Diesel particulate filters (DPF)

01

Check exhaust temperature for passive or active regeneration

US EPA's DPF installation bulletin says the exhaust temperature profile is one of the main factors in choosing a passive or active system. It says the required minimum exhaust temperatures for regeneration of passive DPF systems "depend on the filter design and often range from 210°C for 40 percent of the time to 260°C for 30 percent of the time"; active systems add a heat source and depend less on duty cycle. Exhaust temperature data logging must be done on each vehicle at the DPF installation location, by the filter maker or its authorised representative. [2]

EPA's general bulletin explains that passive regeneration happens when exhaust is hot enough to burn the trapped PM without added fuel, heat or driver action, while active regeneration may need driver action or other sources of fuel or heat; regeneration frequency depends on duty cycle, PM emission rate and filter technology. It notes that catalysed DPFs may increase the NO₂ fraction of NOx, that "DPFs generally do not reduce oxides of nitrogen (NOx) emissions", and that verified DPFs are for ultra-low-sulfur diesel of up to 15 ppm sulfur. [1]

Editorial calculation: on an 8-hour shift, a passive filter needing 210 °C for 40% of the time requires about 3.2 hours with exhaust at or above that temperature at the filter location; idle-heavy or short-trip duty that falls short points to an active system.

Give the supplier the vehicle or equipment type and engine details (make, model, year, displacement, power, EPA engine family, turbocharger, EGR), annual hours or miles, engine-out PM, logged exhaust temperatures at the filter location, space and mounting, vibration, fuel sulfur and oil consumption.

02

Plan backpressure monitoring and ash cleaning

EPA's operation and maintenance bulletin says a DPF causes fluctuating exhaust backpressure as PM accumulates and burns, while ash from lubricating oil and fuel additives builds up gradually; because engine makers limit exhaust backpressure, a backpressure monitoring and operator notification system must be installed with every DPF and periodically inspected. [3]

EPA says "Cleaning of ash from retrofit DPFs is typically required every 6 to 12 months"; it is done by removing the element and cleaning it in a dedicated station with heat and compressed air with vacuum; an engine emitting excessive PM or regenerating poorly will need more frequent cleaning and should be diagnosed. [3] [1]

EPA reports that DPFs verified by EPA and CARB "are typically effective at reducing emissions of PM by 85 to 90 percent or more", that some also cut hydrocarbons and CO by 70 to 90%, and that when properly installed and maintained they "should remain effective for the life of the vehicle, generally five to ten years or 10,000 or more hours of operation"; its 2010 bulletin put retrofit costs at about $5,000 to $15,000 or more, and up to $50,000 for active systems on large nonroad equipment. [1]

03

Understand the wall-flow substrate

A 1983 Corning patent describes honeycomb filters formed from thin porous intersecting walls whose cells are blocked alternately at each end face in a checkerboard pattern, so the exhaust passes through the walls. It gives cell densities of about 10 to 300 cells/in² (1.5 to 46.5 cells/cm²) as useful and 100 to 200 cells/in² (15.5 to 31 cells/cm²) as preferred, with walls preferably 0.25 to 0.76 mm thick and under about 1.5 mm to limit volume and thermal shock problems. [4]

Its test results found maximum particulate capacity in 100 cells/in² filters with 0.435 mm walls. EPA's bulletin notes that "DPFs typically use a porous ceramic or cordierite substrate or metallic filter". [4] [1] Editorial note: higher cell density adds filtration area but narrows channels and raises backpressure, as the patent's upper limit reflects; ask the supplier for the cell density, wall thickness, porosity and material of the actual element.

04

Ceramic substrates, SCR-combined DPF systems and DPFs from exhaust makers

Listings include ceramic honeycomb DPF substrates from ceramic makers, DPF systems with oxidation catalysts and SCR for generators and off-highway engines with liftable individual elements, and DPFs from exhaust system makers. Ask each supplier whether the product is a bare substrate, a canned filter or a complete system with monitoring, and which engines it has been applied to.

05

Substrate, catalyst coating, canning, inlet and outlet, backpressure monitor and active heater

Two rows are options: a catalyst coating, which EPA notes may raise the NO₂ share of NOx, and an active heat source for duty cycles too cool for passive regeneration. [1] [2]

06

PM reduction, soot and ash capacity, backpressure, cell density and substrate for a DPF order

Cell density and wall thickness are the preferred ranges in Corning's 1983 patent, not values for a current element; ask the supplier for those of the filter quoted. [4]

07

Send the engine, duty and maintenance data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Engine: [make; model; year; power; engine family; EGR]
Duty: [hours or miles; logged exhaust temperatures]
Emissions: [engine-out PM; target reduction]
Fuel and oil: [sulfur; oil consumption]
Installation: [space; mounting; vibration]
Maintenance: [monitoring; cleaning service]

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