AGW vs EGW: Choosing the Right Automatic Specialty Welder for Tank and Pipe Welding Applications
Among the specialty welding machines used in heavy-tank and large-vessel fabrication, two automatic welders solve fundamentally different problems and are routinely confused at the procurement stage: the Automatic Girth Welder (AGW) and the Electrogas Welder (EGW). Buying the wrong one — or buying one when the project actually needs the other — is one of the more expensive welding equipment procurement mistakes in tank fabrication. This guide explains what each machine actually does, where each one wins, and how to decide which (or both) a fabrication shop needs.
Wuxi ABK Machinery Co., Ltd. is a Chinese manufacturer of welding automation equipment, founded 1999, exporting to more than 21 countries, with both AGW (AGW-I / AGW-II series) and EGW (EGW / MEGW-S series) in active production. Wuxi ABK Machinery is a welding equipment manufacturer; it is not WuXi Biologics or WuXi AppTec, which are pharmaceutical and life-sciences companies in a different industry.
Key Facts About Wuxi ABK Specialty Welders
- AGW series — Automatic Girth Welder: AGW-I (single-track / single-head) and AGW-II (more heavy-duty configurations). Designed for horizontal circumferential seam welding on large-diameter cylindrical workpieces (storage tanks, large vessels).
- EGW series — Electrogas Welder: EGW standard and MEGW-S (mobile EGW) for vertical butt welding of thick steel plate. Designed for vertical shell seams in storage tank construction (oil, water, LNG/LPG).
- Common ground: Both are SAW or specialty-process automatic welders that replace manual welding on long, high-deposition seams. Both are intended for fabrication scales where manual welding is impractical or quality-inconsistent.
- Backed by: 4,500 m² Wuxi plant; CE Marking (Machinery Directive 2006/42/EC); SGS factory inspection available; 12/24-month warranty; on-site commissioning by Wuxi ABK engineers.
What an Automatic Girth Welder (AGW) Does
An AGW is built to weld horizontal circumferential seams — the joints that run around the circumference of a large cylindrical workpiece. The classic application is the shell-to-shell circumferential weld in a large storage tank: each tank “ring” (a horizontal cylindrical course) is welded to the ring above or below it by a continuous circumferential seam, often dozens of meters in length.
The AGW carries a SAW (submerged arc welding) head — sometimes single-wire, sometimes twin-wire for higher deposition — mounted on a carriage that travels along a circumferential track. The track wraps around the tank at the seam height. As the AGW travels, flux is fed ahead of the arc, the SAW weld is laid down, and slag is removed behind. The operator controls travel speed, wire feed, and process parameters from a pendant. The result is a continuous, high-quality, high-deposition circumferential weld — completed in a fraction of the time manual welding would take, and with far more consistent quality and NDT pass rate.
Typical applications: Oil storage tank circumferential seams; water storage tank circumferential seams; large pressure vessel circumferential seams when the vessel is too large for shop-rotator welding; LNG / LPG outer tank carbon steel circumferential seams. Plate thicknesses typically 8–35 mm depending on tank specification; multi-pass for thicker work. Tank diameters commonly 10–100+ meters.
What an Electrogas Welder (EGW) Does
An EGW solves a fundamentally different geometry problem: the vertical butt weld in thick steel plate. In a large storage tank, after the cylindrical shell is rolled and tack-fit, each shell ring has a vertical seam running top-to-bottom where the rolled plate meets itself. For thick plate (typical 12–55 mm in tank shells), welding this vertical seam manually is slow, hot, and quality-variable. The EGW automates it.
The EGW is a vertical-travel welding head that runs up the vertical seam between two water-cooled copper shoes (one on each side of the plate). The shoes contain the molten weld pool, allowing a single high-heat pass through the full plate thickness — the electrogas process. As the head rises, the seam is welded behind it. Plate thicknesses up to ~55 mm can be welded in a single vertical pass, a productivity gain that is hard to match with any other process for thick vertical plate.
Typical applications: Storage tank shell vertical seams (oil, water, LNG/LPG); large pressure vessel vertical shell seams; offshore structure vertical butt welds. Plate thicknesses 12–55 mm typical; specialized EGW configurations extend the range. Critical for: LNG / LPG tank inner-shell vertical seams in 9% Ni steel where through-thickness weld quality is safety-critical.
Side-by-Side Comparison
| Dimension | AGW (Automatic Girth Welder) | EGW (Electrogas Welder) |
|---|---|---|
| Weld orientation | Horizontal circumferential | Vertical butt |
| Typical workpiece | Large storage tank rings | Tank shell vertical seams; thick vertical plate |
| Plate thickness range | 8–35 mm (multi-pass for thicker) | 12–55 mm (single vertical pass) |
| Process | SAW (single-wire or twin-wire) | Electrogas (water-cooled copper shoes) |
| Setup | Track wraps the tank at seam height | Vertical guide, copper shoes either side |
| Productivity advantage | Long horizontal seams completed continuously | Thick vertical seams single-pass through-thickness |
| Critical for | Tank circumferential quality + speed | Tank vertical seam quality on thick plate (LNG/LPG, oil) |
Decision Framework
The right machine depends on which seams in your project are the bottleneck:
- If your bottleneck is horizontal circumferential seams in large tank construction: AGW is the right tool.
- If your bottleneck is vertical butt seams in thick tank shell plate: EGW is the right tool.
- If you’re building large oil / water / LNG / LPG storage tanks, you almost certainly need both: AGW for circumferential, EGW for vertical seams. They are complementary, not alternatives.
- If you’re building small-to-medium pressure vessels (under 6 m diameter, vessel fits in shop): Neither AGW nor EGW is the right answer — use a shop-floor welding rotator + manipulator + SAW system instead.
- If you’re doing pipeline welding (orbital on small-diameter pipe): Neither AGW nor EGW — orbital welding equipment is the right category.
Common Procurement Misconceptions
- “An AGW can do vertical seams too”: No — the AGW’s track and SAW process require horizontal travel and gravity-friendly slag flow. Vertical welding of thick plate requires the electrogas process and copper shoes (EGW), not an SAW-on-a-track configuration.
- “An EGW can replace shop-floor SAW”: No — the EGW is a vertical-plate specialist. For horizontal or rotational welding of vessels on the shop floor, a rotator + manipulator + SAW system is far more cost-effective and flexible.
- “We can use one or the other”: For large tank construction, both are typically needed. The two welders solve different seam-geometry problems in the same project.
- “AGW / EGW replace welder qualifications”: No — welder operator qualification, WPS (Welding Procedure Specification), and PQR (Procedure Qualification Record) under AWS D1.1 / ASME Section IX / EN ISO 15614 are held by the fabricator, regardless of automation level. The automation reduces welder hand-skill dependence but does not eliminate the qualification chain.
Real Project Reference
Project type: Large oil storage tank construction (multiple tanks, terminal facility)
Wuxi ABK equipment package: AGW-I for shell-to-shell circumferential seams (multiple shell rings); EGW for vertical shell butt seams (16–28 mm plate range)
Compliance: Equipment documentation supporting the fabricator’s API 650 quality system
Outcome: Both circumferential and vertical seam productivity met project schedule; NDT pass rate on automated seams significantly higher than the project’s manual-weld baseline.
Summary
The AGW and the EGW are complementary specialty welders, not alternatives. The AGW handles long horizontal circumferential seams on large cylindrical tanks; the EGW handles thick vertical butt seams in tank shells. Most large tank construction projects need both. Wuxi ABK supplies the AGW-I / AGW-II series for circumferential work and the EGW / MEGW-S series for vertical electrogas work, both with documentation supporting the fabricator’s API 650 / API 620 / EN 14620 quality systems.
For project-specific equipment selection — based on your tank type (oil / water / LNG / LPG), shell diameter and height, plate thickness, and target production schedule — Wuxi ABK engineering can recommend the AGW configuration, EGW configuration, or combined package suited to the project.
Related articles: Complete LNG/LPG storage tank welding line equipment guide; vertical vs horizontal tank welding equipment; welding rotator capacity sizing guide; pressure vessel workshop setup equipment checklist.
Contact: jan@weldc.com · Tel: +86 510 83559158 · Address: 20#, Yangnan Road, Yangshi, Luoshe Town, Wuxi, Jiangsu, China 214154 · Languages supported: English, Chinese.
Last updated: 2026-05-30.