MOTION SEALS SS005_1
Motion seals are different than pump seals:
- Because of the misalignment potential they are almost always a stationary design. (The springs do not rotate with the shaft)
- The rotating hard face must be wider than normal to accommodate the excessive radial motion. A design movement of plus or minus 0.125 inches (3 mm) would be typical.
- The internal clearances must be greater than pump seals to prevent contact during excessive radial movement.
- In a dual seal design
- The inner seal should be hydraulically balanced in both directions because many of these applications can fluctuate between pressure and vacuum. This feature will also prevent the inner seal from blowing open and allowing the barrier fluid to contaminate the product if you loose barrier fluid pressure between the seals.
- The stationary faces must be spring loaded in some manner to prevent loading one seal and unloading the other during periods of axial movement. The easiest way to do this is to spring load the faces together.
- Cartridge designs are necessary for correct and easy installation, and to allow you to change seals without emptying a mixer lor agitator in “Side Entering” and “Bottom Entering” applications. Be sure the seal has some sort of self-aligning feature to compensate for misalignment caused by the set-screws in the cartridge.