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John Crane Safeseal Type SB2 Heavy-Duty Cartridge Seal
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John Crane Safeseal Type SB2 Heavy-Duty Cartridge Seal


The Safeseal Type SB2 is a dual-cartridge seal. Its double-balanced design ensures the reliability and longevity of the seal in the most demanding conditions. The Type SB2 seal is ideal for use with environmentally hazardous and abrasive fluids, most often used in pumps in pulp mills, minerals processing and other slurry duties up to 40 percent solids by weight and a solids hardness of 8 Mohs. The Type SB2 seal is widely used with other process equipment including agitators.
Several variant of the design available for different services:

Type SB2A — designed for ANSI standard dimensions

Type SB2A-PR — designed for ANSI standard dimensions, including integrated pumping device

Type SB2B — designed for big bore dimensions

Type SB2B-PR — designed for big bore back plate dimensions

Type SB2S — designed for special dimensions, including metric sizes

Type SB2S-PR — designed for special dimensions, including integrated pumping device


  • Seal faces are installed using a patented heat shrink process ensuring correct, distortion-free face alignment at all recommended temperatures.
  • The springs are located in the stationary body of the seal in the seal water (barrier fluid). The seal water washes the springs, preventing process chemical corrosion and reduces the risk of the springs becoming clogged. Shaft misalignment does not vibrate or wear out the O-rings.
  • PTFE slot rings replace the traditional O-rings in places where they are exposed to the product, preventing sticking.
  • Protected faces, the seal face carriers are driven by machined fits, preventing metal stress from distorting the face.
  • Patented double-balanced design allows the use of both pressurized and unpressurized seal water (barrier/buffer fluid) and prevents face overload.
  • SB2 series seals will accept ± 0.080"/± 2.0mm axial movement (shaft end play) during normal operation due to their piston design. Impeller adjustments do not affect face stress or spring strength.


  • Process pumps
  • Other rotating equipment


  • Temperature limits: 350°F/180°C
  • Pressure limits:
    • Process pressure: 290 psi(g)/20 bar(g)
    • Barrier fluid: 215 psi(g)/15 bar(g)
  • Speed limits: 65fps/20m/s


Crane Engineering recommends John Crane seals for many sealing applications throughout your facility. We've seen them be put to the test in harsh environments and difficult to seal applications, and succed. Their lines of single cartridge seals offer fast and easy installation for maintenance teams with little time for seal maintenance.


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