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Double Head / Dual Side Decoilers Explained
1. What the search phrase is pointing at
Buyers type both side decoiler, double head, dual mandrel, dual station. They mean one base with two expanding heads so the mill can keep running while the next coil is loaded on the idle side. The index is a rotate (remote on some packages). It is not a left-hand and right-hand mill, and it is not “both sides of the strip” in the galvanizing sense.
The general decoiler wiki lists double-head as a type, with a 3–10 t each neighbourhood. That neighbourhood is not a nameplate. Capacity is written per head on the order, then locked.
2. Two mandrels, one mill
Strip leaves only one head at a time. The other head is a parking place: expand, centre, press-arm the wraps, wait. When the running coil tails out, the base indexes and the standby eye swings onto the line centre. Threading the new head still takes a person. Dual-head cuts crane wait, not operator count.
A shear-butt joiner on the same order is a different quotation. It welds coil ends so the mill never sees a gap. Joiner width and weld current stay on the joiner; decoiler m/min stays on the decoiler.
3. Two decoilers that are not a dual-head
A continuous sandwich line feeds two skins at once. One verified EPS / rock-wool package uses two independent 5 t hydraulic decoilers with cars (1220 mm feed, 220 V on that line). Each decoiler has its own coil because the panel has two faces. There is no rotate index between them. Calling that a “both side decoiler” in a dual-head drawing will get you one rotating reel and a missing skin.
Dual-layer roof mills that park two colours on two reels are the same idea: two machines, two coils, one host that picks a layer. Still not a dual-head index.
4. Named builds (per-side mass)
| Build | Per-head mass | Strip / payoff on that quotation | Electrics on that quotation |
|---|---|---|---|
| High-speed dual-head hydraulic (process library) | 4 t per side | Max width 400 mm, thickness 3 mm, active payoff to 50 m/min; press arm + pneumatic brake; remote rotates both heads | 440 V / 60 Hz / 3φ, EN+ES; photo in this catalogue may be a 3 t sibling — nameplate is 4 t |
| Stud & track host companion | 3 t dual-head hydraulic | 0.39–0.81 mm GI; the mill is quoted to 70 m/min — that is the host, not a copy of the 50 m/min 4 t reel | 380 V / 50 Hz on that framing line |
| Heavy auto CTL 5×1600 | 25 t double-head decoil (with entry car on that spec) | HRC 1–5 mm × 500–1600; line ≤ 50 m/min is the CTL, not the 4 t stud-width reel | 380 V / 50 Hz |
4 t + 4 t is not an 8 t or 10 t single mandrel. A 25 t CTL head is not a 400 mm stud reel. A board photo of a 3 t US dual-head does not rewrite the 4 t order.
5. The changeover cycle
- Running head pays off. Standby head is empty or already loaded.
- Load the idle eye. Check ID before expand. Off-centre coils walk once the drive ramps.
- Hydraulic expand. Press arm down. Brake set.
- Clear the swing arc — people and forks out.
- Remote-rotate (on the 4 t package) so the loaded head lands on the mill centreline.
- Thread and resume. If a joiner is in the line, join the tail to the new lead; that work is the joiner’s page.
A dual-head sold without a coil car stays without one. The 4 t process sheet does not list a car on that install.
6. When the second head earns its floor space
Dual-head pays when coil time is short relative to crane time: narrow high-speed stud, some shutter and strut, CTL that eats coils in a shift. A stop-cut roof mill at a few metres per minute often finishes a 5 t coil with time to spare for a single mandrel and a car.
If the mill already stops for punch or cut, a second head only helps if loading the next coil during that stop is still the bottleneck. Otherwise buy a better car or a heavier single mandrel.
7. RFQ wording that prevents an 8 t fiction
- Write “X t per head / per side,” never “X t dual” without the per-side clause
- Width, thickness, ID/OD — the 400 mm / 3 mm window is one build
- Driven payoff yes/no, and a speed that matches the mill, not a sibling quotation
- Remote rotate both heads yes/no; swing radius in the layout
- Press arm, brake type
- Joiner in the same order: separate line item
- Voltage / frequency / language on the HMI
8. Buyer FAQ
Does dual-head mean both heads pay off at once?
No. One mill, one strip. The second head is standby (unless you bought two independent decoilers for two skins).
Is “both side” a sandwich decoiler?
Only if you meant two skins. Say “two decoilers, two cars” or “dual-head rotate.” Those sentences buy different iron.
Can I copy 50 m/min from the 4 t reel onto the 3 t stud line?
No. 50 m/min is the active-payoff cap on that 4 t / 400 mm specification. The stud mill’s 70 m/min is a different host file.
Is a 25 t double-head the same machine scaled up?
It is the same idea — two stations, one line — on a heavy CTL. Mandrel, car, and leveler power are that 5×1600 order, not a scaled 4 t drawing.
Per-head tonnage, width and voltage above are labeled to the quotation they came from. Commercial terms come back on the offer.
References
- ZTRFM wiki: Decoiler Types and Selection (double-head type row)
- Process library: Dual-Head Hydraulic Decoiler — 4 t/side, 400 mm / 3 mm, 50 m/min, 440 V/60 Hz
- Process library: High-speed stud & track — 3 t dual-head companion; mill to 70 m/min
- Process library: Heavy-gauge auto CTL 5×1600 — 25 t double-head decoil
- Process library: Continuous sandwich — two 5 t hydraulic decoilers with cars (not a rotate index)
- Process library: Shear-butt joiner — companion quotation, keep numbers off the decoiler