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Preservation Line
Product Description:
A steel preservation line is a completely automated line for the surface preparation of steel plates, sections, and other metal sheets. It is standard equipment in steel structures, shipbuilding, and engineering machinery, where steel is blasted and primed before it enters fabrication.
The line removes mill scale, rust, and contaminants from the steel surface and applies a protective shop primer in the same pass, so that the plate resists corrosion during storage and handling and the final coating system bonds to a prepared surface rather than to scale. Blast wheels throw steel shot of a specified size at the surface at high velocity; the impact is what removes scale and rust, and it is the only stage in the line that changes the steel surface.
Working Principle
The line conveys workpieces continuously on a roller conveyor and completes five stages in sequence.
Loading. Steel plate is fed into the line automatically or manually, according to the handling equipment specified.
Shot blasting. Blast wheels throw steel shot at the steel surface, removing mill scale, rust and contaminants. Surface preparation grade reaches Sa 2½ (ISO 8501-1). What a given plate achieves depends on three variables: incoming condition, abrasive specification and line speed.
Priming. A shop primer is applied automatically to form a uniform protective film. Dry film thickness is agreed against the coating system that follows, not fixed by the line.
Drying. The primed plate passes through a hot-air drying chamber and leaves the line dry enough to be handled without damaging the film.
Unloading. Finished plate is discharged onto the outlet conveyor for cutting, fabrication or storage.
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Product Description
Core Features
Continuous operation. Throughput is set by line speed rather than by crane handling, so the surface is produced the same at the first plate and at the ten-thousandth.
Repeatable surface quality. Grade and coating thickness are set by line parameters — abrasive specification, wheel power, line speed and spray settings — and are checked at the line exit rather than asserted in a brochure.
Dust and solvent controlled at source. The blast chamber runs under negative pressure to a dust collector, and primer booth exhaust passes through paint-mist filtration before discharge.
Configured to the plate. Working width, plate thickness, line speed and coating thickness are fixed at the order from the customer's plate range. Sizes outside the catalogue range are engineered to order, with no published parameters and no fixed lead time.
Technical Specifications
Q: What workpieces can a Metal Preservation Line process?
A: The line is designed for steel plates, sections, and other metal sheets. It is a continuous roller-conveyor system, so workpieces must be flat or regular enough to travel on rollers in a stable position. Typical sectors served are steel structures, shipbuilding, and engineering machinery — all cases where surface preparation precedes cutting, welding, or coating.
Q: What plate thickness and width can the line handle?
A: This is configuration-driven, not fixed. Blast wheel power, conveyor speed, roller spacing, and tunnel opening are all sized to the customer's thickness and width range and required throughput, so no single specification applies across installations. The correct approach is to state your maximum and minimum plate thickness, maximum width, and target output in m²/h or tonnes/shift, and have the line sized from those inputs.
Q: What surface cleanliness grade is achievable?
A: Derusting reaches Sa2.5 to Sa3 under ISO 8501-1. Sa2.5 is the commercial benchmark for most protective coating systems; Sa3 is a near-white finish reserved for demanding coating specifications or high-corrosion environments. The grade actually held in production depends on shot size and mixture, wheel power, conveyor speed, and steel condition — which is why grade verification should be agreed as an acceptance criterion at commissioning.
Q: Why must priming follow blasting inside the same line?
A: Blasted steel re-oxidises almost immediately on contact with humid air. Once the surface has been cleaned to Sa2.5–Sa3, the primer must be applied before that reaction can start, which is why blasting, priming, and drying are integrated into a single continuous pass rather than split across separate stations. This is the core technical argument for an inline line over standalone blast and paint equipment — it protects the investment made in the blast stage.
Q: How are coating thickness and adhesion kept consistent?
A: Consistency comes from three control points. Shot parameters are held stable so surface roughness and profile are repeatable, which is what mechanical adhesion keys into. Primer application is automatic rather than manual, removing operator variance. Drying is then controlled so the film cures without blistering or under-cure. Surface roughness profile and coating thickness should both be specified as measurable acceptance criteria.
Q: Which drying method is used, and why does it matter?
A: Hot air or infrared heating, selected according to primer type and line speed. The drying stage is what makes continuous output possible — an under-cured primer cannot be stacked or handled without marking the film. Infrared suits fast surface cure at high line speed; hot air gives more uniform through-cure. The choice should follow the specified primer chemistry, not the reverse.
Q: How does the line fit into an existing cutting and welding workflow?
A: It sits upstream of cutting and welding as a pretreatment stage. Two benefits follow. First, cleaned and primed plate cuts and punches more predictably, with less tool wear and fewer dimensional issues from scale. Second, primed plate can be stored and moved without the rust rework that typically consumes labour between blasting and fabrication. Layout planning matters here — the line's inlet and outlet need to align with existing crane, roller, or transfer arrangements.
Q: What environmental controls are included?
A: The line is supplied with high-efficiency dust removal and exhaust gas treatment. This covers shot dust and fines generated in the blast chamber and solvent or volatile emissions from the primer and drying stages. Two points should be confirmed against local regulation during specification: the emission limits applicable at your site, and whether the exhaust treatment configuration needs to be adapted to the primer system you intend to run.
Q: What information is required to specify and quote a line?
A: Five inputs determine the design and the price.
Workpiece range — maximum and minimum plate thickness, maximum width, and whether sections or profiles must also be handled.
Throughput target — m²/h or tonnes per shift, and shift pattern.
Surface requirement — target Sa grade and any coating specification, roughness profile, and dry film thickness.
Site conditions — available floor length and width, power supply, compressed air, and existing handling equipment.
Compliance requirements — applicable emission standards and any certification needed for the finished product.
Without these, any quoted figure is an assumption rather than a specification.
Q: What are the main operating consumables and cost drivers?
A: Steel shot is the principal consumable, and its consumption rate is driven by shot size and quality, abrasive separators and dust collection efficiency, and blast intensity required to reach the specified grade. Power for blast wheels, dust extraction, and drying is the largest running cost, followed by primer. Shot that is poorly classified or contaminated raises consumption sharply, so the separator and dust removal system are cost-control equipment as much as environmental equipment — not optional extras.
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