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Lap Joint and Loose Flanges

Lap joint and loose flanges rotate freely over a stub end or welded collar, which makes bolt-hole alignment easy and suits frequently dismantled or lined piping. We forge them to ASME B16.5 lap joint and EN 1092-1 type 02/04 loose-plate practice, or to drawing.

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Engineering Snapshot

This is the quick technical view a buyer, EPC engineer or distributor needs before deciding whether this is the right product page.

Lap Joint Flanges Supply Scope

Lap joint and loose flanges rotate freely over a stub end or welded collar, which makes bolt-hole alignment easy and suits frequently dismantled or lined piping. We forge them to ASME B16.5 lap joint and EN 1092-1 type 02/04 loose-plate practice, or to drawing.

  • ASME B16.5 lap joint and EN 1092-1 type 02 / 04 loose flange review
  • Rotating loose flange over stub end or flat welded collar
  • Carbon, low-temperature, stainless and duplex steel grades
  • MTC 3.1, dimensional report and NDT stated before quotation
Send DrawingInspection Documents
Product familyFlanges
Typical scopeASME B16.5 lap joint and EN 1092-1 type 02 / 04 loose flange review; Rotating loose flange over stub end or flat welded collar; Carbon, low-temperature, stainless and duplex steel grades; MTC 3.1, dimensional report and NDT stated before quotation
Standards / drawingsProject drawing or purchase specification; ASME B16.5 where flange dimensions follow ASME classes; EN 1092-1 / DIN where PN and DN requirements are specified; GOST 33259, 12820 or 12821 where CIS project requirements apply; ASTM, EN or project material standards as listed in the RFQ
Material reviewASTM A105 carbon steel; ASTM A350 LF2 low-temperature carbon steel; Stainless steel grades such as 304, 316, 321 or 347; Duplex and super duplex grades when specified by the project; Alloy steel or drawing-specified grades subject to feasibility review
Critical RFQ variablesSize, DN or NPS; Pressure class or PN rating; Drawing revision and critical dimensions; Facing, bore, bolt pattern and machining tolerance; Quantity, destination country and packing requirement
Inspection documentsMTC 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

Product Visual Match and Buying Logic

This section is written for buyers checking whether the picture, product name and quotation scope match the same forged part.

BLD forged lap joint loose flanges photographed at the Shanxi Baolongda plant
Why this image matches Lap Joint FlangesLive loose flanges from the company catalogue photographed in-house; the exact product this page quotes.Factory photo of forged loose flanges for lap joint RFQs controlled by standard, size, rating and stub end or collar scope.
Best-fit RFQ

Best where bolt alignment, frequent dismantling or alloy cost saving over stainless stub ends drives the design.

Buyer application

Stainless and lined lines, water and utility systems, frequently opened piping and distributor stock.

Critical geometry

Flange bore over stub-end barrel, class or PN, facing carried by the stub end, OD and drilling to standard.

Required RFQ data

Send standard reference, NPS or DN, class or PN, stub end or collar scope, material grades, quantity and documents.

Quality focus

Bore clearance, drilling, marking and MTC traceability of both flange and stub end are the review points.

Lap Joint Flanges Technical Data That Changes the RFQ

These product-specific values make the page different from a generic catalogue listing and help engineering buyers send a complete first inquiry.

Technical basisThis product is reviewed against its drawing, standard, material grade, quantity, inspection requirement and destination country.
Product-specific differenceThe RFQ must define the dimensions and tolerances unique to Lap Joint Flanges rather than relying on a generic forged flange description.
Inspection depthMTC 3.1, dimensional report, heat-treatment record, PMI and NDT are confirmed according to project requirement.

Direct Product Datasheet

Lap Joint Flanges RFQ Datasheet PDF

Download the visible product-page technical data as a PDF before sending drawings or line items. This datasheet is generated from the page's published RFQ scope table and does not invent standard dimensions.

Source: the Engineering Snapshot and product technical data already visible on this page. Use: early buyer screening, internal RFQ routing and drawing-preparation notes. Control note: final manufacturing and inspection still follow the buyer's current standard, drawing revision, tolerance note and project specification.
Download RFQ Datasheet PDF Send Product RFQ

This direct link is not gated by a form. For ASME B16.5 Class 150 selected dimensions, use the standard dimension check sheet where shown below.

Product Scope and Use Cases

Open this page when your RFQ matches one of these scope items, or send a drawing if the forged part is non-standard.

ASME B16.5 lap joint and EN 1092-1 type 02 / 04 loose flange review

Rotating loose flange over stub end or flat welded collar

Carbon, low-temperature, stainless and duplex steel grades

MTC 3.1, dimensional report and NDT stated before quotation

Also Known As

These names may appear in drawings, purchase lists, distributor RFQs and supplier shortlists.

lap joint flangeloose flangelive flangeswivel loose flangeEN 1092-1 type 02 / 04 flange

Standards, Materials and Review Data

The strongest RFQ gives the commercial team the same technical language used by engineering, QA and the final buyer.

Standards / Drawings

  • Project drawing or purchase specification
  • ASME B16.5 where flange dimensions follow ASME classes
  • EN 1092-1 / DIN where PN and DN requirements are specified
  • GOST 33259, 12820 or 12821 where CIS project requirements apply
  • ASTM, EN or project material standards as listed in the RFQ

Material Grades

  • ASTM A105 carbon steel
  • ASTM A350 LF2 low-temperature carbon steel
  • Stainless steel grades such as 304, 316, 321 or 347
  • Duplex and super duplex grades when specified by the project
  • Alloy steel or drawing-specified grades subject to feasibility review

Review Points

  • Size, DN or NPS
  • Pressure class or PN rating
  • Drawing revision and critical dimensions
  • Facing, bore, bolt pattern and machining tolerance
  • Quantity, destination country and packing requirement

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.

Material review

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

Forging process confirmation

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

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.

Rough machining

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

Final machining

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

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.

Marking, packing and export document preparation

Marking, packing and export documents are prepared by PO line item so the Lap Joint 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

Required RFQ Data

Send these details in the first message to avoid repeated clarification and mismatched offers.

Standard or drawing

Size / DN / NPS

Pressure class / PN

Material grade

Facing

Bore

Quantity

Heat treatment

Inspection requirement

Destination country

Third-party inspection need

Common RFQ Mistakes

These issues make supplier offers look cheaper or faster than they really are because the technical scope is incomplete.

  • Sending a product name without standard, drawing or pressure rating
  • Leaving bore, facing or bolt pattern unclear
  • Mixing DN, NPS, PN and class references without a drawing
  • Omitting inspection documents until after price discussion
  • Forgetting destination country, packing or third-party inspection requirements

FAQ

Short answers for common RFQ questions.

What is the difference between a lap joint flange and a slip-on flange?

A slip-on flange is welded directly to the pipe. A lap joint flange is not welded at all: it rotates freely behind a stub end or flat collar that carries the sealing face, so bolt holes can be aligned after fit-up and the flange material can differ from the wetted material.

When are loose flanges the economic choice?

On stainless or lined lines, a carbon-steel loose flange over a stainless stub end saves alloy cost; and on lines that are dismantled often, the rotating flange speeds up bolt alignment.

What must an RFQ state for lap joint or loose flanges?

Standard (ASME B16.5 lap joint or EN 1092-1 type 02/04), size and rating, whether stub end or collar is included, material grades for each part, quantity and document scope such as MTC 3.1.

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

Weld Neck vs Slip-On Flanges

Compare weld neck and slip-on flange RFQ decisions including hub design, welding, bore, facing, pressure class, inspection and document scope.

Forged Flange RFQ Checklist

Prepare forged flange RFQs with standard, size, pressure class, material, facing, quantity, inspection documents and destination details before quotation.

EN/DIN vs ASME Flanges

Compare EN 1092-1, DIN legacy and ASME flange RFQ details including DN/PN, NPS/Class, materials, facing, documents and drawings.

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

Blind Flanges

Send blind flange RFQs for ASME, EN, DIN, GOST and project drawing requirements with material, class, facing, bore, NDT and MTC 3.1 review.

Ring Flanges

Send RFQs for ring flanges and forged ring blanks by drawing, OD, ID, height, material, machining allowance, heat treatment and inspection.

Long Weld Neck Flanges

Review long weld neck and high hub flange RFQs by drawing, overall length, bore, facing, material, class and inspection requirements before quotation.

High Pressure Flanges

Send Class 600, 900, 1500 and 2500 high-pressure forged flange RFQs with RF, RTJ, material, NDT and inspection requirements.

ASME B16.5 Flanges

Send RFQs for ASME B16.5 forged flanges, weld neck, slip-on, blind, socket weld, threaded and lap joint types with material and inspection review.

GOST Flanges

Send GOST flange RFQs for Russian and CIS projects with DN, PN, material, drawing, inspection and export document requirements.

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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