John Crane Type 21 Replacement Mechanical Seal

The Standard Choice for OEM and General-Purpose Pumps

What made the Type 21 an OEM standard in the first place is how little it demands from the equipment it's fitted to — its dent-and-groove drive band grips the bellows without overstressing it, and the bellows' own flexibility handles shaft end play and run-out without any sliding contact that could fret the shaft. That combination of simplicity and self-adjustment is why it shows up so widely across centrifugal, rotary, and turbine pumps, as well as compressors and chillers, particularly in water, wastewater, and general processing duty. Our equivalent is built to the same dimensional standard, so it fits directly into existing OEM housings without redesign. For a full breakdown of the fitting sequence and shaft finish requirements, check our detailed guide on the blog.