Line 01
Pickling Lines (PPL & CPL)
Push-pull (PPL) and continuous (CPL) pickling lines for hot-rolled steel strip, planned from scale breaking through to fume treatment.
- Push-pull (PPL) and continuous (CPL)
- 300,000 – 1,200,000 t/yr
- Strip thickness 1.0 – 6.0 mm
- HCl / H₂SO₄ / mixed acid
The first quality gate in steel processing
Pickling is the first process step in cold rolling and in many downstream finishing routes. Hot-rolled strip carries an oxide scale that, if it is left in place, wears cold mill rolls, prints surface defects into the finished product and prevents coating from adhering.
The job of the line is to remove that scale through mechanical and chemical action, and to leave a clean strip surface with controlled roughness — ready for cold rolling, galvanizing, coating, or direct sale as pickled sheet.
- Roll wear and surface defects carried into the cold mill
- Coating adhesion problems in galvanizing and painting
- Rejected strip where scale has been rolled into the surface
Surface cleanliness
Strip leaves the line clean enough for cold rolling or coating without a second cleaning step.
Lower roll wear
Scale-free strip removes the abrasive wear that shortens cold mill roll life.
Controlled acid use
Cascade flow, online concentration control and optional regeneration keep acid consumption within the design figure.
Contained emissions
Sealed tanks, fume scrubbing and waste-acid handling are part of the line scope, not site add-ons.
Where pickled strip goes next
The same pickled coil feeds several downstream routes. The surface requirement differs between them, so it is agreed at specification stage rather than assumed from the grade alone.
| Downstream process | Role of pickled strip |
|---|---|
| Cold rolling | Scale-free substrate that protects rolls and avoids rolled-in defects |
| Hot-dip galvanizing | Pickled hot-rolled strip as the substrate for coated structural grades |
| Colour coating | Clean surface for paint adhesion |
| Direct sale | Pickled sheet and coil for automotive structures, machinery, drums, hardware and tube |
Two platform options: PPL and CPL
Two configurations cover the range: push-pull (PPL) and continuous (CPL). The choice follows capacity target, capital budget and site constraints. We engineer both, and recommend one against your production profile.
| Push-pull (PPL) | Continuous (CPL) | |
|---|---|---|
| Operating principle | Coils pulled through the tanks in sequence, with a stop for coil change | Coils welded end to end for uninterrupted operation |
| Annual capacity | 200,000 – 800,000 t/yr | 600,000 – 1,200,000+ t/yr |
| Capital investment | Lower — no welder or loopers | Higher — welder and entry/exit loopers included |
| Operating efficiency | Coil-change downtime reduces output | No coil-change downtime |
| Yield | Higher head and tail cropping losses | Lower cropping losses |
| Surface quality | Good, standard quality | Uniform from head to tail |
| Typical application | Small to medium scale, multi-product, short runs | Large scale, single product, high volume |
| Footprint | Compact | Larger, with looper pits or towers |
Stage 1 — mechanical scale breaking
Mechanical pre-treatment cracks the scale before chemical pickling, so the acid has less work to do and the bath lasts longer.
| Equipment | Function | Advantage |
|---|---|---|
| Scale breaker (tensile leveler) | Bending and tension create micro-cracks in the oxide layer | Hydraulic roll gap adjustment follows strip thickness and grade |
| Shot blasting (optional) | Mechanical impact removes scale from thick or high-strength strip | Reduces acid demand on difficult grades |
Pre-treatment raises pickling efficiency and allows a lower acid concentration, which extends bath life.
Stage 2 — chemical pickling
Tanks are arranged in a cascade, with acid concentration increasing from entry to exit. Fresh acid enters at the last tank and flows back; spent acid leaves from the first.
| Parameter | Specification | Effect |
|---|---|---|
| Tanks | 3 – 6 stages, cascade arrangement | Progressive pickling along the line |
| Acid type | HCl standard; H₂SO₄ or mixed acid on request | HCl for most carbon steels |
| Temperature | 65 – 85 °C (HCl) / 80 – 95 °C (H₂SO₄) | Set to the reaction kinetics of the grade |
| Concentration control | Online conductivity measurement with automatic replenishment | Holds concentration within a narrow band |
| Turbulent pickling | High-velocity acid flow through the tanks | Shortens the time needed at temperature |
Tank material is PPH or acid-resistant steel, selected against the acid system and operating temperature.
Stage 3 — brushing, rinsing and drying
Residual acid and iron salts have to leave the strip before the exit section, otherwise they show up as staining once the strip is dry.
| Equipment | Function | Features |
|---|---|---|
| Brush scrubbers (optional) | Mechanical removal of residual oxide and salts | Nylon or stainless filament, adjustable pressure |
| Multi-stage rinsing | Removes residual acid and iron salts | Counter-flow design, 3 – 5 stages |
| Squeegee rolls | Removes surface moisture | Acid-resistant rubber |
| Hot-air dryer | Dries the strip before the exit section | Adjustable temperature, no residual moisture |
Environmental protection
Fume, waste acid and spillage are handled inside the line scope, so the plant can meet its emission and discharge limits without retrofitting afterwards.
| System | Technology | Result |
|---|---|---|
| Tank enclosure | Sealed covers with negative-pressure extraction | Acid mist kept out of the workplace |
| Fume scrubbing | Alkaline spray neutralisation with demister | Removal efficiency ≥ 98% |
| Acid regeneration (optional) | Spray roasting or ion exchange | Acid recovery ≥ 99%; saleable Fe₂O₃ by-product |
| Wastewater treatment (optional) | Neutralisation, precipitation and biological treatment | Discharge to standard or water reuse |
| Floor protection | Sealed concrete with acid-resistant lining | Groundwater protection |
Technical specifications
The figures below are the standard range. Capacities and speeds outside it are engineered against the product mix rather than offered as a catalogue option.
Push-pull (PPL) — standard range
| Parameter | Range | Notes |
|---|---|---|
| Annual capacity | 200,000 / 300,000 / 400,000 / 500,000 / 600,000 t | Custom capacities available |
| Strip grades | Carbon, low-alloy, HSLA (≤ 800 MPa); some stainless | Specialty grades need a custom acid formulation |
| Strip width | 600 – 1,250 mm (up to 1,600 mm) | Wider strip requires larger equipment |
| Strip thickness | 1.0 – 4.0 mm standard; up to 6.0 mm extended | Thicker strip needs higher breaker force and longer time |
| Line speed | 60 / 80 / 100 / 120 / 150 m/min | Set by capacity and substrate |
| Pickling tanks | 3 / 4 / 5 / 6 stages | More stages for heavier scale |
| Acid temperature | 65 – 85 °C (HCl) | Closed-loop temperature control |
| Acid consumption | 8 – 15 kg/t (HCl, substrate-dependent) | With cascade control and regeneration |
| Installed power | approx. 600 – 1,500 kW | Depends on capacity and scope |
| Footprint | approx. 1,200 – 3,500 m² | Excludes acid regeneration plant |
Continuous (CPL) — additional specifications
| Parameter | Specification | Notes |
|---|---|---|
| Annual capacity | 600,000 – 1,200,000+ t | Continuous operation for higher throughput |
| Looper capacity | ≥ 2.5 minutes of line operation | Covers coil change without stopping the process section |
| Welder | Resistance seam or laser | Weld strength ≥ 90% of parent metal |
| Yield | ≥ 98.5% | Reduced head and tail cropping |
Standard equipment scope
Scope is supplied as one sequence, with the interfaces between modules defined before manufacturing begins.
| Module | Included equipment | Engineering detail |
|---|---|---|
| Entry section | Uncoiler, pinch leveler, crop shear; welder and entry looper on CPL | Precise expansion control; weld parameters set by grade |
| Scale breaking | Scale breaker (5-roll or 6-roll tensile leveler) | Servo-hydraulic control for different strength grades |
| Pickling section | Multi-stage tanks, heat exchangers, acid circulation pumps, fume hoods | Tank material PPH or acid-resistant steel |
| Rinsing section | Multi-stage rinse tanks, brush scrubbers, squeegee rolls | Counter-flow water design |
| Drying section | Hot-air dryer | Strip dried before the exit section |
| Exit section | Side trimmer (optional), recoiler; looper and recoiler on CPL | Shear accuracy and tight recoils |
| Electrical and automation | PLC, HMI workstations, AC drives, online acid concentration sensors | Platform agreed with the plant standard |
| Fume treatment | Alkaline scrubbing tower, exhaust fans, ductwork | Designed to local emission limits |
| Auxiliary systems | Hydraulic unit, compressed air, acid storage, spent acid tanks, heat exchange station | Single-source supply |
Materials processed
Pickling difficulty varies with grade and scale condition. The line is set for the grades you actually run, not for a nominal carbon steel.
Suitable strip grades
| Grade type | Representative standards | Notes |
|---|---|---|
| Carbon steel | ASTM A1011 / EN S235 / JIS SPHC | Standard process |
| Quality carbon steel | ASTM A1008 / EN S355 / JIS SAPH | Time control to avoid over-pickling |
| HSLA steel | ASTM A572 / EN S420 / JIS SPA-H | Dense scale; stronger breaker |
| Automotive structural | ASTM A1008 / EN DC04 / JIS SPP | High surface requirement |
| Pipe grades | API 5L X42 – X70 | Thick gauge and high strength; dedicated pickling curve |
| Stainless (hot-rolled annealed) | ASTM 304 / 430 | HNO₃ + HF mixed acid system |
Product forms
| Product | Specification | End use |
|---|---|---|
| Pickled coil (full width) | Coil weight 5 – 30 t | Cold rolling feedstock or direct sale |
| Pickled sheet (cut-to-length) | Custom lengths | Machinery, stamping, drums |
| Pickled trimmed coil | Edge-trimmed | High-end cold rolling feedstock |
Supply and delivery options
Scope can be taken as a complete line or as defined modules, depending on the engineering resource available on site.
Supply modes
| Mode | Scope | Best for |
|---|---|---|
| Turnkey | Process design, equipment, installation supervision, commissioning, training and spares | New investors and clients with limited technical teams |
| Core equipment supply | Pickling section — tanks, heating, circulation — and electrical controls | Clients with local fabrication capability |
| Upgrade or retrofit | Diagnostics, design, key equipment replacement, automation upgrade | Existing lines with performance or quality issues |
| Environmental add-on | Fume scrubber, acid regeneration, wastewater treatment | Facilities facing tighter emission regulations |
Standard project timeline
| Phase | Duration | Key activities |
|---|---|---|
| Engineering and design | 30 – 40 days after signing | Mass balance, general layout, foundation drawings, utility requirements |
| Equipment manufacturing | 90 – 180 days, capacity-dependent | Inspector on site, hold-point inspections, quality reports |
| Factory acceptance test | 5 – 7 days before shipment | No-load run and water circulation test |
| Shipping and logistics | Varies by destination | Customs support and export documentation |
| Installation supervision | 90 – 120 days after arrival | Field engineers on site |
| Commissioning and trial run | 15 – 25 days after installation | Cold run, acid circulation, hot trial, performance check |
| Operator training | During commissioning | Classroom, hands-on and SOP manuals |
| Site acceptance | On performance validation | Certificate signed; warranty 12 – 18 months |
Support after handover
Spare parts, retrofit work and diagnostics continue after the warranty period. Common requests are listed below.
- Remote data acquisition for temperature, concentration, speed and tension
- Mobile dashboard with alerts for out-of-band conditions
- Remote engineering diagnostics and parameter optimisation
- Annual performance report with maintenance recommendations
Typical spare parts
| Part | Application | Material |
|---|---|---|
| Scale breaker rolls | Scale breaking section | High-chromium alloy, wear-resistant |
| Pickling tank liners | Pickling section | PPH or acid-resistant rubber |
| Squeegee rolls | Rinsing and pickling exit | Acid-resistant rubber, several hardness grades |
| Brush rolls | Brush section | Nylon or stainless filament, replaceable |
| Acid circulation pumps | Pickling section | Chemical-duty, corrosion resistant |
| Heat exchanger plates and gaskets | Acid heating system | Titanium or Hastelloy options |
| Fume scrubber nozzles | Fume treatment | Acid-corrosion resistant |
| Circular shear blades | Exit trimming | SKD-11 |
Retrofit options
| Retrofit | Scope | Typical driver |
|---|---|---|
| Automatic acid concentration control | Conductivity and density meters with automatic replenishment | High acid consumption or inconsistent quality |
| Fume scrubber upgrade | High-efficiency tower with demister | Emission limits |
| Acid regeneration system | Spray roasting or ion exchange | Spent acid disposal cost and environmental pressure |
| Scale breaker upgrade | Add or upgrade the tensile leveler | Growing share of HSLA grades |
| Automation upgrade | PLC and HMI renewal with remote monitoring | Ageing controls and downtime |
| Capacity debottlenecking | Motors, drives and speed increase | Demand growth on a space-constrained site |
Configuration inputs
What we need to specify this line
- 01Steel grades and the scale condition you run
- 02Strip width, thickness range and coil weight
- 03Target output and the PPL or CPL choice
- 04Acid system, emission limits and site utilities
Questions
Questions we hear on this line
PPL or CPL — how is the choice made?
Capacity target is the first filter. PPL suits multi-product, short-run output with a lower capital outlay; CPL suits high-volume, single-product output where coil-change downtime is not acceptable.
Can an existing pickling line be rebuilt in stages?
In many cases yes. Tanks, rinsing, scale breaking and entry or exit equipment can be replaced separately once the interfaces, foundations and line control have been verified first.
Is acid regeneration part of the line?
It is an optional module. Spray roasting and ion exchange are both offered, selected against the acid system, capacity and the cost of spent acid disposal on site.
Related terms
What engineers search for on this line
- pickling line
- push-pull pickling line
- continuous pickling line
- PPL
- CPL
- steel strip pickling
- hot-rolled pickling
- acid pickling equipment
- acid regeneration system
Other lines
Sections planned in the same scope
Reversing Cold Rolling Mills (CRM & TCRM)
Turnkey single-stand and tandem reversing cold rolling mills for carbon, silicon, stainless and HSLA strip, with hydraulic gauge and automatic flatness control.
Continuous Hot-Dip Galvanizing Line
Turnkey continuous hot-dip galvanizing lines for GI, 55% Al-Zn and Al-Zn-Mg coatings, from cleaning and annealing through the zinc pot, skin-pass and chemical treatment.
Continuous Color Coating Line (CCL)
Turnkey colour coating lines for prepainted steel: 2C2B and 3C3B configurations, PE to PVDF coating systems and RTO fume treatment in one scope.
Planning a new line or an upgrade?
Send the product mix and target capacity, and we will review the configuration.