Small-Diameter vs Large-Diameter Tube Mills: What Actually Changes from Φ5 mm to Φ630 mm

A Φ5 mm line and a Φ630 mm line are not the same machine with a bigger model number. Shafts get thicker, motors multiply, the floor plan grows, and the line adds stations the small line never needed. Here is what changes, and why.

Shaft and motor size: the first real jump

On the small end, the decorative stainless line runs shaft diameters from 40 mm (H) and 25/30 mm (V) on the YH-S40 up to 90 mm (H) and 60 mm (V) on the YH-90. Its main motors are single units from 5.5 kW to 30 kW, and its pipe range runs from Φ6–Φ31.8 mm to Φ114–Φ219 mm.
The industrial line uses the same shaft sizes end to end, but split main motors — 5.5+5.5 kW on the YH-40A (Φ5–Φ15 mm) up to 30+30 kW on the YH-90 (Φ133–Φ219 mm). The second motor is the practical signal: once the forming load and weld duty rise, one drive is no longer enough.
On the large-diameter line the shafts jump to 100–150 mm (H) and 70–110 mm (V). Every model runs twin motors, from 37×2 kW on the YH-100 to 95×2 kW on the YH-150.

The smallest large-line motor pair is already larger than the biggest motor on the decorative line. Wall range climbs with it: from 0.25 mm on the small stainless lines to 12.7 mm on the YH-120, YH-130 and YH-150.
If you want the small-end tables side by side, start with the decorative pipe tube mill and the industrial pipe tube mill.

The extreme ends, briefly

• Smallest bore: YH-G40A (smart SS line, Φ5.0 mm) and YH-40A (industrial line, Φ5 mm), both at wall from 0.25 mm.
• Largest bore: YH-150, Φ426–Φ630 mm, 150/110 mm shafts, wall to 12.7 mm.

The smallest bore is limited by strip thinness and guide tightness; the largest by shaft stiffness and the forming torque needed to bend thick strip. That is why shaft diameter and wall thickness move together in the tables.

Stations the large line adds

This is where the machines differ most.

The large diameter tube mill flow: hydraulic uncoiling → leveling, shear and butt weld → powered guide → forming and welding → internal seam flattening → enclosed seam grinding → in-line black annealing → sizing and straightening → automatic cutting → product storage.

Hydraulic uncoiling

Large coils are heavy and the strip is thick. A hydraulic uncoiler, combined with leveling and shear-and-butt welding, keeps the heavy coil flow continuous. The small lines list plain uncoiling; the industrial line adds nothing beyond that at the coil end.

Internal seam flattening

On large pipe, the inside weld bead has to be flattened in-line. The product data places it before enclosed seam grinding and black annealing. Note that the smart line (Φ5–Φ325 mm) also lists an internal seam levelling step, so this is not exclusive to the large line — but the large line pairs it with a heavier forming duty.

Enclosed seam grinding

A sealed, box-type grinding station contains dust and noise. On Φ630 mm pipe the grinding zone is large and exposed grinding would be a problem for the workshop, not just the finish.

In-line black annealing

Black annealing runs in-line and, per the product data, restores ductility in the weld zone before sizing. The small lines do not run black annealing: the smart line uses online bright annealing between primary sizing and final sizing instead.

Which one you need depends on the end use — bright annealed decorative tube versus industrial pipe that will be further processed.

Where the two ends meet: Φ219–Φ325 mm

One case confuses buyers. The smart stainless line's YH-100 covers Φ219–Φ325 mm at 2.0–8.0 mm wall, 100/70 mm shafts, 37×2 kW, 45×4.3 m footprint.

The large-diameter line's YH-100 covers the same diameter and wall range with the same shaft and motor figures, on a 43×4.2 m footprint. The parameter tables are identical.
The choice is downstream, not in the forming machine:

• Pick the smart line if you need online bright annealing, Ethernet remote service and weld current tracking — see smart stainless steel pipe line.
• Pick the large line if the pipe feeds industrial pipelines and needs internal seam flattening, enclosed grinding and black annealing.

Ask what the pipe becomes (pipeline, food plant, ventilation, decorative) before asking which model to buy.

Footprint comes first

Small lines fit into far less: from 20×1.1 m on the YH-S40 decorative model, with widths of 1.1–4.0 m across the decorative and industrial tables.
The smart line reaches 45×4.3 m on its YH-100. The large-diameter line starts at 43×4.2 m (YH-100) and reaches 60×5.8 m on the YH-150 — about 348 m² for the largest model, plus coil storage and product run-out.
Practical rule: measure your workshop length and width before asking for a layout drawing. If a 60 m length is not available, a long-line footprint will force a redesign of the plant, not the machine.

Quick comparison

Next step

Send your maximum pipe diameter, wall thickness and available shop floor length in meters. We will reply with the matching model row and a layout drawing so you can check the fit before budget.

You can start from the stainless steel tube mill overview or contact us.