I. Dyeing Quality Issues
1. Uneven Color/Shade Variation: Often caused by the fabric remaining relatively stationary while stacked in the machine or by uneven alkali distribution; light-colored fabrics are more susceptible. Remedy: For mild cases, utilize dye migration properties for re-dyeing: start at 60°C, heat to 90°C over 15 minutes, then heat to 130°C over 40 minutes and hold for 60 minutes; use 1–2 g/L of leveling agent and adjust pH to 5–6. Severe cases require stripping the color before re-dyeing.
2. Creases/Chicken-foot Marks: Usually caused by fabric remaining folded and stacked for too long or by cooling down too rapidly. **Remedy:** Reload the fabric, heat to a temperature slightly higher than the original dyeing temperature, and then cool slowly. Strictly control heating and cooling rates throughout the process and avoid forcibly cooling by injecting cold water directly at high temperatures.
3. Color Spots/Dye Aggregation: Caused by excessive electrolytes in the dye bath, poor auxiliary compatibility, or excessively high dye concentration. Remedy: Reduce electrolyte dosage, select auxiliaries with good compatibility, increase dispersant dosage for high dye concentrations, and thoroughly wash the fabric and clean the equipment regularly.
4. Oil Stains: Usually caused by equipment oil leaks or contamination from auxiliaries. Remedy: For small, localized stains, scrub with non-ionic detergent or organic solvent followed by thorough rinsing; for large-scale staining, the entire machine requires degreasing and cleaning.
II. Mechanical Operation Issues
1. Excessive Foaming: Caused by high-speed fabric movement and high-energy turbulence of the dye liquor. Remedy: Prioritize low-foaming dyes and auxiliaries; avoid using defoamers that might stain the fabric. If foam becomes excessive, add a small amount of compliant defoamer to prevent floating fabric from damaging the circulation pump.
2. Fabric Tangling/Knotting: Commonly occurs with lightweight fabrics in fully flooded machines and directly leads to machine stoppage. Remedial measures: Ensure operators follow standard procedures; reasonably control the fabric load per chamber; optimize fabric stacking patterns using reverse jetting and control valves to prevent prolonged localized stacking.
3. Oligomer deposition: Oligomers dissolved at high temperatures precipitate upon cooling, adhering to equipment or fabric surfaces to form white frost or spots. Remedial measures: Perform solvent scouring on the fabric prior to dyeing; add oligomer control agents during the dyeing process; and periodically disassemble and clean heat exchangers and filter screens.
4. Fabric abrasion/pilling: Caused by nozzle diameters being too small, excessive jet pressure, or a mismatch between fabric speed and guide wheel rotation speed. Remedial measures: Select nozzles with appropriate diameters based on fabric weight; adjust jet pressure to a moderate range; and calibrate guide wheel speed to synchronize with fabric speed.
III. Faults related to parameter anomalies
1. Excessive fabric elongation: Caused by insufficient fabric load or excessively high dye liquor levels, which increase running resistance. Remedial measures: Adjust to the standard fabric load; maintain the dye liquor level at the minimum possible height; and reduce fabric running tension.
2. Insufficient circulation pump head: Often caused by foam entering the pump chamber or impeller wear. Remedial measures: Promptly eliminate foam within the machine; regularly inspect the circulation pump impeller for wear; and replace parts promptly if wear is severe.
3. Excessive temperature control deviation: Caused by heat exchanger clogging due to oligomers, resulting in reduced heat transfer efficiency. Remedial measures: Periodically disassemble and clean the heat exchanger; clear heat transfer piping; and calibrate temperature sensors to ensure control accuracy.
