Monday, January 22, 2018

EPA asks for ‘revised guidance’ to assure proper operation of SCR engines


Friday, June 17, 2011
The EPA said, in light of the importance of reducing NOx emissions from heavy-duty diesel engines, it has developed “revised guidance” for “improving capabilities for designing SCR systems to ensure proper operation.”
The EPA said, in light of the importance of reducing NOx emissions from heavy-duty diesel engines, it has developed “revised guidance” for “improving capabilities for designing SCR systems to ensure proper operation.”

Noting that selective catalytic reduction (SCR) engine technology is being improved and refined as it matures, the federal Environmental Protection Agency (EPA) recently proposed that manufacturers go a step further and build in better deterrents to keep drivers from circumventing the technology.

This would include such things as a visual and possibly an audible warning system to tell the driver when the DEF tank is low; an escalating alarm as the DEF approaches the empty stage; activation of the warning system well in advance of the empty level; inability to turn the warning signal off until the DEF is replenished; vehicle speed reduced to 5 mph “at the quickest, safest rate”; and an engine shutdown or limited operation to idle only as a “final inducement” to the driver to restock DEF.

If a manufacturer chooses to implement this final inducement only when the vehicle is stopped, EPA suggested that there be the ability to “trigger” a shut-down when the vehicle is stopped in a safe location.

Prior to a shut-down, the driver should be prompted by a series of things including an engine derate, vehicle speed limitation or a limiting the number of engine restarts, EPA stated in a notice published June 7 in the Federal Register.

The agency is asking for comments by July 7.

Parts of the new guidance came out of a California Air Resources Board (CARB) meeting in July of 2010.

EPA’s comments included the statement that it didn’t agree with Navistar, the only OEM to forego SCR in favor of exhaust gas recirculation or EGR technology. Navistar had protested that it was too easy for drivers to get around the SCR technology, even to the point of using water instead of DEF. But according to EPA, a CARB study found that drivers had to very purposefully circumvent the use of DEF and that it was deterrent enough for drivers to risk costly repairs, financial loss and downtime incurred by not keeping DEF at the effective levels.

And while freely admitting SCR technology is working as it should, EPA stated that developments in SCR technology allow “continuing refinement in SCR design.”

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“Manufacturers are already in the process of improving their SCR designs and overwhelmingly drivers are not waiting for SCR-related warnings or inducements to be triggered before they refill DEF tanks and otherwise maintain proper operation of SCR systems,” EPA wrote.

However, the agency said, in light of the importance of reducing NOx emissions from heavy-duty diesel engines, it has developed “revised guidance” for “improving capabilities for designing SCR systems to ensure proper operation.”

Dorothy Cox of The Trucker staff may be contacted to comment at dlcox@thetrucker.com.

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