Curtis Fine Papers - in-situ drying cylinder regrinding

Metalock Engineering has enabled Curtis Fine Papers to put their machines back into production in quick-timeand resume production of high quality uncoated printing, writing and security papers with minimum downtime.This has been achieved by regrinding paper drying rolls in-situ in less than 30 per cent of the time of a traditionalstrip down and regrind

Most drying rolls used in the paper industry are steam heated nodular cast iron hollow cylinders with a mirrorfinish. To ensure they remain clean during normal 24 hours a day, 7 days a week production, there is a doctorblade in contact with the roll. However, over a long period it is possible for debris to lodge between the blade andthe roll. This can damage or score a roll which in turn cause corresponding marks on the running paper web,particularly on some of the smooth papers that Curtis produce. These imperfections lead to rejects and paper loss.

To remove these imperfections a damaged roll has to be lightly ground but as a paper machine may have asmany 30 interlinked gear-driven rollers of varying sizes in two banks, a particular roll may be extremely difficultto remove without a complete machine strip-down. To strip down a machine, remove a roll, transport it off.sitefor regrind and then reassemble on its return could take 7 days.

Over recent years Metalock has reground seven drying rolls for Curtis Fine Papers. These have ranged from1.22m diameter, 2.5m long to 1.32m diameter by 2.8m long. Using its own purpose- designed in-situ drying-rollgrinding machine, the operation can be carried out enabling the mill to be ready to run in two days.

Metalock’s purpose-designed tooling comprises a hollow mandrel that attaches at each end to the dryer’s rollmountings. The grinding machine is mounted on this mandrel and as well as traversing to and fro along themandrel, allowing the complete drying cylinder length to be covered, it can also be rotated through 360 degrees.

During set-up the grinding head is positioned radially and locked to ensure that contact is only made with thecylinder to be reground. Once in position, the head is locked, the grinding belt tensioned and put in light contactwith the cylinder. The drying machine is started up, to revolve the damaged cylinder and grinding proceeds untilthe surface is cleaned up along its full length with the final cut providing the mirror finish necessary to producefine papers.

As drying cylinders are regarded by the insurers as pressure vessels, following a regrind they are re- assessedbefore the machine is put back into service.

Metalock’s special purpose grinding machinemounts on a mandrel extending the length of thecylinders. The head is positioned radially andlocked to ensure that contact is only made with thecylinder to be reground.