Why duplex goes wrong — and how we control it
A duplex weld can pass visual inspection and dye-penetrant testing and still be the wrong metallurgy. Excess heat input or a high interpass temperature upsets the austenite–ferrite balance and can precipitate intermetallic phases; nitrogen loss from the root weakens pitting resistance. The defect is in the microstructure, so the controls have to be in the procedure:
| Risk | Control at HAIL |
|---|---|
| Phase imbalance from heat | Controlled heat input, written into the WPS |
| Overheating across passes | Controlled interpass temperature |
| Ferrite outside the specified range | Ferrite number verification on the weld |
| Nitrogen loss in super duplex roots | Nitrogen-backed purge gas for super duplex welds |
| Wrong material in the job | PMI and mill test certificate traceability on every plate and weldment |
Materials we fabricate
| Material | Typical service |
|---|---|
| SS 304 / 316 / 316L | Chemical and pharmaceutical equipment, process piping |
| Duplex 2205 | Chloride-bearing and seawater service |
| Super duplex 2507 | Severe chloride and seawater service |
| LTCS, SA 333 Gr.6 | Ammonia and cryogenic piping, with impact-tested weld procedures |
What we make in these materials
Pressure vessels, columns, drums and heat exchangers; pipe spools to ASME B31.3, B31.1 and B31.4; process skids; and precision stainless parts for rolling stock — including SS underframe parts, bogie brackets and gangway frames for railway and metro coaches. Pressure vessels can be built under the workshop’s ASME U-Stamp.
Testing and documentation
- Welders and procedures qualified to ASME Section IX — SMAW, GMAW, GTAW, SAW and FCAW.
- Welds made to 100% radiography quality, with radiography carried out by an approved NDT agency.
- In-house dye-penetrant testing, hydrostatic and pneumatic testing, and dimensional inspection with calibrated gauges and chart recorders.
- Weld maps, ferrite and PMI records, and dimensional reports with every job.
- Third-party inspection accepted: Lloyd’s, BV, TÜV, RINA and IBR.
How to get a job-work quote
Send the drawing and we will come back with a budgetary price and a slot. The fastest route is the form at the foot of this page, or WhatsApp the drawing to +91-95100-34854, or email it to info@hail.ltd. A useful enquiry tells us:
- the drawing, with material grade and plate thickness
- quantity, and whether the job repeats
- whether material is free-issue or for us to procure
- the code or standard, and who inspects (your QA, or a TPI agency)
- the date you need it despatched
Who sends us this work
EPC contractors and equipment manufacturers with a duplex or stainless package and a schedule that cannot absorb a weld repair; process licensors who need a fabricator that will follow their procedure rather than improvise; and rolling-stock suppliers who need precision stainless parts to tight tolerances. If the job has been turned down elsewhere because of the material or the size, that is a good reason to send it to us.
Frequently asked questions — duplex and stainless steel fabrication job work
Do you fabricate duplex and super duplex stainless steel?
Yes — duplex 2205 and super duplex 2507, with controlled heat input, controlled interpass temperature, ferrite number verification and nitrogen-backed purge gas for super duplex welds.
How do you make sure the right material is used?
Every plate and weldment carries PMI and mill test certificate traceability, and ferrite is verified on duplex welds. The records go to you with the job.
Do you fabricate SS 316L for pharmaceutical and chemical equipment?
Yes. SS 304, 316 and 316L are routine at the Kalol workshop for chemical and pharmaceutical equipment and process piping.
Is radiography done in-house?
Welds are made to 100% radiography quality; radiography itself is carried out by an approved NDT agency. Dye-penetrant, hydrostatic, pneumatic and dimensional testing are done in-house.
Can you build ASME U-stamped pressure vessels as job work?
Yes. The workshop operates under ASME U-Stamp certification for pressure vessels, with ASME Section IX qualified welders and procedures.
Do you work in low-temperature carbon steel?
Yes — LTCS to SA 333 Gr.6 for ammonia and cryogenic piping, with impact-tested weld procedures.