Emission control specialist Nett Technologies Inc has received regulatory approval for aftermarket use of its BlueMax-brand urea-based selective catalytic reduction system (SCR) on certain commonly used Caterpillar engines.

The United States Environmental Protection Agency placed the Nett system on the national clean diesel campaign's emerging technologies list on July 10.

The system is applicable for nonroad, four-cycle, heavy-duty diesel Caterpillar engine models 3306, 3116 and 3406 in the 75-450 kW (100-600 horsepower) ranges, originally manufactured from 1996 to 2008.

The system aims to control nitrogen oxide emissions from medium- and heavy-duty diesel engines. A urea control strategy relies on a nitrogen oxide concentration measurement by a sensor that is positioned upstream of the SCR catalyst. A control algorithm calculates the necessary urea-dosing rate.

Mississauga-based Nett has not set final pricing on the system.