Flange

A flange is a forged or cast collar that provides a bolted, removable connection between pressure-piping or vessel components, with a gasket sealing the joint, inspected for surface flaws, face condition, and bolting integrity.

Definition

Flange faces are inspected by visual examination, surface roughness measurement, and (for weld-neck flanges) full UT of the welded transition. ASME B16.5 governs dimensions; ASTM A105/A182 govern materials.

What it is

A bolted joint component providing a demountable pressure-tight connection, with sealing achieved by compressing a gasket between mating faces using controlled bolt load.

Damage mechanisms in service

Leakage is usually assembly rather than component: flange face condition, gasket selection, bolt lubrication and tightening sequence govern it. Inspection covers face damage, distortion, corrosion under the gasket seating area and bolt condition.

Governing codes

ASME B16.5 and B16.47 for dimensions and ratings; ASME PCC-1 for bolted joint assembly; ASME Section VIII Appendix 2 for flange design.

The common oversight

Chasing a leaking joint with more torque. Beyond a point, additional load distorts the flange and crushes the gasket, and the joint then cannot seal at any torque until the gasket and faces are addressed.

Where Flange fits in an inspection programme

A term is only useful when it connects to a decision. Flange appears in written procedures, in technique sheets, and in the records an owner or accreditation body reviews afterwards — which means the way it is defined in your documentation has to match the way it is applied on site. Where the two drift apart, audits find it. Atlantis writes and reviews procedures against the governing codes, trains inspection personnel to apply them, and builds the record-keeping that makes the evidence retrievable years later. Procedure development and code consulting · NDT training and certification · Ask us about your programme.

Related terms

Gasket — A gasket is a deformable sealing element installed between two flange faces to fill micro-irregularities and create a leak-tight pressure seal, available in spiral-wound, ring-joint, kammprofile, soft-cut, and other configurations.
Welded Joint — A welded joint is the connection produced when two metal components are fused together by welding, classified by joint type (butt, fillet, lap, corner, edge) and groove geometry (V, U, J, square), with NDT scope driven by joint type and code.
Butt Weld — A butt weld is a weld in a butt joint, joining two components edge-to-edge in approximately the same plane, with groove preparation (V, U, J) that allows full-penetration welding from one or both sides.
Valve — A valve is a pressure-containing mechanical device that regulates, directs, or controls the flow of a fluid by opening, closing, or partially obstructing passageways, inspected by visual, MT/PT, UT, and pressure testing.

More asset-type terms

Pressure Vessel · Storage Tank · Heat Exchanger · Fired Heater · Pipeline · FPSO · Riser · Jacket · Topsides · Wellhead

Where this comes up in practice

Terms like this one appear in three places that matter commercially: the written practice that governs how your personnel are qualified, the procedures and technique sheets that define how an examination is actually performed, and the evidence an auditor or client asks for when they want to know why an inspection was accepted. Getting the terminology right is the easy part; being able to produce the qualification record, the calibration traceability and the procedure revision that applied on the day of the inspection is the part that decides audits.

Atlantis NDT provides NDT training and certification against ASNT SNT-TC-1A and ISO 9712, ASNT Level III consulting for written practices and procedure approval, inspection management software that holds qualification, calibration and procedure-revision evidence in recoverable form, and an asset integrity platform that binds inspection results to the asset they describe. Browse the full NDT glossary or ask a Level III directly.