Wire guide lost
If a wire guide is lost in a paper machine, there are several steps that can be taken to address the issue: 1. Initially, one can guide the forming fabric by hand until repairs can be made. This involves manually aligning and guiding the fabric to ensure it runs smoothly through the machine. 2. If […]
Formation improvement
1. Reduce headbox consistency if drainage capacity of forming table permits. 2. If other aspects of paper quality allow it: (a) change furnish to one of shorter fibers. — for coating rawstock or offset bond use more hardwood. — for groundwood papers, lower the groundwood freeness and/or increase amount of groundwood. (b) where appropriate, refine […]
Wire life, short
1. The fourdrinier table must be accurately lined up and in good mechanical condition. — all drainage devices must be firm and set at uniform height. — see that stretcher and automatic tension controls do not bounce. 2. A major cause of short wire life is poor condition of forming table and general housekeeping. — […]
Wire damage, prevention
1. Make certain that couch is ground often enough. 2. Bleed the edges at both ends of couch (about 2.5 cm of vacuum) in order that there be no stock build-up on couch roll. — build-up on the couch is often not visible, but can be felt by hand. 3. Check filters on showers: (a) […]
Water flow to headbox, excess
1. Consistency of the stock in the headbox is of utmost importance. When water flow is either greater than that which gives the critical velocity in the headbox (avoiding flocculation), or is greater than that which can be drained effectively, then it is excessive. 2. If the slice is not properly adjusted, formation will be […]
Strings, elimination
1. Stock bundles, referred to as strings, usually arise from the screens, pump impellers, or cleaners. 2. Use adequate and well-maintained screening. — check clearance of the Selectifier screen paddles. 3. Avoid protuberances at pipe joints. — use special flanges after screens, i.e., only metal-to-metal (no gaskets) with all welded joints between final screen and […]
Stock temperature varying
Stock temperature varying in headbox of paper machine 1. Check that primary temperature control is at source instead of at each machine. 2. Control fresh water addition and keep it to a minimum. 3. Make periodic (once yearly) heat balances around machines so that system is fully understood. 4. Ensure that furnish supply is steady. […]
Stock skating on wire
1. Real skating is usually due to a poor distribution system. — the only permanent remedy is to change this. — forming board adjustments that help set the sheet sooner minimizes effect. 2. The effect of a poor distribution system is reduced if proper perforated rolls are positioned without excessive gaps between the roll and […]
Stock jumping
1. Most common cause of stock jump is foil angles are too high. — check and correct. 2. Stock jump may be due to wake effect if rectifier roll is too close to slice. — check roll position, hole size, and speed. 3. Stock jump is often generated through pitch or dirt accumulated at slice […]
Grainy edges, reduction
Note. Forming fabrics too narrow for width of sheet being attempted will accentuate many of the causes of grainy edges. See Feathered and jagged edges. 1. Maintain an even basis weight and use edge bleeds correctly. 2. Check deckles to reduce rollback of flow at the edge. 3. Maintain proper load-to-crown relationship at presses. 4. […]