Fleet operators who have made the switch to natural gas fueled trucks advised those in the industry who are eyeing a transition to compressed natural gas, or CNG, or LNG-powered engines to be prepared for new maintenance and operation challenges.
While the trucking industry debates the big picture economic issues around natural gas as a vehicle fuel, those in the industry that work most closely with NGVs have begun to see the more granular impacts of a fuel switch, engineers and company representatives said at the American Trucking Associations' Natural Gas in Trucking Summit.
At the beginning of his company's transition to natural gas trucks, Mike Lickert, fleet manager for Giant Eagle Inc. of Pittsburgh, Pa., said there was limited data available on the maintenance costs a company could face. The company budgeted a 2-cent-per-mile increase, unsure of what to expect. While the types of costs have changed for Lickert's fleet, he has not found an overall increase in maintenance expenses.
"While we're changing spark plugs on a natural gas truck, on a diesel truck we were working on injector cups and sleeves and so forth, so I think it's a tradeoff to be quite honest," Lickert said.
But natural gas trucks do require much more frequent oil changes than their diesel-fueled counterparts, according to Lickert, who has found his company's NGVs needing an oil change every 15,000 miles - twice as often as diesel trucks. "That's not acceptable to our industry, so we're going to work hard to extend that and make it more diesel-like," Lickert said, noting that his company is pushing for aggressive testing at major engine oil manufacturers to lengthen that interval.
Maintenance workers and truck operators also must familiarize themselves with a new set of safety and upkeep protocols, some of which may not be expected. Scott Perry, Ryder Fleet Management Solutions vice president of supply management, warned operators that they should be wary of stations without the proper fuel filtration systems in place. Contaminants could compromise the entire fuel system, forcing operators to remove, clean and reinstall fuel systems, he said.
"[It caused] a signification interruption of service [and] significant cost," Perry said of his company's experience. "It all could have been avoided had the proper steps been taken on the front end to put the right filtration in place. Station maintenance and design and ongoing service is an extremely important aspect of the operation, so don't take any shortcuts here."
Perry has also found that natural gas trucks' spark plug and ignition assemblies are highly susceptible to damage if they are not properly handled. Further, he and his company have struggled with getting an accurate understanding of the new vehicle's fuel economy, noting that in the analysis of and conversion from natural gas to gasoline gallon equivalents to diesel gallon equivalents, a degree of clarity is lost. Lickert agreed.
"He's absolutely right. You'll go crazy trying to figure out GGE and DGE and so on and so forth," Lickert said, but added that the calculations do not have to be so complicated. "The metric per miles per gallon is a couple of things. First of all it's a ways and means to get to the total cost per mile, so if you really just factor that in, and take your fuel cost per mile for a natural gas truck versus a diesel truck."
Companies considering transitioning from diesel to natural gas fuel also have a choice between LNG and compressed natural gas, and the factors are not limited to fuel economy, availability and vehicle type, Lickert noted. Because LNG is chilled to about minus 260 degrees Fahrenheit, the odorant that is usually present in natural gas, mercaptan, cannot be included, presenting an added safety concern, Lickert said.
"[With mercaptan], if there is any type of leak you can pick that up pretty quickly, but unfortunately with LNG, the mercaptan drops out at those cold temperatures," Lickert said. "It was something to consider."
Further, when refueling, truck operators are required to wear protective gloves and face masks to protect themselves from the cryogenically stored fuel, and natural gas vehicle maintenance stations also require additional safety considerations, according to Nadine Haupt, engineer and Navistar Inc's North American truck operations' director of alternative fuels.
While natural gas has a much higher ignition temperature than diesel or gasoline and has a narrower flammability range in terms of the required air-fuel mixture, natural gas maintenance stations must be aware fuel's ability to rise above air and collect undetected near the ceiling.
"The most important is that top 18 inches," Haupt said. "You want to have some ventilation opportunities. You want to take away any ignition points."
No electrical components that could provide a spark or pilot lights for heating should be allowed in that top foot and a half, and a many of the facility's methane detectors should be placed there to trigger automatic safety precautions, Haupt added.
