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Author: Site Editor Publish Time: 2026-07-06 Origin: Site
In industrial piping systems, flange connections are one of the most commonly used detachable connection methods. Their sealing performance directly affects system safety and operational stability. The core of sealing performance lies in the proper selection of flange sealing materials and accurate evaluation of their corrosion resistance. In industries such as petrochemical, power generation, pharmaceuticals, and food processing, different media, temperatures, and pressure conditions impose significantly different requirements on sealing materials.
This article systematically analyzes the scientific selection of flange sealing materials from multiple perspectives, including material classification, performance characteristics, corrosion mechanisms, and selection strategies.
Flange sealing materials are typically used to manufacture gaskets. They vary widely in sealing performance, temperature resistance, and corrosion resistance.
Non-metallic gaskets are the most widely used and are suitable for medium- and low-pressure as well as moderate service conditions.
Rubber Materials (NBR, EPDM, FKM)
Rubber materials offer excellent elasticity and compression recovery, enabling effective sealing under relatively low preload. NBR is suitable for oil-based media, while EPDM performs better in water and steam environments. FKM provides superior resistance to high temperatures and chemicals. However, rubber materials have limited temperature resistance (generally below 200°C) and are prone to aging in strong oxidizing environments.
Polytetrafluoroethylene (PTFE)
PTFE has outstanding chemical stability and is resistant to almost all acids, alkalis, and solvents, earning it the nickname “the king of plastics.” However, it exhibits cold flow (creep) under high pressure, which may require filling modifications or composite structures for improvement.
Flexible Graphite
Graphite offers excellent high-temperature resistance (up to 450°C or higher) and good corrosion resistance against a wide range of media, making it suitable for high-temperature steam and chemical environments. However, it may oxidize in strong oxidizing media such as concentrated nitric acid.
These materials are suitable for high-temperature, high-pressure, and harsh service conditions.
Spiral Wound Gaskets
Made by alternating layers of metal strips (such as stainless steel) and soft filler materials (such as graphite or PTFE), these gaskets combine strength and sealing performance and can handle fluctuations in temperature and pressure.
Ring Type Joint (RTJ) Gaskets
Commonly used in high-pressure systems (e.g., API applications), they achieve sealing through metal-to-metal line contact and require high machining accuracy of flange surfaces.
Kammprofile Gaskets
These combine the rigidity of metal cores with soft sealing layers, providing stable performance in demanding operating conditions.
In complex service conditions, corrosion is a key factor affecting the lifespan of sealing materials. Understanding corrosion mechanisms helps achieve accurate material selection.
Chemical corrosion results from direct interaction with acids, alkalis, or organic solvents. For example:
Sulfuric acid can severely degrade rubber materials
Strong alkaline environments may decompose certain polymers
Due to its stable molecular structure, PTFE performs exceptionally well in such environments.
This is more common in metallic sealing materials. When electrolytes are present, different metals may form galvanic cells, accelerating corrosion. Therefore, direct contact between metals with different potentials should be avoided when selecting spiral wound gaskets.
Under high temperature and pressure, materials may experience cracking or deformation due to the combined effects of stress and corrosive media. For example:
PTFE is prone to creep at elevated temperatures
Stainless steel may suffer stress corrosion cracking in chloride-containing environments
Material Type | Acid Resistance | Alkali Resistance | Solvent Resistance | Temperature Range (°C) | Typical Applications |
NBR Rubber | Moderate | Fair | Good (oils) | -40 ~ 120 | Petroleum & lubricating systems |
EPDM Rubber | Good | Excellent | Fair | -50 ~ 150 | Water treatment, steam systems |
FKM Rubber | Excellent | Good | Excellent | -20 ~ 200 | Chemical and fuel systems |
PTFE | Excellent | Excellent | Excellent | -200 ~ 260 | Highly corrosive media |
Flexible Graphite | Good | Good | Good | -200 ~ 450 | High-temperature steam |
Spiral Wound (SS-based) | Depends on material | Depends on material | Good | ≤600 | High-temperature & high-pressure systems |
In practical engineering, the selection of sealing materials must consider multiple variables rather than a single performance parameter.
Different media exhibit significantly different corrosiveness. For example:
Strong acidic environments favor PTFE or fluoroelastomers
Chloride-containing media require avoiding standard stainless steel
Temperature and pressure directly affect material stability:
High-temperature environments require graphite or metallic gaskets
High-pressure systems typically use RTJ or spiral wound gaskets
Different flange types (e.g., raised face RF, ring-type joint RTJ) correspond to different sealing structures. Proper matching is essential; otherwise, even high-performance materials cannot achieve effective sealing.
While meeting safety requirements, it is also important to consider material cost and replacement cycles. For example, although PTFE offers excellent performance, its higher cost can be optimized by using composite gaskets.
In real-world applications, the reliability of flange sealing systems depends not only on material performance but also on installation quality and maintenance practices. The following aspects are critical for optimization:
Insufficient preload can lead to leakage, while excessive preload may damage the gasket or flange surface. A cross-tightening sequence and torque-controlled tools are recommended to ensure uniform load distribution.
Before installation, flange faces should be inspected for scratches, corrosion, or contaminants and kept clean. Proper surface condition enhances gasket conformity and sealing effectiveness.
Temperature fluctuations can cause differences in thermal expansion, affecting sealing stress. For such conditions, composite gaskets with good resilience are recommended.
Select materials compatible with the process medium and avoid direct contact between dissimilar metals to minimize galvanic corrosion risks.
Routine inspections, including leakage checks and bolt condition monitoring, help identify potential issues early. For critical systems, preventive maintenance strategies are strongly recommended.
The selection of flange sealing materials is a highly specialized engineering decision that requires comprehensive consideration of medium characteristics, temperature and pressure conditions, corrosion mechanisms, and economic factors. By scientifically analyzing material performance and aligning it with actual operating conditions, it is possible to significantly improve sealing reliability, extend equipment lifespan, and reduce maintenance costs.
As industrial systems become increasingly complex, a deep understanding of corrosion resistance in sealing materials has become a core competency for engineers aiming to achieve safe and efficient operations.
For more information about industrial flange,please visit our website: www.fuchen-steam.com. Or you can contact us at Fuchen@fuchensteam.com or +86-19357103769 if you need.
