What is an ASME B16.5 weld-neck flange?
As a specialist manufacturer and exporter of flanges, we produce precision ASME B16.5 weld neck flanges engineered for high-integrity piping systems across oil & gas, petrochemical, power generation, shipbuilding, and industrial process plants. Weld neck flanges (commonly called weld-neck or weld neck PN/ASME flanges) provide superior mechanical strength, excellent butt-weld transition, and low-stress flow characteristics — ideal for high-pressure, high-temperature, and cyclic-load applications.
Why choose an ASME B16.5 weld neck flange?
- High mechanical integrity: The tapered hub reduces stress concentration at the weld, delivering improved fatigue resistance compared with slip-on or threaded flanges.
- Better flow characteristics: Smooth bore and butt-weld connection minimize turbulence and pressure drop.
- Full-penetration butt weld: Ensures strong, leak-resistant joints for critical services.
- Wide pressure–temperature range: ASME B16.5 classification covers pressure classes from 150 to 2500, suitable for a broad spectrum of industrial conditions.
- Traceability & inspection friendly: Our production includes material certificates, PMI/chemical analysis, and welding procedure records for export compliance.
Standards & certifications
- Standard: ASME B16.5 — Pipe Flanges and Flanged Fittings (covering NPS 1/2 through NPS 24 and pressure classes 150–2500).
- Design & manufacture: ASME, ANSI, ASTM, DIN (on request), and customers’ proprietary specs.
- Quality systems: ISO 9001 certified manufacturing.
- Material and testing: EN/ASTM material specs, 3.1/3.2 material certificates (IV), PMI, UT, RT, MPI/PT as required.
- Traceability: Mill test reports (MTRs), NDT reports, heat treatment records, welding procedure specifications (WPS/PQR), and material traceability from heat to part number.
Materials, pressure classes and sizes we supply
We fabricate ASME B16.5 weld neck flanges from a wide range of materials to match process conditions:
- Carbon steels: A105, A350 LF2 (low-temperature service)
- Stainless steels: SS304, SS304L, SS316, SS316L, Duplex (2205), Super Duplex (2507)
- Alloy steels: ASTM A182 F11, F22, F5, F9, F91
- Nickel alloys: Inconel 625/825, Monel
- Copper-nickel and specialty alloys (upon request)
Manufacturing process & quality assurance
- Raw material procurement: certified seamless/heavy plate material from qualified mills.
- Cutting & profiling: CNC cutting or oxy-fuel/plasma for larger sizes.
- Forging/rolling: Forged hubs for pressure classes requiring higher strength; rolled plate machining where applicable.
- Heat treatment: Normalizing, quenching & tempering, or annealing as required by material spec.
- CNC machining: Face finish, bore, hub taper, and flange thickness to ASME tolerances.
- Drilling & facing: Bolt-hole pattern, raised face/RTJ groove, and finish to specification.
- NDE & inspection: Visual, PMI, UT/RT/MPI/PT per order.
- Cleaning & coating: Pickling/passivation for stainless, varnish/primer/packing for export.
- Documentation & packaging: MTRs, NDT reports, WPS/PQR, and export-grade packing.
- Product types & facing options
Industrial Standard: ASME B16.5 Weld Neck Flange
- Weld neck flange types: Standard, long weld neck (for added strength), and reduced bore (for small-diameter pipelines).
- Material options: A105 (mild steel), SS304, SS316, Alloy steel, etc.
- Facing options: Raised Face (RF), Ring Type Joint (RTJ), Flat Face (FF), Tongue & Groove (specials).
- Bore options: Full bore, reduced bore, counter-bored for specific piping.
- Pressure classes & size range (ASME B16.5)
- ASME B16.5 covers NPS 1/2 through NPS 24 for flange pressure classes 150, 300, 400, 600, 900, 1500, and 2500. Below is an industry-oriented summary table of typical sizes, materials, and recommended applications.
Industrial data — ASME B16.5 Weld Neck Flange (summary table)
| NPS (inch) | Pressure Class (common) | Typical Material | Typical Face | Typical Use / Application |
| 1/2 – 2 | 150, 300 | A105 / SS304, SS316 | RF, FF | Instrumentation, utility lines |
| 2-1/2 – 6 | 150, 300, 600 | A105 / SS316 / Duplex | RF, RTJ | Refinery, chemical process piping |
| 8 – 12 | 150, 300, 600, 900 | A105, A182-F11, SS316L | RF, RTJ | High-temp steam, heaters |
| 14 – 20 | 150, 300, 600, 900, 1500 | A182-F22, Duplex | RF, RTJ | High-pressure oil & gas lines |
| 24 | 150–600 (common), up to 1500 | Alloy steels / Duplex | RF, RTJ | Large diameter trunk lines |
- Face flatness: per ASME B16.5 requirements.
- Surface finish: Raised face typically 250–500 µin Ra (6–12 µm) unless otherwise specified.
- Concentricity & bore tolerance: Machined to ASME tolerances relevant to pipe size and class.
Testing, certification and export documentation
- PMI / chemical composition check (for material verification).
- Hardness testing (HRC/HV) for heat-treated alloys.
- Radiographic testing (RT) or ultrasonic testing (UT) for critical pressure classes.
- Positive Material Identification Certificate (3.1/3.2), MTRs.
- Hydrostatic test of welded assemblies where applicable.
- Third-party inspection (TPI) by client-approved agencies (ABS, BV, DNV, Lloyd’s, SGS).
Packing, shipping and delivery options
- Individual wooden boxes / crates with anti-corrosion packing.
- VCI (Vapor Corrosion Inhibitor) paper and desiccants for humid routes.
- Marking: Part number, heat number, material, size, pressure class, and manufacturing date on each flange.
- Documentation pack: MTRs, inspection reports, packing list, commercial invoice, certificate of origin (if required), and export customs paperwork.
- Options: FOB, CIF, DDP quotes; container stuffing & lashing; bulk or project-by-project logistics.
Quality assurance & traceability
- Heat-to-part traceability recorded; unique serial/heat numbers laser-etched.
- Full MTRs (ASTM/EN) and 3.1/3.2 certificates issued by default.
- Welding records (WPS/PQR), NDT logs and inspector sign-offs available.
- Continuous improvement via process monitoring and internal audits.
Typical industries and applications
- Upstream and midstream oil & gas pipelines and processing facilities.
- Refinery and petrochemical plants (high-temperature/high-pressure reactors, exchangers).
- Power plants (HP/LP steam systems, feedwater).
- Shipbuilding and offshore platforms.
- Water treatment and desalination (selected grades).
- Heavy industry and chemical processing.
Custom & value-added services
- Custom bore sizes, special facing, and special alloy production.
- Pre-fabrication: welding to pipe spools, assembly, and hydro-testing.
- RTJ machining and finishing to customer RTJ ring specs.
- In-house PMI and third-party inspection coordination.
- Vendor-managed inventory (VMI) and scheduled deliveries for large projects.
Pricing & lead times (indicative)
- Pricing depends on material grade, pressure class, size, certification level (3.1/3.2), NDT requirements, and quantity.
- Typical lead times (standard materials): 2–6 weeks for common sizes and classes; 6–12+ weeks for special alloys, high-pressure classes, or large forged parts.
Request a quote
For firm quotes: provide required NPS, pressure class, material grade, face type, quantity, and destination port/terms