Equipment World Digital Magazine
Issue link: https://read.dmtmag.com/i/85689
maintenance | by Tom Jackson DPFs and DOCs Ultra-low sulfur diesel must be used in DOCs to prevent the sulfur from "poisoning" the catalysts. Low-ash, API CJ-4 lube oil should be used to prevent ash from building up in the DPF. Diesel Particulate Filter (DPF) Diesel Oxidation Catalyst (DOC) P The new components at the heart of your Tier 4 engine lumbed into the exhaust stream of many diesel powered off-road ma- chines you buy today is either a diesel oxidation catalyst (DOC) or a diesel particu- late fi lter (DPF) or both. While there has been much talk and concern over these changes, the reality is that these engines and their emissions control systems are here to stay. Tier 4 Interim engines are more expensive. But for many of these engines the increased costs will be partially offset by gains in fuel effi ciency and power. They are more complex, yes; but vastly bet- ter for the air we all breathe. Your maintenance protocols will change little on these new engines. DOCs and DPFs, however, were not just stuck on to the exhaust ports of these engines as an afterthought. So when buying new equipment today you need to know: or a DPF – or both – selective catalytic reduction, or none of the above? to the engine upstream of the exhaust? change as a result? Downstream details Depending on the horsepower category, some engines can get by without either a DOC or DPF, some use just a DOC, and a good many will use both plumbed together in line in a single canister. In this arrangement the DOC is the fi rst component to receive exhaust gas from the engine. "Un- der normal conditions the DOC reacts with exhaust gases to reduce carbon monoxide, hydrocarbons and some PM," says Doug Laudick, manager of product planning at John Deere Power systems. The DOC also protects the DPF. interfere with the DPF's ability to trap and remove particulate matter, so manufacturers route the exhaust through the DOC fi rst, then into the EquipmentWorld.com | September 2012 39 Source: John Deere Power Systems