Is a Better by xiangpeng

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									Is
               a Better
The air in tires is 78-percent nitrogen. There appear to be many
advantages to filling tires with 99-percent pure nitrogen. Equipment
                                                                                                                            By Paul Dexler
is available for centrally managed fleets to do the job.


                                                                                                  The Benefits of Nitrogen


T
            raditionally, tires have been         Over time it loses elasticity and strength,
            filled with compressed air. It’s      just like an old rubber band. Likewise, the       The use of nitrogen to inflate tires:
            cheap, easy, and available, but       oxygen in inflated tires permeates the tire       • Slows pressure loss from permeation.
            has had problems that now can         structure and ultimately the tread. This is       • Stabilizes pressure and virtually
be resolved.                                      why tire manufacturers recommend re-                eliminates pressure fluctuations due
   If air pressure in tires is not kept at the    placing tires that are six years old, even if       to temperature change.
correct level, at best, they wear out too soon.   the tread is still good.                          • Reduces tire oxidation.
At worst, they could cause a serious acci-           One way to solve the problems of air-          • Eliminates interior wheel corrosion.
dent. The most important factor in tire per-      inflated tires is to inflate them with an         • Reduces running temperatures.
formance and life is correct air pressure. Re-    inert gas, such as nitrogen.                      • Decreases false alarms and activa-
search indicates that nearly 83 percent of           In the past, the equipment needed to pro-        tion of tire pressure-monitoring
tire problems start with low tire pressure.       duce nitrogen was large and expensive. The          systems.
   The air in a tire leaks. Even with perfect     only alternative was to use externally filled     Nitrogen use in tires is not new. It has
valves and unblemished casings, air leaks         high-pressure nitrogen bottles, which were      been used on earth-moving equipment
permeate the rubber itself and the inter-         also expensive and a safety hazard.             and aircraft tires and in racecars. Air is not
face between the tire and the rim. As a tire         The NitroFill company, which produces        used in those applications because it is
heats during driving, the air inside ex-          nitrogen tire inflation equipment, has de-      one-fifth oxygen, and oxygen fuels fires.
pands, then contracts when the tire cools         veloped a solution to these problems. In-       Aircraft and racecar tires can become so
down. This means that tire pressures must         stead of using stored nitrogen, NitroFill       hot they actually catch fire. Nitrogen does
be checked prior to driving more than a           takes advantage of technology that allows       not support combustion.
mile or so, since recommended tire pres-          nitrogen to be separated from the air. The        A heavy truck fleet running the system
sures always refer to the cold state.             process is done under low pressure and          in Class 8 tractors reports that tires run
                                                  results in highly purified nitrogen.            cooler; and it found a 2-percent fuel
Air is 78-Percent Nitrogen                           The purity of nitrogen available from        economy improvement.
   The air that we breathe is about 78-per-       nitrogen generators generally ranges from         The air inside a tire eats away at the rub-
cent nitrogen, 21-percent oxygen, and 1-          95 percent (low purity) to 99.9 percent         ber casing, and the moisture in the air can
percent other gases. Nitrogen is inert, non-      (high purity). NitroFill generators can         contribute to wheel corrosion. Nitrogen
combustible, and noncorrosive. Oxygen,            produce nitrogen in excess of 99.9 percent      has no moisture, therefore, no wheel cor-
on the other hand, is corrosive and im-           purity and provide the procedures to guar-      rosion. An inert gas, it doesn’t permeate
mensely destructive to rubber and other           antee a minimum of 95-percent purity in         the molecular structure of the tire casing.
tire materials. As soon as a tire is manufac-     a serviced tire, the minimum purity that        A nitrogen-filled tire holds its pressure
tured and exposed to air, the effects of oxi-     must be maintained in the tire to enjoy the     longer and runs cooler, both of which
dation begin to deteriorate the rubber.           benefits that nitrogen provides.                contribute to longer tire life. GF


20    Government Fleet September / October 2006

								
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