Welded Stainless Steel & Alloy Instrumentation Tubing

This instrumentation tube is welded and drawn, produced in stainless and nickel/CRA alloys, and it's fitting-ready to ASTM A269. Available in imperial and metric, heat-traceable throughout. We serve US customers, with delivery in 6-8 weeks.

Reviewed by the Crestflo Engineering Team

What Is Welded Tubing?

Welded tubing starts as small-diameter tube for fluid systems. It's made by rolling flat strip into a cylinder and joining the edges with a continuous longitudinal fusion weld. For instrumentation service, the tube is then cold-drawn over a mandrel and bright-annealed, which leaves it soft, dimensionally accurate, and ready to fit. Crestflo supplies welded tube in stainless steel and nickel or corrosion-resistant alloys, in both imperial and metric sizes, built to ASTM A269 and ASTM A249. On this page, "welded tubing" refers specifically to small-bore stainless-steel and nickel-alloy tube used in instrumentation and fluid systems. It doesn't include structural or ornamental tube, mechanical drawn-over-mandrel (DOM) tube, or electric-resistance-welded pipe used for framing.

Welded Tube Designations: ERW, Welded-and-Drawn, TIG & Laser-Welded

Crestflo runs into this product under a dozen different names across the industry, though it's always the same thing: a longitudinally welded fluid-system tube. Buyers ask for welded tube, welded steel tube, welded stainless tube, welded stainless steel tubing, or stainless steel welded tubing. Some just say "welded steel tubing", but in that context it always refers to the stainless and nickel/CRA product, never carbon-steel line pipe. Then there are the process-led names. ERW tubing is one, short for electric resistance welded tubing. TIG-welded and laser-welded tube fall in here too, along with as-welded tube. When the weld gets followed by cold reduction and re-annealing, the terms shift to welded-and-drawn (W&D) or double-annealed tube. Finish drives its own vocabulary as well, giving you bright-annealed welded tube. Whatever term shows up on a print, Crestflo quotes the equivalent instrumentation grade, condition, and spec.

How Welded Instrumentation Tube Is Made: Weld, Draw & Bright-Anneal

Production kicks off with a precision-slit strip of the chosen alloy, roll-formed and joined edge-to-edge by a continuous longitudinal weld (typically high-frequency, TIG, or laser). For instrumentation work, the as-welded tube then gets cold-drawn over a plug or mandrel to refine the outside diameter, wall thickness, and concentricity, then bright-annealed under a protective atmosphere. That relieves weld and drawing stresses and brings back a soft, ductile grain structure. This welded-and-drawn route produces tube whose weld zone has been worked and re-annealed to properties close to the parent metal. Structural ERW or DOM tube is a different animal entirely, built for strength rather than sealing. Crestflo manufactures instrumentation tube; it doesn't resell mill product. That's why weld process, draw schedule, and anneal are all controlled to whatever tolerance the fitting demands.

Welded Tube Grades & Alloys: 304L, 316L, Duplex, Inconel, Hastelloy & Titanium

Welded instrumentation tube comes in the full stainless, duplex, nickel, and titanium range. Each grade links out to its metallurgy page and to a dedicated tube page with grade-specific detail. Compositions follow the applicable ASTM/UNS standard. In the US, the material scope centers on stainless and corrosion-resistant alloys; brass, copper, and aluminum aren't offered.

Crestflo's alloy tubing hub also covers additional nickel and super-austenitic grades.

Welded Tube Sizes, OD & Wall: Imperial & Metric

Welded instrumentation tube comes in both imperial, fractional-inch, and metric small-bore sizes, so one spec can cover US and international drawings alike. Outside diameter, wall thickness, and tolerance follow the tables in ASTM A269 (and A249 where applicable) for whatever grade and condition you order; the values sit within the applicable standard but can be tailored to what you need. Check Crestflo's tubing size chart for the full OD, wall, and pressure-lookup tables. Wall thickness isn't picked on its own; it's chosen alongside pressure and fitting requirements.

Annealed Condition, Hardness & Compression-Fitting Compatibility

For a compression fitting to seal, the tube must be softer than the ferrule so the ferrule can bite and swage into the tube wall. Instrumentation welded tube is therefore supplied fully annealed / bright-annealed, which is why the welded-and-drawn route matters, the final anneal restores the ductility a leak-tight make-up depends on. Because Crestflo also manufactures the mating compression tube fittings, qualified to ASTM F1387, the tube and the fitting are specified as one sealing system rather than sourced blind from separate suppliers. Hardness is controlled to the annealed range of the governing standard for the grade.

Surface Finishes: Bright-Anneal, Passivation & Electropolish

Welded tube comes bright-annealed as standard, with passivation applied to strip free iron and rebuild the passive chromium-oxide layer. For high-purity and ultra-clean service, an electropolished (EP) internal finish is also available. Crestflo covers it in full on the electropolished tubing page, where surface-roughness targets are spelled out per the applicable SEMI/ASME BPE standard on the RFQ. Finishes get selected by service, and they're customizable to whatever the requirement calls for.

Welded Tubing Pressure Rating & Weld-Joint Efficiency (ASME B31.3)

The allowable working pressure of welded tube isn't one fixed number. It's calculated from the outside diameter, wall thickness, the alloy's allowable stress (S), a weld-joint quality factor (E or W), and the temperature coefficient (Y), all per ASME B31.3. The joint-quality factor reflects how the weld was made: as-welded tube gets a reduced factor, but welded-and-drawn (double-annealed) tube can qualify for a higher one under the code, since the weld has been worked and re-annealed. Crestflo hands back the code-calculated rating alongside your quoted size, grade, and condition. Values follow the applicable standard and can be tailored to your requirement.

Welded vs Seamless Instrumentation Tubing: Which to Specify

Welded tube and seamless tube differ in how the body gets formed, not in whether either one can handle instrumentation duty. For most instrument hook-up, impulse, and sensing lines, fully annealed welded-and-drawn tube in the right grade holds up just as well as seamless. Seamless earns its place only at the highest pressures, or when a project spec or code calls for a seamless product outright. The table below is the decision short-list. For the seamless product itself, see Crestflo's seamless instrumentation tubing.

A quick note on what falls outside this scope: drawn-over-mandrel (DOM) tube is a mechanical or structural product, and welded pipe is its own separate product class. Neither one qualifies as an instrumentation fluid-system tube. For high-pressure bite-type or DIN 2353 tube, look at hydraulic tubing. For a broader overview, instrumentation tubing is the place to start.

Standards Conformance: ASTM A269, A249 & A213

Most welded austenitic stainless instrumentation tube ships under two specifications: ASTM A269, which covers seamless and welded austenitic stainless tubing for general service, and ASTM A249, which covers welded austenitic tube for boiler, superheater, heat-exchanger, and condenser service. ASTM A213 comes up here for one reason: contrast. It's a seamless boiler/heat-exchanger specification, and it doesn't cover welded tube at all. Nickel-alloy welded tube follows whichever ASTM B-series specification applies to that particular alloy. Crestflo carries the standard approvals for this product type, and conformance is stated against the current edition of the governing standard.

Certifications, Traceability & Testing for Welded Tube

Every length carries a heat/lot number and ships with an EN 10204 material test certificate: MTC 3.1 as standard, 3.2 on request. Crestflo holds ISO 9001 / 14001 / 45001 certification, plus PED certification. Welded tube undergoes the non-destructive weld examination A269/A249 requires, either eddy-current or hydrostatic testing, along with flattening, flaring, and reverse-flattening tests, positive material identification (PMI), and in-house non-destructive testing. Destructive testing happens at ISO/IEC 17025-accredited laboratories, and third-party inspection is available on request. For sour service, welded tube comes in NACE MR0175 / ISO 15156-compliant alloys. Specify the service, and we'll quote the qualifying grade. Full traceability detail is on the traceability page.

Welded Instrumentation Tubing Products & Request a Quote

Welded tube gets quoted by grade, OD, wall, condition, finish, spec, and certificate level to build the RFQ line. Ready stock covers the standard items. Specials don't ship off the shelf; they're made to order, 6-8 weeks out. Standard product is Indian in origin, though US and European melt is available on request, with full material traceability. Datasheets and CAD go out to customers on request as well. To move a specification forward: request a quote, request a sample, or open a distributor or OEM / private-label inquiry. Crestflo's US sales team is reachable at sales@crestflousa.com or +1 346 594 9005, out of Houston, TX.

Why Crestflo for Welded Stainless & Alloy Tubing

Crestflo is the instrumentation division of an export house that's been in business for four decades, recognized by the Government of India, with a delivery track record across the Middle East and now serving the US market. On welded tube, the advantages stack up fast. Lead time runs 6-8 weeks, against the 20-plus weeks you'd wait on from the majors. Sizing comes in both imperial and metric. The alloy range runs stainless through exotic, spanning 316L to Hastelloy C276. Welded-and-drawn tube is engineered to seat in Crestflo's own F1387-qualified compression fittings. Minimum order quantities stay small, and private-label options are available. Every length ships with heat-number traceability and an MTC. We Engineer Confidence.

Welded Tubing FAQ

Related Tubing, Materials & Standards

• All instrumentation tubing, the tubing hub
• Seamless instrumentation tubing, the seamless counterpart
• Welded tube size & wall chart
• Electropolished / high-purity tube
• Nickel-alloy tubing
• ASTM A269 standard · ASTM A213, its seamless counterpart · EN 10204 MTC
• Compression tube fittings, the mating F1387-qualified system