, has required “very low maintenance,” he said, adding that he did purchase a larger air compressor to better filter the air sent to the membrane.

On average, the generator is used daily but does not run continuously, he said.

To calculate fuel savings, the company used six baseline trucks with known miles-per-gallon standards, kept the same trailers and drivers and tracked their fuel costs for 10,000 miles during the end of the summer months. Those trucks traveled through changing elevations on long trips from Michigan, through the Rockies and into California.

“Our tires are hitting every climate, every altitude, from sea level to the top,” Larsen said.

As for savings from the tires, he said the carrier was getting one or two retreads per tire, on average. Now, with nitrogen-filled tires, it is getting four or five retreads.

“That’s $130 per cap versus $400 for a new tire,” Larsen said. “That’s a huge bottom-line increase.”

He said he also has noticed a reduction in on-road service calls for tire failures. When company drivers need to add air to a tire when they’re on the road, they report it and the tire undergoes inspection after the driver returns, Larsen said. If the tire has dropped below the company’s nitrogen purity standard, a technician bleeds it and recharges it with nitrogen, he said.

Supermarket chain Safeway Inc. adopted nitrogen tire inflation for its private truck fleet about two years ago, said Duane Woods, the company’s director of transportation operations.

After an eight-month testing period, Safeway found that nitrogen-filled tires held pressure better than those inflated with regular air, he said.

Through the testing phase, the company tracked the nitrogen-filled tires through seasonal changes in the Chicago, Denver and Phoenix areas.

“They maintained pressure really well over compressed air,” Woods said.

The nitrogen tires held pressure especially well in the heat in the Phoenix area, he said.

After the test, Safeway decided to purchase nitrogen generators for its maintenance shops, Woods said, adding that the fleet of about 900 tractors is now running on nitrogen-inflated tires.

“If you can maintain constant pressure, it’s obviously going to get better fuel economy and wear on that tire,” Woods said. “Everybody in our team is confident it’s working.”

The company is generally not using nitrogen inflation with its trailers, though, because most of them were already equipped with automatic inflation systems, he said.

Safeway, headquartered in Pleasanton, Calif., ranks No. 24 on the Transport Topics Top 100 list of the largest U.S. and Canadian private carriers.

Adams Motor Express Inc., a shorthaul carrier based in Carnsville, Ga., has been using nitrogen tire inflation for about four years, said Paul Mincey, the company’s director of maintenance. He said the company did not switch to nitrogen inflation to improve fuel economy or tire casing life, but to better maintain tire pressure.

“Our main goal was to have our tires hold air longer,” Mincey said.

Adams, which primarily hauls construction equipment, owns 46 tractors and 250 trailers. Given the company’s 1-to-5 ratio of tractors to trailers, many of its trailers sit for extended periods of time.

To help the tires on those trailers retain air better, Adams purchased a nitrogen generator from Parker Hannifin Corp. for about $14,000.

At the same time, Adams began a training program with its drivers to “let them know how important it was to check tire pressure.” The result was a dramatic decrease in tire failures, Mincey said.

The year before switching to nitrogen inflation, the company experienced 57 tire failures. The year after adopting nitrogen, that number plunged to two and has remained in the single digits each year since then, he said.

Mincey attributes the fewer tire failures to a combination of the nitrogen inflation itself and the training effort the company started simultaneously.

“If you use nitrogen, have a good tire program and train your drivers; it’s a super benefit for you,” Mincey said.

Although providers of nitrogen inflation sometimes cite about 2% fuel savings as one of the benefits of nitrogen, Mincey said it’s hard for fleets to quantify that because there are so many variables involved.

“A driver can eat up 10% just in his habits,” he said.

However, Gypsum Express, a truckload carrier based in Baldwinsville, N.Y., did not see the benefits of nitrogen tire inflation.

Chuck Frost, the company’s director of tire maintenance, said the carrier gave nitrogen inflation a try about eight years ago but saw no improvement in its regular tire-pressure maintenance after a six-month trial.

“It sounded great. It just didn’t pan out,” he said.

Frost said the carrier tested nitrogen inflation on a number of its heavy-haul trucks, but when they returned to the terminal, the company still needed to adjust their tire pressure.

Gypsum Express also did not find improvements in tire life or fuel economy during the trial, he said — and after six months, the company decided to return its demo nitrogen generator.

Since then, Gypsum Express has improved tire pressure maintenance by installing pressure monitoring systems on the company’s fleet of 550 tractors.

These systems, from Doran and PressurePro, have made the company’s drivers “more air-pressure conscious,” Frost said.

The carrier also has reduced rolling resistance by installing constant air pressure systems from Hendrickson and Meritor PSI on its trailers, he added.