Common Materials for Sealing Gaskets of Cracking Reactors

Common Materials for Sealing Gaskets of Cracking Reactors

Sealing gaskets for cracking reactors must be suitable for working conditions of 300~500℃ high temperature, certain pressure, and contact with oil and gas/carbon black residue, with core requirements of high temperature resistance, oil resistance, anti-aging, good elasticity and sealing fit. The mainstream materials are divided into conventional general types and high-end wear-resistant types, adapted to different production loads and application scenarios, as follows:

Graphite Composite Gasket: The first choice and most widely used for batch-type oil refining reactors, composed of flexible graphite reinforced with 304/316 stainless steel metal foil composite. It resists temperature ≤650℃ and pressure ≤4.0MPa, with oil/acid/alkali resistance and thermal aging resistance, suitable for key sealing positions such as reactor doors and flanges. It features excellent sealing performance, high fit, no easy hardening or deformation at high temperature, and high cost performance; the metal reinforcement layer improves tear resistance, adapting to mechanical friction from reactor opening and closing, and is suitable for medium and high-load production of batch-type thermal cracking reactors processing waste tires/plastics/rubber.

Fluororubber Gasket (FKM/Viton): An oil-resistant special type made of fluororubber elastomer, which can be reinforced with fibers. The general grade resists temperature ≤200~250℃ and the high-end grade ≤300℃, with excellent oil resistance and hydrocarbon medium erosion resistance, good elasticity and tight sealing fit to prevent oil leakage, suitable for cracking conditions with high oil content in raw materials. Its disadvantage is lower high temperature resistance than graphite gaskets; it is prone to aging and embrittlement when used above 300℃ for a long time, requiring a shorter replacement cycle.

Polytetrafluoroethylene Gasket (PTFE/Teflon): A wear-resistant and corrosion-resistant type, including pure grade and modified grade filled with glass fiber/carbon fiber. It resists temperature ≤260℃, with strong acid and alkali resistance, wear resistance and non-stick property to avoid carbon black adhesion to the sealing surface, suitable for frequently opened and closed reactor doors. Note that its elasticity decreases at high temperature and the pure grade is prone to cold flow; modified grade is recommended, and it is not suitable for long-term high temperature working conditions above 300℃.

Metal Wound Gasket: A high temperature and high pressure special type made of 304/316L stainless steel strip wound with graphite/PTFE filler, which can be reinforced with metal rings. It resists temperature ≤600~800℃ and pressure ≤10MPa, with excellent high temperature and pressure resistance, stable sealing performance and long service life, suitable for large-scale reactors, continuous equipment and high-load production of batch-type reactors. Its disadvantages are high cost and strict requirements for the flatness of the sealing surface; improper installation may damage the sealing surface.

Asbestos Rubber Gasket: An obsolete and prohibited type for historical reference only. Banned in industrial equipment at home and abroad due to the carcinogenicity of its dust.

Key Selection Principles

For batch-type thermal cracking reactors under the mainstream working condition of 300~500℃, graphite composite gaskets are the first choice;

For working conditions with temperature ≤280℃ and high oil content in raw materials, fluororubber gaskets are recommended;

For large-scale reactors and high pressure/high-load working conditions, metal wound gaskets filled with graphite are suitable;

For all gaskets, 304/316 stainless steel reinforced grades are preferred to prevent tearing and deformation at high temperature and extend service life.