A reliable flange purchase begins with a controlled joint definition. Material, dimensions, pressure-temperature design, sealing face, gasket, bolting, mating pipe, inspection and assembly must tell the same story.
1. Start with the Service and Design Scope
Record the medium, concentration and contaminants, operating and design temperature/pressure, corrosion allowance, design life, piping code, line class, mating components, external loads and owner/EPC requirements. Identify the responsible engineering authority for material and joint design.
Name material specification, Grade/F-Grade, flange standard/edition, type, size, Class/PN, face and bore.
Control revision, datums, raw route, tolerances, face/groove, bore, bolt pattern, inspection and deviation approval.
2. Select the Flange Type by Joint Function
| Type | Definition to freeze | Interface to confirm |
|---|---|---|
| Weld neck | Hub, bore/schedule, transition and weld end | Mating pipe, WPS, face, gasket and bolting |
| Slip-on | Bore/clearance, thickness, weld scope and face | Pipe OD, insertion, weld detail and inspection |
| Blind | Raw route, thickness/profile and face | Pressure/design basis, gasket and bolting |
| Lap joint | Bore, thickness, bolt pattern and rotation | Stub-end lap, pipe, gasket and backing arrangement |
| Threaded/socket weld | Thread/socket, Class, bore and face | Pipe, assembly/weld procedure and service limitations |
| Long weld neck/custom | Neck/profile, bore, face and drawing datums | Equipment/nozzle design and project drawing |
3. Use a Standards Map, Not a Standards List
| Document | Typical role | Do not assume |
|---|---|---|
| ASTM B381 / ASME SB-381 when invoked | Titanium forging material, F-Grade, properties and purchaser-specified NDE within scope | It defines the finished flange dimensions or joint rating |
| ASTM B265 | Titanium plate/sheet material where an approved plate-cut route applies | It qualifies a finished flange automatically |
| ASME B16.5 | Flange materials, ratings, dimensions, tolerances, marking, testing and joint requirements within scope | Its listed material ratings automatically apply to every titanium Grade |
| ASME B16.47 | Large-diameter flange system within its stated scope | A steel-flange rating table can be transferred to titanium without engineering approval |
| EN / DIN / JIS pattern | Exact flange dimensional system and edition named by the project | Different PN/Class systems are directly interchangeable |
| EN 10204 3.1 | Inspection document type | It is a flange material or design standard |
4. Freeze the Raw-Material Route
State whether the flange starts from a forging, rolled ring, plate-cut blank or another approved form. The route can affect material specification, grain flow, heat treatment, machining allowance, NDE and design acceptance.
Define F-Grade, forging specification/edition, heat treatment, test basis and required NDE.
Define ring specification, reduction/route evidence, heat treatment, dimensions and traceability.
Use only when permitted; define plate Grade/specification, orientation, thickness, testing and finished design basis.
Do not use “100% forged” as a page-wide claim when blind, loose backing, plate-cut or custom products may follow different approved routes.
5. Grade Selection and Service Boundary
Select Grade/F-Grade using the actual medium, contaminants, temperature, stress, fabrication, crevice conditions and corrosion experience. Align the flange with mating pipe, stub end, gasket, bolting and any dissimilar-metal controls.
- Verify that the exact Grade/F-Grade is permitted by the project material specification and line class.
- Confirm chemistry/mechanical requirements and heat-treatment condition.
- Use corrosion data or a qualified materials engineer where service conditions are uncertain.
- Do not infer complete joint suitability from raw-material conformity.
6. NPS/DN, Class/PN and Pressure-Temperature Responsibility
State NPS or DN, Class or PN, dimensional system and edition. A Class/PN label does not automatically establish a titanium flange’s allowable pressure. The responsible engineer must confirm listed-material applicability or establish the design basis under the governing piping code.
- Record design and operating pressure/temperature as review inputs.
- Confirm corrosion allowance, external loads, fatigue, vibration and thermal cycling.
- Identify whether the requested standard is used as a full code basis or only a dimensional pattern.
- Document engineering assumptions and exceptions in the quotation.
7. Bore, Hub, End Preparation and Mating Pipe
For weld-neck and related flanges, state bore or matching pipe schedule/wall, hub dimensions, transition, weld-end preparation, internal alignment and machining tolerance. Provide mating pipe OD, wall, specification and WPS/fit-up requirements.
Confirm actual pipe OD/wall, bore, taper/transition, root face and bevel. A common schedule label does not by itself establish alignment or weld fit-up.
8. Face, Gasket, Groove and Surface Finish
Define RF, FF, RTJ or drawing-specific face; dimensions; facing finish or roughness/serration where required; groove geometry; runout/flatness; gasket type/material; cleanliness; and protective cover.
- Match gasket and face type to the project joint design.
- For RTJ, confirm ring/groove dimensions, ring material, hardness compatibility and inspection method.
- Do not describe every machined face as suitable for every gasket.
- Protect sealing surfaces from impact, abrasion, corrosion and contamination.
9. Bolt Pattern, Bolting and Assembly Interface
State bolt-circle diameter, hole count and diameter, hole orientation where relevant, flange thickness, bolt/stud specification, nuts/washers, gasket, lubrication policy, tightening method and responsible installer.
Torque cannot be selected from flange Class alone. It depends on fastener material and size, lubricant/friction, gasket characteristics, target preload, joint stiffness, service and the approved assembly procedure. Titanium thread galling controls must be project-approved and compatible with the service.
10. Manufacturing Route and Change Control
The route may include blank procurement, heat treatment, rough machining, drilling, bore/hub machining, facing/grooving, cleaning, inspection, marking and packing. Identify who performs each step and which changes require buyer approval.
- Approve raw form, Grade/F-Grade, heat/lot and heat treatment.
- Freeze dimensional standard or drawing revision and machining plan.
- Define hold/witness points before final facing or irreversible steps.
- Require written approval for source, route, subcontractor, material or drawing changes.
11. Inspection, Dimensional Control and NDE
Create an inspection plan that connects each requirement to a method, sampling rate, acceptance criterion and record. NDE type and extent should come from the material specification, design code, project specification and raw-material route.
| Control | Possible method when specified | Acceptance evidence |
|---|---|---|
| Material identity | MTC review, heat/lot verification, PMI if required | PO, certificate and marking agree |
| Dimensions | Calibrated inspection, gauges or CMM as appropriate | NPS/DN, thickness, bolt pattern, bore and hub conform |
| Face/groove | Profile, roughness/serration, runout and visual checks | Method and measurable criteria align |
| Raw material / surface | UT, PT, VT or other specified NDE | Extent, procedure, personnel and acceptance stated |
| Custom features | Drawing-based dimensional report | Revision, datums and critical dimensions match |
12. Traceability, Marking and Document Package
Maintain the link from raw heat/lot through heat treatment, machining, inspection, marking and packing. Agree the document index before production.
- MTC or inspection certificate linked to the ordered Grade/F-Grade and raw form.
- Dimensional, bore, bolt-pattern and face/groove report for the ordered sample plan.
- Heat-treatment, PMI, UT/PT and third-party reports where specified.
- Marking, deviation approvals, certificate index and packing list.
- EN 10204 3.1 only where requested as a document type and supported by the actual certification chain.
13. Packing, Handling and Delivery
Protect sealing faces, grooves, hubs, threads, bores and machined edges from impact, abrasion, moisture and contamination. Define caps/covers, separation, wraps, crates, lifting and maximum package weight.
- Separate line items, grades and heats/lots.
- Prevent direct contact that could damage faces or contaminate titanium.
- Align packing sequence with site or fabrication-shop priorities.
- State destination, Incoterm, named place and wood-packaging requirements.
14. Cost and Quotation Comparison
Price can be driven by Grade/F-Grade, raw-material route, type, size, Class/PN, face, bore, hub, machining allowance, NDE, dimensional reporting, quantity, packing and logistics. Normalize these items before comparing unit price.
- Compare identical material and dimensional specifications/editions.
- Separate raw blank, machining, tooling, inspection, packing and freight where useful.
- Record stock/MTO, MOQ, quantity tolerance, schedule stages and quotation validity.
- Place technical exceptions and exclusions beside the commercial offer.
15. Complete Titanium Pipe Flanges Purchase Guard
15.1 Service and design basis
- State media, temperature/pressure, corrosion allowance and design life.
- Name piping code, line class and responsible engineering authority.
- Identify external loads, fatigue, vibration and thermal requirements.
15.2 Flange type and raw route
- State weld neck, slip-on, blind, lap-joint, threaded, socket or custom.
- State forging, rolled ring, plate or approved raw form.
- Define hub, neck, loose/backing or special geometry.
15.3 Material and standards
- Name Grade/F-Grade/UNS and material specification/edition.
- Name flange dimensional standard/edition or drawing separately.
- Define permitted substitutions and approval route.
15.4 Size, Class/PN and dimensions
- State NPS/DN, Class/PN and whether the standard is full-code or dimensional reference.
- Define thickness, OD, bolt circle, holes, orientation and tolerances.
- Control custom geometry by drawing and revision.
15.5 Bore, hub and pipe interface
- Provide bore or mating pipe OD/wall/schedule.
- Define hub/transition, end preparation and internal alignment.
- Align WPS and fit-up requirements.
15.6 Face, gasket and groove
- State RF/FF/RTJ or custom face and dimensions.
- Define finish/serration/roughness, runout and inspection.
- Identify gasket or ring material and compatibility basis.
15.7 Bolting and assembly
- State bolt/stud, nut/washer and coating/lubrication requirements.
- Define tightening method and assembly responsibility.
- Use an approved preload/torque procedure rather than a generic table.
15.8 Inspection and evidence
- For every check, state method, extent/sampling, acceptance and report.
- Link heat/lot, finished flange, marking and documents.
- Define PMI, UT/PT, witness and third-party requirements.
15.9 Commercial and change control
- Normalize quantity, MOQ, currency, payment, validity and Incoterm.
- Separate raw material, machining, NDE, packing and freight.
- Record exceptions, deviations and schedule-reset events.
15.10 Packing and delivery
- Protect faces, grooves, threads, bores and hubs.
- Separate items by line, Grade and heat/lot.
- Align crate labels, packing list, documents and delivery sequence.
Red flags before purchase order
Blind, loose/backing and custom products have no confirmed raw-material route.
Material-table applicability and piping-code design responsibility are missing.
Finish, gasket/ring, bolting, preload and assembly basis are absent.
The MTC or NDE report cannot be traced to the finished marking and shipment item.
Decision gate
Do not release the order until service, flange type, material route, Grade, dimensions, face/bore, joint design, inspection, evidence, exceptions, packing and commercial terms describe the same deliverable.
16. RFQ and Pre-Order Checklist
Media, temperature/pressure, code, line class and corrosion basis.
Type, raw route, Grade/F-Grade, size, Class/PN and quantity.
Face/groove, bore, hub/end, bolt pattern and mating components.
Material and dimensional specifications/editions or drawing revision.
MTC, dimensions, face/groove, PMI/NDE, marking and traceability.
Quantity basis, MOQ, validity, packing, destination, Incoterm and date.
17. Titanium Pipe Flanges Purchasing FAQ
What is the difference between ASTM B381 and ASME B16.5?
ASTM B381 is a titanium-forging material specification. ASME B16.5 covers pressure-temperature ratings, materials, dimensions, tolerances, marking, testing and joint-related requirements for flanges within its scope. A purchase order may need both roles, but one does not replace the other.
Can ASME B16.5 dimensions be used for a titanium flange?
They may be specified as the dimensional pattern when the project approves that basis. Do not automatically transfer pressure-temperature ratings from listed material groups to a titanium material that is not covered by the applicable table.
When can a blind flange use plate material?
Only when the governing standard, design code and project specification permit the plate route and the ordered Grade, thickness, testing and traceability are defined. Do not treat plate-cut and forged routes as interchangeable without approval.
What should be matched on a weld-neck flange?
Match bore or pipe schedule/wall, hub and transition geometry, weld end preparation, NPS, face, bolt pattern, mating flange, gasket and project welding requirements.
Does RTJ automatically suit every titanium service?
No. Ring-groove dimensions, surface condition, ring material, hardness compatibility, bolting, load and project qualification must be reviewed as a complete joint.
How should two flange quotations be compared?
Normalize type, material specification and edition, Grade/F-Grade, raw route, size, Class/PN, face, bore, dimensions, inspection/NDE, documents, quantity, packing, Incoterm, schedule assumptions and exclusions.