Buna Seals: Are They Safe For Diesel Fuel?

Buna, also referred to as nitrile or Buna-N, is a widely used elastomeric material known for its tensile strength and high resistance to fuel and oil. It is commonly used in fuel tanks and other components for automotive, marine, and aerospace applications. However, Buna's compatibility with diesel fuel is a subject of discussion. While Buna offers excellent resistance to petroleum-based oils and fuels, its compatibility with biodiesel blends is questionable. Research suggests that Buna-N is susceptible to chemical oxidation when exposed to biodiesel, leading to gasket degradation. Therefore, when considering Buna seals for diesel fuel applications, it is essential to understand the specific fuel composition and environmental conditions to ensure effective sealing performance.

Buna-N is susceptible to chemical oxidation in diesel fuel systems

Buna-N, also referred to as nitrile or NBR rubber, is a widely used elastomeric material in the fuel oil industry. It is known for its high tensile strength and resistance to petroleum-based oils and fuels, water, alcohols, silicone greases, and hydraulic fluids. However, Buna-N is susceptible to chemical oxidation in diesel fuel systems, which can lead to gasket degradation and failure.

The susceptibility of Buna-N to chemical oxidation in diesel fuel systems has been a well-documented issue. Research has shown that Buna-N gaskets are vulnerable to chemical attacks that oxidize the rubber, leading to severe degradation in some cases. This oxidation can be caused by the presence of biodiesel fuel blends, which contain Methyl Oleate, or by the use of copper, tin, and zinc alloys that catalyze the breakdown of biodiesel. The longer storage times and higher fuel temperatures associated with biodiesel further contribute to the increased susceptibility of Buna-N to chemical oxidation.

The fuel oil industry has traditionally favored Buna-N gaskets for flanged connections in diesel fuel oil supply systems due to their excellent resistance to petroleum-based oils and fuels. However, with the increasing availability and use of biodiesel, the limitations of Buna-N in these systems have become more apparent. While Buna-N offers superior abrasion and tear resistance, its compatibility with diesel fuel, especially biodiesel, has been called into question.

To address the issue of chemical oxidation in diesel fuel systems, alternative gasket materials such as PTFE, Teflon, or Viton have been recommended. These materials are not susceptible to biodiesel chemical attacks and provide better resistance to oxidation and degradation. Viton, in particular, offers universal chemical resistance to oils, fuels, and mineral acids, making it a more suitable choice for diesel fuel sealing applications. Additionally, the use of Baylast, a proprietary rubber polymer, has been introduced to solve compatibility problems between seals used for gasoline and ethanol.

In conclusion, Buna-N's susceptibility to chemical oxidation in diesel fuel systems, especially those containing biodiesel, has been a significant concern in the fuel oil industry. While Buna-N offers excellent resistance to petroleum-based oils and fuels, its compatibility with biodiesel blends and certain alloys can lead to gasket degradation and failure. To ensure the longevity and effectiveness of diesel fuel systems, alternative gasket materials that are resistant to chemical oxidation, such as Viton, should be considered.

Buna-N is not compatible with biodiesel

Buna-N, also referred to as nitrile or NBR, is a widely used elastomeric material known for its tensile strength and high resistance to fuel and oil. It is commonly used in the fuel oil industry as the gasket of choice for flanged connections in diesel fuel oil supply systems.

However, recent research has brought to light the fact that Buna-N is not compatible with biodiesel. Buna-N gaskets have been found to be susceptible to chemical attacks that oxidize the rubber, causing severe degradation. This is due to the Methyl Oleate that makes up biodiesel. The Brookhaven National Laboratory concluded that while one type of Butadiene-based elastomer, NBR, can be used with biodiesel blends because of its high acrylonitrile monomer, pure Buna-N is not suitable for any concentration of biodiesel.

The root cause of gasket degradation is the use of Nitrile Butadiene elastomer-based gaskets in a system using a biodiesel fuel blend. The introduction of another chemical into the system, such as biodiesel, can initiate a chemical reaction that oxidizes the Buna-N rubber. This is supported by the observation that Butadiene-based gaskets used in fuel systems without biodiesel blends showed no noticeable degradation.

Additionally, copper, tin, and zinc alloys have been found to catalyze the breakdown of biodiesel, increasing the acid number of the fuel over time. This can further contribute to the oxidation of Buna-N rubber in biodiesel fuel systems. As such, it is recommended to minimize the use of these alloys in diesel fuel oil systems and to instead use gaskets made from materials that are not susceptible to biodiesel chemical attack, such as PTFE, Teflon, or Viton.

Buna-N offers excellent resistance to petroleum-based oils and fuels

Buna-N, also referred to as nitrile or Buna, is an NBR rubber that offers excellent resistance to petroleum-based oils and fuels. It is a widely used elastomeric material known for its tensile strength, high fuel and oil-resistant properties, and abrasion resistance.

Buna-N has been the gasket of choice for flanged connections in diesel fuel oil supply systems for years. Its compatibility with petroleum-based oils and fuels, as well as water, various alcohols, silicone greases, and hydraulic fluids, makes it a popular sealing material for fuel tanks and other components in automotive, marine, and aerospace applications.

However, Buna-N is not without its drawbacks. It has low ozone resistance and poor flame resistance, making it unsuitable for outdoor applications or those involving open flames. Additionally, Buna-N is not compatible with all fuels and can be susceptible to chemical attacks that oxidize the rubber, especially when exposed to biodiesel or certain additives.

When selecting a sealing material, it is crucial to consider the specific application requirements, including the type of fuel or liquid involved, temperature extremes, and exposure to harsh chemicals or environmental conditions. While Buna-N offers excellent resistance to petroleum-based oils and fuels, alternative materials like Viton, FKM, or EPDM may be more suitable for certain applications where resistance to temperature extremes, chemicals, or compatibility with biofuels is a priority.

Buna-N is less universally resistant than FKM Type 2

Buna-N, also referred to as nitrile or Buna, is an NBR rubber that combines resistance with a low compression set and high abrasion resistance. It is widely used in the fuel oil industry due to its excellent resistance to petroleum-based oils and fuels, water, alcohols, silicone greases, and hydraulic fluids. Buna-N is also known for its tensile strength and high fuel and oil-resistant properties.

However, Buna-N is less universally resistant than FKM Type 2. Modern fuel additives tend to attack Buna-N, limiting its compatibility with all fuels. For example, research has shown that Buna-N is not compatible with the Methyl Oleate that makes up biodiesel. Additionally, Buna-N is susceptible to chemical attacks that oxidize the rubber, especially when exposed to small amounts of ozone.

FKM, on the other hand, has become increasingly important with the rise of ethanol and other biofuels. While seals that work well with gasoline may not work with ethanol, FKM offers a solution by providing compatibility with both. The different types of FKM seals vary in fluorine content, with higher fluorine content resulting in higher resistance to chemical degradation.

When choosing a material for a seal, gasket, or O-ring, it is crucial to consider all aspects of the application. The specific mechanical properties desired, such as temperature ranges and resistance to oils, fuels, and chemicals, will determine the most suitable material.

Buna-N is not compatible with all fuels

Buna-N, also known as Nitrile, is a widely used elastomeric material known for its tensile strength and high resistance to fuel and oil. It is often used in the fuel oil industry for gaskets in diesel fuel oil supply systems. Buna-N offers excellent resistance to petroleum-based oils and fuels, as well as water, various alcohols, silicone greases, and hydraulic fluids.

However, Buna-N is not compatible with all fuels. While it offers superior strength and resistance to oils and acids, Buna-N's flexibility is limited. Additionally, Buna-N has low ozone resistance and poor flame resistance, making it unsuitable for applications involving open flames. It should also not be used with brake fluids or acetones, as it cannot withstand long-term exposure to these chemicals.

One of the most significant issues with Buna-N is its susceptibility to oxidation in diesel fuel systems. Research has shown that Buna-N gaskets are vulnerable to chemical attacks that oxidize the rubber, particularly when used with biodiesel fuel blends. The presence of copper, tin, and zinc alloys can catalyze the breakdown of biodiesel, making it more harmful to Buna-N. Therefore, Buna-N is not recommended for use in systems containing biodiesel.

Furthermore, Buna-N's chemical resistance is lower than that of other materials like Viton, which offers universal chemical resistance for sealing applications involving oils, fuels, and mineral acids. Viton also exhibits superior weatherability, resistance to mould, fungus, oxidation, ozone, and UV exposure. While Buna-N provides superior abrasion and tear resistance, its limited chemical resistance restricts its use in certain applications.

In summary, Buna-N is a versatile and widely used material for sealing applications, offering excellent resistance to petroleum-based fuels and various other substances. However, it is important to recognize that Buna-N is not compatible with all fuels, particularly biodiesel, and its use should be carefully considered based on the specific application requirements.

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