Applications of this nature can incorporate a number of small coil springs spaced around the rotary seal face unit. These small springs are not as susceptible to distortion at high speeds as is the single coil spring, and they consequently exert an even compression on the seal face at all times. Friction drive seal use the secondary sealing member to drive the rotary seal face. Because it depends on this friction to drive the rotary face this type of seal driving can only be employed with fluids having relatively low viscosities as starting and operating viscous torque can easily exceed the frictional force available. Multiple spring positive drive mechanical seals generally will incorporate a rotary compression assembly where the collar of a multiple spring seal is normally secured to the shaft by set screws, or placed in alignment with rotation drive pins fixed to the pump shaft.
Pins link a compression ring to the collar.
This compression ring presses against and energizes the shaft secondary sealing o-ring and drive the rotating seal face. The collar, compression ring, pins, springs, and set screws comprise a single assembly.