Expired Tanks Force Grounding of CNG School Buses in California Several Califor-
nia school districts have taken CNG school buses out of service because their
fuel tanks
have reached their 15-year lifespan, and no grant mon- ies are available to fund replacement. Ralph
Knight,
transportation director at Napa Valley Unified School District, said he has grounded seven buses. “We all knew sooner or later these tanks would need to be
replaced,” added Knight. “But 15 years came really fast.” Mike Rea, executive director of the West County Transporta-
tion Agency in Santa Rosa, said he has grounded more than half of the buses in his fleet of 22 buses because of expired tanks.
In Southern California, Pete Meslin, transportation director
at Newport-Mesa Unified School District, noted that his district has not had to replace any tanks yet, as the district’s CNG buses are less than 15 years old. “We hope grant money will be available when our tanks age
out of compliance. Our CNG buses have required more mainte- nance than we would have hoped,” he said, adding that they’ve replaced UEGO sensors about every two years, as well as heads, valves and gaskets. Since 2000, the California Air Resources Board’s (CARB) Low-
er-Emission School Bus Program has provided more than $100 million to air quality districts to help school districts purchase new school buses, including CNG, that meet strict emissions reg- ulations. But program funds made available through Proposition 1B funds have yet to surface for replacement tanks, which cost about $20,000 each. For now, CARB recommends that school districts work di-
rectly with their local air districts for money derived from motor vehicle registration surcharges.
Latest Fuel Economy Testing Compares SCR with EGR Technology Blue Bird released data in June that claims
SCR technology of the Cummins ISB6.7 diesel engine can achieve a more than 12-percent overall increase in fuel economy than Ad- vanced EGR technology. Tomas Built Buses produced its own report in February that claimed the ISB6.7 with SCR increased fuel ef- ficiency by 27 percent over the MaxxForce DT with EGR. Last summer, IC Bus released its own data that reported a 4.5-percent advantage in “fluid economy,” which describes the measure- ment of Diesel Exhaust Fluid (DEF) used by a vehicle’s SCR emissions reduction system. Te Blue Bird tests were conducted at
the Bosch Automotive Proving Grounds and complied with SAE J1526–recom- mended fuel consumption standards and procedures. Tere were three separate tests per route to compare the ISB6.7 in a 2012 Blue Bird Vision with Navistar’s 6.7L MaxxForce 7, as well as with the 7.6L Maxx- Force DT installed in IC Bus CE Series. Blue Bird tested stop-and-go urban routes
at driving speeds of 25, 30 and 40 mph for 27 miles on an enclosed test track. Each three-mile lap included seven stops to simu- late student loading and unloading, and the highway test simulated a 59-mile activity trip at an average speed of 58 mph. Blue Bird said actual fuel economy results may vary depending on type of route, terrain, driver
behavior, weather conditions and loading. Te company said the Vision pow-
ered by the Cummins ISB6.7 resulted in 10.67-percent increase in fuel economy over the IC Bus CE Series with MaxxForce 7. Urban routes claimed 8.07 mpg for the Vision compared to 7.32 for the CE, and highway tests showed 9.81 mpg in the Vi- sion and 8.84 in the CE. Overall, the study reported the Vision’s mpg was 9.19 com- pared to 8.31 for the CE. John Kwapis, chief operating officer for
Blue Bird, said the IC Maxxforce 7 and DT did not experience a regeneration cycle, which he explained happens in normal operating conditions. Blue Bird said the total annual
fuel
savings of the ISB6.7 was $864.23 and operators would pay $8,161.04 a year for every 20,000 miles traveled at $3.75 per gallon, while paying $9,025.27 for the MaxxForce 7. According to Blue Bird, the Vision’s vehicle range was 924 miles based on fuel capacity of 100 miles and mpg, as compared to the CE’s range of 820 miles. Cummins said its data indicates that 2
percent to 3 percent of diesel fuel used must be DEF. For example, if the engine uses 100 gallons of diesel fuel over a pe- riod of time, the SCR system used two to three gallons of DEF in the same period.
Attendees at the 2011 STN EXPO Trade Show check out the Cummins ISB.
www.stnonline.com 15
Blue Bird also compared the Vision
ISB6.7 with a CE Series powered by the MaxxForce 7.6L DT engine. Te OEM claimed that the fuel economy improve- ment increased to 12.64 percent overall and up to 16.74 percent on urban routes. To meet current EPA requirements,
Navistar’s EGR technology treats oxides of nitrogen (NOx) in the engine, whereas Cummins’ SCR treats the emissions in the tailpipe by using DEF.
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60