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Siddhgiri Overseas manufactures stainless steel tube in Mumbai across the austenitic grades and the chromoly range, and supplies buyers in Cape Town. In production since 1962.
Tube is ordered by actual outside diameter and wall thickness, and on tube the grade is rarely the hardest part of the specification. Tolerance class, internal finish and the standard the tube is made to decide as much as the alloy does. Each grade below links to its own page.
The same grade supplied to four different standards is four different products, and substituting between them is how tube orders go wrong.
| Standard | Scope | Watch for |
|---|---|---|
| ASTM A213 | Seamless boiler, superheater and heat exchanger tube | Mandatory NDT per length; the exchanger default |
| ASTM A269 | Seamless and welded tube, general corrosion-resisting service | The general-purpose standard; not a pressure spec |
| ASTM A270 | Sanitary tube | Surface finish requirements the others do not carry |
| ASTM A554 | Welded mechanical and ornamental tube | Never substitute into a pressure application |
A554 tube that measures correctly and looks identical is not qualified for a duty A213 governs. If an offer is materially cheaper than the others, check which standard it was quoted against before assuming it is a better deal.
| Grade | Typical tube duty | Minimum tensile / yield |
|---|---|---|
| 202 | Interior architectural and furniture tube | 515 / 275 MPa |
| 304 | General mechanical and structural tube | 515 / 205 MPa |
| 304L | Orbital-welded and hygienic runs, no chlorides | 485 / 170 MPa |
| 316 | Instrumentation, hydraulics, marine | 515 / 205 MPa |
| 316L | Dairy, brewing, pharma, welded chloride service | 485 / 170 MPa |
| 321 | Exhaust, bellows, superheater elements | 515 / 205 MPa |
| 347H | Creep service in refinery and power plant | 515 / 205 MPa |
| 310 | Furnace, radiant and recuperator tube | 515 / 205 MPa |
| Chromoly / 4130 | Structural and motorsport tube where strength-to-weight governs | See the grade page |
Note the pattern in the last column: the L grades give up 30 MPa of tensile and 35 MPa of yield for their lower carbon. On a thin-wall tube under internal pressure that can mean a heavier wall, so check it against the design code rather than assuming the grades swap freely.
Exchanger tubesheets and compression fittings depend on the interference between the tube and the hole or ferrule. A tube at the loose end of its OD band in a hole at the generous end will not make a sound joint, and the leak appears at hydrotest after the bundle is built.
For hygienic and instrumentation duty the bore is the product. "Polished" on a purchase order means nothing; a number means something. Ra governs the manufacturing route, so it belongs in the enquiry rather than in a later email.
Annealed, bright annealed, or cold-worked to a hardness range; pickled; passivated; electropolished. These are separate operations and one does not imply another. Tube can be polished to a fine finish and still carry embedded iron from the polishing media, which will bleed rust in service and look like a material failure.
Seamless tube for high pressure, cyclic duty, sour service and tight cold-forming. Welded tube for general service, structural work and sanitary lines, where it performs the same for less and holds a tighter wall tolerance. The tube overview covers the full range.
|
SS 202 Tube |
Lower-nickel, higher-manganese austenitic grade (~17-19% Cr, 4-6% Ni, 7.5-10% Mn); budget alternative to 304 |
Dry indoor tubing — decorative and furniture-grade applications, non-critical trim |
|
SS 304 Tube |
Standard "18/8" austenitic grade (~18% Cr, 8% Ni); yield 205 MPa, tensile 515 MPa; produced to ASTM A213/A269 |
General-purpose instrumentation and process tubing, heat exchangers in non-aggressive service |
|
SS 304L Tube |
Low-carbon version of 304 (carbon capped at 0.03% vs 0.08%); yield 170 MPa, tensile 485 MPa |
Heavily welded tube assemblies and tube-to-tubesheet joints where weld-decay resistance matters |
|
SS 316 Tube |
Adds 2-3% molybdenum over 304 for markedly better pitting and crevice corrosion resistance from chlorides |
Marine, coastal and chemically aggressive hydraulic and process tubing |
|
SS 316L Tube |
Low-carbon version of 316 with the same molybdenum addition; yield 170 MPa, tensile 485 MPa |
Welded tube assemblies in marine or chemical-process service, high-purity and sanitary lines |
|
SS 321 Tube |
Titanium-stabilized grade; titanium binds with carbon so weld decay resistance holds without low-carbon content; yield 205 MPa, tensile 515 MPa |
Heat exchanger and exhaust-related tubing from 427°C to 816°C |
|
SS 310 Tube |
High-chromium, high-nickel grade (24-26% Cr, 19-22% Ni) for extreme-temperature service |
Furnace, radiant, and high-temperature process tubing up to about 1,150°C in dry air |
|
SS 347H Tube |
Niobium-stabilized, controlled higher-carbon-range grade (0.04-0.10% C); niobium carbides are more thermally stable than titanium and don't burn off during welding |
Boiler, superheater, and refinery process tubing under ASTM A213 in the 400-815°C range |
General instrumentation and process tubing. SS 304 Tube covers the majority of standard instrumentation, sensing, and general process lines where there's no unusual chloride exposure or high-temperature demand, produced to ASTM A269 for general service. SS 304L Tube is the same grade adjusted for tube assemblies with significant fabrication welding.
Hydraulic, marine, and chemical-process tubing. SS 316 Tube and SS 316L Tube are the standard choice wherever a tube carries chloride-bearing fluids or operates in a marine or coastal environment, including hydraulic and pneumatic circuits and chemical-process lines. Specify the L version when the tube assembly involves substantial welding at fittings or tube sheets.
Heat exchanger and boiler tubing. Under ASTM A213, SS 321 Tube suits heat exchanger and thermal-cycling service between 427°C and 816°C. SS 347H Tube is the fit for boiler, superheater, and refinery process tubing in the 400-815°C range, where sustained strength and weld-seam stability both matter over long service runs. SS 310 Tube is reserved for the most extreme end of this range — continuous high-temperature service up to roughly 1,150°C in furnace and radiant-tube applications.
Budget and non-critical tubing. SS 202 Tube is the choice when cost matters most and the tube stays dry, indoors, and out of any pressure-critical or corrosive-service role — decorative and general trim work rather than instrumentation, hydraulic, or heat-exchanger duty.
Siddhgiri Overseas is ISO certified for quality, occupational health & safety and environment management, and holds the import and export certification required to supply stainless steel pipe and tube to customers worldwide. Certificate copies are available on request for buyers who need them for their own compliance records.
Works certificates with heat number, chemical analysis and mechanical results, matched to the marking on the tube. Where a project specifies a particular EN 10204 type or third-party inspection, that is a production-stage requirement; the certificate guide explains why 3.2 cannot be issued after despatch.
ISO 9001, ISO 45001 and ISO 14001 certified, with PED requirements applied to export material for pressure duty.
A554 is a mechanical and ornamental standard. If the line holds pressure, specify A269 or A213 depending on the duty, whatever the pressure is.
Because it is. The lower carbon costs 30 MPa of minimum tensile and 35 MPa of yield. Dual-certified 316/316L meets both sets of minima and is usually the practical answer.
It comes from your process and your cleaning regime rather than from a general rule. Send the requirement your client or auditor has set and we will quote against it; if none has been set, say so and we will tell you what is commonly specified for that duty.
Send the dimensions in whichever system the drawing uses, with the tolerance. Converting between the two is where half of all tube ordering errors start.
Standard, grade, outside diameter, wall thickness, length and tolerance, quantity, delivered condition, and the Ra figure if the bore matters. For exchanger work add the tubesheet hole size and the joint type.
SS 316 tube contains 2-3% molybdenum, which SS 304 tube does not. That addition gives SS 316 significantly better resistance to pitting and crevice corrosion from chlorides, making it the better choice for marine, coastal, or chemically aggressive tubing such as hydraulic circuits and process lines, while SS 304 tube remains suited to general-purpose instrumentation and process service.
Choose an L grade when the tube assembly involves significant welding — at fittings, tube sheets, or fabricated joints. The lower carbon content (0.03% max) prevents chromium carbide precipitation in the heat-affected zone during welding, which avoids weld-decay corrosion. It comes with a modest reduction in yield and tensile strength compared to the standard grade.
It depends on the operating temperature. SS 321 and SS 347H tube, both produced to ASTM A213, are suited to sustained service in the 400-816°C range, with 347H specifically used in boiler, superheater, and refinery tubing. For continuous extreme heat up to around 1,150°C, such as furnace or radiant-tube applications, SS 310 tube is the appropriate grade.
Our stainless steel tubes are manufactured to standards including ASTM A213, which covers ferritic and austenitic alloy steel tubes for boilers, superheaters, and heat exchangers, and ASTM A269, which covers seamless and welded austenitic tubing for general service. Grade-specific chemistry and mechanical property requirements follow these standards for each of the eight grades supplied.
SS 202 is generally the most budget-friendly grade in this range, since it replaces a portion of the nickel content used in SS 304 with manganese. In tube form it's suited to dry, indoor, non-critical applications only and isn't recommended for instrumentation, hydraulic, or heat-exchanger duty where moisture or pressure cycling is involved.
Yes, it's common to specify different grades for different parts of the same system based on what each section is exposed to — for example, SS 304 tube for general instrumentation runs and SS 316L tube for sections exposed to chlorides or heavy welding. Siddhgiri Overseas supplies across the full grade range so mixed specifications can be sourced together.
The "H" denotes a controlled higher-carbon range (0.04-0.10%), which helps the grade retain strength during sustained high-temperature service such as boiler and superheater tubing. Like SS 321 tube, it resists weld decay through stabilization — SS 321 uses titanium, while SS 347H uses niobium, whose carbides are more thermally stable and don't burn off during welding, making 347H suited to demanding refinery and power-generation tube service.
Yes. Siddhgiri Overseas has manufactured stainless steel tube in Mumbai since 1962 and supplies this full 200-series, 300-series, and H-series grade range in both seamless and welded construction, to the OD and wall-thickness tolerances required for instrumentation, hydraulic, and heat-exchanger applications, with Mill Test Certificates provided for traceability.
