VERT: PM filter tests can be wisely limited to one

Diesel Fuel News, March 18, 2002

Detroit -- Europe's pioneering "VERT" project to verify the efficiency and performance of diesel particulate filters (DPFs) makes a strong case for limiting test evaluations to a single trap (representing the same trap family) on one representative diesel engine under all conditions expected.

If VERT's well-established testing scheme is adopted by more regulatory authorities, then DPF technology developers could avoid having to run tests on large numbers of engines, at huge cost in time and money, the VERT developers argue.

This is seen as urgent now that environmental authorities are beginning to require massive diesel emissions retrofit projects as in California, Switzerland and elsewhere.

"Plans to retrofit the total fleet of existing engines of any brand, age and duty, as envisaged by the California risk reduction plan or the Swiss heavy-duty retrofit initiative, would require a prohibitive large number of verification tests, time consuming and expensive," as Andreas Mayer of TTM (Switzerland) explained in a paper (SAE 20020-01-0435) to the Society of Automotive Engineers World Congress here.

While more extensive testing might be required for oxidation catalysts or DeNox catalysts, a "simplified approach" is justified for DPFs, Mayer showed.

The VERT approach evaluates solid particles (metals, ash, soot, minerals) and separately considers droplets condensed from hydrocarbons, sulfuric acid and water vapor. The latter isn't any health concern, and sulfuric acid will be minimal with low-sulfur diesel "as expected within retrofit projects," the VERT project developers explain in their SAE paper. Oxidation catalysts (and some catalyzed filters) could take care of the hydrocarbons, they said.

VERT also checks for de-novo synthesis of dioxins and furanes; a problem discovered with copper-based fuel additives in DPFs years ago (see Diesel Fuel News 4/9/97, P5).

The basic VERT protocol now uses ultra-low sulfur diesel (ULSD of less than 10 ppm sulfur) and special lubricants without sulfur or metal ash and a total base number of <3.

The test trap "must be matched to the test engine such that it reaches the highest space velocity ever expected during the test cycle," which includes full-speed/load points.

The protocol also requires annual free-acceleration opacity test on trap-equipped engines. "Experience shows that trap failures can be positively detected by this simple and low-cost test procedure," the VERT authors said.

VERT's procedure has won wide approval including Swiss BUWAL, German UBA, and occupational health agencies of Switzerland, Germany and Austria, the U.S. National Institute for Occupational Safety & Health (NIOSH), as well as the Canadian mining industry's DEEP project.