Carbon, Ceramic, Ni-resist, Silicon Carbide, Tungsten Carbide, and GFPTFE are popular seal faces. Coated seal faces are another category. Plasma coatings are silicon or tungsten carbide sprayed on a stainless steel seal head. Major mechanical seal firms sell them under numerous brands, but we think they’re overpriced. Once the coating wears, it must be reapplied. Silicon Carbide or Tungsten Carbide seal faces may be re-lapped and polished, enabling a second, third, or even fourth use of the same seal head.
Ni-resist is a kind of stainless steel with nickel added to reduce friction. It’s a cheap fresh water seal face.
Glass-filled PTFE (Teflon(R)). Glass must be added for face hardness and to avoid PTFE’s cold flow difficulties.
Ceramic – A 99.5% aluminum oxide with good wear properties. Chemically inert, it may be used in almost any product. Ni-resist or 17-4 chairs can endure thermal shocks better than ceramic. They’ll shatter on concrete.
Silicon Carbide is made from silica and coke. It’s related to Ceramic (thanks to Silica), but it’s tougher and lubricates better. Silicon carbide is the most frequent. Alpha Sintered Silicon Carbide is suited for chemical applications. Lack of unreacted free carbon in Alpha Sintered Silicon Carbide reduces Pressure Velocity ratios. Either grade of SIC may be lapped and polished.
Tungsten Carbide is versatile like Silicon Carbide. It’s hard like silicon carbide, but it’s hefty, so it’s simple to tell apart. High elasticity prevents face deformation in high-pressure applications. Tungsten carbide may be re-lapped and polished.
If you have any questions about mechanical seals, please get in touch with Junty.