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What Is a Diesel Particulate Filter and How Do You Maintain It?

What Is a Diesel Particulate Filter and How Do You Maintain It?

A fleet of construction equipment on a job site

What Is a Diesel Particulate Filter and How Do You Maintain It?

Reading time: 6 min

Regulations introduced at  state and federal levels have imposed certain emissions standards for diesel vehicles and heavy equipment. One such standard, introduced in 2007, requires diesel equipment to feature special filters called diesel particulate filters (DPFs). These filters play an important role in capturing and eliminating soot and other particulate matter from the exhaust gasses of diesel engines.

Diesel particulate filters are part of a broader set of implementations known collectively as Tier 4 Technologies. Tier 4, established by the EPA, mandates substantial reductions in nitrogen oxide (NOx) emissions and particulate matter emissions through the use of novel emissions-reducing technologies.

To meet the requirements of Tier 4 legislation, new diesel-powered heavy equipment must use DPFs and other Tier 4 technologies. Therefore, fleet managers and operators alike must understand the intricacies of diesel particulate filters and how to keep them working optimally. In this article, we’ll go over the basics of diesel particulate filters, including their function and maintenance requirements.

The Basics of Diesel Particulate Filters

Understanding the role of diesel particulate filters begins with understanding diesel particulate matter. Often referred to as diesel particulate, this substance consists of a mixture of tiny particles that are emitted during the combustion process of a diesel engine. 

These particles, made up primarily of carbon, ash, sulfates and silicates, pose significant environmental and health hazards. The particulate matter is known for its ability to penetrate the lungs and contribute to respiratory and cardiovascular issues.

In heavy construction equipment, such as excavators, bulldozers and loaders, the DPF is located within the exhaust system. Typically, it is located in the exhaust manifold or close to the engine where it can effectively capture particulate matter before it is emitted into the atmosphere. 

This proximity to the engine and the exhaust manifold allows the DPF to function efficiently, utilizing the heat of the exhaust gasses to help burn off accumulated particulate matter.

The DPF has a notable impact on the exhaust system of heavy machinery. It not only reduces the emission of harmful particulates but also affects the back pressure in the exhaust system. Increased back pressure can influence engine performance and fuel efficiency. Regular maintenance of the DPF is crucial to ensure it functions effectively without negatively impacting the engine’s performance or fuel efficiency.

Related Components

The DPF is just one component of a larger network of components designed to reduce pollutants. These critical components that work in tandem with the DPF include:

  • Diesel Oxidation Catalysts (DOC): The diesel oxidation catalyst is typically placed upstream of the DEF. It is similar to a catalytic converter, converting harmful components in the exhaust stream into less harmful ones like carbon dioxide and water.
  • Selective Catalytic Reduction (SCR): Selective catalytic reduction is another key technology that complements the DPF. It involves a chemical reaction where DEF is injected into the exhaust stream, converting NOx into nitrogen and water vapor.
  • Diesel Exhaust Fluid (DEF): DEF enables the process that occurs in the SCR system, where NOx is converted into nitrogen and water. The efficiency of the SCR system is highly dependent on the quality and consistency of the DEF.
A diagram showing the DPF in relation to the engine and DEF tank

Overview of The Filtration Process

Diesel particulate filters are specially designed to remove particulate matter from the exhaust gas of diesel engines, playing a crucial role in reducing emissions. The filter captures soot and ash particles as the exhaust gasses pass through it. 

The core of the DPF is typically made of a ceramic material that is formed into a honeycomb structure. This structure provides a large surface area to capture the particulate matter while allowing the gasses to flow through. The particles are trapped in the tiny pores of the filter walls, preventing them from being released into the atmosphere.

A key aspect of DPF functionality is filter regeneration, the process of burning off accumulated particulates in the DPF. Over time, the trapped soot and ash can build up, leading to reduced efficiency and potential clogging. 

To counteract this, regeneration involves increasing the temperature of the filter to a point where the soot is burned off, turning it into harmless ash and carbon dioxide.

There are two primary types of regeneration: continuous (or passive) and active (or periodic). Continuous regeneration occurs during normal engine operation, while periodic regeneration is a process initiated by the engine's control system when sensors detect an excessive buildup of particulates.

Early signs of a clogged DPF include reduced engine performance, increased fuel consumption and a noticeable increase in exhaust smoke. The vehicle's onboard diagnostic system may also trigger a warning light indicating a DPF issue. 

Paying close attention to these signs is crucial to prevent more severe problems and ensure compliance with emission standards.

DPF Preventive Maintenance

Effective maintenance of diesel particulate filters is essential to prevent clogging and potential failure. Regular inspections and cleaning are recommended to ensure optimal performance. 

The most common initial symptoms of DPF issues include reduced engine power, increased fuel consumption, and a dashboard warning light. These signs often indicate a clogged filter or a malfunctioning regeneration process. 

Maintenance issues usually arise from insufficient regeneration, often due to frequent short trips that prevent the exhaust system from reaching the temperatures required for passive regeneration. 

Active regeneration should be performed according to the manufacturer's guidelines, typically every 300 to 500 hours of operation, depending on usage conditions.

Over time, the DPF and its related components, such as sensors and the diesel oxidation catalyst, may need replacement. Replacing a DPF can be expensive, often ranging from several thousand dollars, depending on the make and model of the equipment.

In extreme cases, a completely clogged DPF can cause engine shutdown, leading to operational downtime and additional expenses. Regular maintenance and careful attention to any warning signs are crucial in avoiding these issues and ensuring the long term health of your heavy equipment.

Final Thoughts

Regular preventive maintenance for DPFs and their related components is vital for ensuring the longevity and efficiency of diesel engines in heavy equipment. Regular maintenance prevents clogging and failure, helping you avoid costly repairs and operational downtime.

If your engine experiences issues, they could be related to a failing DPF. When this happens, related components may also suffer. When it’s time to replace them, look no further than the EquipmentShare Shop. Our growing catalog of OEM and aftermarket parts has your fleet covered. Find engine components, service kits, filters, hardware, and more. Can’t find exactly what you need? Reach out to our dedicated parts experts to place a custom order.

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