Welded stainless steel instrumentation tube in grades 304L and 316L, from 6mm to 63.5mm OD with 0.4mm to 2mm wall thickness, to ASTM A269, with the tight OD and wall-thickness tolerances instrumentation fittings require.
Instrumentation tube does something most other tube applications don't: it connects directly to compression-style fittings — pressure gauges, transmitters, sensor lines — that seal against the tube's outer diameter itself, without a gasket in between. That single fact changes what actually matters in manufacturing this tube. Wall thickness and general corrosion resistance still matter, but OD consistency and ovality control matter more here than in almost any other application we supply, because even a small out-of-round or oversize section can prevent a proper seal or create a leak path that a welded assembly would never reveal in the same way.
We manufacture instrumentation tube in 304L and 316L — both low-carbon grades chosen for a clean, weld-friendly composition and reliable corrosion resistance in control and sensing applications — to ASTM A269, the standard most commonly specified for this use.
General welded tube going into a structural or welded assembly has some forgiveness built in — the weld itself accommodates minor dimensional variation. Instrumentation tube going into a compression fitting has no such forgiveness. The fitting's ferrule bites directly onto the tube's outer surface, and out-of-spec ovality or OD variation shows up immediately as a leak, not as a hidden defect.
| Finish | Description | Typically specified for |
|---|---|---|
| As-Welded | Mill finish — 2B surface, for applications that don't require surface finishing, or those that require additional finishing done at later stages | Applications that require any additional working on the tube and then finishing it, or applications that are purely industrial and don't need smooth surfaces |
| AP (Annealed & Pickled) | Standard mill finish — heat-treated and chemically cleaned | General instrumentation and control-line use |
| EP (Electropolished) | The smoothest finish we offer, removing microscopic surface irregularities | High-purity process lines, semiconductor, applications where interior cleanliness is critical |
| OD | 6mm to 63.5mm |
| Wall thickness | 0.4mm to 2mm |
| Grades | 304L, 316L |
| Standards | ASTM A269 |
| Finish | As-welded, AP, or EP |
304L and 316L are part of our 300 Series range — see 304/304L and 316/316L for full grade detail, or the series table for how these compare to other 300-series options.
Grade, size, standard, quantity — send what you have and we'll respond with availability, lead time and pricing.