Steel Coil Wrapping and Packing: Circumferential Strapping, Layers and Strap Use

Executive summary

A steel coil leaves the mill worth far more than its packing, yet most transport damage comes from weak packing: rust from moisture, crushed edges, and coils that telescope when straps slip. Good practice builds the pack in layers: edge protection, VCI paper or film, an outer cover, then radial and circumferential straps. This page explains each layer, how our automatic circumferential strapping machine fits into the line, and how to work out strap use per coil.

The coil arrives eye-horizontal on a coil car and stops inside the strapping gantry. The strapping head moves in to the coil OD; once it reaches the coil surface, the strap is fed around the outside of the coil, tensioned and sealed. The strap passes under the coil through a fixed dispenser track, so operators do not have to thread heavy strapping by hand.

Table of Contents

What goes wrong in transport

Export and domestic steel coils face multi-axis dynamic forces, humidity fluctuations, and harsh handling during sea voyages and intermodal transit. Without systematic packaging, structural coil integrity degrades rapidly:

Damage Cause Packing answer
Rust and white rust moisture and condensation VCI paper or film, sealed cover
Crushed edges handling and stacking ID and OD edge protectors
Telescoping layers slide sideways radial straps through the eye
Loose outer wraps coil springs open circumferential straps around the OD
Coil moves on pallet weak tie-down bands from coil to pallet

The packing layers, in order

Applying packaging materials in the correct mechanical sequence creates a structural barrier against mechanical impact and atmospheric corrosion:

  1. ID protection: ID hole protector and ID edge protector, so the forklift tines or crane C-hook cannot cut or notch the inner wraps during transfer.
  2. OD edge protection: Steel or heavy-duty pressed cardboard edge protectors fitted on both outer circumferences to distribute strapping strap tension evenly.
  3. Corrosion protection: VCI (Vapor Corrosion Inhibitor) paper covering, or VCI stretch film wrapped with pre-stretch elongation up to 50% to actively passivate metal surfaces against moisture.
  4. Outer cover: High-density cardboard or galvanized steel sheet OD outer covering combined with robust side disk covers.
  5. Strapping: Radial straps passed through the ID eye, followed by circumferential straps tensioned firmly around the OD circumference.
  6. Labels: Weatherproof barcode/shipping labels placed on the end sidewall and on the OD wrapper for traceability.

Not every coil needs every layer. Domestic cold-rolled coil may only need VCI and straps; export coil going by sea needs the full set.

Circumferential and radial strapping

Strapping coils requires dividing containment tasks between two distinct strap orientations:

Type Path Job
Circumferential around the OD holds outer wraps and edge protectors; in our palletized cold-rolled line, 4 or more bands also pass around the pallet to tie coil and pallet together
Radial through the eye stops telescoping; 2 straps typical, up to 6 on our radial strapper

Our standard heavy-duty radial strapper runs 19–32 mm steel belt with 2, 3, 4 or 6 belts applied per coil. For operations processing both hot-rolled and cold-rolled coils, the radial strapper utilizes a modular design for quick maintenance turnaround, featuring a rotating strapping head and arch assembly that executes 360° orbital strapping cycles across both semi-automatic and fully automated program modes. The industrial strapping head delivers a verified service life rated up to 1,000,000 strapping cycles [manufacturer rating] (subject to final RFQ specification and routine servicing), certified under CE and ISO 9001 quality management with a 2-year warranty.

Where surface-critical coils require alternative strapping media, dedicated automated PET radial strapping machines run high-tensile PET strap (strap width 12 mm × thickness 0.8–1.2 mm) [manufacturer rating]. These PET strapping units are built as separate dedicated machine models available in horizontal (eye-horizontal) and perpendicular axis (eye-to-sky) configurations, offering multiple thermal or friction joint options to match line throughput requirements. Most export coils need both circumferential and radial types.

How the circumferential strapper works

The automated circumferential strapper stabilizes outer wraps through an automated sequence:

  1. The coil car brings the coil, aligned with the centre of the line.
  2. The head adjusts automatically to the coil OD.
  3. On contact with the coil surface, strapping starts.
  4. The strap runs from a fixed dispenser through the bottom of the coil, around the OD, and is tensioned and sealed.
  5. For several bands, the head steps to the next position across the width.

A double-head configuration is available for wide coils requiring synchronized twin strapping to double line throughput. The system reliably suits galvanized, cold-rolled, hot-rolled and aluminium coil, maintaining a strapping success rate up to 99%.

Strap use per coil

Accurate consumable estimation prevents line starvation and clarifies strapping material ROI:

Circumferential band ≈ 3.14 × OD + sealing overlap. Radial loop ≈ 2 × width + (OD − ID) + overlap.

For a 1,600 mm OD, 508 mm ID, 1,250 mm wide coil with a 0.2 m overlap (example only):

Check Calculation Result
One circumferential band 3.14 × 1.6 + 0.2 about 5.2 m
4 circumferential bands 4 × 5.2 20.8 m
One radial loop 2 × 1.25 + (1.6 − 0.508) + 0.2 about 3.8 m
2 radial loops 2 × 3.8 7.6 m
Total per coil 20.8 + 7.6 about 28.4 m

Multiply by coils per year and your strap price to compare steel and PET strap.

Where it sits in a packing line

In a full automated line, the coil first passes an in-line weigh scale with an integrated label printer, followed by an optical ID and OD profile scanner that automatically transmits dimensional parameters to set up the stretch wrapper.

The master coil then indexes smoothly through designated protection fitting stations, proceeds through radial and circumferential strapping gantries, and discharges onto an exit queue engineered for up to 4 palletized coils. Our complete cold-rolled coil packing line operates with an aggregate power consumption of about 15 kW and requires a regulated pneumatic supply of 0.6 MPa compressed air. A single circumferential strapper can also stand alone on an existing coil car line.

Selection checklist

  1. Coil OD, ID, width and weight range?
  2. Loading by crane or coil car?
  3. Strap type and width?
  4. How many circumferential and radial bands?
  5. Which protection layers before strapping?
  6. Coils per hour?

Safety

The machine is designed to EN ISO 12100:2010 for risk assessment, EN 415-10 for packaging machine safety and EN 60204-1 for electrical equipment. The moving head, the strap path and the coil car are the main hazards, so the area is fenced with interlocked safety guarding and the head stops instantly on contact via tactile safety edges.

Engineering FAQ

Q: Do I need both radial and circumferential straps? A: For export coil, usually yes: radial stops telescoping, circumferential holds the outer wraps.

Q: How many circumferential bands? A: Four or more when the bands also tie the coil to the pallet.

Q: Does the head adjust to each coil? A: Yes, it adjusts automatically to the OD.

Q: What should I send for a quote? A: Min and max OD, ID and weight, loading method and strapping layout.

Next step

  1. Send your coil range, loading method and strap layout to info@fhopepack.com.
  2. We design the strapping and packing stations to your layout.
  3. We reply within 24 hours with a proposal and quotation.

Sources

Last updated: 2026-10-29

Last reviewed: 2026-10-29

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