A spiral-welded tank wagon has a tank shell formed from steel strip wound into a cylinder and joined by one continuous helical seam, the method used to make large-diameter line pipe. Erciyas Rail introduced the technology to tank wagons in 2022 together with its sister company Erciyas Steel Pipe. In the current range, the Zags 117 m³ LPG tank wagon is the model built this way.
How a conventional tank shell is built
A conventional tank wagon shell is assembled from rolled plate sections. Each section is closed with a longitudinal seam, and the sections are joined to one another with circumferential seams. Wherever a longitudinal seam meets a circumferential seam, the two welds cross and form a T-joint.
T-joints concentrate weld metal, residual stress and changes in geometry in one place. That is why inspection plans pay particular attention to them, and why each one adds to the non-destructive testing (NDT) work needed before and during service.
What spiral welding changes
Spiral welding forms the shell from a continuous strip wound at an angle, so the seam runs as a single helix along the whole length of the tank. There are no circumferential cross seams between shell sections, and the number of points where seams intersect falls sharply.
Erciyas Rail reports the following results for its spiral-welded tanks compared with conventional multi-joint shells. The figures come from the company's own engineering data.
| Measure | Result |
|---|---|
| Inspection points (T-joints) | about 71% fewer |
| Fatigue life under cyclic stress | 13% longer |
| Tank production | 20 times faster |
| Seam inspection | 100%, by ultrasound and X-ray |
| Service life | about 4 years longer, on a 30-year design life |
| Cross seams along the tank | none |
Lamination control is applied both to the incoming plate and to the finished tank. Because the tank is no longer the slowest step in the line, production planning for a series of wagons becomes simpler.
Why the pipeline record matters
Spiral welding is not new as a process. Large-diameter spiral-welded line pipe has been used for decades in oil and gas transmission lines, where seams face pressure cycling over long service lives. Erciyas Steel Pipe manufactures such line pipe, and the tank wagon process builds on that production experience rather than starting from zero.
The company showed a cut-open spiral-welded tank at InnoTrans 2022 in Berlin, and exhibited a four-axle 117 m³ LPG tank wagon at InnoTrans 2024.
The Zags 117 m³ LPG tank wagon
The Zags 117 is designed for LPG transport across European rail networks. Its main values:
- Capacity 117 m³, maximum payload 57.5 t, tare weight 32.5 t, axle load 22.5 t
- Length over buffers 18,000 mm, tank outside diameter 3,100 mm
- Tank code P27BH, tank material P460NL, maximum operating and test pressure 27 bar
- Tank working temperature -25°C to +40°C
- Y25Ls-K bogies, 920 mm wheels, KEf-GP-A brake with K composite blocks
- Hydraulic valves, rapid charging and a design compatible with 14 m weighbridges
The full specification is on the Zags 117 product page.
Which standards apply
As a pressure tank wagon for a dangerous good, the Zags 117 falls under RID, the regulations for the international carriage of dangerous goods by rail, which also define its tank code. Its pressure tank is covered by EN 14025, the standard for metallic pressure tanks for dangerous goods, and wagon-level requirements come from TSI WAG. Erciyas Rail holds EN 14025 and EN 15085-2 certification for tank and railway welding work. The certifications page lists every certificate and the compliance of each model.
Frequently asked questions
Does spiral welding change how the tank is approved?
The tank is designed within the same RID tank code system as any other pressure tank, P27BH in the case of the Zags 117. Spiral welding is the method used to form and weld the shell; type approval follows the normal route for the wagon and its tank.
Which Erciyas Rail tank wagon is spiral-welded?
The Zags 117 m³ LPG tank wagon is the spiral-welded model in the current range. For other capacities or cargoes, the engineering team can assess the options during quotation.
Where can I get technical data?
Every value is published on the Zags 117 product page. The full product catalogue is available as a PDF on the downloads page, and the quote configurator collects your quantity and delivery date.