Forming section troubleshooting checklist extends wire life

Hard material or lumps passing between outside rolls and wire.

Stock contains large fiber bundles, sand, scale and similar foreign material.

Foreign material falling onto fourdrinier and passing through the nip at the dandy roll, lumpbreaker or pickup roll nip.

Check screening and cleaning equipment for proper operation.

Plastic wires will forgive a few of these lumps.

Weld spatter will affect both plastic and metallic wires. Burns from cigarettes or welding sparks will affect plastics but may not affect metallic wires.

Sand, scale or other foreign material between inside rolls and wire.

Check shower water supply.

Check savealls for leaks.

Completely clean fourdrinier to eliminate deposits of stock, scale or rust which may fall onto the wire.

Check doctors on inside wire rolls for proper adjustment.

Ensure careful cleaning during washup at wire change to remove material inside wire.

Check for carbon steel piping or valves in the shower supply lines.

Small nicks or burrs on rolls which repeatedly affect one area of the wire.

Check couch roll and table elements for damage. Can be caused by walking on the fourdrinier table.

Nicks or burrs will damage plastics as well as metallic wires.

Stock or scale buildup on wire rolls.

Check doctor fit and doctor oscillators for effective operation.

Check shower water supply for sand and scale.

Check effectiveness of wire cleaning showers for plugged nozzles and adequate water pressure.

Not critical for short time on plastics. must be large and over long period of time.

Sand is very bad for plastics.

Uneven wear of suction box covers.

Check suction box covers.

Use ceramic covers for plastics.

Stock dropping onto wire.

Check savealls for leaks.

Suction boxes guiding wire.

Noticeable if wire runs true on slotted box before stock placed on wire; wire runs off after stock placed on wire.

Guiding problem for plastics.

Wire slippage over rolls.

Check doctor fit and doctor pressure against roll to be certain doctor is not interfering with free roll turning.

Use rubber covered rolls.

Rolls which are badly worn or improperly ground.

Lumpbreaker crown and/or loading not correct.

Check all rolls for uneven wear and proper crown.

Shower water temperatures considerably different than stock temperatures (+/- 10°) cause uneven tensions from thermal expansion. Sudden ridging may occur when the showers are turned on.

Check shower water temperatures to eliminate thermal shock to the wire.

Hot stock on plastics forms central ridges which subside as temperature equalizes around wire run. May be reduced by lowering vacuum on flat boxes and by maintaining equal heat on return run especially below breast roll.

Rolls throughout fourdrinier out of level or out of alignment.

Check level and alignment of all rolls.

Rolls which have deflected excessively while not rotating.

Shell thickness may have been reduced by grinding so that the roll tends to whip after standing for a short period of time. Rolls with high wire wrap angles are most likely to produce damage.

Rolls warped by shower water hitting only one side during shutdown.

Knock-off showers, nozzles at one end start showering first. High pressure and temperature differential produces tension and thrust momentarily.

Shut off shower water or be certain that roll is uniformly covered by shower water.

Turn on shower valve slowly.

Localized stretching such slippage between wire and roll.

Start fourdrinier slowly and bring up to speed slowly to reduce slippage.

Check doctor angle fit and loading to be certain that rolls are able to turn freely. Hard starting rolls cause slippage of the wire.

Rubber covers are necessary to drive plastics.

Water in wire pit comes in contact with wire.

Check stock piping system. Prevent entrained air from entering wire pit causing surging and bubbling.

Short term. Plastics most likely will not be affected.

Damage during wire stringing. Depending upon damage, ridges may not appear immediately. Damage may produce either long or short ridges.

Damage must be very severe to affect plastics.

Uneven wire tensions.

Rolls which are out of alignment or out of level.

Suction boxes out of alignment. Automatic guide with erratic or too fast action. Wrinkles develop sometime after startup.

Check all components in fourdriner which contact the wire for alignment and level.

Most of these problems exist for plastics to a lesser degree and some are not apparent at all, especially short term items such as swinging guides.

Guide roll at too great an angle to the wire will alternately grip and slip on the wire. Each transition from gripping to slipping can produce a wrinkle.

Check guide roll angles to wire. Combination guide rolls especially cause this damage.

Plastics accept greater guide angles.

Raising suction pickup roll from wire with vacuum on.

Shut off vacuum before lifting suction pickup. Check auto vacuum breakers action if such equipment is used.

Stringing new wire at slight angle to the machine.

Check wire stringing procedure.

Wire guide palm too far from guide roll or improper signal from palm to guide roll places diagonal stresses on wire during inching.

Relocate guide palm to return run.

Swing type guide and floating type tension controller located next to each otehr may cause interaction during startup and over-travel of the guide.

Limit guide action by means of stops. Water dampen tension contoller action.

Guide limits not required for plastics.

Misaligned lumpbreaker roll not coming down uniformly.

Check lumpbreaker roll for alignment.

Edges of the wire stretched longer than the body of the wire.

Check all rolls for wear. End of rolls may be larger than body.

Worn suction box covers, or other table elements.

Check these items for wear which may leave the ends higher than center.

Lumpbreaker roll crown or loading.

Check lumpbreaker roll for correct crown and correct loading.

Corrosion of wire. Unequal corrosion between center and edge will cause a difference in stretch rate at these two places.

See "Corrosion" in later list.

Fatigue failure of machine direction wires. Fatigue stress is caused by repeated sharp bending.

Check setting of forming board and deflector to eliminate sharp break over the leading edge.

Check suction box position for sharp break of wire over leading edge.

Check wire tension. Slack wire condition will cause wire to drape and break over leading edge of table components.

Sharp bending of the edges caused by worn table equipment.

Check forming board, deflectors, foils and suction box covers for wear which may leave high ends.

Worn wire return rolls larger at the ends than at the center.

Check wire return rolls for wear which may leave high ends.

Overzealous use of wire edge relieving fork is often the cause of edge cracks.

Check wire return rolls for wear which leaves the ends of the roll larger than the center.

Incorrect use of trimming tool when removing edge cracks.

Check wire for corrosion at the edges which make it susceptible to cracking.

Dub highly wrapped rolls per OEM instructions.

Flexing of the wire within machine direction such as high lumpbreaker loading against a couch roll with oversize holes.

Check lumpbreaker loading.

Lumpbreaker crown and loading not matched produces varying flow of rubber through the nip which causes cracks.

Check lumpbreaker crown and loading.

Lumpbreaker cover non-uniform hardness causes flexing. New lumpbreaker covers are usually uniform. As cover is ground away and becomes thin, hard spots appear.

Check lumpbreaker cover hardness. Check for hard lumps.

Cutting edges on table components.

Inspect entire wire run in area of crack for sharp corners or foreign materials.

Over-flexing of wire because of stock buildup on dirty wire.

Check wire cleaning equipment for effective cleaning of wire edge.

Stretching of wire in local areas by worn rolls or suction box covers.

Check all items under those shown for ridging.

Reducing wire tension from presiously used tensions.

Check tension as comparison to that previously run.

Warped or out of balance wire return rolls.

Check wire return rolls.

Wire rolls worn to a tapered shape.

Check wire rolls for roundness, taper, etc.

High suction box loads or high wire creep rate over the couch.

Reduce suction box vacuum. Start with 1 to 1-1/2 inches (25-35 mm) of vacuum (mercury) in the first box increasing to 4 to 5 inches (10-12.5 cm) in the last box. This may reduce drag and still provide proper drainage. It may be necessary to revise suction box arrangements or add Flo-Vac unit to reduce drag and maintain drainage.

Wear on plastics is as much a problem as with metallic wires.

Drag over soft covers is greater with plastics: the best corrective action is ceramic covers or a Flo-Vac.

Wire creep over suction box area of couch.

If machine has wire turning roll and driven wire rolls, shift power input so that smooth rolls drive the wire and the couch drive just overcomes couch friction losses.

If couch drive input is too great, with plastics "power ridges" are produced also. Maximum of 40% advised.

Wire drive in poor condition. uneven speed of drive rolls causes very rapid wire wear.

Check for worn drive couplings. Inspect drive gear unit for gear or bearing failure.

Inspect bearings of driven and non-driven rolls for bearing failure.

Appearance may not be the same on plastics.

Hunting in an electric drive motor.

Check drive system for constant speed operation.

Slippage of wire rolls either driven or undriven.

Tighten wire to reduce slippage. Check wire rolls for highly polished appearance. This is generally where slippage appears.

Inspect wire rolls for bearing failure, balance and improperly set doctors which may increase drag and cause slippage against the wire.

Make sure that driven rolls are rubber covered. Glass surfaces drive poorly and metal surfaces almost not at all on plastic wires.

Pivoted lumpbreaker roll with pivot arm at too high an angle from normal 90° to the nip radian. Nip pressure will be greater than calculated and unstable.

Inspect lumpbreaker roll mounting for correct geometry. (Similar conditions will cause short felt life in a felted area.)

Sand and similar material carried by the stock becomes embedded in suction box covers, forming boards and deflectors.

Inspect and improve stock cleaning system.

Abrasive additives - clays, talcs, etc.

"Refined" talc is more abrasive than "natural".

Grind suction box covers, forming board and deflectors frequently to remove embedded particles.

If covers are ceramic they may lose surface finish.

Can be returned to supplier for regrind and polish.

Frequently this is electrolytic type from white water trapped at the edges. This may produce cracks or machine direction splits. Usually occurs at the edge or 1 inch (25 mm) or so in from that point.

Check edge showers for thorough cleaning of wire. Removal of deposits eliminates trapping of whte water.

Corrosion to plastics does not appear to be a problem. The future may show some adverse chemical reaction. However, plastic wire manufacturers will no doubt correct for any local condition.

Chemicals in stock or water attacking the wire.

Check stock for traces of bleach liquor, cooking liquor or corrosive type additives.

Chemicals used, (i.e. zinc hydrosulfite) may be sufficiently valuable to justify high corrosion rate.

Switching from bronze to stainless steel is sometimes an economic solution.

The use of plastics is probably the best cure for corrosion to wires.

Similar to overall corrosion except edge of wire is kept relatively clean by deckle board and trim showers. Wire stretches in the center, thereby producing edge curling or cracking.

Edge relieving may be required, either by mechanical or chemical means.

There are coatings which improve corrosion resistance - check with wire supplier.

Certain chemical additives can also be applied. Check with additive suppliers.

The use of plastics is probably the best cure for corrosion to wires.