Monday, June 17, 2013

What do DPFs and your kitchen stove have in common?

During my years working in diesel emissions, I’ve come across some interesting relationships between myths - one of the most interesting between "self-cleaning" ovens and “maintenance-free" diesel particulate filters (DPFs).

By design, a DPF captures solid combustion byproducts within the exhaust stream – burning them off to clean itself when the DPF reaches a certain temperature for a specific time period. This burn-off (also known as DPF regeneration) is almost identical to a self-cleaning cycle for the stove in your kitchen.

But similar to your stove, burning-off creates remnant non-combustible ash that remains inside. Just like you still have to clean the ash out of the bottom of a "self-cleaning" oven, ash still needs to be manually removed from a "maintenance-free" DPF to keep it from eventually plugging-up.

While you usually only need to sweep the ash out of the bottom of your kitchen stove, cleaning a DPF is a much more elaborate operation. Inside a DPF, ash must typically be removed using a reverse flow of forced air to loosen and remove the ash, sometimes accompanied by addition heating in an oven to ensure thorough soot burn-off.

A few DPF manufacturers have tried to claim their DPFs are “maintenance-free”, with disappointing results – in some cases going so far as “de-listing” of their CARB verifications and being forced to change their designs.

As you evaluate DPFs during your CARB compliance process, I recommend approaching “maintenance-free” claims with a healthy dose of skepticism. And if you already own a “maintenance-free” DPF, you should still get it checked routinely for inevitable ash buildup, before it causes a problem.

While you’re at it, you may want to go home and check out that "self-cleaning" kitchen stove too.

As always, if you have questions about CARB compliant DPFs or CARB requirements, feel free to contact us via email or at 800-331-9247 (press 9).

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