Going Loco For DPFs: Johnson Matthey supplies DPFs to a switch locomotive in Los Angeles, California, U.S.A., ports
by amanda m. klemp
The U.S. Environmental Protection Agency’s (EPA) Tier 4 standards for locomotives go into effect in 2015, and locomotive manufacturers and operators are getting a head start on deciding which track to take whether it’s SCR, EGR, DOCs, DPFs or any combination thereof.
To get on track early, the California Air Resources Board (CARB) is helping to fund a project through its Air Quality Improvement Program (AQIP) to outfit a switch locomotive operating in the Port of Los Angeles (POLA) and Port of Long Beach (POLB) with diesel particulate filters (DPFs) from Johnson Matthey. Funding from AQIP’s Assembly Bill 118 will cover 50% of the cost of the project, while Johnson Matthey, the locomotive operator and the ports share the other 50%.
The switch locomotive from NREC is powered by three generator sets driven by Cummins EPA Tier 3 (for off-road) 19 L QSK19 diesel engines rated 522 continuous kW. By designing the locomotive with three separate electric drive units, wear and tear on the engines may be reduced. Each of the three engines will be outfitted with an individual DPF system, comprising multiple filters and diesel oxidation catalysts (DOCs). This is the first time Johnson Matthey has installed multiple locomotive DPF systems on a locomotive with multiple drivers.
There are a couple of considerations for the DPF designs for switch locomotive applications. “It has to be shock resistant,” said Wilson Chu, business development manager, Johnson Matthey. “Especially for a switch locomotive; all they do is bang into cars all day long.” To meet this need, Johnson Matthey incorporated shock isolators in the DPF design.
Additionally, switch locomotives spend a lot of time idling in the rail yard. “You need to quickly be able to get up to speed and regenerate the filters,” said Chu. “The DPFs are formulated to allow you to do that at the lowest possible temperatures.” This comes from a proprietary catalyst formulation.
The locomotive DPF design is based on the company’s CRT technology for on-highway trucks and stationary generators. The system uses a DOC to covert NO from the engine to NO2, which is more aggressive than air, to combust and vaporize the soot. While the soot is vaporized, ash can have a tendency to build up in the filters, which causes backpressure. Chu said, “The railroads don’t want to clean the filters that often, so if they want a one-year or six-month cleaning interval, you need to size the DPF system appropriately to hold the ash and to accommodate backpressure. Since the ash does not go through the filters, the filters must be periodically cleaned to remove the ash.”
For a switch locomotive, cleaning intervals are subject to run-time variables. Depending on how much time the locomotive spends idling, and if the operator installed an anti-idling system that completely shuts down the locomotive after a set amount of idling time, cleaning intervals can be extended further. Still early in the project, Johnson Matthey predicts completion within one to two years, largely dependent on how many hours of operation CARB determines is necessary for field durability testing. Once testing is complete, the DPF system will be CARB verified to meet EPA Tier 4 PM standards.
Source: Diesel & Gas Turbine Worldwide