A 5-ton coil came off the mandrel at a factory in Bangladesh. The operator had loaded it onto a manual decoiler, walked away to check the roll former, and the coil started rotating under its own weight. It unspooled three meters of strip across the floor before someone hit the emergency stop. Nobody was hurt, but the strip was kinked and 200 kg of material was scrapped. The owner called me the next day asking about hydraulic decoilers with braking systems.
I'm Iris Xu, sales engineer at ZTRFM. I've quoted decoilers for lines producing everything from 0.3 mm roofing sheet to 4 mm guardrail. The decoiler is the first station on the line and the most overlooked — buyers focus on the roll former and treat the decoiler as an afterthought. This article covers the three types, their capacities, and how to choose.
Type 1: Manual Decoiler
The simplest and cheapest option. The mandrel is expanded and contracted by turning a hand crank. There's no motor — the coil is pulled by the roll former's drive system. A manual brake (typically a friction pad or band brake) provides resistance to prevent overspooling.
Capacity: 1–3 tons. Some heavy-duty manual decoilers go to 5 tons, but at that weight, hand-crank expansion becomes difficult and the braking system struggles to control the inertia.
Mandrel ID: 508 mm (20 inch) is standard. Some models offer 610 mm (24 inch) or adjustable sleeves.
Cost: $300–$800. Often included free with budget roll forming lines.
Best for: Light material (0.3–0.8 mm), narrow coil (under 1000 mm), single-shift operations with moderate volume. Roofing sheet lines, downpipe lines, small-section roll formers.
Limitations: The friction brake is imprecise. With heavy coil or high line speed, the brake can't stop the coil fast enough when the line stops — the coil keeps spinning and strip piles up on the floor (overspooling). Loading a 3-ton coil onto a manual decoiler requires two workers and a forklift. There's no edge guide, so strip tracking depends entirely on the roll former's entry guides.
Type 2: Hydraulic Decoiler
The standard for mid-range and heavy-duty lines. The mandrel is expanded hydraulically by a foot pedal or button — no hand cranking. A motor drives the mandrel at a controlled speed, synchronized with the roll former's demand. An automatic braking system stops the coil when the line stops.
Capacity: 5–15 tons. The hydraulic expansion can grip heavy coils securely.
Features:
- Hydraulic expansion: 4-jaw or 6-jaw mandrel, expands from 470 mm to 530 mm (or equivalent range for 610 mm ID)
- Motorized rotation: 1.5–5.5 kW motor with VFD speed control
- Automatic brake: pneumatic or hydraulic disc brake that engages when the line stops
- Edge guide (optional): hydraulic or photoelectric sensor that keeps the strip centered
- Coil car (optional): hydraulic platform that lifts the coil onto the mandrel — eliminates manual loading
- Press arm (optional): hydraulic arm that holds the outer end of the coil to prevent overspooling during initial threading
Cost: $2,000–$8,000 depending on capacity and options.
Best for: Medium to heavy material (0.8–4.0 mm), wide coil (1000–1500 mm), multi-shift operations. Floor decking lines, purlin lines, guardrail lines, and any line running 5-ton or heavier coils.
The Bangladesh factory that had the overspooling incident upgraded from a manual to a hydraulic decoiler with an automatic brake. The brake engages within 0.5 seconds of the line stopping — the coil might rotate one more revolution, but it won't unspool. The press arm holds the outer end during threading, so the operator doesn't need to manually control the loose end.
Type 3: Double-Head (Twin) Decoiler
Two mandrels on a single frame, mounted side by side or on a rotating turret. While one coil runs, the operator stages the next coil on the second mandrel. When the first coil runs out, the line pauses briefly while the strip end is spliced to the new coil, then the second mandrel takes over.
Capacity per head: 5–10 tons each.
Splice time: With a double-head decoiler, coil change time drops from 15–30 minutes (single head: stop, remove empty coil, load new coil, thread, restart) to 3–5 minutes (double head: splice while new coil is already loaded, switch mandrels, restart).
Cost: $5,000–$15,000 — roughly 2x a single hydraulic decoiler of the same capacity.
Best for: High-volume operations where coil change downtime is costly. Three-shift roofing lines, guardrail production for highway projects, any line where the order book justifies maximum uptime.
How to Choose: The Decision Matrix
| Your situation | Recommended type | Why |
|---|---|---|
| 0.3–0.8 mm, coil < 3 tons, single shift | Manual | Light loads are manageable manually; brake is adequate |
| 0.8–1.5 mm, coil 3–5 tons, 1–2 shifts | Hydraulic (no coil car) | Hydraulic expansion for safe loading; motorized feed for consistent tension |
| 1.5–4.0 mm, coil 5–10 tons, 2–3 shifts | Hydraulic with coil car + press arm | Heavy coils need powered loading; press arm prevents overspooling |
| Any thickness, high volume, 3 shifts | Double-head hydraulic | Minimizes coil change downtime; payback through increased throughput |
| Multiple product lines sharing coil | Double-head with different widths | Stage different coil widths for different profiles |
Mandrel ID: Don't Get This Wrong
The decoiler mandrel must match the coil's inner diameter. Most Chinese mills supply 508 mm ID (20 inch) coil. Some international mills (particularly in Europe and India) use 610 mm ID (24 inch).
If your decoiler is 508 mm and you buy 610 mm ID coil, you need an adapter sleeve. The sleeve works but introduces wobble at higher speeds. If your decoiler is 610 mm and you buy 508 mm coil, the coil won't fit on the mandrel at all.
Specify the ID when ordering the decoiler, and verify that your steel supplier can consistently deliver that ID. If you buy from multiple suppliers with different IDs, order a dual-ID mandrel or adapter sleeves.
Safety Features Worth Paying For
A decoiler holding 5 tons of steel is a serious piece of equipment. These safety features are worth the cost:
- Automatic brake: Non-negotiable for any coil over 2 tons. Prevents overspooling when the line stops.
- Press arm (hold-down): Holds the outer coil end during threading. Prevents the end from whipping free when the strapping is cut.
- Coil car: Eliminates manual coil loading. The car lifts the coil from floor level and inserts it onto the mandrel. Prevents back injuries and dropped coils.
- Guard fence: Physical barrier around the decoiler. Prevents workers from walking into the rotating coil.
- Speed monitoring: Sensor that detects if the mandrel is rotating faster than the line is pulling (indicates brake failure). Triggers an alarm.
The decoiler is the least glamorous part of a roll forming line, but a failure there can be the most dangerous. Choose wisely, specify the safety features, and maintain the brake system regularly.
