Stainless Steel & Alloy Tubing for Instrumentation & Fluid Systems
Stainless steel tubing is round, OD-sized metal tube that carries process fluid or gas between components and seats into compression tube-fitting ferrules, forming a leak-tight, make-and-break joint. Crestflo supplies seamless and welded stainless steel tubing in 304/304L, 316/316L and 904L, plus higher alloy tube in duplex, super duplex, 6Mo, nickel and titanium grades. Sizes come in both imperial and metric, built to ASTM A269 and ASTM A213. Every part carries a heat number, backed by an EN 10204 mill test certificate. "We Engineer Confidence." Request a quote.
Here, "tubing" means round stainless-steel and alloy instrumentation and fluid-system tube, OD-sized for compression and tube-fitting connections. It is not oilfield coiled tubing for downhole well intervention, not structural or ornamental square tube, and not pipe specified by nominal pipe size (NPS) and schedule.
Also Known As: SS Tubing, Instrument Tube & OD Tube
Buyers and specifiers know this same product under many names, and stainless steel tubing suppliers list it accordingly. Most commonly it's called stainless steel tube, stainless tubing, tubing stainless steel, SS tubing or s.s. Tubing. In instrumentation and analytical work, the terms shift to instrument tubing, instrumentation tubing or stainless steel instrument tubing. Construction gives it two more labels: seamless stainless steel tubing on one hand, welded (or welded-and-drawn) tubing on the other. Grade is where the naming really multiplies. There's 304 stainless steel tubing, 316 or 316L stainless steel tubing, and 904L tubing. Duplex 2205 tubing sits alongside super duplex 2507 or Zeron 100 tubing, plus 254 SMO or AL-6XN tubing. Nickel-alloy tube covers Inconel, Incoloy, Monel (including Monel K500) and Hastelloy (including Hastelloy C-22) tubing. Standards add yet another layer: it's specified as ASTM A269 tubing, with SA-269 as the boiler-code equivalent, and as ASTM A213 tubing.
How to Specify Stainless Steel Tubing: The Four Axes
Four axes settle a tube order. Pin down each one and the tube is fully specified. Below, each axis links to the page that holds its details. Values follow the applicable ASTM standard, though they can be adjusted to what's needed.
| Axis | Options | Where to go |
|---|---|---|
| Construction | Seamless; welded-and-drawn | Seamless tubing · Welded tubing |
| Material grade | 304/304L, 316/316L, 904L, duplex, super duplex, 6Mo, nickel alloys, Ti Gr2 | Tubing materials |
| Size (OD × wall) | Imperial 1/8″–1″ and metric 6–12 mm common; standard walls | Tubing size chart |
| Standard | ASTM A269, A213, A249, A789; ASME B31.3 for pressure | ASTM A269 · ASTM A213 |
Stainless Steel Tube Attributes at a Glance
| Attribute | Value (per applicable standard; customizable to requirement) |
|---|---|
| Product family | Round stainless-steel and alloy tube for instrumentation, hydraulic and fluid-system service |
| Construction | Seamless; welded (welded-and-drawn) |
| Stainless grades | 304/304L, 316/316L, 904L |
| Higher alloys | Duplex 2205, super duplex 2507, 254 SMO, AL-6XN, Alloy 20, Inconel, Incoloy, Monel, Hastelloy, Nickel 200/201, Titanium Gr2 |
| Common OD | 1/8″, 1/4″, 3/8″, 1/2″, 5/8″, 3/4″, 1″ and 6, 8, 10, 12 mm |
| Common wall | 0.028″–0.083″ for instrument service |
| Units | Imperial and metric |
| Condition | Instrument-grade tube typically fully annealed for bending and coning; guidance ≤ HRB 80 |
| Finish | Material finish; passivation; electropolish (EP); oxygen/UHP cleaning |
| Working pressure | A function of OD × wall × grade allowable stress per ASME B31.3, no single blanket rating |
| Traceability | Heat/lot number on every part; EN 10204 MTC 3.1 standard, 3.2 on request; PMI |
| Origin | Indian origin; US / European melt available on request, with full material traceability |
Seamless vs Welded Stainless Steel Tubing
Both are built to austenitic tube standards, and both accept a compression fitting the same way. Seamless tube is drawn without a longitudinal weld. That makes it the default pick where you need maximum integrity for higher-pressure or critical service. Welded-and-drawn tube, by contrast, is formed from strip, seam-welded, then cold-drawn; it's dimensionally consistent and cost-effective for general instrument and fluid-system work. Crestflo supplies both to ASTM A269, A213 and A249.
| Attribute | Seamless tube | Welded-and-drawn tube |
|---|---|---|
| Method | Hollow drawn, no seam | Strip formed, seam-welded, cold-drawn |
| Typical use | Higher-pressure, critical, sour or cyclic service | General instrument and fluid-system service |
| Standard | ASTM A213 / A269 | ASTM A249 / A269 |
Not sure which to pick? Take a look at the deep dives on seamless stainless steel tubing and welded stainless steel tubing before deciding.
Stainless Steel Tubing Materials: 304, 316/316L, Duplex & Nickel Alloys
Grade selection tracks the service conditions: chloride level, temperature, and whether the medium runs sour. Crestflo covers each grade in depth on its material pages and offers it only in instrumentation forms: tube, fittings, and valves. Nickel-alloy and 6Mo tube sit together on the alloy tubing page. For sour service, selection draws on NACE MR0175 / ISO 15156 compliant alloys.
| Grade | Family | Typical service | Material data |
|---|---|---|---|
| 304 / 304L | Austenitic stainless | General instrument, air, water | 304/304L |
| 316 / 316L | Austenitic stainless | Standard process, marine-adjacent, chloride | 316/316L |
| 904L | Super-austenitic | Sulfuric and dilute acids | 904L |
| Duplex 2205 | Duplex | Chloride stress-corrosion resistance | Duplex 2205 |
| Super duplex 2507 | Super duplex | Seawater, high-chloride, higher strength | Super duplex 2507 |
| 254 SMO / AL-6XN | 6Mo super-austenitic | Seawater, bleach, offshore | 254 SMO · AL-6XN |
| Alloy 20 | Nickel-iron-chromium | Sulfuric-acid service | Alloy 20 |
| Inconel 625 / 825 | Nickel | High temperature, sour, corrosive | Inconel 625 · Inconel 825 |
| Monel 400 | Nickel-copper | Hydrofluoric acid, seawater | Monel 400 |
| Hastelloy C-276 | Nickel-moly-chromium | Aggressive chemical, wet chlorine | Hastelloy C-276 |
| Titanium Gr2 | Titanium | Seawater, oxidising, chloride | Titanium Gr2 |
Stainless Steel Tubing Sizes: OD, Wall & Imperial/Metric
Instrument tube gets specified by its actual outside diameter and wall thickness, given in both imperial and metric units. Common ODs run from 1/8″ up to 1″ (or 6 to 12 mm), in standard wall thicknesses. The full OD by wall matrix, complete with weight and metric equivalents, sits on Crestflo's tubing size chart. Working pressure isn't a single figure, though. It gets calculated from OD, wall thickness and grade allowable stress per ASME B31.3, which means it's stated per size and grade instead of as one blanket rating.
| Imperial OD | Nearest metric OD | Common walls |
|---|---|---|
| 1/8″ | 3 mm | 0.028″, 0.035″ |
| 1/4″ | 6 mm | 0.028″, 0.035″, 0.049″ |
| 3/8″ | 10 mm | 0.035″, 0.049″, 0.065″ |
| 1/2″ | 12 mm | 0.035″, 0.049″, 0.065″, 0.083″ |
| 3/4″ | 18 mm | 0.049″, 0.065″, 0.083″ |
| 1″ | 25 mm | 0.065″, 0.083″ |
Values per applicable standard; customizable to requirement. See the tube sizing and wall thickness guide for how to work back from pressure to wall.
Tubing Types: Instrument, Seamless, Welded, Hydraulic, Coiled, Alloy & EP
This pillar sends every tube sub-type to the page that owns it. No dead ends.
- Instrumentation tubing, Crestflo's fully annealed, instrument-grade tube built for gauge, transmitter and analyzer lines.
- Seamless tubing, drawn seamless tube for jobs that demand higher integrity.
- Welded tubing, welded-and-drawn tube for general service.
- Hydraulic tubing, thicker-wall tube for high-pressure hydraulic systems.
- Coiled tubing, continuous coils for tracing and long runs.
- Alloy tubing: duplex, 6Mo, Inconel, Monel, Hastelloy, and titanium tube, all covered.
- Electropolished tubing: EP and high-purity tube built for UHP gas service.
- Tubing size chart: Crestflo's full OD by wall dimensional table.
Finishes & Cleanliness: Passivation, Electropolish & Oxygen-Clean
Crestflo ships tube in material finish as standard, though passivation, electropolishing and oxygen/UHP cleaning are all available for high-purity and oxygen service. Standard UHP electropolish targets can be specified right on the RFQ. Take a look at electropolished tubing and oxygen and UHP cleaning for more.
Stainless Steel Tubing Standards: ASTM A269, A213, A789 & ASME B31.3
| Standard | Scope | Applies to |
|---|---|---|
| ASTM A269 | Seamless & welded austenitic SS tube, general service | 304/316 instrument tube |
| ASTM A213 | Seamless ferritic/austenitic alloy tube | Seamless SS & alloy tube |
| ASTM A249 | Welded austenitic tube | Welded-and-drawn tube |
| ASTM A789 | Seamless & welded duplex tube | Duplex / super duplex tube |
| ASME B31.3 | Process-piping allowable pressure | Wall / pressure calculation |
| NACE MR0175 / ISO 15156 | Sour-service materials | Sour-service alloy selection |
Crestflo carries the standard approvals required for instrumentation tube, and it's certified to ISO 9001, 14001, 45001, and PED.
Tube Plus Fittings: One Dimensionally Matched System
The differentiator on this pillar is that the tube and the fitting come from one source, dimensionally matched. Crestflo supplies stainless and alloy tube alongside compression tube fittings and ferrules that are tested to ASTM F1387, so the ferrule set seats correctly on the tube OD and wall you ordered. Moving off a major brand? Request your Swagelok® or Parker® cross-reference and our engineers will map the drop-in equivalent. Datasheets and CAD are available to customers on request.
Why Crestflo for Stainless Steel & Alloy Tubing
Crestflo makes instrumentation tube, fittings and valves for customers across the US. It's also the instrumentation division of an export house that's been recognized by the Government of India for four decades, with a track record of deliveries into the Middle East. For the tube buyer, that means:
- Metallurgy depth, stainless, duplex, 6Mo, high-nickel and titanium tube from one supplier.
- Traceability, every part carries a heat and lot number. Crestflo issues EN 10204 MTC 3.1 as standard, with 3.2 available on request, and backs that up with PMI verification. Full details are here: traceability.
- A matched system, tube plus F1387-tested fittings and ferrules that fit the tube you bought.
- Flexible supply, standard items ship from ready stock, and specials get built to order. Count on 6–8 weeks for delivery. MOQs stay small, and private-label is on the table too.
- Served across the US, you won't find a local branch or a "near me" trade counter here, because you don't need one. Crestflo ships to buyers nationwide, with tube built for US drop-in and delivered on that same 6–8 week schedule.
- Honest origin, the material comes from India. US and European melt are available on request, backed by full material traceability and TAA/DFARS handling.
Testing covers in-house NDT and destructive testing at labs accredited to ISO/IEC 17025, plus third-party inspection whenever it's requested. For details, check Crestflo's pages on testing & inspection and lead time.
How to Buy: RFQ, Samples, Distributor & OEM Paths
Distributors who become a distributor get a line card and stocking terms, plus stocking programs for wholesale and bulk stainless steel tubing orders. OEMs and equipment manufacturers, meanwhile, can just send a print for private-label and made-to-print tube. End users, EPC contractors and panel fabricators have their own route: request a quote or request a sample. Crestflo's US sales team is reachable at sales@crestflousa.com or +1 346 594 9005, out of Houston, TX.
Stainless Steel Tubing FAQ
What is the difference between tubing and pipe?
Tubing gets specified by its actual outside diameter (OD) and wall thickness, and it seals into compression or tube fittings. Pipe works differently: it's specified by nominal pipe size (NPS) and schedule, and it's usually threaded, welded or flanged. Crestflo's instrumentation range is OD tube, not NPS pipe.
What grades of stainless steel tubing do you supply?
We work with 304/304L, 316/316L and 904L stainless, along with duplex 2205, super duplex 2507, 254 SMO, AL-6XN, Alloy 20, Inconel, Incoloy, Monel, Hastelloy, and Nickel 200/201, plus Titanium Gr2. The service dictates the grade. Full composition and corrosion detail live on the material pages.
Seamless or welded stainless steel tubing, which should I choose?
Tube drawn without a weld seam gives maximum integrity for higher-pressure and critical service. Welded-and-drawn tube, by contrast, is the cost-effective option for general instrument work. Both are supplied to the same austenitic standards: ASTM A269, A213 and A249. And there's no difference in how they connect: both take a compression fitting the same way.
What sizes and wall thicknesses are available?
Standard OD sizes span 1/8″ to 1″, or 6 to 12 mm in metric terms, with wall thicknesses from 0.028″ to 0.083″. Check the tubing size chart for the complete OD-by-wall matrix. Values follow the applicable standard, but they're adjustable to whatever the job requires.
What standards does your stainless steel tubing meet?
Tube selection follows a clear standard: ASTM A269 covers general-service stainless, ASTM A213 covers seamless alloy, A249 handles welded austenitic, and A789 handles duplex. Each has an SA- equivalent under the ASME boiler code. Working pressure limits aren't arbitrary either; they're calculated to ASME B31.3. And when the service turns sour, alloys meeting NACE MR0175 / ISO 15156 are available.
Do you provide material test certificates for tubing?
Every part is stamped with a heat/lot number. An EN 10204 MTC 3.1 comes as standard, and we'll issue a 3.2 on request, along with PMI material verification. Crestflo holds ISO 9001 / 14001 / 45001 certification and is PED certified as well.
Is the tubing fully annealed for bending and fitting make-up?
Instrument-grade tube typically ships fully annealed, with hardness held around HRB 80 or lower. That's what lets it cone and bend cleanly into ferrule fittings. You can call out the condition on the RFQ to your own standard.
Can I get the tube and matching fittings from one source?
Yes. Crestflo supplies tube alongside compression tube fittings and ferrules that are dimensionally matched and tested to ASTM F1387, so the ferrule set seats correctly on the ordered tube OD and wall. It's one drop-in system.
Are you a US stainless steel tubing manufacturer?
Crestflo manufactures for the US market, and every product is engineered to drop in without modification. Lead times run 6–8 weeks. Standard items ship from ready stock, while specials are made to order.
The origin is Indian. US or European melt is available on request, and Crestflo provides full material traceability so buyers can review it against TAA and DFARS requirements.
Which alloy tubing suits sour or seawater service?
Duplex and super duplex grades handle sour and high-chloride service well, and so do the 6Mo grades, 254 SMO and AL-6XN, along with nickel alloys meeting NACE MR0175. Check the alloy tubing page and the linked material data to compare options.
Related Tubing, Materials & Standards
Start with Crestflo's instrumentation tubing line, then look at the alloy tubing options if the application calls for something tougher. Need exact dimensions? The tubing size chart has them.
Material specs matter just as much as size. Pull up the 316/316L material data sheet or the 304/304L material data sheet, and browse all tubing materials for anything beyond 304 and 316.
Fittings complete the assembly. Browse tube fittings, narrow in on ferrules, or head to the products hub for the full catalog.
Compliance documentation rounds it out, and it's all here: ASTM A269, ASTM A213, and the EN 10204 MTC standard.
Swagelok® belongs to Swagelok Company as a registered trademark, and Parker® is one belonging to Parker Hannifin Corporation. We use these names only for cross-reference identification. Crestflo isn't affiliated with, endorsed by, or sponsored by either company.