How steel pipes and tubes are made in India
Seamless pipe starts as a round billet that is heated, pierced and rolled over a mandrel; stainless and small-bore tubes are then often cold drawn or pilgered to size and annealed. Welded pipe starts as strip or plate: electric resistance welded (ERW or HFW) pipe is formed from coil and welded along a straight seam, while larger sizes are submerged arc welded with a longitudinal or spiral seam. Stainless welded pipe is usually formed from coil and welded by TIG or plasma, then solution annealed and pickled.
After forming, pipes are straightened, cut, end finished (plain, bevelled or threaded), tested and marked. Some pipe is then galvanised, varnished or coated with fusion-bonded epoxy or three-layer polyethylene. Many exporters are traders or processors who buy hollows or finished pipe from mills, which is why traceability matters so much.
Department of Commerce TradeStat shows FY2025-26 exports (provisional) of US$771.6 million for welded tubes and pipes (HS 7306), US$251.3 million for seamless stainless tubes (HS 730441) and US$1,017 million for large welded pipe over 406.4 mm diameter (HS 7305). We have not found an official source naming pipe clusters, so we name no town.
Which pipe standard your order names
| Standard | Covers | What it changes at inspection |
|---|---|---|
| API 5L | Seamless and welded line pipe for oil and gas pipelines, in two levels, PSL 1 and PSL 2 | PSL 2 adds tighter chemistry and more testing; check the mill's API monogram licence on the API Composite List |
| API 5CT | Casing and tubing for wells | Threads and couplings gauged; grade colour bands and stencils checked |
| ASTM A106 | Seamless carbon steel pipe for high-temperature service | Seamless only: no weld seam should be visible inside or out |
| ASTM A53 | Seamless and welded carbon steel pipe, black and hot-dip galvanised | Type (seamless, ERW or furnace butt weld) marked and matched to the certificate |
| ASTM A312 | Seamless and welded austenitic stainless steel pipe | PMI by grade (304/304L, 316/316L), pickling, weld bead |
| EN 10216 / EN 10217 | Seamless and welded steel tubes for pressure purposes, in parts by steel type | Test category and inspection document type set in the order |
What we check on steel pipes and tubes
| Check | How it is checked | What fails |
|---|---|---|
| Outside diameter and ovality | Circumference tape and calipers at both ends and mid-length; maximum and minimum diameter at one section | OD or out-of-roundness beyond the standard's tolerance, often at the pipe ends |
| Wall thickness | Ultrasonic thickness gauge around the circumference and along the length; micrometer at the ends | Any reading below the minimum wall the standard allows |
| Length, straightness, ends | Lengths measured; straightness with a taut line; bevel angle, root face and squareness gauged | Short lengths, bow, damaged bevels, threads out of gauge |
| Surface | Visual inspection outside and, with a lamp, inside the bore | Laps, seams, slivers, deep pits, dents, weld-seam undercut or excess flash |
| Hydrostatic test | Factory's test witnessed: test pressure, hold time, gauge calibration date and chart recorder | Leak, pressure drop or pressure lower than the standard requires |
| UT or eddy-current test | Factory's certified operator witnessed; calibration on a reference tube with artificial notches or holes checked before and after the run | Unexplained indications passed; reference not run; operator certificate missing |
| PMI | Handheld XRF or spark analyser used in the inspector's presence on sampled lengths, or every length where ordered | Grade does not match the stencil or certificate |
| Coating | Dry film or zinc thickness by gauge; holiday (spark) test of coated line pipe at the voltage the coating standard sets; cut-back length at ends | Thin coating, holidays, damaged or missing cut-backs |
| Marking and traceability | Stencil read on sampled lengths: maker, standard, grade, size, wall, heat number, test pressure; matched to the 3.1 certificate | Missing or illegible heat numbers; heat not on the certificate |
Galvanised pipe is worth a note: ISO 1461 excludes tubes galvanised in automatic plants, so the zinc requirement comes from the pipe standard or the order, not from ISO 1461.
Common defects in steel pipes and tubes
| Defect | Why it matters | Class |
|---|---|---|
| Wrong grade found by PMI (for example 304 supplied as 316) | Corrosion resistance and pressure rating are not what the design assumed | Critical |
| Wall below minimum | Lower pressure capacity than calculated | Critical |
| Leak or failure in the witnessed hydro test | Pipe cannot hold rated pressure | Critical |
| Heat number missing or not on the certificate | No proof of material properties for that length | Major |
| Weld seam undercut or lack of fusion indication | Weak point in welded pipe | Major |
| Ovality or OD out of tolerance at the ends | Difficult fit-up and poor girth welds on site | Major |
| Coating holidays or thin coating | Corrosion starts at bare spots once buried | Major |
| Damaged bevels or threads without protectors | Re-machining needed before welding or make-up | Major |
| Light surface rust, minor scratches, faint stencil | Usually removable | Minor |
Sour service, certificates and import rules
NACE MR0175 / ISO 15156 sets material requirements for equipment in oil and gas production exposed to hydrogen sulphide. For pipe this usually means hardness limits and, for line pipe, hydrogen-induced cracking tests on samples, done by a lab. At the factory we check that the certificate states compliance and shows the required hardness results, and that sour-service lengths are marked and kept apart from standard pipe.
Inspection certificates. Pipe is normally bought with EN 10204 type 3.1 certificates. Some projects and pressure applications call for 3.2, validated by the purchaser's representative or an inspector designated by official regulations; Clear To Load does not issue those. See mill test certificates and EN 10204.
CBAM. Tubes and pipes in HS 7304 to 7306 are covered by the EU Carbon Border Adjustment Mechanism, in its definitive period since 1 January 2026, with an exemption for importers of up to 50 tonnes of CBAM goods a year. It is the importer's obligation, not an inspection check.
Packing, transit and your purchase order
Small-bore pipe is bundled and strapped; large pipe ships loose. Bevel protectors and thread caps belong on every length. Stainless pipe must not touch carbon steel in bundling or lifting, because iron contamination causes rust spots: look for nylon slings, wooden or plastic separators and end caps. Coated pipe needs padded supports and limited stack height. Long lengths may not fit a standard container, so the length and the choice of open-top or flat-rack equipment should be settled before production. Our loading supervision checks bundle counts and stowage.
Put these in your purchase order:
- Standard and edition, grade, PSL or test category, seamless or welded type.
- OD, wall or schedule, length range and end finish.
- Hydro test pressure and whether NDT may replace it; NDT method and acceptance level.
- Sour-service requirements and supplementary tests.
- Coating system, thickness, holiday test voltage and cut-back length.
- EN 10204 certificate type, and any third party for a 3.2.
- Marking, bundling, end protection and the tests you will witness.
Flanges and fittings for the same line are covered on flanges and pipe fittings. Book an inspection anywhere in India.
Sources
- Department of Commerce, TradeStat: commodity-wise exports (HS 7305, 7306, 730441; FY2025-26 provisional)
- API: Specification 5L, Line Pipe, 46th edition
- API Composite List of monogram licensees
- ISO 1461:2022 Hot dip galvanized coatings on fabricated iron and steel articles
- Regulation (EU) 2023/956, carbon border adjustment mechanism, Annex I (EUR-Lex)
- Regulation (EU) 2025/2083 amending the CBAM Regulation (EUR-Lex)