The petrochemical and chemical industry operates continuously with corrosive, toxic, flammable, or high-viscosity media. A properly selected mechanical seal helps reduce leakage, protect operators and the environment, and extend the time between maintenance intervals. This article summarizes the points to consider when choosing a sealing solution for pumps, agitators, and compressors in petrochemical and chemical plants.
In the same plant, there can be dozens of different media, from solvents, acids, and alkalis to monomers and polymers. Operating conditions vary by process, so there is no single seal suitable for all. Seal selection should be based on the actual composition of the medium, temperature, pressure, and safety requirements.
For less hazardous media, a single seal with a simple flushing scheme like Plan 11 or cooling like Plan 21 and Plan 23 is usually sufficient. For moderately hazardous media, a double seal without pressure increase according to Plan 52 provides an additional layer of protection. For toxic or flammable media, a double seal with pressure increase according to Plan 53 or Plan 54 allows the barrier fluid to always have higher pressure than the medium, preventing the medium from escaping. These configurations are standardized in API 682.
The seal face typically uses sintered silicon carbide for strongly corrosive media or tungsten carbide when impact resistance is needed. The auxiliary gasket can use FFKM, PTFE, or chemical-resistant elastomers, while metal parts can be 316L stainless steel, duplex, or Hastelloy alloy depending on the corrosion level. It is necessary to check the chemical compatibility table of the manufacturer for each medium.
Agitators have long shafts, are prone to vibration and shaft misalignment, and often work in a vacuum or under pressure. Double cartridge seals with barrier fluid are a popular choice because they prevent media from escaping and prevent air or barrier fluid from entering the product when needed.
Many plants implement Leak Detection and Repair (LDAR) programs to control VOC emissions. Seals with pressure, temperature, and barrier fluid level monitoring systems help detect abnormalities before leaks spread.
SNS-VN supports consulting on mechanical seal selection, auxiliary systems, and maintenance services for petrochemical, chemical, fertilizer, and polymer plants. Please contact us for consultation according to your specific conditions.