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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

Confirm in one screen that the photo, the product name and the supply scope all describe 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.

Product family: Flanges

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
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Lap Joint Flanges Technical Specification

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

Scope and rating
Technical basisThis product is reviewed against its drawing, standard, material grade, quantity, inspection requirement and destination country.
Standards and materials
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
Geometry, tolerance and inspection
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.
Reviewed before quotation
  • 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
Buying logic
Best-fit RFQBest where bolt alignment, frequent dismantling or alloy cost saving over stainless stub ends drives the design.
Buyer applicationStainless and lined lines, water and utility systems, frequently opened piping and distributor stock.
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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.

Also known as

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

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 Lap Joint 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 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

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

  • Standard or drawing
  • Size / DN / NPS
  • Pressure class / PN
  • Material grade
  • Facing
  • Bore
  • Quantity
  • Heat treatment
  • Inspection requirement
  • Destination country
  • Third-party inspection need

Avoid these omissions

  • 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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