Challenge: Picking the Right Mechanical Seal for Mixers and Agitators

split cartridge mechanical seal

Every mixer and agitator model is distinctive, engineered for a specific use and, in some instances, can appear to be similar to a pump application. Consequently, conventional pump seals such as single or double seal assemblies, lip seals, or packing material are often used to seal mixers and agitators. However, these pieces of equipment are known for having much larger radial shaft run out than a typical pump which can cause pump seals to quickly fail. For long-term sealing success, it is extremely important to utilize a seal specifically designed specifically as a mechanical seal for mixers and agitators.


Today’s Common Mixer Options

  • Sanitary mixers are designed for applications like sanitary agitation, biopharma, food, beverage, and biofuels. These applications have demanding quality standards, as well as a need for efficient, consistent mixing.
  • Bottom entry mixers and agitators are used for processes such as storage tank mixing, fermentations, and bioreactors. These applications often encounter accumulating solids around the seal.
  • Top entry mixers are common in chemical processing, food industries, and industrial waste water. These powerful mixing systems still command the majority of the mixer market.
  • Side entry mixers are standard equipment for most storage tank mixing, fuel oil blending, and wastewater agitation. Excessive run out is the number one challenge when sealing side entry mixers.


Flexaseal’s Style 85M Fully Split Cartridge Mechanical Seal addresses the sealing concerns in mixer and agitator usage.

    • Large radial clearance allows for shaft movement without damage to the seal’s components. This clearance effectively addresses the matter of run out – the main concern when sealing mixers and agitators.
    • The two-piece fully split cartridge mechanical seal design is the fastest, easiest, and simplest to install. No measurements, shims, or special tools needed. And more importantly in the case of side or bottom entry mixers: no emptying the tank to install or adjust the seal!
    • Which means this is the only split cartridge mechanical seal installation in which the impeller can be adjusted without removing the seal. Simply reinstall the setting clips, release the set screws and adjust the impeller position then tighten the set screws and remove the clips.
    • The precision lapped seal faces are protected within the two cartridge halves. Dirt and grease cannot get impacted between the faces. In addition, the faces are hydraulically balanced, providing a wider range of operating pressures.
    • The stationary multi-spring design ensures that springs do not have to flex with every revolution. And since the springs are encased within the seal assembly, they do not come into contact with the sealed fluid which means no clogging or corrosion!
    • The seal’s O-ring is located outside the stuffing box, away from any damage caused by prior packing wear on the mixer’s shaft or sleeve.
    • And most importantly, the Style 85 Fully Split Cartridge Mechanical Seal is the only split cartridge mechanical seal design that arrives at your facility having been fully assembled and pressure tested at our facility, ensuring sealing integrity and providing the highest success rate for your installation.
    • To learn if Flexaseal’s Style 85M Fully Split Cartridge Mechanical Seal is the answer to your mixer and agitator needs,

click here