Closed system cooled covered roll and methods of forming and operating cooled covered roll

Abstract

Roll, method of forming roll and method of operating roll. Roll includes a roll body, a deformable cover coupled to the roll body, a pluggable input, a pluggable output, and a coolant contained within the roll body at least in an amount sufficient for a rimming mode to occur during normal operation of the roll. The present abstract is neither intended to define the invention disclosed in this specification nor intended to limit the scope of the invention in any way.

Description

DISCUSSION OF BACKGROUND INFORMATION[0001]1. Field of the Invention[0002]The present invention is for use in paper machines having rolls covered with roll covers In particular, the roll covers can be made of polymers, e.g., rubbers, polyurethanes, epoxies, thermosets, thermoplastics, etc., and these paper-machine rolls are internally water cooled in the present state-of-the-art.[0003]2. Discussion of Background Information[0004]Roll covers utilized in critical applications of paper machines are generally water-cooled to counter the internal heating of the cover material as it rolls through the nip. In this regard, the thermo-visco-elasticity of typical roll cover materials increase the internal heating of the cover with increasing nip loads, increasing speeds, and increasing cover thickness. Moreover, with everything else being held constant, the internally generated heat increases for materials having lower thermal conductivity, for materials with lower stiffness, i.e., lower stora...

AI Technical Summary

Benefits of technology

[0048]According to another feature of the present invention, rotation of the roll can provide cooling in a machine direction and in a cross-machine direction.

Problems solved by technology

In the known designs, it is also important, and difficult, to maintain a constant inlet temperature all year round, since available stream water used for cooling these paper machine rolls in most mills can vary more than 22° C. depending on the season.

While a heat exchanger can ensure constant incoming cooling water temperatures, this requires additional expenses (including increased energy consumption costs) and increases the maintenance issues.

In this regard, if water continues to enter the roll during a shutdown, the roll may fill with water.

This can be particularly problematic when the roll during shutdown is partly filled with water colder than the cover temperature, and the top of the roll is not able to cool down to the same temperature as the cold water.

Upon start-up of this distorted roll, non-uniform cross-machine direction contact (and nip pressure profile problems) occurs at the nip, and severe vibrations may arise depending on the severity of the (thermally) bent roll shape.

Therefore, as use of water flowing through a roll to control the heat generation of a cover can create a number of problems and additional costs, it is not surprising that paper mills prefer a roll cover that does not require water flow through the roll to operate.

The fluid film eventually becomes unstable and the fluid motion changes to a sloshing motion on the rising side of the roll.

Images