In the core area of the petrochemical industry, harsh working conditions of high temperature, strong corrosion and large pressure difference are everywhere. From the hot furnace tubes of the cracking furnace, to the high pressure environment of the hydrogenation reactor, to various strong acid and alkali transmission pipelines, the safe sealing of the equipment bears the heavy responsibility of the entire process. A tiny leak can cause the loss of expensive raw materials and environmental pollution, or even cause safety accidents. Therefore, seeking reliable sealing materials under extreme conditions is the cornerstone of long-term stable operation of petrochemical equipment.
And fluororubber (FKM) seals, especially its high temperature resistant series (with a tolerance range of -50℃~300°C), are professional solutions that have emerged to meet these harsh challenges.
1. Performance Advantages: Core Capabilities to Conquer Extreme Working Conditions
The reason why fluororubber stands out in the petrochemical field is due to its unique molecular structure and excellent material properties:
Excellent high temperature resistance (-50℃~300℃):
High temperature stability: The fluorocarbon bond energy is extremely high (486 kJ/mol), which is much higher than the carbon-carbon bond (348 kJ/mol) or carbon-oxygen bond of ordinary rubber, giving it the ability to resist high temperature damage, inhibit decomposition and hardening (embrittlement). Even after long-term exposure to high temperatures of 300°C, it can still maintain excellent elasticity and sealing properties.
Resistant to low temperature flexure: Through specific polymer design and formulation improvements (such as the introduction of flexible monomers), high-end fluororubber can maintain sufficient flexibility at -50℃ or even lower temperatures to prevent low temperature brittle cracking.
Top chemical media corrosion resistance:
Resistance to the "king of solvents": It has strong tolerance to aliphatic hydrocarbons, aromatic hydrocarbons (such as benzene, toluene, xylene), chlorinated hydrocarbons (such as carbon tetrachloride), fuel oil (gasoline, aviation kerosene, diesel), lubricating oil, etc. This is the key reason why it is called the "king of rubber".
Acid and alkali resistance: It has good resistance to most strong acids (such as sulfuric acid, hydrochloric acid, nitric acid, especially oxygen-containing acids) and strong alkalis.
Anti-swelling and deterioration: The molecular structure is dense (small free volume), and fluorine atoms form a spatial shield, which can effectively resist medium penetration, greatly inhibit swelling, and have excellent aging resistance.
Excellent air tightness:
The intermolecular force of fluororubber is strong, the molecular chains are tightly stacked, and the diffusion of gas molecules is effectively blocked. The extremely low air permeability is an ideal choice for manufacturing high-performance O-rings, gaskets and other dynamic/static seals.
Good mechanical properties:
Maintain sufficient strength, hardness and elasticity in a wide temperature range to meet the sealing requirements under high pressure, vibration and other working conditions.
2. Key applications: core sealing battlefield in the petrochemical field
With the above performance, high temperature resistant fluororubber seals play an irreplaceable role in many core devices such as oil refining, ethylene, chemical fiber, fertilizer, etc.:
High temperature and high pressure core equipment seals:
Hydrogenation reactor & refining unit: seals of reactor flanges, manholes, inlets and outlets, valves, and pumps. The working conditions include high temperature (200-450°C), high pressure (10-20MPa), and hydrogen-rich environment, which is prone to hydrogen embrittlement. Fluororubber is almost the preferred material for sealing in high pressure hydrogen-rich environment.
Catalytic cracking unit (FCC): seals of high temperature regeneration slide valves, waiting slide valves, and high temperature pipeline flanges, which withstand catalyst dust erosion and high temperature oil and gas corrosion.
Ethylene cracking unit: Seals (such as valve packing) in the preheating, heat exchange and transportation links before the deep cooling unit (-30~ -100℃) of the cracking gas separation system are also faced with the test of high temperature and complex hydrocarbon mixtures.
Reliable guarantee of corrosive medium sealing:
Acid washing & alkali washing unit: Sulfuric acid, hydrofluoric acid, caustic soda (NaOH) delivery pumps, valves, flanges of reactors, stirring shaft seals, etc.
Sulfur recovery unit (SRU): Seals of pipelines, valves and pumps for sulfur- and acid-containing (H2S, SO2. SO3) gas and liquid phases.
Solvent oil processing unit: Seals for solvent systems (such as benzene, toluene, cyclopentane, furfural, etc.) in aromatics extraction, lubricating oil refining and other units.
Safety barrier for special chemical transportation:
Dynamic and static seals of pipelines, storage tanks and metering pumps for various strong solvents, special additives, additives, etc., fluororubber has become a key line of defense to prevent medium leakage and leakage.
Compressor unit & hot oil system seals:
Cylinder and piston rod seals (packing rings, oil scraper rings) of process gas compressors and hydrogen compressors. Seals for high-temperature pumps and valves in thermal oil systems (used for reaction heating, distillation insulation, etc.).
3. Selection and application points
Only by choosing the right fluororubber seals can their value be maximized and potential failure risks be avoided:
Accurate identification of working conditions: It is important to clearly identify key parameters such as the maximum/minimum temperature, pressure (peak), medium type (concentration, impurities), dynamic/static, and whether or not they are in contact with steam (ordinary FKM has limited steam resistance and requires special grades).
Reasonable grade selection:
Standard FKM: widely used, with excellent overall performance.
High fluorine content FKM (such as FFKM-based seals, which have excellent performance but are extremely expensive): better resistance to strong solvents, strong acids and alkalis, and higher costs.
Perfluoroether rubber (FFKM): Top performance, resistant to high temperatures above 300°C, strong oxidants, and ultra-wide-spectrum chemical media (almost all solvents and chemicals), but expensive, often used in the most demanding key parts that cannot be shut down for maintenance.
Low-temperature improved FKM: Focus on improving low-temperature performance.
Steam-resistant FKM: Specific formula to resist high-temperature and high-pressure hot water steam.
Precision structural design: O-rings, combined gaskets, packing rings, etc. need to be carefully designed with grooves, compression rates, stretching, etc. according to working conditions (such as pressure, movement mode).
Scientific installation and maintenance: Ensure that the contact surface is flawless and pollution-free; follow the correct installation method and torque requirements; establish a regular inspection and replacement system.
Conclusion
In the "sealing battlefield" of petrochemical industry with high temperature, high pressure and strong corrosion, high temperature resistant fluororubber (-50℃~300°C) seals have become the core barrier to ensure the safe, stable and long-term operation of the equipment with their tough weather resistance, unparalleled chemical resistance and reliable airtightness. From the key seals inside the hydrogenation reactor to the pipelines for conveying strong solvents, fluororubber is almost "everywhere", silently guarding the efficient operation and safety bottom line. Mastering its characteristics and being proficient in selection and maintenance, petrochemical equipment will continue to have the calmness and stability brought by this sealing barrier.
