Editor's Desk

Taking on Tier 4 engines

As emissions requirements continue to evolve and the extractive industry reaches the final stage of current emissions standards, equipment operators will soon make the switch to working with Tier 4 Final engines — if they haven’t already.

With additional emissions control technology, making the jump to Tier 4 engines may seem like an overwhelming transition at first. However, transitioning to Tier 4 is simply another step in the history of diesel technology advancement. For example, when electronics were first introduced during the Tier 2 emissions stage, end users were initially concerned about the addition. Today, it has become the standard, as almost every engine features electronics.

It is also important to note the on-highway market has been involved with Tier 4 Final engine technology longer than off-highway plant and equipment, and manufacturers have learnt from the insights gleaned from its implementation.

There are three main reasons why users may find Tier 4 Final equipment intimidating:

  1. A lack of familiarity with new emissions technologies.
  2. A fear of complexity impacting equipment performance.
  3. Conflicting information about how new technologies impact long-term engine care.

With the perceived intricacy of emissions systems, paired with varied approaches between manufacturers, general education is key to making the transition to Tier 4. Experts at John Deere Power Systems in the USA have explained how emissions technologies work together in a Tier 4 Final engine, and outlined simple maintenance practices to help ensure users are prepared.

The road to tier 4

“John Deere engines are built on a legacy of heavy-duty off-road engines,” Ryan Cawelti, the manager of worldwide engine market planning at John Deere Power Systems, said. “John Deere has been on a journey to deliver engines that meet Tier 4 Final emissions over the last 20 years. We have used a building block approach that has allowed us to add scalable technology to meet each subsequent emissions regulation.”

The industry introduced a combination of technologies and after treatment systems to meet Tier 4 regulations. To achieve the needed nitrogen oxide (NOx) and particulate matter (PM) reductions, different combinations of the following technologies are used:

  • High pressure common rail (HPCR) fuel system. The HPCR fuel system was introduced during the Tier 2 emissions phase and provides constant control over fuel injection variables such as pressure, timing, duration and multiple injections. The HPCR fuel system provides higher injection pressures, resulting in more efficient combustion, which, in turn, leads to a reduction in particulate matter.
  • Cooled exhaust gas recirculation (EGR). Cooled EGR was introduced with the start of the Tier 3 engines. The system mixes measured amounts of cooled exhaust gas with incoming fresh air back into the intake manifold to lower the engine’s exhaust temperature, thereby reducing NOx emissions to an acceptable level. The use of cooled EGR enables smaller SCR systems when used to meet Tier 4 emissions regulations.
  • Diesel oxidation catalyst (DOC) and diesel particulate filter (DPF): Many Tier 4 engines feature an exhaust filter that contains a diesel oxidation catalyst and a diesel particulate filter. The DOC reacts with exhaust gases to reduce carbon monoxide, hydrocarbons and some particulate matter. DPFs operate in conjunction with a diesel oxidation catalyst located upstream of the particulate filter. The downstream DPF forces exhaust gases to flow through porous channel walls, trapping and holding particulate matter. Trapped particles are eventually oxidised within the DPF through a continuous cleaning process called passive regeneration, using exhaust heat created under normal operating conditions.
  • Selective catalytic reduction (SCR) system. The SCR system uses a urea-based additive, often referred to as diesel exhaust fluid (DEF). DEF is injected into the exhaust stream prior to the SCR catalyst, which then converts NOx in the exhaust stream into nitrogen and water, helping to further reduce NOx emissions.
  • Each of these systems dynamically interact with each other to adapt to various operating conditions and ensure Tier 4 emissions compliance.


Three keys to a good system

There are three primary maintenance practices extractive operators should keep in mind with Tier 4 engines:

1. System cleanliness. Cleanliness is essential when using diesel exhaust fluid (DEF) to ensure reliability of the SCR system. This includes making sure storage tanks and any equipment used to handle or transport DEF are clean and free of debris.

Bryan Wood, the manager of OEM applications at John Deere, has recommended operators “treat the DEF circuit like a hydraulic circuit. Taking precautions to preserve the cleanliness of the fluid will help ensure a trouble-free system in the long run”.

Ensuring a clean system also includes setting aside containers to use only for DEF. Operators can benefit from using specialised DEF equipment, such as totes, stainless steel pumps and fuel lines, as DEF can be corrosive to certain materials such as steel, iron, zinc, nickel, copper, aluminium, and magnesium. DEF contamination, even with trace amounts of metals, can damage the catalyst in the SCR system.

2. Proper storage and handling of DEF is critical, as they can directly impact the fluid’s quality. “Users should be aware that there is a shelf life for DEF, and it will start to degrade depending on how well it’s preserved during storage,” Wood said.

DEF freezes at about -11oC, and it cannot be directly exposed to sunlight. However, DEF can still be used, even if it freezes solid. On the engine or equipment, the DEF tank is equipped with a heating element that uses engine coolant to thaw DEF in temperatures below -11oC. Antifreeze fluid products should not be used to “winterise” pumps, nozzles, and hoses, as the residual antifreeze fluid can damage the SCR system.

3. Using the correct materials, including fuel and engine oil that is specified for off-highway applications. Through the various off-highway emissions stages, engine oil has been specifically formulated to reduce the build-up of ash in the DPF, which differs from engine oils used for on-highway vehicles.

Using the correct fuel, although routine, is crucial in keeping the exhaust system running smoothly on a Tier 4 engine. “Fuel filtration needs have increased as we’ve moved to high pressure common rail fuel systems,” Wood said. “Using diesel fuel that meets operator manual specifications is essential to assure adequate filter life and keep the fuel system operating efficiently.

“In addition, excess sulphur content in the fuel will reduce efficiency of the SCR system and lead to diagnostic trouble codes and unscheduled machine downtime. It is critical to use fuels with sulphur contents that meet ultra-low sulphur diesel specifications.”

Other than taking extra precautions to ensure system cleanliness and proper storage, basic maintenance practices, such as abiding by proper service intervals and using the correct fluids, remain the same as with Tier 3 engines.

Maintaining DPFS

Diesel particulate filters trap particulate matter that exists in the exhaust stream, much of which is cleaned during regular operating conditions through passive regeneration. However, over time, the filter reaches a point where it needs to be cleaned by raising exhaust temperatures, otherwise known as active regeneration.

An active regeneration cycle will happen automatically without operator action. It shouldn’t affect normal operation and will only be noticeable by an indicator light on the dashboard when it is in process. It is also important to note that users should not override an active regeneration cycle when it is in process.

“One of the main takeaways for operators is to let the system work, which includes letting it run through necessary regeneration cycles,” Cawelti said. “When left to operate under normal conditions, the system will run as it should.”

One of the biggest things operators can do to ensure a smooth engine operating experience is to keep lines of communications open.

“Talk to your OEM and to the engine manufacturer representatives,” Wood said. “Learn about what’s there and what you can and cannot do.

“Becoming informed about the new technology, whether through conversations with engine manufacturers or product research, will generally ease the transition into Tier 4.

“In fact, many of these technologies have been implemented in the on-highway market for some time, so users may already have experience with Tier 4 technology from driving their trucks, for example.”

When it comes to operating a Tier 4 piece of equipment, extractive operators are encouraged to capitalise on their experience.

“Work your machine like it wants to be worked,” Wood said. “Maintain it by keeping proper service intervals, which are defined for the different systems on the engine, and use the right fluids.”

Article courtesy of Aggregates Manager (US). Visit AggMan.com

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