Technology Today: Train for Emissions Technology

By Pat Crail, CEM | May 31, 2012

Fleet managers are beginning to receive Tier 4-Interim engines in large off-road equipment. Although manufacturers use various technologies to meet Tier 4-I requirements, they have a number of items in common: high-pressure fuel systems and greater control over the combustion process combined with exhaust aftertreatment in the form of diesel oxidation catalysts (DOC), diesel particulate filters (DPF), or combination units that perform both functions.

Increased recirculation of exhaust gas (EGR), variable displacement turbochargers, and selective catalytic reduction (SCR) are among the strategies used to meet these increasingly tighter emissions regulations. We must educate our operators and service personnel about the unique operating characteristics and maintenance needs of these engines.

These new engines generally claim increased power and improved fuel economy, but we are seeing a significant up-front cost increase in the price of the equipment. These engines require a new motor oil and must burn ultra low sulfur diesel. They will also require periodic maintenance of the DPF, the aftertreatment device designed to capture engine soot.

During normal operation, the soot produced by the engine accumulates in the DPF, along with a small amount of ash resulting from the combustion of the engine oil that lubricates the piston rings. The engine’s ECM needs to periodically regenerate, or burn off the accumulated soot, in order to avoid plugging and, ultimately, restricting the exhaust system. For the most part, although each manufacturer approaches it differently, the regeneration process occurs automatically as needed during normal engine operation.

Even though the process is largely automatic, it is critical that the operator know what occurs during regeneration.

Regeneration involves extremely high exhaust temperatures in order to allow the soot to burn off. These temperatures can create a fire hazard in certain environments, so the operator must be aware of both the potential fire hazard and the fact that the DPF is about to begin (or is already in) a regeneration cycle. The operator can either move the machine to a safe area that is free of flammable material, or he can override the regeneration cycle if there is no safe area.

Manufacturers use lighted, amber indicator icons (conforming to ISO standards) to notify the operator that the engine is about to regenerate. This is where untrained operators can cause problems.

We have trained operators that a light on in the cab means that there is a problem and they should shut the machine down before notifying the shop or dealer. Now, certain amber lights mean that everything is fine: The DPF is either about to regenerate or is currently regenerating.

We have seen several instances where operators shut the machine off when they see this indicator, which interrupts the regeneration cycle. When they start it up again, the light remains off until the machine attempts another regeneration cycle, at which time the operator shuts the machine off again in order to get the light to turn off.

After a few cycles of this behavior, the DPF becomes clogged to the point where the engine begins to lose power, either through exhaust restriction or ECM-controlled “de-rating” of the engine to avoid damage. Either way, this quickly leads to a trip from the dealer, which, we can tell you from experience, is not covered by warranty.

We cannot simply instruct the operator to ignore all lights related to the DPF system. Some of them are important and do indicate a problem, such as a system that hasn’t been able to regenerate and is about to de-rate. Also, the DPFs need to be serviced at approximately 4,500 to 5,000 hours to remove the ash that cannot burn off during regeneration. A light may be indicating that service is due. The key with Tier 4-I engines is operator training. Make sure they attend the delivery training, have access to operators’ manuals and cab cards, and know who to call with questions when the lights come on.