Sanitary TIG welding on 304 or 316 stainless tubing is unforgiving — the difference between a clean weld and a sugared one is a few seconds of purge time and a few amps of heat input. Here is the setup we use on food, dairy and pharmaceutical jobs.
Purge Gas
- Gas: 99.997% pure argon, both shielding and purge.
- ID purge flow: 5–15 CFH depending on pipe diameter.
- Pre-purge time: long enough to reach <25 ppm O₂ at the joint — verify with an analyzer for BPE work.
- Purge dams: water-soluble paper for tee branches; inflatable dams for long runs.
Tungsten
- Type: 2% lanthanated (blue) or 2% ceriated (orange) — never thoriated for sanitary work.
- Diameter: 1/16" for tubing up to 1.5", 3/32" for larger.
- Grind: Pointed taper, 2× diameter long, dedicated stainless grinding wheel.
Amperage by Wall Thickness
Starting amperage on autogenous (no filler) sanitary tubing welds:
| Wall thickness | Amperage range |
|---|---|
| .049" (16 ga) | 35–55 A |
| .065" (14 ga) | 55–75 A |
| .083" (12 ga) | 75–95 A |
| .109" (10 ga) | 95–120 A |
Adjust based on position, fit-up and how much heat the part is sinking away. Always test on a coupon of the same heat of material.
Common Mistakes
- Insufficient pre-purge. Most "sugared" welds were started before the oxygen was actually displaced.
- Too much heat. Wide, blue, concave welds. Drop the amps and increase travel speed.
- Cross-contamination. Carbon-steel grinder near stainless = embedded iron, future rust. Dedicated tools only.
- No post-purge hold. Stop the gas too early and the weld oxidizes while still hot.
Need this work done in your plant?
We perform sanitary TIG welding on stainless process piping nationwide, with full documentation per ASME BPE and 3-A.