Specifying stainless steel pipe for a new plant, a boiler overhaul or a ship outfit is rarely a matter of simply picking "304" or "316" off a catalog. A single line pipe can be sourced against a dozen competing standards, fabricated by seamless or welded routes, supplied in any of ten schedules, and then married to a flange, a fitting, a valve and a gasket that all have to share the same material pedigree. Get one item wrong and the inspection punch list on a refinery turnaround gets very long, very fast.

This guide walks through the questions our mill's export team answers every week for EPC contractors in Southeast Asia, the Middle East, South America and Eastern Europe — the same questions we wish every buyer had answered before sending the first RFQ.

1. Start With the Service, Not the Grade

The single biggest mistake we see in first-time RFQs is starting with a grade and working backward. A buyer asks for "316L pipe, SCH 40, 6-inch, 12 meters" and then later discovers the line is for boiler feed water at 320 °C with a chloride limit of 200 ppm — which is a duplex or super-duplex job, not a 316L one.

Before you open a catalog, lock down four service parameters:

• Design temperature and pressure (and whether they are steady-state or cyclic).
• Fluid chemistry — especially chlorides, H₂S, CO₂ and free oxygen.
• Welding and post-weld heat treatment constraints (does the line need to be stress-relieved in the field?).
• Applicable code — ASME B31.1, B31.3, B31.4, B31.8, EN 13480, or a national regulation such as China's GB 150 or Russia's GOST.

Once those four are written down, the grade almost picks itself.

2. Pipe Type: Seamless, Welded, ERW or EFW?

All four can be certified to ASTM/ASME, but they are not interchangeable. The choice is driven by diameter, pressure and the inspection regime the inspector will accept.

Seamless pipe

Made from a solid billet pierced and rolled. No longitudinal weld, so it is the default for high-pressure, high-temperature and cyclic service. We typically supply seamless stainless in sizes from 1/2" NB up to 16" NB, against ASTM A312/A312M (austenitic), ASTM A213 (boiler tubes), EN 10216-5 and GOST 9941. For refineries, power-plant superheaters and chemical reactors, seamless is almost always specified.

Welded pipe — ERW and EFW

Formed from strip or plate and welded. Modern austenitic welded pipes made to ASTM A312, A249, A269 and EN 10217 can match the corrosion performance of seamless pipe, with two caveats: the weld seam must be 100% radiographed or eddy-current tested, and the pipe must be solution-annealed to restore corrosion resistance in the heat-affected zone.

ERW (electric resistance welded) covers the 1/2"–24" range and is the economical choice for lower-pressure process lines, water service, and structural use. EFW (electric fusion welded) starts at 6" NB and runs well above 100" NB — it is the workhorse for large-diameter stainless headers and offshore piping where forged flanges are not practical.

Hollow structural sections

For non-pressure applications — handrails, supports, architectural and ship outfit — ASTM A554 round, square and rectangular mechanical tubes are usually the right pick. They are made to tighter dimensional tolerances than pressure pipe, but the inspection regime is lighter, so they should never be substituted into a pressure envelope.

3. Choosing the Right Grade Family

Five families cover the vast majority of industrial stainless pipe orders. Each has a clear sweet spot.

Three rules of thumb our metallurgists repeat to almost every buyer:

• If chloride is below 200 ppm and temperature stays under 60 °C, 304/304L is the safe default.
• For chloride-rich service (cooling water, white liquor in pulp mills, marine), step up to 316L, 904L or 2205 duplex — not 304.
• For refinery hydroprocessing, hot amines or sour service, request NACE MR0175 compliance at the RFQ stage. Not every "316L" on the market is NACE-certified.

4. Standards: A Quick Map for Global Buyers

Buyers often have a list of competing specifications in front of them. The table below summarizes the most commonly cross-referenced ones for industrial pipe.

5. Don't Forget the System Around the Pipe

A pipe that is perfect on its own still fails in the field if the fittings, flanges, gaskets and valves around it are not on the same metallurgical page. The most common field failure we are called in to investigate is galvanic or weld-mismatch cracking at the pipe/flange interface, where the pipe is 316L but the companion flange is a generic 304 or a low-grade "dual-certified" material that does not actually meet the spec.

The cleanest way to avoid this is to source the whole piping package — pipe, pipe fittings, pipe flanges, gaskets, stud bolts and industrial valves — from a single mill that controls heat traceability end to end. EZ Steel runs that integrated model: every component ships with the same heat number on the MTC, the same country of origin, and one point of contact if a non-conformance shows up in receiving inspection.

6. Documents to Ask For Before You Pay

For pressure-service stainless pipe, the minimum document set the buyer's inspector should expect is:

• Mill Test Certificate to EN 10204 3.1 (3.2 if a third-party witness is required).
• 100% radiography or eddy-current test report for welded pipe.
• Hydrostatic test report (mandatory for pressure pipe per ASTM A999).
• Solution-anneal and pickling & passivation records for austenitic grades.
• PMI (positive material identification) report on a defined sampling basis.
• Raw-material traceability back to the steel mill heat.
• For sour service: NACE MR0175 / ISO 15156 compliance statement.

If your supplier cannot produce these on the shipment, the price is too high no matter how low the invoice is.

7. Where EZ Steel Adds Value on Stainless Line Pipe

EZ STEEL INDUSTRIAL has been producing stainless and special-alloy pipe in China for three decades, and our export program is built around a few things EPC and OEM buyers consistently tell us they need:

• Full-cycle manufacturing. From raw-material selection through hot forming, cold finishing, solution anneal, pickling, NDT and final inspection, every step happens on the same production campus. That is what gives us the heat-to-MTC traceability buyers ask for.
• Comprehensive inventory. Common ASTM A312, A213, A249, A269 and EN 10216-5 grades in popular sizes are kept in stock, which shortens lead time on MRO and turnaround work.
• Project-bundled supply. A single RFQ can cover stainless line pipe plus heat efficiency tubes, fittings, flanges, gaskets and valves, all on one purchase order and one bill of lading.
• International certification. Our quality system is certified to ISO 9001, our piping is manufactured under API, EN and ASME accreditation, and our welders hold ASME and AWS qualifications.

For an inside view of our stainless line — grades, standards, sizes and pressure ratings — the live catalog is at ezindustrialtube.com/products/stainless_steel/.