Steel Pipe & Tube Glossary

API specification for line pipe used in oil and gas transportation systems.

API 5L is the American Petroleum Institute specification for line pipe used in oil and gas pipeline transportation systems. It defines two product specification levels: PSL 1 (standard quality) and PSL 2 (mandatory chemical composition, notch toughness, and non-destructive testing). The standard covers grades from B to X70 with increasing yield strength, and includes provisions for sour service (NACE MR0175) for hydrogen sulfide environments.

American standard for seamless carbon steel pipe for high-temperature service.

ASTM A106/A106M specifies seamless carbon steel pipe for high-temperature service in NPS 1/8 to NPS 48. It covers three grades (A, B, and C) with increasing carbon content and tensile strength. The standard requires heat treatment, NDE testing, and strict dimensional tolerances, making it the reference specification for high-pressure steam, boiler feedwater, and process piping in petrochemical and power generation industries.

American standard for welded and seamless black and hot-dipped galvanized steel pipe.

ASTM A53/A53M is the American Society for Testing and Materials specification covering seamless and welded black and hot-dipped galvanized steel pipe in NPS 1/8 to NPS 26. It includes two grades (A and B) with Grade B offering higher tensile strength. The standard defines chemical composition, mechanical properties, and testing requirements for pressure and mechanical applications, and is widely referenced for export orders and cross-border projects in India.

Indian Boiler Regulations certificate mandatory for boiler-grade steel tubes installation.

Form III-C is the certificate of manufacture and test for boiler tubes issued under the Indian Boiler Regulations, 1950. It certifies that tubes were manufactured, tested, and inspected by an Inspecting Authority recognized by the Central Boilers Board. The certificate documents the manufacturer, heat number, grade, chemical composition, mechanical properties, and dimensional compliance. IBR Form III-C is mandatory for any tube installed in a boiler operating above the IBR pressure threshold in India.

BIS standard governing mild steel tubes for water, gas and sewage applications in India.

IS 1239 (Parts 1 and 2) is the Bureau of Indian Standards specification for mild steel tubes used in water, gas and sewage conveyance. Part 1 covers steel tubes with outside diameter up to 150 mm, while Part 2 covers tubes above 150 mm. The standard defines light, medium and heavy classes based on wall thickness, and specifies material grades, dimensions, and testing requirements for ERW pipes in Indian plumbing and industrial applications.

BIS standard for steel pipes 168.3 mm to 2540 mm OD for water and sewage applications.

IS 3589:2001 specifies requirements for electrically welded steel pipes with outside diameters from 168.3 mm to 2540 mm intended for water and sewage services. It covers grade Fe 330, Fe 410 and Fe 490 pipes with varying wall thicknesses, and includes provisions for hydrostatic testing, flattening tests, and chemical composition. This standard governs large-diameter ERW pipes for municipal water distribution and drainage projects in India.

International standard for materials resistant to sulfide stress cracking in sour service.

NACE MR0175/ISO 15156 specifies requirements for materials used in equipment exposed to oilfield environments containing hydrogen sulfide (H2S). It defines hardness limits, heat treatment requirements, and chemical composition restrictions to prevent sulfide stress cracking. Steel pipes certified to NACE MR0175 are mandatory for sour gas pipelines, refinery process lines, and oilfield applications where H2S is present above threshold partial pressures.

ASME specification for seamless carbon steel boiler tubes for high-pressure service.

SA-192 is the ASME Boiler and Pressure Vessel Code Section II specification for seamless carbon steel boiler tubes for high-pressure service. It covers minimum-wall-thickness tubes in sizes up to 127 mm OD with a maximum carbon content of 0.27%. The standard mandates flattening, flaring, and hydrostatic tests, and is commonly specified for water-wall tubes, economizers, and low-to-medium pressure boiler applications under IBR regulations in India.

ASME specification for seamless medium-carbon steel boiler and superheater tubes.

SA-210 is the ASME specification for seamless medium-carbon steel boiler and superheater tubes. It includes two grades: Grade A-1 with minimum tensile strength 415 MPa, and Grade C with higher carbon content and tensile strength 485 MPa. The standard governs tubes up to 127 mm OD with maximum wall thickness 12.7 mm, and requires strict dimensional tolerances and heat treatment. SA210 is the default specification for high-pressure boiler tubes in Indian power plants and sugar mills.

ASME specification for seamless ferritic and austenitic alloy steel boiler tubes.

SA-213 is the ASME specification for seamless ferritic and austenitic alloy steel boiler, superheater, and heat-exchanger tubes. It covers multiple grades including T11 (1.25Cr-0.5Mo), T12 (1Cr-0.5Mo), and T22 (2.25Cr-1Mo) for high-temperature service up to 650°C. The standard mandates stringent chemical analysis, mechanical testing, and non-destructive examination, making it essential for superheater and reheater tubes in thermal power stations and high-pressure process plants.

Pipe end prepared with an angled cut to facilitate butt welding in pipeline construction.

Bevel End refers to pipe ends machined at an angle (typically 30° to 37.5°) to create a V-groove for butt welding. The bevel allows complete weld penetration when joining pipe sections, ensuring structural integrity and leak-tight joints. Standard bevels include plain bevel (V-type), compound bevel (J-type), and U-type for thick-walled pipes. Bevel end is the default preparation for line pipe (API 5L), structural fabrication, and process piping where welded joints are required.

Water pressure test applied to verify pipe integrity and leak-tightness before dispatch.

Hydrotest Pressure is the internal water pressure applied to pipes during manufacturing to verify weld integrity, wall thickness adequacy, and leak-tightness. Standard hydrotest pressures are calculated as 2× design pressure or per formula (2×S×t)/OD where S is allowable stress and t is wall thickness. IS 1239 specifies minimum 50 bar for light class and 75 bar for medium class. Failed pipes show visible leakage or permanent deformation and are rejected. Hydrotest certificates are recorded on the MTC.

Approximate internal diameter designation in inches for pipe sizing and selection.

Nominal Bore (NB) or Nominal Pipe Size (NPS) is a dimensionless designator indicating the approximate internal diameter of a pipe in inches. It is not the actual measured dimension but a standardized designation used for pipe selection and compatibility. For example, a 2" NB pipe has an approximate internal diameter of around 50 mm, though the exact dimension varies by schedule (wall thickness). NB is the traditional Indian convention while NPS is the American equivalent.

The measured external diameter of a pipe in millimeters or inches, critical for fitment.

Outside Diameter (OD) is the precise measured distance across the external surface of a pipe, expressed in millimeters (mm) or inches. Unlike Nominal Bore, OD is an exact dimension that determines pipe fitment in flanges, fittings, and structural applications. Indian standards specify OD in mm (e.g., 48.3 mm, 60.3 mm), while American standards often use fractional inches. OD tolerance is typically ±0.4 mm for standard commercial pipes and tighter for precision applications.

Wall thickness designation indicating pressure rating and pipe strength classes.

Schedule (Sch) is a standardized wall thickness designation for pipes that correlates directly with pressure rating. Common schedules include Sch 40 (standard weight), Sch 80 (extra-strong), Sch 160 (double extra-strong), and Sch XXS. Higher schedule numbers indicate thicker walls and higher pressure capacity for the same nominal pipe size. For example, a 2" NB Sch 40 pipe has 3.91 mm wall thickness while Sch 80 has 5.54 mm, significantly increasing pressure rating.

Permissible deviation from nominal dimensions, categorized as standard or precision grades.

Tolerance Class defines the allowable deviation from nominal dimensions (OD, wall thickness, length) in steel pipe manufacturing. Standard commercial pipes follow Class A (±0.4 mm OD, ±12.5% WT), while precision applications require Class B (±0.2 mm OD, ±10% WT) or Class C (±0.1 mm OD, ±7.5% WT). DIN 2391 and EN 10305 define tolerance classes T1 through T4 for precision tubes. Tighter tolerances increase cost but are essential for hydraulic cylinders, instrumentation, and high-pressure applications.

The radial thickness of pipe material determining strength, weight, and pressure capacity.

Wall Thickness (WT) is the radial distance between the inner and outer surfaces of a pipe, measured in millimeters or inches. It is the primary determinant of a pipe's pressure rating, structural strength, and weight per meter. Indian standards define light, medium, and heavy classes by wall thickness ranges. For seamless pipes, wall thickness tolerance is typically +15%/-12.5%, while precision tubes may achieve ±7.5% or tighter. WT must be specified alongside OD for complete pipe specification.

Pipe formed by rolling steel strip and welding the seam using electric resistance heat.

Electric Resistance Welded (ERW) pipe is manufactured by cold-forming a flat steel strip into a cylindrical shape and welding the longitudinal seam using high-frequency electric resistance heating. The process is continuous, fast, and produces pipes from 15 mm to 500 mm OD with consistent dimensions. ERW is the most cost-effective method for water, gas, structural, and general engineering applications up to ~10 bar pressure, governed by IS 1239 and ASTM A53 standards in India.

Steel pipe coated with zinc layer for corrosion resistance in outdoor and wet environments.

Galvanised Iron (GI) pipe is steel pipe with a protective zinc coating applied by hot-dip galvanizing (HDG) per IS 4736 or IS 1239 Part 2. The zinc layer (typically 60-600 g/m²) provides sacrificial corrosion protection, extending service life 5-10 times compared to black steel in outdoor, wet, or saline environments. GI pipes are specified for water plumbing, fencing, borewell casing in saline zones, and outdoor structural applications. Internal zinc can affect potable water quality in some pH conditions.

Spiral-welded pipe formed by helical winding of steel coil with submerged arc welding.

Helical Submerged Arc Welded (HSAW) or Spiral SAW pipe is manufactured by forming steel coil into a helical (spiral) cylinder and welding the seam using submerged arc welding. The spiral weld allows efficient production of large-diameter pipes (400 mm to 3000 mm+) from narrow coil. HSAW pipes are economical for water transmission, piling, and low-pressure applications, though the helical weld seam limits them to lower pressure classes compared to LSAW. IS 3589 and API 5L govern large-diameter HSAW pipes.

Pipe with straight longitudinal weld made by submerged arc welding of formed plate.

Longitudinal Submerged Arc Welded (LSAW) pipe is manufactured by forming steel plate into a cylinder and welding the longitudinal seam using submerged arc welding (SAW). Unlike HSAW, the weld runs straight along the pipe length, providing uniform stress distribution for high-pressure service. LSAW pipes range from 400 mm to 1600 mm OD with wall thicknesses up to 40 mm. They are specified for oil and gas transmission, high-pressure water lines, and structural piles where integrity is critical.

Pipe without weld seam, manufactured by hot-piercing solid steel billet.

Seamless pipe is manufactured by heating a solid steel billet and piercing it over a mandrel to form a hollow tube, followed by rolling and sizing operations. No weld seam exists, providing uniform strength in all directions and isotropic properties essential for high-pressure and high-temperature service. Seamless pipes are mandatory for IBR boiler applications, hydraulic systems, and sour service. ASME SA grades (SA179, SA192, SA210, SA213) and ASTM A106 govern seamless pipe specifications.

Seamless pipe pulled through dies at room temperature for tight tolerances and smooth finish.

Cold-drawn seamless pipe is produced by pulling a hot-pierced mother hollow through dies and over a mandrel at room temperature. The process tightens dimensional tolerances to ±0.1 mm or better, improves surface finish to Ra 1.6 μm or less, and increases tensile strength through work hardening. Cold drawing is essential for precision hydraulic tubes, instrumentation tubing, and applications requiring tight assembly tolerances. Grades like SA179 and DIN 2391 ST52 are commonly cold-drawn.

Internal surface finished by abrasive honing to precise diameter and surface roughness.

Honed bore refers to the internal surface finishing of a tube using abrasive honing stones that produce a controlled cross-hatch pattern and precise diameter tolerance. Honing achieves bore tolerances of H8 (±0.027 mm at 50 mm) or H9, and surface roughness Ra 0.2-0.4 μm. Honed-bore tubes (often designated BK+S H8) are mandatory for hydraulic cylinders to ensure proper piston seal contact and prevent leakage. The process follows cold drawing for seamless hydraulic tubes per DIN 2391.

Seamless pipe formed and sized while steel is at high temperature (~1200°C).

Hot-finished seamless pipe is produced by forming and sizing the pipe while the steel is at elevated temperature (~1100-1200°C). The process includes heating a billet, piercing it over a mandrel, and rolling/stretch-reducing to final dimensions while hot. Hot-finished pipes have relaxed dimensional tolerances (±1% OD, ±12.5% WT) and a mill-scale surface finish. They are cost-effective for boiler tubes, line pipe, and structural applications where tight tolerances are not required.

Surface treated with phosphate coating for corrosion resistance and lubricant retention.

Phosphating is a chemical surface treatment that converts steel surface into an insoluble phosphate coating (typically manganese or zinc phosphate). The crystalline coating provides corrosion protection during storage, improves paint adhesion, and retains lubricating oil for subsequent forming operations. Phosphated tubes are specified for hydraulic systems (oil retention), automotive components, and as a pretreatment before painting or powder coating. The process follows cleaning and acid pickling in the surface preparation sequence.

Internal surface machined by cutting tool to remove imperfections and improve finish.

Skiving is a machining process that uses a cutting tool to remove a thin layer from the internal surface of a tube, eliminating internal weld beads, scale, or surface imperfections. Unlike honing which abrades the surface, skiving cuts with defined geometry. Skived and roller burnished (SRB) tubes combine skiving with cold working for superior internal finish. The process is used for hydraulic cylinders, honed tube pre-processing, and applications requiring specific internal surface characteristics.

Unique identifier for a batch of steel from a single furnace melt, traceable on MTC.

Heat Number (or Heat Code) is the unique alphanumeric identifier assigned to a batch of steel produced from a single furnace melt. It enables traceability from finished pipe back to the original chemical composition and mechanical test results recorded on the MTC. Heat numbers are stamped or stenciled on pipe ends and appear on all quality documentation. In case of quality issues, the heat number allows investigation of the specific steel batch and identification of affected material in inventory or the field.

Detailed test results document covering chemistry, mechanicals, and dimensional compliance.

Material Test Report (MTR) is the comprehensive document detailing all test results for a specific heat of steel, including chemical composition analysis (C, Si, Mn, P, S, Cr, Mo, Ni), mechanical test results (yield strength, tensile strength, elongation, hardness), and dimensional verification. MTR is synonymous with MTC in common usage, though technically MTR refers specifically to the test data portion. The MTR provides the evidence of compliance to specified grades like SA192, SA210, or ASTM A53.

Manufacturer document certifying chemical composition, mechanical properties, and test results.

Mill Test Certificate (MTC) or Mill Test Report (MTR) is the manufacturer's document certifying the actual chemical composition, mechanical properties, and test results for a specific heat of steel. EN 10204 defines four types: 2.1 (compliance statement), 2.2 (non-specific test results), 3.1 (specific test results by manufacturer QC), and 3.2 (specific results countersigned by third party). Type 3.1 is standard B2B documentation, while 3.2 is required for IBR and critical applications. Every dispatch from RP Sales includes an MTC.

Formal documentation of non-conforming material to be returned or replaced by supplier.

Rejection Note is the formal documentation issued by a buyer to a supplier identifying material that fails to meet specification requirements. It details the nature of non-conformance (dimensional out-of-tolerance, chemical deviation, mechanical failure, surface defects), references the MTC heat number, and states disposition (return for credit, replacement, or scrap). Rejection notes trigger supplier corrective action and are essential for quality tracking and supplier performance evaluation in B2B procurement.

Independent inspection by agencies like SGS, BV, or Lloyds for quality verification.

Third-Party Inspection (TPI) involves independent quality verification of steel pipes by accredited agencies such as SGS, Bureau Veritas (BV), Lloyds Register, or TUV Rheinland. TPI inspectors witness manufacturing, review MTCs, perform dimensional checks, and verify compliance to standards. TPI is mandatory for IBR Form III-C certification, often required for oil and gas contracts (API 5L), and common in public sector tenders. TPI adds 5-10 days lead time and 3-5% cost but provides buyer confidence in material authenticity.

Incoterm where seller delivers goods to named destination, ready for unloading.

DAP (Delivered at Place) is an Incoterm 2020 rule where the seller bears all costs and risks transporting goods to the named destination, ready for unloading. The seller handles export clearance, freight, and transit risk, but not import clearance or unloading. DAP is commonly used for domestic steel pipe deliveries where the supplier arranges transport to the buyer's site. Under DAP, the buyer assumes risk once goods are available for unloading at the destination.

Document accompanying goods dispatch detailing items, quantities, and delivery information.

Dispatch Challan (Delivery Note or Packing List) is the document accompanying a shipment that details the items, quantities, dimensions, heat numbers, and delivery information. It is proof of dispatch, enables goods receipt verification, and supports e-way bill generation for GST compliance in India. The challan references the order/invoice number and includes MTC references for traceability. Buyers sign the challan upon receipt as acknowledgment of goods received in stated condition.

Incoterm where buyer collects goods from seller premises, bearing all transport costs.

EXW (Ex Works) is the Incoterm placing minimum obligation on the seller: goods are made available at the seller's premises (Kanpur warehouse), and the buyer bears all costs and risks from that point including loading, transport, insurance, and unloading. EXW provides the lowest quoted price but requires the buyer to arrange all logistics. It suits buyers with existing transport arrangements or those seeking maximum control over the shipping process.

Delivery term where seller loads goods onto rail transport, buyer arranges thereafter.

FOR (Free On Rail) is a delivery term where the seller's responsibility ends when goods are loaded onto railway wagons at the specified origin station. The buyer assumes risk and cost for rail freight, transit insurance, and unloading. FOR is common for Kanpur-origin steel pipe deliveries across North India. The seller provides the railway receipt (RR) as proof of dispatch, and the buyer tracks and collects material at the destination station using the RR.

Bank-issued payment guarantee providing security for buyer and supplier in large transactions.

Letter of Credit (LC) is a bank-issued document guaranteeing payment to the supplier upon presentation of compliant shipping documents. The LC substitutes bank credit for buyer credit, reducing supplier risk in large or first-time transactions. Types include irrevocable, confirmed, and transferable LCs. LC transactions add 7-14 days to procurement cycle for document processing and require careful attention to terms and document presentation. RP Sales accepts LC for export orders and large public-sector contracts.

Time elapsed from order confirmation to goods ready for dispatch or delivery.

Lead Time is the total time from order confirmation to goods being ready for dispatch or delivery. Stock items: 3-7 days. Mill-direct standard grades: 14-21 days. Mill-direct alloy grades (SA213 T11/T22): 21-30 days. IBR Form III-C adds 5-10 days; TPI adds 5-10 days. Lead time varies by quantity, grade availability, mill schedule, and inspection requirements. Understanding lead time is critical for project planning, especially for boiler maintenance windows and construction schedules.

Smallest quantity a supplier will accept for an order, often measured in metric tonnes.

Minimum Order Quantity (MOQ) is the smallest quantity of material a supplier will accept for a single order, typically expressed in metric tonnes (MT) for steel pipes. Stock sizes may have no MOQ (selling by the piece), while mill-direct orders typically require 5-25 MT MOQ depending on grade and size. Alloy grades (SA213 T11/T22) and special sizes often have higher MOQs than commodity ERW. MOQ affects pricing (lower per-kg cost at higher volumes) and should be clarified at RFQ stage.

Buyer document requesting supplier pricing for specified pipe requirements.

Request for Quotation (RFQ) is the formal document a buyer sends to suppliers requesting pricing for specific pipe requirements. A complete RFQ includes: process (ERW/seamless), grade, OD, wall thickness/schedule, length, quantity, end finish, coating, MTC type, IBR/TPI requirements, and delivery location. Clear RFQs enable accurate, comparable quotations and faster procurement cycles. RP Sales responds to RFQs within 4 working hours with complete technical and commercial offers.