Stainless Steel EFW Pipes Manufacturer & Supplier | ASTM A358

Standard: ASTM A358 / ASME SA358 · Classes 1 to 5 · Grades: 304/L, 316/L, 321, 310S · Size: 6" to 48" NB, larger against order

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Above a certain diameter, the economics of pipe change shape. Metinox Overseas is a stainless steel EFW pipes manufacturer and supplier in Mumbai, producing electric fusion welded pipe to ASTM A358 from 6" to 48" NB against order, radiographed by class, and exporting to project sites across India, the USA, the Middle East and Africa with full plate-to-pipe traceability. When a header is measured in feet rather than inches, EFW is not the compromise route; it is the only sensible one. The grade family sits at Stainless Steel Pipes.

Placement within the trio is simple. Below 6", the welded route covers general service. From 6" upward, and especially past 24" where nothing else plays, this page takes over. The flagship grade version is SS 304 EFW Pipes, where the workaday numbers live.

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Types of Stainless Steel EFW Pipes

What EFW Pipe Is (and Why Filler Is the Point)

EFW pipe starts as stainless plate, rolled to a cylinder and joined by electric fusion welding with filler metal added, one or two longitudinal seams depending on diameter. That filler is the deliberate difference from A312 ERW, which fuses strip without it: at plate thicknesses, a filler-fed multi-pass weld is how you build a sound joint through a heavy wall. The weld is then examined to the level the class demands, and the pipe heat treated per the ordered grade.

The ASTM A358 Class System

A358 does something clever: instead of one testing rule, it sells assurance by class, so the spec buys exactly the confidence the line needs.

ClassWeldRadiographyWhere it gets specified
Class 1Double welded (inside and out)100% RTThe most critical pressure lines
Class 3Single welded100% RTCritical service where single-side access suffices
Class 5Double weldedSpot RTPressure duty with a lighter examination budget
Classes 2 & 4Double / single weldedNo RTServices where the spec accepts unradiographed seams

Quote the class with the enquiry. Two identical-looking pipes in different classes are different products at different prices, legitimately.

Why Large Bores Go EFW

Seamless above 16" is a special order against mill schedules; strip-based welding runs out of practical width soon after 24". Plate has neither limit: it rolls to any reasonable diameter and any wall the design wants, and the cost curve stays nearly flat as diameter grows. That is why every big stainless header, duct and column you have seen was EFW, whatever the nameplate said.

EFW Pipe Testing & Radiography

The seam is examined per class, hydrostatic testing follows per the standard, and the paper trail runs from plate heat number through weld map to finished pipe. On project orders the weld procedure and welder qualifications travel with the documentation, because at these diameters the weld is the product and everyone involved should be able to prove it.

Where EFW Fits (and Where It Does Not)

  • Fits: large-bore pressure headers, plant ducting, columns and any line the smaller routes cannot reach economically.
  • Does not: small-bore process lines, where welded or seamless beat it on cost and availability. EFW below 6" is almost always a specification typo; we will ask before we quote it.

EFW Pipe Applications

  • Water & Desalination Plants: intake, outfall and process headers across Middle East and African projects.
  • Refinery & Petrochemical: large process and flare lines on Gulf EPC packages.
  • Power & FGD: ducting and scrubber piping where diameter rules the drawing.
  • Pulp, Paper & Chemicals: stock and liquor lines in the big-bore sizes.
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SS EFW Testing, Certification & Export to USA, Middle East & Africa

Every order ships with EN 10204 3.1 certification covering plate and pipe, heat-number traceable end to end, with 3.2 witnessing through BV, SGS or TUV at order stage. Metinox Overseas is ISO 9001 and PED certified, approved to SABIC, ADNOC, KNPC, EIL, IOCL and BPCL standards; see Quality Policy. Large-bore cargo moves from Mumbai to the USA, the Middle East and Africa saddle-packed and end-protected per Packing and Dispatch. EFW is made to order; typical delivery runs 4 to 6 weeks by size and class.

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Stainless Steel EFW Pipes: Frequently Asked Questions

Feedstock and filler. ERW under A312 forms strip and fuses it without filler metal, and it tops out near 24 inch. EFW under A358 rolls plate and welds it with filler added, which is how heavy walls and big diameters get sound seams. Different standards, different size worlds, both legitimate.

They set the weld construction and the radiography extent. Class 1 is double welded with 100 percent RT, Class 3 single welded with 100 percent RT, Class 5 double welded with spot RT, and Classes 2 and 4 carry no radiography. The class belongs in the purchase order, because it changes both assurance and price.

6 to 48 inch NB against order as standard capability, with larger diameters taken up per project. Walls follow the design rather than a schedule book, since plate sourcing removes the usual limits.

Yes. Large-bore consolidations move from Mumbai with saddle packing and end protection, and the documentation set covers plate certificates, weld records and the 3.1 MTC so customs and client QA clear in one pass at all three destinations.

Yes, when ordered to the right A358 class for the duty. The class system exists precisely so pressure lines can buy 100 percent radiographed double-welded seams while lighter services pay for less. Match the class to the line and EFW carries pressure with a clear conscience.

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