Overview

The decision to speed up a paper machine, whether it produces tissue, kraft, or coated papers, usually results from economic and marketing concerns. Since a paper machine represents an extremely large capital investment, it is natural to try to achieve the maximum output / hour.

After the desired output has been determined, the speed of the machine necessary to deliver that can also be set. Generally, since several grades of paper are made on a specific machine, a desired speed range is prescribed.

Next, decisions on necessary drying capacity, felt and wire configurations, and any new drive requirements are made. A machine modification plan then can be devised and implemented.

One factor often ignored in the planning of a machine speedup is the resulting change in vibration of the machine's numerous components. This can lead to disastrous results. In the normal course of events, a mill never finds out that the excessive vibration of some particular roll will prevent the machine from achieving planned operating speeds until a commitment for delivery of the paper has been long established and cannot be met.

An example of the need to anticipate these vibration problems came as a result of investigations made on a twin-wire tissue machine at a large paper facility. A speed-up was planned in two stages. The first stage was to be a 7.5% speed increase, and the second stage was to be a 19% increase.

The first stage speed-up was such a failure that more than a year...