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316/316L contains molybdenum and generally offers improved resistance to pitting in many chloride-bearing environments. The “L” grade has lower carbon, commonly preferred where welding and resistance to sensitisation are important.

• Use service media, concentration and temperature—not grade name alone.
• Confirm the correct product standard: pipe, fitting, flange or plate.
• Marine or severe chloride exposure may require a higher alloy after engineering review.

Carbon steel is widely used for general industrial duties; alloy steels support elevated-temperature service; stainless and duplex families address corrosion and strength; nickel alloys are selected for demanding media and temperature combinations.

Final selection must follow the process design basis, corrosion allowance, applicable code and purchaser specification.

A material family can have different ASTM specifications by product form. For example, a piping system may reference ASTM A335 pipe, ASTM A234 fittings and ASTM A182 flanges. A matching alloy family does not make the product specifications interchangeable.

NPS/NB identifies nominal size. Outside diameter normally remains fixed for a given nominal pipe size while wall thickness increases with schedule, reducing the inside diameter.

• Always state nominal size, schedule and applicable dimensional standard.
• For stainless pipe, “S” schedules such as 10S and 40S may apply.
• Check actual wall tolerance and calculated minimum wall separately.

Seamless pipe is produced without a longitudinal weld. ERW uses electrical resistance at the seam. EFW uses fusion welding, while SAW uses submerged-arc welding and is common in larger diameters and heavier sections.

The acceptable route depends on material specification, size, service, design code and project requirements.

Common references include ASTM A106 for seamless carbon-steel pipe, ASTM A312 for austenitic stainless-steel pipe, API 5L for line pipe, IS 1239 for steel tubes and IS 3589 for water/sewage service. Each governs a different product and acceptance framework.

Elbows, tees, reducers, caps and stub ends are commonly dimensioned to ASME B16.9. An RFQ should identify type, nominal size, schedule/wall, material specification, seamless or welded construction where relevant, and required testing.

Forged socket-weld and threaded fittings are commonly specified to ASME B16.11. State connection type, size, pressure class, material grade, thread standard and any sour-service or low-temperature requirements.

Weld-neck flanges support demanding pressure/temperature duties and smoother load transfer. Slip-on flanges simplify fit-up in suitable services. Blind flanges close a line; lap-joint assemblies aid alignment; RTJ facing is used for specified high-pressure/high-temperature systems.

A flange class such as 150 or 300 is a pressure-temperature rating designation, not a direct pressure value. Allowable pressure changes with material group and temperature. PN systems are separate and should not be assumed dimensionally interchangeable.

A 3.1 inspection certificate is validated by the manufacturer’s authorised inspection representative independent of manufacturing. A 3.2 certificate involves validation by the manufacturer’s authorised representative and the purchaser’s representative or designated official inspector.

Always confirm the project’s exact certification and witnessing requirements before ordering.

Positive Material Identification helps verify alloy chemistry using suitable instruments and procedures. PMI supports grade verification but does not replace mechanical testing, full chemical analysis, dimensional inspection or traceability documentation.

UT uses sound for internal examination; RT uses radiation imaging; DPT reveals surface-breaking discontinuities in non-porous materials; MPI is for surface/near-surface flaws in ferromagnetic materials; hydro testing checks pressure integrity under defined conditions.

Reliable traceability connects product marking and records to the originating heat and inspection documents. Cutting, machining and fabrication procedures should maintain identification through each stage.

A Quality Assurance Plan or Inspection and Test Plan defines review, witness and hold points. Third-party inspectors may witness tests, review documents and verify conformity according to the approved scope—not automatically certify every aspect of design.

• Product type and quantity
• Nominal size and schedule/thickness
• Material and product specification
• Dimensions, class/facing/end connection
• Construction route and heat treatment
• MTC, NDT, TPI and supplementary requirements
• Delivery location and required date

Similar chemistry or strength does not prove interchangeability. Compare product form, manufacturing route, heat treatment, dimensions, testing, impact requirements, code acceptance and purchaser approval before accepting a substitute.

Calculator results use nominal dimensions and density. Actual supply weight can vary because of dimensional tolerances, manufacturing variation, machining, coating and scale. Commercial settlement should follow the agreed basis.