The short answer
Size an uncoiler by coil weight first, then choose the capacity class, then decide between single-head and double-head. A double-head hydraulic uncoiler has two mandrels back to back: while one pays off, the next coil is loaded on the other, and the head rotates 180 degrees at coil change. That removes the loading wait, which suits tube mills running narrower strip and lighter coils. A single-head hydraulic uncoiler works with a hydraulic coil car and an outboard support arm, which suits wide strip and heavy coils. The final choice also depends on coil ID and OD, the workshop crane and the floor space, and is confirmed by our engineers for each project.
Determining the full coil weight
The full coil weight depends on the coil OD, ID and strip width, and is estimated from the actual coil dimensions for selection. For the actual coil weight, use the steel mill's coil tag or a scale reading.
Rated capacity, OD and coil weight: whichever limit comes first
An uncoiler's rated capacity is the load the mandrel can carry. It does not mean every coil will reach that weight: at the same OD, a narrower strip gives a lighter coil. Some specifications list both an OD limit (for example 1,800 mm) and a weight limit (for example 10 t); the two limits can contradict each other, and the one reached first applies. In an inquiry, please state your actual maximum coil weight together with the coil ID and OD.
Single-head vs. double-head at a glance
- How it works: a double-head uncoiler carries two mandrels back to back on a rotating base, one paying off while the other is loaded, and turns 180 degrees at coil change. A single-head uncoiler has one cantilever mandrel; the next coil goes on after the previous one has run out.
- Typical use: double-head for tube mills with narrower strip and lighter coils; single-head for wide strip and heavy coils.
- Loading: double-head machines are usually loaded with the workshop crane. Single-head machines use a hydraulic coil car that lifts the coil, lines it up with the mandrel and pushes it on.
- Waiting time: on a double-head machine the next coil is ready during payoff. On a single-head machine the next coil goes on after the previous one has run out; a coil storage stand can hold coils waiting to be loaded.
- Rotation (double-head): manual, hydraulic motor with slewing ring and pneumatic locating pin, or electric, depending on configuration.
- Civil work: a single-head uncoiler with a pit-type coil car needs a pit for the car; where a pit is not possible, a floor-mounted car can be built. Installation level and foundations follow the project foundation drawing.
Does a double-head uncoiler keep the mill running?
A double-head uncoiler removes the loading wait, but at every coil change the strip tail and head still have to be sheared, aligned and welded, and the strip at the uncoiler end is stopped during that time. What keeps the tube mill running is the spiral accumulator: it stores enough strip before the change and keeps feeding the mill while the coils are changed and joined. Accumulator storage length must cover the full coil change and joining cycle.
Catalog standard classes (reference values)
InGen MillTek hydraulic uncoilers are listed in the catalog by coil weight class; reference upper limits for the 3 t, 5 t and 10 t classes are shown below. Width and thickness figures are the upper limit for each class, not a combination that is reached at the same time. Values depend on configuration and are confirmed in the technical proposal.
- 3 t class: strip width up to 450 mm, thickness up to 4 mm
- 5 t class: strip width up to 550 mm, thickness up to 6 mm
- 10 t class: strip width up to 800 mm, thickness up to 10 mm
- For heavier coils, larger single-head hydraulic uncoilers are configured per project and confirmed in the technical proposal.
- For wider and heavier coils, such as wide coils for a slitting line, a double-cone uncoiler can be supplied after a project review.
Selection sequence
- Step 1, coil weight: calculate it from actual width, ID and OD, or use the weight on the steel mill's coil tag.
- Step 2, capacity class: choose a class that covers your actual maximum coil weight.
- Step 3, single-head or double-head: based on strip width, coil weight, coil change rhythm and loading method.
- Step 4, center height and expanding range: the center height must leave floor clearance for the maximum coil OD (as a reference, center height ≥ coil OD ÷ 2 + 100–200 mm), and the expanding range must cover every coil ID you use (for example 508, 500 and 610 mm).
- Step 5, options: powered payoff, hold-down, support arm, side shift and coil car.
What to send us
Uncoilers are configured to order and quoted individually.
- Maximum coil weight, coil ID and OD
- Strip width and thickness range, material grade with yield and tensile strength
- Preferred type (single-head or double-head) and loading method (crane or coil car)
- Workshop crane capacity, and whether a pit can be dug at the uncoiler position
- For an uncoiler only: strip center height of the existing line and feed direction (left-hand or right-hand)
- Local supply voltage and frequency
Frequently asked questions
Prepared by the InGen Engineering Team. All values are reference values and are confirmed in the technical proposal and technical agreement.
- Why can a narrow-strip coil not fill a 5 t uncoiler? The rating is the mandrel capacity. With narrow strip, the coil weight stays low within any practical OD.
- Can a double-head uncoiler replace a spiral accumulator? No. It removes the loading wait, but shearing and welding still take time; the mill keeps running on the strip stored in the accumulator.
- My workshop cannot have a pit. Can a single-head uncoiler still have a coil car? Yes, a floor-mounted coil car can be built after a site review.
- What does an uncoiler cost? It is configured to coil weight, strip width and options, and quoted individually.