Alloy Instrumentation Tubing: Stainless, Duplex & High-Nickel CRA Grades

Alloy instrumentation tubing is cold-drawn seamless or welded-and-drawn tube made from corrosion-resistant and high-nickel alloys, stainless, duplex, super-austenitic, nickel and titanium grades. It's sized as instrumentation tube, fractional or metric OD by wall, to feed tube-fitting fluid, gas and sample systems. Crestflo manufactures alloy tubing across the full corrosion-resistant-alloy (CRA) and high-nickel range. Both imperial and metric sizes are available, seamless or welded, made to the applicable ASTM tube standard. Every length carries a heat number and EN 10204 MTC 3.1.

Crestflo supplies corrosion-resistant and high-nickel instrumentation tube. Not aluminum-alloy round tube. Not 4130 chromoly alloy-steel tube. And not structural or architectural tubing, either.

Ready stock for standard items, made-to-order for specials, 6–8 week delivery. Origin is Indian, with US / European melt available on request and full material traceability. Request a quote or request a sample.

Also Known As: Nickel Alloy Tube, CRA Tubing, Exotic & High-Performance Alloy Tube

Engineers and buyers call this product by many names. You'll see it written as alloy tube, alloy tubing, tubing alloy, tube alloy or instrument alloy tube, and grouped by class as corrosion-resistant alloy (CRA) tubing, high-nickel alloy tubing, nickel alloy tube, exotic alloy tubing, special alloy tubing, super-alloy tubing or high-performance alloy tubing. Construction gives it still more labels: seamless alloy tube, welded (welded-and-drawn) alloy tube, cold-drawn alloy tubing, drawn alloy tube or annealed alloy tubing. Name it by grade, and the same tube becomes Inconel tubing, Incoloy tubing, Monel tubing, Hastelloy tubing, 904L tubing, duplex tubing, super duplex tubing, 254 SMO tubing, AL-6XN tubing, Alloy 20 (Carpenter 20) tubing, Nickel 200/201 tubing, titanium tubing or titanium Grade 2 tubing. Whatever the label, each term points to the same corrosion-resistant instrumentation tube detailed below.

What Alloy Tubing Is: and Is Not (CRA Instrument Tube vs Aluminum & 4130 Alloy-Steel)

"Alloy instrumentation tubing" refers to a corrosion-resistant or high-nickel metal tube built to an instrumentation size and tube specification. It's picked for how it holds up against chlorides, sour service, acids or high temperature, not for structural strength. A CRA (corrosion-resistant alloy) covers any grade suited to the job: duplex, 6-moly, nickel-based or titanium, chosen so the tube can survive a media that would eat through standard carbon or low-alloy steel. This is a different animal from the two products people usually mean when they say "alloy tubing": aluminum-alloy round tube (6061/6063) and 4130 (chromoly) alloy-steel tube. Both of those are structural or mechanical products, not instrumentation CRA. Crestflo doesn't supply aluminum, brass, copper or 4130 structural tube. The scope here is stainless and high-alloy instrumentation tube, full stop.

Alloy Families & Grades We Supply: Stainless, Duplex, Super-Austenitic, Nickel & Titanium

Alloy tubing comes in five families, and each grade has its own material page covering composition, PREN and mechanical properties. Crestflo supplies these grades strictly as instrumentation product: tubing, fittings and valves. Bar, sheet, plate and mill product aren't part of the offering.

UNS numbers and standard designations follow the published unified numbering system and ASTM specifications. Alloy selection gets confirmed on the material test certificate for each order.

Seamless vs Welded Alloy Tubing: Construction & Condition

Alloy tubing comes in two constructions. Seamless tubing is cold-drawn from a pierced or extruded hollow, so there's no weld line anywhere in the wall, while welded-and-drawn tubing starts as roll-formed strip, gets welded continuously, then is cold-drawn down to final size. For the toughest jobs, seamless is usually the pick, particularly where pressures run high or the service turns sour; welded-and-drawn, on the other hand, holds tight tolerances and comes in long lengths at a lower cost, which makes it a practical choice across many CRA grades. Both types ship in an annealed condition, whether that's bright annealed, fully annealed or solution-annealed, so the tube stays soft enough to bend and seat properly in a compression fitting. Exact values follow the applicable standard, though they can be adjusted to fit specific requirements. See seamless tubing, welded tubing and the parent range of stainless steel & alloy tubing.

Alloy Tubing Sizes: Imperial (1/16″–2″) & Metric OD × Wall

Alloy tubing comes in instrumentation sizes matched to the tube-fitting line, available in both imperial and metric outside diameters, up to 2″ (50 mm) OD end connections. Fractional sizes run 1/16″, 1/8″, 3/16″, 1/4″, 5/16″, 3/8″, 1/2″, 5/8″, 3/4″, 7/8″, 1″ and up to 2″ OD. Metric sizes run 3, 6, 8, 10, 12, 16, 20, 25, 38 and 50 mm OD, including the common 6 mm and 12 mm instrument sizes. The line spans a wide range of alloy tube sizes and wall thicknesses. Thin-wall alloy tubing suits low-pressure sample lines. Heavy-wall alloy tube handles high-pressure duty instead.

Allowable working pressure depends on OD, wall thickness and grade. That's why the figures below are only illustrative: standard allowable working pressures for annealed 316/316L seamless tube per ASME B31.3. Values follow the applicable standard and can be adjusted to the requirement at hand, and each alloy grade carries its own derated figures.

You'll find every OD, wall thickness, and pressure combination across all grades laid out on the tubing size chart. Match your requirement to instrumentation tubing, hydraulic tubing, or coiled tubing; for high-purity duty, look to electropolished tubing instead.

Alloy Tube Standards & Specifications: ASTM A269, A213, A789/A790 & B-Series

Every alloy family gets supplied to its applicable ASTM tube specification. Stainless instrumentation tube falls under the A-series. Nickel alloys and titanium, on the other hand, follow the B-series published for each grade.

Standard editions apply. Each order's certificate spells out which specification it conforms to. For sour service, material options meet NACE MR0175 / ISO 15156, and oxygen-clean tube meets ASTM G93.

Selecting an Alloy by Service: Chlorides, Sour H₂S, Acids, High Temperature & Seawater

Alloy selection tracks the media, temperature and pressure involved in service. Below, common drivers are mapped to candidate alloy families. The final grade isn't fixed by that alone; it comes down to concentration, temperature and partial pressure.

Beyond grade, the same alloy tube gets specified by duty too: high-pressure alloy tubing for hydraulic and process lines, steam-tracing tubing for heat maintenance, and analyzer tubing or sample-line tubing for analytical and sampling systems. Surface finish comes as-drawn, passivated, or electropolished. Crestflo preps oxygen-clean tubing to ASTM G93 for oxygen and high-purity service. Take a look at electropolished tubing for the details.

Certifications, Testing & Traceability: NACE MR0175, MTC 3.1 & Heat-Number

Crestflo holds ISO 9001 / 14001 / 45001 & PED certification. Alloy tubing ships with EN 10204 MTC 3.1 as standard, with 3.2 available on request. Every length gets its own heat/lot number, so full traceability isn't ever in question. See EN 10204 MTC for the full standard. Sour-service grades are furnished to NACE MR0175 / ISO 15156, with hardness and microstructure limits applied as each grade requires. Positive material identification (PMI) confirms grade. NDT is handled in-house. Destructive testing, though, goes out to labs accredited under ISO/IEC 17025, and third-party inspection can be arranged on request. Datasheets and CAD files are available to customers who ask for them.

Why Crestflo: Your US-Serving Alloy Tubing Supplier & Manufacturer

Crestflo is the instrumentation arm of a export house that's been operating for four decades, recognized by the Government of India, with a proven delivery record across the Middle East. It now manufactures corrosion-resistant and high-nickel tube for buyers in the US. Unlike many alloy tubing suppliers and manufacturers serving the USA, Crestflo actually makes the tube rather than reselling someone else's. That means plants searching for an alloy tubing supplier in the USA, a local alloy tubing stockist, or simply "alloy tubing near me" can buy factory-direct. Pricing gets quoted per grade, OD × wall and quantity on your RFQ, not pulled from some fixed alloy tubing price list.

Confidence gets built into every length. The full CRA, high-nickel and titanium range comes from one source. Both imperial and metric OD are available. Construction can be seamless or welded. Every batch carries heat-number traceability with MTC 3.1, and NACE-compliant grades are ready for sour service. Lead time runs 6-8 weeks, against the 20+ weeks typical of the majors. Small MOQ and private-label programs round out the offering.

Origin is Indian, though US and European melt are available on request, along with full material traceability for jobs that require domestic-melt or TAA sourcing. See US-serving origin & compliance and the 6-8 week lead-time methodology for details. US buyers can reach the Crestflo sales desk at sales@crestflousa.com or +1 346 594 9005 (Houston, TX).

Order Alloy Tubing or Request a Cross-Reference

Give us the grade, OD × wall, construction type (seamless or welded), condition, whether you want cut lengths or coil, and the certificate level you need. Crestflo issues an ordering-code and part-number series with every quotation, so ask the engineering team for the ordering-code guide and they'll send it over. Request a quote, request a sample, or take a look at the distributor program. Standard items ship from stock. Specials are made to order, and delivery runs 6-8 weeks.

Frequently Asked Questions: Alloy Tubing

Related Tubing & Material Pages

• Instrumentation tubing
• Seamless tubing
• Welded tubing
• Electropolished tubing
• Tubing size chart
• Inconel 625 metallurgy · Hastelloy C-276 · Super Duplex 2507
• All stainless steel & alloy tubing

Reviewed by the Crestflo Engineering Team