John Crane Type 109U Replacement Mechanical Seal

A Cost-Effective Wedge Seal for Moderate-Pressure Corrosive Service

Being the unbalanced sibling of the 109B, this seal keeps the same wedge-based secondary sealing that tolerates the extreme temperatures and aggressive chemistry a rubber elastomer never could, but without the added face balancing that pushes up both cost and pressure capability. That makes it the more economical choice wherever process pressures stay moderate but temperature or chemical exposure still rules out standard O-ring seals — chemical processing lines, refinery duty, and general corrosive service where a full balanced design isn't necessary. Like its balanced counterpart, the wedge geometry keeps the working length compact and DIN 24960 compliant despite the specialized internals. Full installation steps for wedge-style secondary sealing are covered in our blog.