Metal bellow type mechanical seal
Nxx series DICKOW PUMPEN KG

Face-type mechanical seals with O-ring or other elastomeres utilize springs to keep the faces together. At bellows seals, the bellows itself acts as a spring to close the faces, provides a dynamic seal force, and transmits the torque from the shaft to the face. Hence, the bellows seal offers a number of advantages over other face-type seals. These can be summarized as follows:

* No hang-up on the shaft sleeve.

Wear between the seal faces must be eliminated by the spring. The spring must move the complete rotating part with the O-ring.

Every leakage can clogg on the sleeve surface, especially when handling fluids which react on the atmosphere.

Finally, the clogged product prevents any movement of the O-ring, the seal shows heavy leakage although the faces are still in a good shape.

The absence of sliding elastomeres eliminates drag or hang-up which is probably the biggest single cause of failure at O-ring type mechanical seals.

Hang-up of the seal can also be generated by fretting due to corrosion or wear of the shaft sleeve in the area of the O-ring or the elastomere.