A steel coil carrier is sized by the coil, not by the tonnage on the nameplate. Outside diameter sets the portal and the lifting height, coil width and eye orientation decide the attachment, and the storage method — cradle, saddle or stacked — decides how much of the yard the machine can reach. Two yards handling the same 25 t coil can need machines that differ by several metres in width.
Container handling and coil handling look similar from a distance: a portal frame, four or eight wheels, a load between the legs. Up close they are different problems. A 40 ft container spreads roughly 30 t over twelve metres of deck. A steel coil puts the same mass into a two-metre footprint, and it arrives with a surface that cannot be touched, an axis that has to stay in a fixed orientation, and a shape that will roll if it is set down carelessly.
This page covers how we specify a straddle carrier around coil duty: what the coil data changes, which attachment does what, how the yard and the ground constrain the machine, and what to send with an enquiry.
Why coil handling is a different duty
Four properties of a coil drive most of the design decisions.
- Density. The load is concentrated. The frame, the attachment and the wheel arrangement all see higher local forces than the same tonnage carried as a container or a beam.
- Surface. The outer wrap, the edges and the bore are all finished surfaces. Marks, dents and edge damage are quality claims, so the attachment has to carry the coil without sliding, pinching or bearing on the wrap.
- Orientation. A coil has an axis. It is stored eye-to-sky (axis vertical) or eye-to-wall (axis horizontal), and the two need different attachments and different clearance. If the machine has to change orientation, it needs a rotating head — and that changes the load case.
- Stability. A coil standing on its edge is held by friction and gravity. Ground slope, a hard brake, or a sling that pulls sideways can start it moving.
Duty class matters as much as the load. A coil yard that runs three shifts, seven days a week, accumulates a very different number of lifting cycles from a service centre that moves a few coils a day. That difference belongs in the classification of the machine, not in a margin added at the end.
The coil as a load
Coil dimensions vary more than buyers expect. In general trade a single hot-rolled coil is often between 5 and 30 t, with an outside diameter around 1.2 to 2.2 m, a bore of 0.5 to 0.8 m and a width of 0.6 to 2.0 m — but cold-rolled, galvanised, stainless and narrow slit coils all sit outside that, and a single mill may ship several families from the same yard.
What matters for the machine is not the average coil but the extremes, and how often they occur.
| Coil data | What it changes |
|---|---|
| Weight range | Rated capacity at the actual load centre, and the wheel loads that go back to the slab or hardstanding. |
| Outside diameter | Portal inside width, clear lift height, and whether a tong can open far enough to grip the coil. |
| Bore diameter | Whether a C-hook or a mandrel can enter the eye, and how much clearance the hook body needs. |
| Coil width | Attachment size, saddle length and the footprint the coil occupies in storage. |
| Eye orientation | Attachment type, head rotation, and the height the machine must lift to clear a stack. |
| Storage method | Cradle, saddle, A-frame or floor — and therefore how close the machine can get and how high it can reach. |
| Throughput | Duty classification, drive choice, and whether one machine or two is the cheaper answer. |
Send the range, not the average. The machine is normally sized by the heaviest coil times the number of coils handled per move, and checked against the lightest, because a very light coil can be harder to grip than a heavy one.
Lifting attachments
The attachment is the part of a coil carrier that is genuinely custom, and it is usually decided before the machine itself. There are four options in normal use.
| Attachment | Works well for | Watch out for |
|---|---|---|
| C-hook | Eye-to-wall coils, where the hook enters the bore and the coil hangs on the hook body. | Needs bore clearance and a clear approach; the coil swings unless the hook is guided or the machine has anti-sway. |
| Coil tong | Eye-to-sky coils, gripped on the outside diameter. | Contact pressure on the wrap; grip range has to cover both the largest and the smallest coil in the yard. |
| Lifting beam with slings or saddles | Coils that must stay horizontal, or loads that have to be supported along the width rather than gripped. | More manual work per lift, and the sling angle has to be controlled to avoid squeezing the coil. |
| Magnet | Ferrous loads in some yards, mainly for scrap and plate rather than finished coil. | Residual magnetism, surface marking, and a load that can slip if the contact face is not clean and flat. |
A rotating head is often added so the machine can present a coil either way. It is a structural and stability decision, not an accessory.
Two rules come out of practice. First, the attachment must cover the whole coil range, not the common coil: a tong that grips 1.2 to 2.0 m but cannot close on a 1.0 m coil will leave part of the yard unserviceable. Second, protection is part of the attachment — replaceable pads, saddle liners and radiused contact faces are cheaper than a claim for a marked coil.
Machine configuration
With the load settled, the machine is a set of clearances and weights.
- Portal inside width is set by the widest coil plus its saddle plus operating clearance — not by the coil alone. Where the machine must straddle a storage row, the row width governs.
- Clear lift height is set by the highest stack the yard will build, plus the attachment depth. A stack of three coils on cradles is a different machine from a single tier.
- Rated capacity is quoted at a load centre. With coil duty the centre is short and the load is dense, so the capacity curve behaves differently from a container spreader — always compare at the real centre of gravity.
- Wheel arrangement follows the ground. Coil yards are often concrete or compacted hardstanding with tight turning areas, and the loaded wheel load is the number the structural engineer needs.
- Cab position and visibility are more critical than in container work, because the operator has to see the bore, the tong jaws and the stack at the same time.
- Steering modes decide how the machine gets out of a storage bay. Crab and four-wheel steering reduce the swept path in yards where the aisles were laid out for forklifts.
The published 35 t, 60 t and 80 t models on the specifications page show the dimensions we can quote without a project-specific design. Above that, and for unusual coil geometry, the machine is designed around the duty — the selection guide sets out the order in which those numbers should be fixed.
Yard, route and storage
Coil storage is usually the tightest constraint in the project. Rows are close together, the coils sit low, and the space between them was rarely designed with a portal machine in mind.
- Aisle width measured along the full loaded route, including corners and the approach to each storage bay.
- Storage geometry: cradle spacing, row pitch, and whether coils are stacked or single-tier.
- Transport interface: flatbed trailer, coil car or rail wagon, and the height and approach angle of each.
- Overhead obstructions: crane runways, pipe bridges, lighting and roof structure — checked for the tallest stack, not the average lift.
- Ground: slab joints, drains, slopes and any area where the hardstanding is thinner than the rest.
Two measurements catch people out. The first is the turning envelope of a long portal with a coil carried off-centre; the machine may fit the aisle but the coil will not. The second is the gap between rows: a carrier needs clearance on both sides at once, and a bay that was fine for a side-loader can be too tight for a straddle.
Safety and control
Coil incidents tend to be expensive rather than frequent, and most of them start with the load rather than the machine.
- Damaged coils must be segregated. A telescoped or edge-crushed coil can behave unpredictably under a tong or on a hook. It belongs in a quarantine area, not back in the stack.
- The coil must not be able to roll. Saddles, cradles and chocks are part of the handling system; a coil set down on flat steel with nothing to hold it is a stored risk.
- Load monitoring and limits should be visible to the operator, not only recorded. Overload protection, hoist limits and anti-sway are standard on this class of machine.
- Exclusion zones during lifting, because a swinging coil has a larger footprint than the machine and the operator cannot see all of it.
- Weather matters outdoors: wind load on a suspended coil, and ice or water on the hardstanding.
Where the operator cannot see the bore or the far side of the stack, the answer is usually a combination of cab position, camera coverage and a banksman procedure — decided with the yard, before the machine is built.
Drive and environment
Coil yards are split roughly evenly between outdoor hardstanding and covered bays, and the drive choice follows the building.
- Diesel remains the default for outdoor yards with long routes: no trailing cable, no charging infrastructure, and full performance on gradients.
- Electric suits covered bays and indoor warehouses, where exhaust and noise are the constraint. It needs a charging or cable strategy that fits the shift pattern.
- Hybrid sits between them: smaller engine, recovering energy from hoist lowering, and lower fuel burn in stop-start duty.
- Cold and dusty environments change the specification: hydraulic oil grade, battery behaviour, filtration and the operator cab.
Duty class and drive should be decided together. A three-shift electric machine with no time to charge is a worse investment than a diesel one, and an indoor diesel machine may not be permitted at all. The cost drivers page explains how drive, duty and attachment affect the total rather than the purchase price alone.
Standards and documentation
Coil carriers are designed and documented against the same crane standards as other lifting machines. The relevant ones for this duty are:
- ISO 4301-1 and ISO 4301-5 — classification of the machine by duty.
- EN 15011 — bridge and gantry cranes, which covers the structural approach for portal machines.
- IEC 60204-32 — electrical equipment of hoisting machines.
- ISO 12488-1 — tolerances for wheels and travel tracks.
Standards are cited by number here; the edition that applies to a given contract is confirmed with the drawing package, because editions change and a machine designed to a withdrawn edition is a documentation problem at handover. Ask for the classification, the load chart and the wheel-load calculation as a set — they should agree with each other.
Beyond coil: plate, billet and long product
Most coil yards also handle other steel. If the machine is going to serve the whole site, say so at the start; a carrier specified for coil alone may be the wrong shape for plate.
Plate and section
Wide, flat loads that need a beam or a spreader rather than a tong, and a different stability case.
Pipe and bar stock
Long products sit in racks and on the ground. The portal has to clear the rack, not just the load.
Loading and dispatch
The last few metres — trailer, wagon or coil car — decide how much control the operator needs.
Storage density
Stacking height, cradle spacing and the aisle width that the storage plan actually leaves.
The documented case library includes heavy straddle carriers and gantry machines built for steel and heavy-industry yards, which is often the fastest way to see how a similar duty was solved.
What to send with an enquiry
Six items are enough for a first configuration. Without them, any reply is a guess.
- Coil weight range, and the outside diameter, bore and width for each family.
- Eye orientation in storage, and whether the machine must rotate the coil.
- Storage method and maximum stack height.
- A yard plan with storage rows, aisles, transport interface and overhead obstructions.
- Ground information: surface, slab or hardstanding, and any structural drawing available.
- Throughput and shift pattern, so duty class and drive can be set against the real workload.
Send them as drawings, photographs or a spreadsheet — whatever exists. The review usually identifies one or two numbers that decide the machine, and those are rarely the ones on the enquiry form.
Steel coil FAQ
Can one machine handle both eye-to-sky and eye-to-wall coils?
Yes, with a rotating head and a suitable attachment — typically a tong for one orientation and a C-hook or beam for the other. The load case changes with the rotation, so the stability and the wheel loads have to be checked in both positions.
Is a forklift or a reach stacker cheaper for a small coil yard?
Often, yes. A straddle carrier pays back on volume, on storage density and on route length. Below a certain number of moves per shift, a forklift with a coil boom or a reach stacker is the more sensible purchase, and we will say so.
How is the coil protected from damage?
The attachment carries the coil on a controlled contact face — tong pads, saddle liners or a hook body — rather than on slings bearing against the wrap. Edge protection and a no-drag rule at set-down matter as much as the attachment itself.
Can the machine work indoors?
Yes. Electric and hybrid drives are common for covered bays, where exhaust and noise are the constraints. The building height, the floor loading and the charging strategy all become part of the specification.
What ground bearing capacity is needed?
It depends on the loaded wheel loads, which depend on the machine, the coil and the attachment. We return wheel loads per configuration — loaded and unladen — so your structural engineer can check the slab or hardstanding against the real machine rather than an estimate.
Do you provide the load chart and classification?
Yes, with the drawing package. The load chart is quoted at the real load centres for your coil range, and the classification follows the duty cycle agreed at the technical review.