Technical Guides
Practical, engineer-reviewed guides to materials, standards, inspection and buying.
Materials fundamentals 6
Types of Stainless SteelStainless steels fall into five families by microstructure: austenitic (SS 304, SS 316), ferritic (SS 430, SS 409), martensitic (SS 410, SS 420), duplex (2205, 2507) and precipitation-hardening.Stainless Steel Grade Numbering ExplainedStainless grades carry several names for the same steel.What Are Nickel Alloys? Inconel, Incoloy, Monel & Hastelloy ExplainedNickel alloys are used where stainless steel cannot cope: hot concentrated acids, severe chlorides, sour gas, very high temperatures and seawater-critical parts.Duplex Stainless Steel ExplainedDuplex stainless steel has a mixed microstructure of roughly half austenite and half ferrite.Chrome-Moly Alloy Steels GuideChoose the Cr-Mo grade by temperature and hydrogen service: P1 and P11 for moderate steam temperatures, P22 for higher temperatures and hydrogen service, P5 and P9 for oxidation and sulphidation in refineries, and P91 for the highest creep strength in modern power plants..Wear Plate Selection GuideChoose wear plate by the type of wear first: harder plate (AR450 to AR500) for sliding abrasion, tougher plate (AR400) where impact and forming are involved, and economical 200 BHN plate for moderate wear.
Corrosion & properties 5
PRENPREN, the Pitting Resistance Equivalent Number, ranks how well a stainless steel or nickel alloy resists chloride pitting.Sensitisation & Intergranular CorrosionSensitisation happens when austenitic stainless steel is held between about 425 and 815 °C, for example in a weld heat-affected zone.Stainless Steel H GradesAn H grade, such as SS 304H, SS 321H or SS 347H, has carbon held between 0.04 and 0.10% and a coarse grain size, which together give reliable creep-rupture strength above about 500 °C.Chloride Stress Corrosion CrackingChloride stress-corrosion cracking needs three things together: tensile stress, chlorides and temperature, usually above about 60 °C.Sour Service MaterialsNACE MR0175 / ISO 15156 sets requirements for metals in oil and gas production containing H₂S.
Dimensions & standards 4
Pipe Schedules, NPS and DN Explained (with Common Sizes)Pipe schedule is a number that sets wall thickness for a given nominal pipe size (NPS).Pipe vs TubeOrder pipe when the line carries fluid with standard fittings and flanges, sized by NPS and schedule.Flange Types and Pressure ClassesFlange pressure classes, 150, 300, 600, 900, 1500 and 2500 under ASME B16.5, set the pressure a flange can carry.Stainless Steel Surface Finishes2B is the standard cold-rolled, annealed and pickled finish, smooth and slightly reflective.
Inspection & documentation 6
Mill Test CertificatesA 3.1 certificate is issued by the manufacturer and validated by its own authorised inspection representative, independent of production.PMI TestingXRF analysers identify most alloying elements quickly and non-destructively, but cannot measure carbon, so they cannot separate SS 316 from SS 316L or SS 304 from SS 304H.Heat Numbers and Material TraceabilityA heat number identifies the specific melt of steel that a product was made from.How to Read Pipe MarkingsA pipe marking usually shows the manufacturer, specification (for example ASTM A312), grade (TP316L), manufacturing type (SMLS or WLD), size and schedule (2" Sch 40S), heat number and test marking such as HT or NDE.Hydrostatic Testing and NDT for Pipes, Tubes and PlatesPipes are checked by hydrostatic testing, which proves pressure tightness, and by non-destructive testing: ultrasonic (UT) for wall and internal defects, eddy current (ET) for tubes, radiography (RT) for welds, and magnetic particle (MPI) or dye penetrant (PT) for surface cracks..Third-Party Inspection (TPI) for Metal ProductsThird-party inspection is independent verification, by an agency the buyer appoints, that material meets the order before dispatch.
Procurement 4
IBR Materials ExplainedIBR material is pipe, tube, plate or fittings certified under India's boiler regulations for use in boilers and steam piping in India.Flange Bolting Selection GuideChoose flange bolting by temperature and environment: A193 B7 with 2H nuts for general service, B7M with 2HM for sour service, B16 for high temperature, A320 L7 for low temperature down to about −100 °C, and B8 or B8M stainless for corrosive or cryogenic service, with strength checked against the gasket load..How to Write an RFQ for Pipes, Plates, Fittings & Flanges (Checklist)A complete RFQ for pipes, plates, fittings or flanges lists the specification and grade, product form, size and schedule or thickness, quantity, ends or finish, tests, certificate type, inspection, marking and packing, delivery location and required date.What Drives Stainless Steel, Nickel Alloy and Pipe Prices?Stainless pipe prices depend mainly on alloy content (nickel, molybdenum, chromium), the product form and specification, size and wall, testing and certification, quantity, mill origin, and logistics.
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