The Impact of Descaling Water Filtration Systems on Second-Hand Hot Rolling Mills’ Equipment Longevity

Descaling water filtration systems are critical auxiliary components in second-hand hot rolling mills, purifying the high-pressure water (15-30 MPa) used to remove oxide scale from hot slabs. Second-hand mills often use unfiltered or poorly filtered water—containing scale particles (5-50μm) and sediment—that clogs descaling nozzles, scratches work rolls, and accelerates pump wear. Upgrading to a high-efficiency filtration system resolves these issues, reducing nozzle clogging by 90% and extending work roll/pump life by 40-50%.

1. Nozzle Clogging Prevention for Consistent DescalingClogged descaling nozzles (a common issue in unfiltered systems) reduce water flow by 30-50%, leaving residual scale on slabs—causing scale pits (depth ≥0.1mm) on hot-rolled strips and increasing scrap rates by 8-10%. The filtration system uses a two-stage process:

• Primary filtration (50μm mesh) removes large scale particles and sediment.
• Secondary filtration (5μm cartridge filters) captures fine particles that cause micro-clogging.For a second-hand mill processing 500 tons of slabs daily, this maintains consistent water flow (deviation ≤5%) across all nozzles, reducing scale-related scrap to <2%. Additionally, the system’s automatic backwashing function (triggered when pressure drop exceeds 0.2 MPa) eliminates manual filter cleaning—saving 2-3 labor hours daily.

2. Roll & Pump Protection for Reduced MaintenanceUnfiltered water contains hard scale particles that act as abrasives: they scratch work roll surfaces (0.05mm wear per 1,000 tons of slabs) and cause pump impeller erosion (leading to 15-20% reduced flow after 6 months). The 5μm filtration removes 99% of these particles, reducing work roll wear to 0.02mm per 1,000 tons and extending pump life from 8 months to 14-16 months. For a mill using cast iron work rolls ($6,000 per set) and high-pressure pumps ($12,000 each), this saves $36,000-$48,000 annually in replacement costs.

3. Water Recycling for Cost & Environmental BenefitsTraditional descaling systems in second-hand mills use 15-20 m³ of fresh water per ton of steel and discharge contaminated water—incurring high water costs and environmental fines. The filtration system enables closed-loop water recycling: filtered water is cooled (to 30-40°C) and reused, reducing fresh water consumption to 2-3 m³ per ton. For a mill processing 1,000 tons of steel monthly, this cuts annual water costs by $24,000-$36,000 (based on $1/m³ water cost) and eliminates discharge fees ($5,000-$10,000 annually in many regions). The system also reduces chemical treatment needs (by 30%)—filtered water has fewer contaminants, so less corrosion inhibitor is required.

Practical Maintenance Strategies

• Replace secondary filter cartridges monthly (or when pressure drop exceeds 0.3 MPa) to maintain filtration efficiency.
• Inspect primary filter meshes weekly for tears; repair or replace if mesh openings exceed 50μm.
• Clean the backwashing system quarterly to remove accumulated scale—blocked backwash valves reduce cleaning effectiveness by 40%.

For second-hand hot rolling mills aiming to reduce maintenance costs and environmental impact, the descaling water filtration system is a high-impact upgrade that ensures reliable descaling, protects critical equipment, and aligns with sustainability goals—essential for long-term competitiveness in the steel industry.

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