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Marine and Shipbuilding Flanges and Forgings - ABS, BV, DNV, LR, KR and ClassNK Approvals

Six classification societies have approved or recognised our steel-forging manufacture: ABS, Bureau Veritas, DNV, Lloyd's Register, Korean Register and ClassNK. Each document covers our process for the material families and limits printed on it; the flanges for a classed ship are still certified order by order, under that society's rules.

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Marine and Shipbuilding Flanges Explained

What an approval gives a yard or an owner is a manufacturer the society has already assessed - plant, process and quality procedures for the materials it lists - so a classed order starts from a known supplier instead of a first-time survey. What it does not give is a certified flange: the society's rules and its surveyor still decide the tests, the witness points and the certificate for each order or batch.

The limits differ from document to document, and they are kept that way on this page. ABS, BV and LR print the same weight limits per steel family; DNV prints its own weights with section and heat-treatment columns; KR prints one limit for its whole approval; ClassNK prints none. We match each order to the approval of the society that classes the ship.

Engineering Snapshot

Product family, supply scope and the next two steps, in one place.

Product family: Flanges

Marine and Shipbuilding Flanges Supply Scope

Marine flange and forging RFQs are checked for the classification society and rule edition, the society or ASTM grade, the flange standard and size, the weight of each forging against the approval that covers it, survey hold points and the certificate type before quotation.

  • Six class-society approvals of our forging manufacture, each with its printed scope
  • What an approval covers - and why each classed order is still certified by the surveyor
  • Class RFQ checklist: society, rules, grade, hold points, raw-material condition
Send DrawingInspection Documents

Six class-society documents, as printed

Society, number, validity, scope, material families with their limits, forging method and rules basis - each exactly as its own document prints them. No figure is carried from one document to another.

Our classification-society approvals and recognition, with the scope each document prints
SocietyDocument and numberValidity as printedScope as printedMaterial families and limits as printedForging method as printedRules basis
ABSCertificate of Forging Facility and Process Approval FOR-0055952 (work order WO0055952)25 September 2024 to 24 September 2029, subject to annual endorsementSteel forging and stainless steel forging components for marine applicationsFrom the work-order attachment: C and C-Mn 3,000 kg; alloy 1,000 kg; austenitic stainless 1,000 kg; duplex stainless 500 kgFree forge; die forgeABS Rules for Materials and Welding, Part 2 (2024)
Bureau VeritasRecognition for BV Mode II scheme SMS.W.II./152398/A.0 (range FORGING - G0247)Issued 22 December 2025; expires 25 November 2029; periodical auditsSteel forgings; the products are to be certified individually or per batch by Bureau VeritasC and C-Mn 3 t; alloy 1 t; austenitic stainless 1 t; duplex stainless 500 kgNot printedBV NR320
DNVApproval of manufacturer AMMM000038829 November 2024 to 28 November 2027Forgings for boilers, pressure vessels and piping systems; stainless steel forgingsC and C-Mn (NV F450H, NV F490H) 4,000 kg, 230 mm, QT; alloy (NV F0.5Mo, NV F1Cr0.5Mo, NV F2.25Cr1Mo) 1,000 kg, 200 mm, N/NT/QT; austenitic CrNi 1,000 kg, 200 mm and CrNiMo 600 kg, 150 mm; 22Cr and 25Cr duplex 600 kg, 150 mm; stainless solution heat treatedOpen die for C/C-Mn and alloy; closed and open die for austenitic and duplexDNV rules for classification - Ships; DNV-CP-0247
Lloyd's RegisterApproved Manufacturer of Steel Forgings LR25409452WA08/12/2025 to 07/12/2028Steel forgings, subject to LR's Rules for the Manufacture, Testing and Certification of MaterialsCarbon and C-Mn 3,000 kg; alloy 1,000 kg; austenitic stainless 1,000 kg; duplex stainless 500 kgOpen die (free) forgingLR Rules for the Manufacture, Testing and Certification of Materials
Korean RegisterApproval Certificate for Manufacturing Process [Steel Forgings] DLN51990-SF00115 December 2025 to 14 December 2030Carbon, alloy, austenitic stainless, 22Cr and 25Cr duplex stainless steel forgings; individual product certification is required unless specifically exemptedMax. 3,000 kg - one limit for the whole approvalOpen diePt. 2, Ch. 1, Art. 601 and 602, Rules for Classification of Steel Ships
ClassNKApproval of Manufacturing Process, Approval No. ST628CF, Certificate No. TA2677E23 January 2026 to 22 January 2031Carbon steels, alloy steels, stainless steels and duplex stainless steels (ASTM A182/A182M); process: forging and heat treatmentNo weight or section limit printedForging; method not printed1.2, Part K, Rules for the Survey and Construction of Steel Ships; Ch. 3, Part 2, Guidance for the Approval and Type Approval of Materials and Equipment for Marine Use

ClassNK prints its ASTM A182/A182M reference on the duplex line only. KR and ClassNK also set a raw-material condition: semi-finished material from society-approved makers, or satisfactory to the surveyor (KR).

What an approval covers - and what it does not

Each document approves or recognises our manufacturing of steel forgings for the families and limits it prints: our plant, our process and, where printed, our heat treatment. That lets the society's surveyor start a classed order from an assessed manufacturer.

  • It is not a product certificate. Flanges for a classed ship are certified by the society's surveyor, individually or per batch, where its rules require it - BV and KR state this on the certificate itself.
  • It is not a type approval of a flange design, and it is not a JIS, KS, API or ASME mark.
  • It does not reach past its printed limits: a duplex forging over 500 kg is outside the ABS, BV and LR documents, and alloy grades above 2.25Cr-1Mo are not on DNV's list.
  • It does not lend one society's limit to another: KR's 3,000 kg covers its whole approval, DNV's 600 kg is its duplex line, and ClassNK prints no limit at all.
  • It says nothing beyond its printed dates; endorsements and periodic audits are each society's own record.

Class RFQ checklist

A classed order is quoted against the society's rules as much as against the flange standard. These items decide which approval applies and what the surveyor will witness.

  • The classification society and the rule edition the ship is built to.
  • The material as a society grade - for example DNV NV F490H - or as an ASTM grade that the society accepts for the application.
  • The flange standard, rating, type and size, or the drawing - including JIS B 2220 or KS B 1503 dimensions where the yard uses them.
  • The weight and thickness of each forging, so the order sits inside the printed limits of the right approval.
  • Survey hold points: which tests the surveyor witnesses, and at what stage.
  • The certificate: the society's product certificate, EN 10204 3.2, or both, and who issues each.
  • Any raw-material condition beyond the one KR and ClassNK already print.

JIS and KS flanges on classed ships

Yards that build to Japanese or Korean practice often write piping to JIS B 2220 or KS B 1503 dimensions. We make flanges to those dimensions on order, and our ClassNK and KR approvals cover the forging process - but neither approval is a JIS or KS certification: we do not hold the JIS Mark or the KS mark, and no such mark is applied. JIS B 2220 flanges, with KS B 1503

Our DNV approval notes that stainless steel forgings shall be in accordance with recognised standards and names JIS G 3214 among them, with DNV's supplementary requirements. That is DNV's rule for the material; it does not give us JIS certification.

The six documents

Readable previews with the full PDF of each approval; the same files sit on our certificate wall.

BLD ABS forge facility approval certificate preview

ABS Facility Approval

ABS forge facility and process approval reference for marine and offshore supplier review.

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BLD Bureau Veritas forging recognition certificate preview

Bureau Veritas Recognition

BV recognition reference for steel forging approval and qualification document review.

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BLD DNV steel forgings approval certificate preview

DNV Steel Forgings Approval

DNV approval reference for steel forgings and project supplier qualification files.

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BLD Lloyd's Register steel forgings approval certificate preview

Lloyd's Register Approval

Lloyd's Register approval reference for steel forgings and marine project review.

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BLD Korean Register manufacturing process approval certificate preview

Korean Register Approval

KR manufacturing process approval reference for steel forgings and related project review.

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Our ClassNK approval of manufacturing process certificate (ST628CF), preview

ClassNK Manufacturing Process Approval

Nippon Kaiji Kyokai approval of our manufacturing process - forging and heat treatment - for carbon, alloy, stainless and duplex stainless steels (the duplex line printed with ASTM A182/A182M). Approval No. ST628CF, Certificate No. TA2677E, valid 23 January 2026 to 22 January 2031.

An approval of our process under Part K of the NK Rules, not a product certificate and not a JIS certification: products for NK-classed ships are still manufactured, tested and inspected to the NK Rules.

Open PDF

Marine and Shipbuilding Flanges Technical Specification

The single authoritative view of what we can supply against your standard, drawing, material and inspection requirements.

Scope and rating
Approvals on fileABS FOR-0055952, Bureau Veritas SMS.W.II./152398/A.0, DNV AMMM0000388, Lloyd's Register LR25409452WA, Korean Register DLN51990-SF001 and ClassNK ST628CF - each with the scope and limits printed on it.
Standards and materials
Standards / drawings
  • ASME B16.5 and B16.47 by class
  • EN 1092-1 by PN
  • JIS B 2220 and KS B 1503 by K rating
  • Yard or machinery drawings
  • The classification society's rules for materials
Material grades
  • Carbon and C-Mn steel forgings, e.g. DNV NV F490H or ASTM A105
  • Alloy steel forgings within each society's printed list
  • Austenitic stainless forgings, e.g. ASTM A182 F316L
  • Duplex stainless forgings, e.g. ASTM A182 F51 / F60
Geometry, tolerance and inspection
Product certificationFlanges for a classed ship are certified per order or batch by the society's surveyor where its rules require it; an approval is not a product certificate.
Critical dimensionsFlange standard and rating (ASME, EN, JIS B 2220, KS B 1503 or drawing), size, facing, bore and the weight of each forging.
Inspection depthThe society's witnessed tests and hold points, EN 10204 3.1 or 3.2 as ordered, dimensional report, UT/MT/PT and PMI as named.
Reviewed before quotation
  • Society, rule edition and the approval that covers the material
  • Weight and section of each forging against that approval's limits
  • Survey hold points and witnessed tests
  • Certificate type: society product certificate, EN 10204 3.2 or both
  • Raw-material source condition set by the society
Buying logic
Best-fit RFQBest for flanges and forgings for classed ships, offshore units and marine machinery where a classification society's rules and surveyor apply.
Buyer applicationShipyards, marine engine and machinery builders, offshore topsides and ship repair buying to ABS, BV, DNV, LR, KR or ClassNK rules.
Download this table as PDF Send Product RFQ

Generated from the published values above - it does not invent standard dimensions. Final manufacturing and inspection follow your current standard, drawing revision and project specification.

ClassNK: What the Newest Approval Says

The answer comes first, then the evidence, where it applies and where it stops. Each value is read from the document it links to.

What exactly did ClassNK approve?

ClassNK approved our manufacturing process - forging and heat treatment - for carbon steels, alloy steels, stainless steels and duplex stainless steels, the duplex line printed with ASTM A182/A182M, under 1.2, Part K of its Rules for the Survey and Construction of Steel Ships (Approval No. ST628CF, Certificate No. TA2677E, valid 23 January 2026 to 22 January 2031).

Evidence

  • Certificate heading: NIPPON KAIJI KYOKAI, Approval No. ST628CF, Certificate No. TA2677E, APPROVAL OF MANUFACTURING PROCESS, issued at Tokyo on 23 January 2026
  • MATERIALS: Carbon Steels; Alloy Steels; Stainless Steels; Duplex Stainless Steels (ASTM A182/A182M). PROCESS: Forging / Heat Treatment
  • REMARK: semi-finished products are to be supplied by Society-approved manufacturers able to deliver the specified chemical composition
  • The certificate states that products for ships classed with the Society are to be manufactured, tested and inspected in compliance with the Rules

Applies when

Relevant when the ship is classed with ClassNK, or when a yard's approved-supplier file asks for a manufacturing-process approval from NK.

Limits

The certificate prints no weight, section or forging-method limit, so none is claimed here, and its ASTM A182/A182M reference sits on the duplex line only. It is an approval of our process, not a product certificate and not a JIS certification: flanges for NK-classed ships are still made, tested and inspected to the NK Rules for each order.

Sources

Every value above was checked against the linked documents on 2026-09-26.

Also known as

marine flangeshipbuilding flangeship flangeclass approved flange forging

Manufacturing and Inspection Route

Use this route to understand what has to be confirmed before price, lead time, MTC 3.1 and third-party inspection commitments are made.

  1. Material review

    Material grade, heat number, certificate basis and substitution limits are checked against the Marine and Shipbuilding Flanges drawing or standard before procurement is released.

  2. Forging process confirmation

    The forging route is selected around flange type, section thickness, bore allowance, hub or neck geometry and pressure-service requirements.

  3. Heat treatment

    Heat treatment is planned with the required record package, mechanical testing basis and impact-test condition where low-temperature or alloy service applies.

  4. Rough machining

    Rough machining opens reference faces, bore, hub, neck or sealing-face stock needed to control allowance before final flange machining.

  5. Final machining

    Final machining controls facing, bore, bolt pattern, groove, sealing surface and flange-table or drawing tolerances before dimensional inspection is issued.

  6. Inspection and document review

    Inspection covers dimensional report, MTC 3.1, PMI and required UT, MT or PT records before the release documents are matched to the purchase order.

  7. Marking, packing and export document preparation

    Marking, packing and export documents are prepared by PO line item so the Marine and Shipbuilding Flanges shipment can clear customs and be identified at site receiving.

Inspection and Documents

Include document requirements with the first RFQ so inspection cost and timing are visible before offer comparison.

  • MTC EN 10204 3.1
  • Heat treatment record
  • Dimensional report
  • PMI when alloy verification is required
  • UT, MT or PT when specified
  • Tensile, impact or hardness test records when required
  • Third-party inspection support by project request

How to Send This RFQ

Complete offers come back fastest when the first message carries the data below - and avoids the omissions that make quotations look cheaper than they are.

Send these details

  • Classification society and rule edition of the ship
  • Material as a society grade or an ASTM grade accepted by the society
  • Flange standard and rating, size and type, or the drawing
  • Weight and thickness of each forging
  • Survey hold points and witnessed tests
  • Certificate type and who issues it
  • NDT methods and acceptance standard
  • Marking, quantity and delivery port

Avoid these omissions

  • Reading an approval as a product certificate for your flanges
  • Taking one society's weight limit and applying it to another
  • Leaving the society and rule edition off the RFQ
  • Naming a society grade without the rules it comes from
  • Adding survey hold points after the price is agreed

FAQ

Short answers for common RFQ questions.

Are your flanges class-approved?

Our manufacturing process is approved or recognised by six societies; the flanges themselves are certified per order or batch under the rules of the society that classes the ship. Name the society and rules on the RFQ so the survey and certificate can be quoted.

Which weight limit applies to a duplex forging?

The one printed by the society that classes your ship: 500 kg under ABS, BV and LR, 600 kg with a 150 mm section limit under DNV, and 3,000 kg under KR, whose single limit covers its whole approval. ClassNK prints no weight limit.

Does the ClassNK approval mean JIS certification?

No. ClassNK approved our manufacturing process under its ship rules. JIS certification is a separate scheme under which a certified business may apply the JIS Mark; we do not hold it. We make flanges to JIS B 2220 dimensions on order.

Can you forge F91 or other chrome-moly grades for a DNV-classed ship?

DNV's printed alloy list on our approval stops at 2.25Cr-1Mo (NV F0.5Mo, NV F1Cr0.5Mo, NV F2.25Cr1Mo). For a higher alloy on a DNV-classed ship, send the RFQ with the rule reference first so the route can be agreed with the society.

Use these guides to prepare drawings, material notes, inspection requirements and documents before sending the RFQ.

Duplex / Super Duplex Flange Guide

Duplex and super duplex forged flange RFQ guide, with the third-party type-test data measured on one of our own S22053 weld neck flanges.

Inspection Document Checklist

Forged flange inspection documents at RFQ stage: MTC 3.1, PMI, NDT and dimensional scope, with a complete third-party type-test report as a worked example.

MTC 3.1 Guide

How to read and verify an EN 10204 3.1 MTC, shown on a real BLD certificate for 304L forged flanges: heat traceability, chemistry, mechanical results.

Use these pages when the RFQ belongs to a more specific forged part category.

Stainless Steel Forged Flanges

Send RFQs for stainless steel and duplex forged flanges with ASTM A182 grade, standard, class or PN, PMI, corrosion service and MTC requirements.

Chrome-Moly Alloy Steel Flanges

ASTM A182 F11, F22, F5, F9 and F91 forged flanges for high-temperature service: EN, JIS, Chinese and GOST designations, heat treatment and F91 test data.

High Pressure Flanges

High-pressure flanges by standard: ASME Class 600–2500, EN PN 100–400, JIS 30K–63K, GOST PN 100–250 - ring-joint grooves, hardness and ordered NDT.

Weld Neck Flanges

Send weld neck flange RFQs with ASME, EN, DIN, GOST or drawing requirements, bore, facing, class, material, NDT and MTC 3.1.

Custom Forged Rings

Send forged ring RFQs with drawing, material grade, OD, ID, height, machining allowance, heat treatment and inspection requirements.

JIS B 2220 Flanges

JIS B 2220 steel pipe flanges from 5K to 63K and 10A to 1500A, with KS B 1503: types, JIS materials, our JIS-size 3.1 record, and no JIS Mark claimed.

Send your RFQ or drawing directly to BLD Forge Direct.

Email quote@bldforgedirect.com with standard, drawing, material, quantity and inspection requirements.

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