Stock Preparation Wear Parts

Stock preparation spare parts for the full line: bale intake to machine chest outlet. Six process stages, in line order.

1. Pulping & Detrashing

Function: defibre raw furnish; remove coarse, heavy and stringy contaminants at source.

Components: pulper rotors (LC / HC / drum) · extraction and screen plates · vat wear plates and liners · rope cutter blades · ragger, grab and junk trap components · detrashing unit rotors and plates · conveyor chains, slats and wear strips

Parameter

Selection Basis

Rotor type	Consistency — LC (typically 3–6%) vaned or S-type; MC (typically 8–12%); HC (typically 12–18%) helical or ribbed; drum pulper (typically 14–18%)
Rotor material	High-chromium cast iron, or alloy steel with hardfaced tips for OCC
Extraction plate hole diameter	6–16 mm; 8–12 mm most common
Plate thickness	Typically 6–25 mm, set by furnish abrasiveness

Key wear point: rotor tip clearance to the screen plate. As tips erode, defibring efficiency drops before motor load shows any change. Measure clearance at each inspection.

2. Coarse Cleaning & Screening

Function: protection stage. Remove heavy contaminants by density, then medium contaminants by size.

High-density cleaners are installed after the pulpers and before the coarse screens. Their rejects — stones, metal, concrete, heavy staples — would damage downstream equipment.

Components: HD cleaner bodies, ceramic liners and reject valves · sand separator components · coarse screen baskets (holed and slotted) · coarse screen rotors · reject separators · light impurity separators and float purger parts

Parameter

Typical range

HD cleaner feed consistency	Typically 3–5%
Coarse basket hole diameter	1.2–3.0 mm
Coarse basket plate thickness	6–12 mm
Basket material	304 / 316L stainless or duplex; hard chrome plated or hardfaced wear zone on OCC lines

3. Fine Screening & Cleaning

Function: cleanliness stage. Remove stickies and fine contaminants by slot geometry and by density difference.

Components: slotted fine screen baskets (wedge wire / drilled) · foil, bump and closed rotors · rotor wing blades and blocks · LC forward and reverse cleaner cones · wear-resistant inlet heads · reject nozzles · glass tubes and lock nuts · mechanical seals and shaft sleeves

Parameter

Typical range

Fine screen feed consistency	Typically 1.5–3.5% in stock preparation; 0.8–1.2% at the machine screen
Fine screen slot width	Typically 0.10–0.35 mm
Contour height	Typically 0.3–0.9 mm
Rotor tip clearance	A design value, not a wear tolerance
LC cleaner feed consistency	Typically 0.5–1.0%
LC cleaner differential pressure	Typically 100–200 kPa

Rotor and basket are selected as a pair. Replacing one without the other reduces capacity or increases rotor power.

Key wear point: reject nozzle bore. Enlargement raises reject rate and fibre loss with no process alarm. Replace nozzles as a matched set across the bank — mixed bores cannot be balanced.

4. Fractionation

Function: separate cleaned stock into long-fibre and short-fibre fractions for separate treatment and separate plies.

Applies to multi-ply containerboard and carton board. Long fibre goes to the liner plies for strength; short fibre to the middle ply for bulk and cost.

Components: fractionation screen baskets · fractionation screen rotors · hydrocyclone fractionator components · reject and accept dilution components · seals and shaft sleeves

Parameter

Selection basis

Aperture type	Holes are more selective by fibre length; slots are used where fractionation and stickies removal are combined
Aperture diameter	Target split ratio, therefore liner ply strength
Reject rate	Long-fibre yield — not a loss figure in this position

Key wear point: hole enlargement dilutes the long-fibre fraction. Liner strength drifts down over months with no alarm, and is usually compensated by higher refining energy or added virgin fibre. Measure and record hole diameter at every basket inspection.

5. Thickening & Dispersion

Function: raise consistency, remove filtrate, disperse residual contaminants below visible size.

Components: disc filter sectors, plates and bags · inclined screen mesh · screw press flights and baskets · plug, shredding and heating screw components · disperger and thermal dispersion discs · gravity decker mesh · static plates, shower nozzles and seals

Key wear point: shower nozzles. Nozzle condition governs filtering surface cleaning, which governs thickener capacity. Treat as a scheduled replacement item, not a breakdown item.

6. Refining & Stock Storage

Function: develop fibre bonding; hold and blend stock to specification before the machine. In recycled lines refining is the last operation, after dispersion.

Components: disc refiner plates · conical refiner fillings · deflaker plates · refiner loading and sealing components · chest and tower agitators and propellers · agitator shaft seals

Parameter

Effect

Bar width	Narrow bars fibrillate; wide bars cut
Groove width and depth	Stock flow and residence time in the refining zone
Cutting edge length (CEL)	Total bar edge per revolution
Specific edge load (SEL)	Refining intensity, Ws/m

SEL = net refining power ÷ (rotational speed × CEL). CEL is expressed in km/rev, SEL in Ws/m. Typical LC refining consistency is 3–5%; typical specific energy is 40–120 kWh/t depending on furnish and target.

Typical SEL by furnish: unbleached softwood kraft 2.0–3.0 · bleached softwood kraft 1.0–2.0 · hardwood / eucalyptus 0.2–0.6 · recycled 0.2–0.8 Ws/m

Deflaker plates are listed here as a component family. In the line itself, deflakers normally sit on the reject line or after coarse screening rather than alongside LC refining.

A finer pattern gives longer CEL and therefore lower SEL at the same power. Replace plates as complete matched sets; mixed wear stages produce an uneven gap.

Fault diagnosis

Observation

Likely cause

Defibring efficiency falling at unchanged power	Rotor tip wear; clearance to screen plate
Flakes or shives increasing downstream	Screen plate hole enlargement
Contaminants reaching fine screens	Plate wear, or detrashing capacity exceeded
Screen differential pressure rising	Basket plugging — check rotor tip wear first
Dirt specks in the sheet	Cleaner cone erosion; consistency above design; low differential
Fibre loss in cleaner rejects	Reject nozzles worn
Liner strength drifting down	Fractionation basket hole enlargement
Thickener capacity falling	Blinded surface; worn or plugged shower nozzles
Strength development falling at constant refining power	Refiner bar edges rounded
Specific energy per tonne rising	Worn plate pattern, or gap closed to compensate

Frequently asked questions