High Frequency Straight Seam Pipe Making Line — ZT Series Tube Mills

A straight seam pipe making line forms steel strip into tube and welds the longitudinal seam with a high-frequency current at the strip edges, without filler metal. The eight models published on this site run from the ZT-32 (7mm-25mm pipe) to the ZT-165 (50mm-165mm pipe), and the wall thickness covered by the series runs from 0.3 mm to 5.0 mm.

ZT series model range and specifications

The table below collects the pipe range, wall thickness and line speed published on each model page. It is sorted by the smallest pipe the model will run, so the models that cover a given size sit next to each other.

How to choose a model

Start from the pipe outside diameter and the wall thickness you actually run. The published ranges overlap on purpose: the ZT-25 (8-32 mm) sits inside the ZT-28 range (10-50.8 mm), and the ZT-50, ZT-60 and ZT-76 overlap between 30 mm and 76 mm. Where two models both cover your size, the difference is line speed and the equipment list rather than the pipe range.

Line speed separates the models more than diameter does. Five of the eight models are rated 30-100 m/min. The ZT-76 has the lowest minimum line speed in the range at 15 m/min, and the ZT-165 has the narrowest band at 30-50 m/min.

What the line consists of

The models are published with two equipment configurations. The smaller sizes are listed as a 13-unit line and the larger sizes as a 7-unit line; the unit lists below are the ones published on the model pages, reproduced here so the two configurations can be compared in one place.

13-unit configuration (ZT-25, ZT-28, ZT-32)

7-unit configuration (ZT-127, ZT-165, ZT-50, ZT-60, ZT-76)

Process flow

Uncoiling → Cutting and welding → cage accumulator → feeding → forming → HF welding → squeezing → deburring → water cooling → sizing → rough straightening → flying saw → checking and collecting → packing → storage.

The welding step itself is explained in more detail in [what is high frequency welding pipe machine](/posts/what-is-high-frequency-welding-pipe-machine).

Model pages in this range

Full specifications for each model: [ZT-32](/posts/high-frequency-straight-seam-pipe-making-line-model-zt-32), [ZT-25](/posts/high-frequency-straight-seam-pipe-making-line-model-zt-25), [ZT-28](/posts/high-frequency-straight-seam-pipe-making-line-model-zt-28), [ZT-50](/posts/high-frequency-straight-seam-pipe-making-line-model-zt-50), [ZT-60](/posts/high-frequency-straight-seam-pipe-making-line-model-zt-60), [ZT-76](/posts/high-frequency-straight-seam-pipe-making-line-model-zt-76), [ZT-127](/posts/high-frequency-straight-seam-pipe-making-line-model-zt-127), [ZT-165](/posts/high-frequency-straight-seam-pipe-making-line-model-zt-165).

Frequently asked questions

Which ZT model covers 50 mm pipe?

Six of the eight models cover 50 mm pipe: ZT-28 (10-50.8 mm), ZT-50 (19-76 mm), ZT-60 (25-80 mm), ZT-76 (30-90 mm), ZT-127 (32-127 mm) and ZT-165 (50-165 mm). The ZT-25 (8-32 mm) and ZT-32 (7-25 mm) stop below that size.

What is the wall thickness range of the series?

0.3 mm at the thin end, on the ZT-32, to 5.0 mm at the heavy end, on the ZT-165. Each model has its own band, listed in the table above.