TIRES continue to be the number one maintenance cost for commercial fleets, according to Al Cohn, director of new market development and engineering support for Pressure Systems International (PSI).
And the number one maintenance issue fleets face today is tire-inflation pressure, he said during a presentation on the benefits of automatic tire inflation systems presented during the National Tank Truck Carriers 2015 Annual Conference April 26-28 in Boston, Massachusetts..
“It takes too long to check 18 or 22 tires,” Cohn said. “The inside dual is difficult to reach, and inflation gauges are inaccurate—they’re plus-or-minus three psi accuracy. The valve cap can be lost after a pressure check, and the valve cores stick in the cold and lose air. Trailer tires typically have the worst air pressure.”
The top four reasons why tires lose air:
• Tread punctures. “It’s not a massive, sudden blowout,” Cohn said. “It’s getting a puncture in the tread and losing air, and before you know it, you have a big problem. The #1 puncturing object is a 20-penny nail that’s 3½ inches long.”
• Osmosis through the casing of one to four psi per month. It depends on tire materials and construction.
• Sidewall damage.
• Leaking valve stems. “Everyone always wants to overtighten that valve core. There is a tool that is pre-torqued to four inch-pounds. You tend to have fewer problems when you use that.”
Cohn said PSI has surveyed 30,000 vehicles at truck stops, and steer tires always have the best air pressure, then the first drive axle.
“The farther back you go, the worse the pressure is,” he said. “The left side of the vehicle is better than the right side. If you see a driver at a truck stop, say, ‘I’ll bet you $5 that the lowest air pressure tire on your vehicle is the right rear inside trailer tire. You’ll win $5 98% of the time.”
Tire under-inflation only leads to problems and increased fleet costs.
“Irregular wear leads to premature removal,” he said. “Tire punctures increase because of a longer footprint—you tend to suck up more puncturing objects—and the rubber becomes hot and ‘softer.’ Tire casings become hot from overflexing, which reduces retreadability. Heat is a tire’s worst enemy. Fuel economy drops significantly.”
At zero degrees, pressure drops to 80 psi from 100 psi. With 18% more rubber on the road at 70 psi, there is a 3% negative impact on fuel economy.
Under Federal Motor Carrier Safety Administration’s Compliance, Safety, Accountability (CSA) rules, there is an eight-point penalty for a flat tire or fabric exposed; ply or belt material exposed; tread and/or sidewall separation; flat tire and/or audible air leak; a cut that exposed ply and/or belt material; steer tire tread depth of less than 4/32”; and drive, trailer, or dollie tire tread depth of less than 2/32”.
What is a flat tire? He said there are various definitions, but the Commercial Vehicle Safety Alliance (CVSA) states a flat tire is when the tire pressure drops to 50% or less of what is the maximum tire inflation molded into the tire sidewall. For example: If the tire sidewall says “120 psi max,” then 50% of 120 psi equals 60 psi.
A vehicle found with even one flat tire is considered out of service.
“If you have a tire-inflation system on your vehicle, they typically don’t even measure air pressure because they know the system is doing its job, and you can save up to 17 minutes in inspection time,” Cohn said.
An underinflated tire is three points. He said nobody knows the definition—there are only published definitions of a flat tire. The worst states for focusing on under inflation are Texas, Florida, and Minnesota.
“Inspectors there figured this is a good revenue generator,” he said. “Fleets are concerned that a zealous inspector can start assigning three points to tires that are five, 10, or 20 psi underinflated.”
Steve Robinson, director original equipment manufacturer (OEM) sales for PSI, said there are abundant oil well service fleet opportunities for automatic tire inflation systems (ATIS). Large numbers of heavy-duty vehicles are used in oilfield support operations.
He said there are 90 million barrels of oil and gas produced per day worldwide, according to 2012 statistics, and 21% of that is in the United States. Fifty percent of US consumption was imported, and 2013 was the first time the US produced more than it imported. The US has 800 billion barrels of recoverable oil, compared to Saudi Arabia’s 267 billion. US unconventional oil (shale or tight oil) has risen 25% since 2008, when fracking techniques went horizontal.
In 2002, shale gas production was only 2% of total US natural gas output, but today it’s 37%. US employment attributable to fracking will account for over 3.9 million jobs and $500 billion to the US GDP by 2025. US oil-import requirements are down from 60% in 2005 to 42% today.
Oil production has risen 25% since 2008, due to production of tight oil.
Why should midstream oilfield service fleets consider ATIS?
• Elimination or reduction of roadside service calls due to flats.
• Fuel economy improves by as much as 3.8%.
• Casings last longer.
• Tread life is 10% longer.
• ThermALERT warning could save wheel-end and avoid tire or even trailer fires.
• There is a $5,000-per-hour cost at the wellhead for equipment on the ground during drilling and/or fracking, and they can’t have down time.
• 1,500 to 2,000 trailer/tanker trips are required per horizontal wellhead.
• The CSA impact is profound on midstream oil well service fleets.
The benefits of ATIS for tanker industry fleets:
• PSI invented automatic tire inflation 21 years ago.
• ATIS systems are now on over 70% of the top 200 for-hire and private fleets at some level.
• ATIS systems are now being specified on over 40% of new North American OEM vans and reefers.
• ATIS utilization in the tanker industry is 10%.
• 1,000,000 trailers will be running with ATIS by end of 2015.
Robinson said a tire-inflation system will provide a significant reduction in tire-related roadside service calls, improved vehicle fuel economy (3.8% according to an FMCSA study in 2010), longer tread life (over 10%), short ROI (seven to 10 months), and very low maintenance. ♦
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