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The Role of Diesel Exhaust Systems in Construction Equipment (With Maintenance Tips)

The Role of Diesel Exhaust Systems in Construction Equipment (With Maintenance Tips)

Two drum rollers and one loader pushing dirt along a job site.

The Role of Diesel Exhaust Systems in Construction Equipment (With Maintenance Tips)

Reading time: 5 min

Diesel engines convert diesel fuel into power, enabling heavy equipment like dozers, loaders and excavators to perform critical tasks on construction sites. As diesel engines combust fuel, they create exhaust fumes that are expelled into the surrounding environment.

To improve air quality, reduce pollution and mitigate excessive noise, modern heavy equipment machinery is equipped with advanced exhaust systems. These systems make machines cleaner, quieter and more efficient.

A well-maintained exhaust system is crucial for prolonging the lifespan of a machine’s diesel engine. Not only is proper maintenance of the diesel exhaust system critical to improving a machine’s longevity, but it’s also the key to reducing emissions and keeping your fleet in compliance with clean air regulations.

In this article, we’ll dig into the role of diesel exhaust systems in construction equipment. Understanding and properly maintaining your machine’s diesel exhaust system is essential for the efficient and compliant operation of construction equipment.

A diagram showing the flow of diesel exhaust in a heavy equipment engine system.

Understanding Diesel Exhaust Systems In Construction Equipment

The exhaust system of heavy construction equipment comprises several crucial components, each with a specific function. Here is a detailed outline of the main parts involved in the process of emitting and cleansing diesel exhaust.


1. Diesel Particulate Filter (DPF)

The DPF is a cylindrical component, typically made of a ceramic material laced with a honeycomb structure. It's designed to withstand high temperatures and is often encased in a metal shell.

Function and Operation:

Its primary role is to capture and store soot (particulate matter) produced during diesel combustion. Over time, the DPF becomes filled with this particulate matter and needs to be 'regenerated' or cleaned. This is typically achieved by burning off the soot at high temperatures.

Location in Exhaust System:

It's located in the exhaust system after the engine and before the SCR unit. The placement ensures that the exhaust gasses pass through it, allowing it to trap particulates.

2. Diesel Exhaust Fluid Headers (DEF)

DEF Headers are a part of the DEF injection system. They include nozzles and pipes made of materials resistant to corrosion by DEF (urea and water solution).

Function and Operation:

DEF Headers are responsible for injecting DEF into the exhaust stream. The DEF, when heated in the exhaust stream, breaks down into ammonia which is then used in the SCR system to reduce NOx emissions.

Location in Exhaust System:

These headers are situated close to the SCR unit, ensuring that DEF is injected into the exhaust gasses before they enter the SCR system.


3. Selective Catalytic Reduction (SCR)

The SCR system consists of a catalyst bed, often made of materials like vanadium or zeolite. It is enclosed in a solid housing, often with a series of pipes and sensors to manage the chemical reactions.

Function and Operation:

SCR is used for the reduction of nitrogen oxides (NOx) in the exhaust gasses. When the exhaust gasses mixed with ammonia (from the DEF) pass through the SCR, a chemical reaction occurs that converts NOx into nitrogen and water, which are harmless.

Location in Exhaust System:

The SCR system is typically located after the DPF in the exhaust system. This placement ensures that the exhaust gasses are first cleared of particulate matter before undergoing the NOx reduction process.

Muffler System

The muffler system consists of a large, elongated chamber made of metal and a series of internal tubes.

Function and Operation:

Its main function is to reduce exhaust noise. It does this by disrupting and spreading out the sound waves traveling through the exhaust system, thereby diminishing the sound intensity.

Location in Exhaust System:

It is typically found near the end of the exhaust system, often visible from the exterior of the machine.

Each of these components is essential to reducing emissions and ensuring your heavy equipment operates efficiently and in compliance with environmental regulations.

Common Exhaust System Issues

Exhaust systems in heavy construction equipment can encounter several problems which, if not addressed promptly, can lead to significant performance issues.

One of the most common issues is the clogging of the DPF (diesel particulate filter). This usually occurs due to excessive soot accumulation, a consequence of low-speed operations or excessive idling. Another common problem involves DEF nozzles becoming blocked in the SCR system, which hinders the emission control process.

Some telltale signs that there might be an issue with the exhaust system include a noticeable decrease in engine performance or fuel efficiency. An increase in exhaust smoke or a change in its color could also signal a malfunctioning exhaust system component.

Modern construction equipment often features diagnostic systems that can flag exhaust issues by issuing error codes, helping operators pinpoint specific exhaust system problems. Regular inspections and maintenance are crucial for identifying these issues early and keeping the exhaust system functioning optimally.

Preventive Maintenance For Diesel Exhaust Systems

Implementing certain preventive maintenance practices is essential to maintaining the efficiency and reliability of diesel exhaust systems in construction equipment. These practices not only extend the life of exhaust components but also ensure compliance with environmental regulations.

Importantly, the DPF (diesel particulate filter) requires regular attention. Cleaning and replacing the DPF at the intervals set out in your machine’s service manual helps prevent clogging by soot, which can significantly hamper performance.

The SCR (selective catalytic reduction) system also requires periodic maintenance. DEF needs to be refilled regularly and the system needs to be inspected to ensure blockages have not formed in the DEF injection system.

A service technician should thoroughly inspect your machine’s diesel exhaust system at least once per year. If you are operating your heavy equipment in harsh environments, more frequent inspections may be necessary. By adhering to these preventive maintenance practices, you can significantly reduce the likelihood of exhaust system failures.

Final Thoughts

As environmental regulations become more stringent, effective exhaust systems capable of regulating your fleet’s emissions are essential. By regularly inspecting and maintaining your machine’s diesel exhaust system, you can improve the effectiveness and longevity of your heavy equipment.

If you are looking for OEM and aftermarket parts related to the diesel exhaust system of your heavy equipment, be sure to check out the EquipmentShare Shop. Our online catalog makes it easy to shop for heavy equipment exhaust system parts and get them shipped right to your door. Having trouble locating a specific component? Reach out to our dedicated parts experts and get personalized assistance.

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