How to choose a PP woven bag washing line

PP woven bags, raffia bags and jumbo bags are among the hardest plastics to wash. The fabric traps sand and soil between the tapes, the bags arrive tangled and folded, and many are printed. A line that works well on clean stretch film will struggle with them. This guide explains what a woven bag washing line needs and how to compare offers.

Why woven bags need their own line

• Dirt is trapped in the weave. Soil and sand sit between the tapes and only come out with repeated pre-washing and strong friction.
• Bags are long and fibrous. Whole bags wrap around shafts, so they are shredded before they reach the crusher.
• Sand destroys blades and screws. Every kilogram of sand that reaches the crusher or the extruder shortens wear-part life.
• Washed film holds water. Thin, light flakes carry a lot of water after washing, which the pelletizing line then has to drive off.

The stages a woven bag line needs

1. Pre-shredding. A shredder cuts whole bags and bales into strips so they can be washed and crushed.
2. Repeated pre-washing. Several pre-washers, with screw loaders between them, remove most of the sand and soil before size reduction.
3. Wet crushing. A crusher with water feed cuts the strips into flakes and keeps the blades cool.
4. High-speed friction washing. Scrubs the flake surface to release the remaining dirt.
5. Floating separation. In the floating tanks, PP and PE float while sand, stones and metal sink.
6. Dewatering and squeeze drying. A centrifugal dewatering machine removes most of the water, and a squeeze dryer brings moisture down to about 1 to 3 percent.

The Jiangsu PURUI woven bag line runs 20 machines in this order: belt conveyor, pre-shredder, belt conveyor, pre-washer, screw loader, pre-washer, screw loader, high-pressure washing tank, pre-washer, belt conveyor, wet crusher, pre-washer, high-speed friction washer, floating washer A, screw loader, dewatering machine, floating washer B, dual-discharge screw loader, screw loader and squeeze dryer.

How to size the capacity

Jiangsu PURUI builds film and woven bag washing lines at 500, 800, 1,000, 1,500 and 2,000 kg/h. When you compare quotations, check three things:

• Input or output. Ask whether the capacity refers to dirty input or clean output. With heavily soiled bags, the difference is large.
• Your dirtiest material, not your average. Size the pre-washing for the worst bales you buy.
• The pelletizing line after it. The washing line and the pelletizer should be sized together, so neither waits for the other.

Why the squeeze dryer matters

Moisture is the main reason washed film pellets come out with bubbles and why the extruder loses output. A squeeze dryer compresses the washed flakes and brings moisture down to 1 to 3 percent, so the pelletizing line spends its energy melting plastic instead of boiling water.

What to send for a quotation

• Photos of your bales, opened and closed
• An estimate of the dirt content and the type: sand, soil, cement, fertilizer
• Target output in kg/h and working hours per day
• What the pellets will be used for
• Available water, power and floor space

See the line specifications on the recycling machines page.