nip roll

You can set the pressure in the cylinders to push against the weight of the top nip roll and adjust it down to zero nip pressure if necessary.

Tension adjustment is necessary due to several mechanical factors: oscillations caused by mechanical misalignments, differing inertial response (lag) of mechanical elements during web acceleration, out-of-round unwind and tension rolls, slipping through nip rolls, and over-aggressive web-guide correction.