A blind flange is the solid disc you bolt on to close the end of a pipe run, the unused nozzle on a vessel, or any spool that you may want to take out for cleaning. RP Sales handles blind-flange enquiries across several ASME pressure classes, forged-material families and RF, FF or RTJ face types. The safe comparison starts with the controlled piping class and mating equipment: size, class, material, face, finish, bolting and inspection must agree. A dated quotation then records the offered source, document package, current availability, commercial basis and Kanpur delivery commitment.
Pressure classes and RFQ controls
ASME pressure class is not a stand-alone pressure limit. The permitted rating depends on material group, temperature and the controlled standard edition. Use the table as an enquiry checklist; request current availability and dates separately.
| Pressure class | Enquiry detail | Engineering check |
|---|---|---|
| Class 150 | State size, material, face and quantity | Verify rating in the controlled standard tables |
| Class 300 | State size, material, face and quantity | Verify rating in the controlled standard tables |
| Class 600 | State size, material, face and quantity | Verify rating in the controlled standard tables |
| Class 900 | State size, material, face and quantity | Verify rating in the controlled standard tables |
| Class 1500 | State size, material, face and quantity | Verify rating in the controlled standard tables |
| Class 2500 | State size, material, face and quantity | Verify rating in the controlled standard tables |
Materials — A105 through F22
These are familiar forging grade families, not automatic application mappings. The project material specification and design code control the selection and acceptance tests.
ASTM A105 (carbon steel forging)
A carbon-steel forging specification frequently seen on piping material schedules. Suitability depends on the applicable code, design-temperature limits, toughness requirements, fluid and corrosion provisions; availability is confirmed on the quotation.
ASTM A182 F304 / F304L (austenitic stainless)
An austenitic stainless forging grade family. The project materials engineer should evaluate the actual chemistry, fabrication route, corrosion mechanism and code rules; a sector label does not prove suitability.
ASTM A182 F316 / F316L (Mo-bearing austenitic stainless)
A molybdenum-bearing austenitic stainless forging grade family. Selection still requires the project corrosion review, material specification and design conditions rather than a universal F304-versus-F316 rule.
ASTM A182 F11 (1.25 Cr 0.5 Mo)
A chromium-molybdenum alloy forging grade. Do not infer a service-temperature band or interchangeability with a tube grade from the alloy shorthand; verify the governing material and design-code tables.
ASTM A182 F22 (2.25 Cr 1 Mo)
A chromium-molybdenum alloy forging grade. The design engineer must check allowable stress, heat treatment, compatibility, joining and code requirements for the exact material specification and edition.
Face types — RF, FF, RTJ
- Raised Face (RF): a raised gasket- seating geometry. State the required face finish and gasket specification and verify both against the mating flange and controlled piping class.
- Flat Face (FF): a face without the RF projection. Use it only when the equipment and piping specifications call for that mating arrangement; review bolting and gasket loading with the responsible engineer.
- Ring-Type Joint (RTJ): a machined groove for a specified ring gasket. Class alone does not make RTJ the default; groove details, ring material and the mating flange must match the project specification.
How to compare a delivered blind-flange offer in Kanpur
A source location does not by itself establish landed cost or delivery time. For a Kanpur requirement, give each bidder the same destination PIN code, unloading constraint, required date, packing need and quantity. Ask for the ex-works point, freight basis, taxes as applicable, validity, current availability and promised dispatch date as separate fields.
Compare manufacturer identity, traceability and document schedule before comparing totals. If inspection is needed, define the witness point, notice period, acceptance record and release responsibility in the enquiry. These details prevent a nominally lower quote from hiding a different scope. See the wider Kanpur steel market guide for the freight-geography picture.
Keep the technical and commercial comparisons separate. The technical tab should record every bidder's standard edition, manufacturer, drawing revision, material specification, heat- treatment condition, dimensions, facing, marking and proposed deviations. The commercial tab should record quantity basis, packing, freight, applicable taxes, validity and dates. This prevents a lower landed total from being accepted when the offer actually uses a different face, material or document scope.
For replacement work, collect the existing flange nameplate or records, a measured bolt-circle sketch and photographs, but do not treat field measurements as the design authority. The maintenance or piping engineer should reconcile them with the controlled line class and equipment drawing. A matching outside diameter or bolt pattern alone cannot confirm the pressure class, facing, material or gasket arrangement.
Before order release, close every bidder exception in writing. The purchase order should identify the approved datasheet and drawing revisions, inspection notice point, marking, packing and document due dates. For Kanpur site delivery, also state vehicle access, unloading responsibility and whether bolting or gaskets are separate line items. Final acceptance should compare physical identification and records with that approved schedule, not with generic website copy.
What to include in a blind flange enquiry
- Standard: ASME B16.5 (1/2"–24") or B16.47 Series A/B for larger sizes.
- Size: nominal pipe size (NPS / NB) the flange mates to.
- Pressure class: 150 / 300 / 600 / 900 / 1500 / 2500.
- Material grade: A105 / F304 / F316 / F11 / F22 / LCC / F91.
- Face type: RF / FF / RTJ (and surface finish if not standard).
- Quantity and destination PIN code.
- Inspection documents: state the required document type, traceability and witness scope; do not assume EN 10204 3.1 or 3.2 from the product name.
Choosing between a blind flange and a welded cap
Blind flanges suit pipe-end isolation points that need access for cleaning, inspection, pressure testing or a future tie-in. The piping class should define the matching flange standard, pressure class, material, facing, gasket and bolting. Kanpur buyers should send that piping-class sheet with the BOQ so the closure is checked as an assembly rather than quoted as a loose disc.
A welded cap may suit a permanent closure when the approved piping design does not require later access. That choice belongs to the project engineer because maintenance strategy, welding procedure, examination scope and system isolation all affect it. Procurement should not replace a specified blind flange with a cap, or a cap with a blind flange, without an approved drawing revision.
Estimating blind flange shipment weight
Sourcing teams need shipment mass for handling and commercial comparisons. A solid-disc geometry calculation can provide an early estimate when the approved manufacturer drawing gives the outside diameter and thickness:
Estimated blank mass = solid-disc volume × material density
Treat that result only as a geometry estimate. It is not an ASME B16.5 table value, and a finished flange differs from a plain disc because of bolt holes, facing details, machining allowances and material density. Do not insert assumed dimensions when the drawing has not been issued.
For quotation, ask the manufacturer for the unit mass tied to the offered size, class, material, facing and drawing revision.
Before transport booking, reconcile the estimate with the offered manufacturer's drawing, final packing list and weighment record. Those documents account for finished geometry, protective packing and any separately ordered bolting or gaskets.
Common procurement mistakes in blind flange sourcing
A recurring error is leaving gasket-face finish unstated. The applicable flange standard, project piping class and gasket specification control the required finish; a generic roughness band copied from another job may not apply to the offered face or edition. Put the finish and inspection method on the drawing and verify the mating components together.
Second, buyers fail to cross-reference the applicable pressure-temperature rating. A pressure class by itself is not a maximum allowable working pressure. The engineer must check the controlled ASME B16.5 table for the specified material group and design temperature, then confirm that basis on the approved datasheet. We do not publish a substitute rating from an unverified secondary table.
Sources and standard references
The physical and chemical criteria on this page are compiled from primary industry specifications and regulatory standards. Engineers can verify these criteria through these reference materials:
- American Society of Mechanical Engineers (ASME): use the controlled project edition of ASME B16.5 for flange dimensions, facings and pressure-temperature ratings.
- American Society for Testing and Materials (ASTM): ASTM A105/A105M Forged Carbon Steel Piping Components specification. (Retrieved: 3 September 2026)
- ASTM International: ASTM A182 Forged Alloy and Stainless Steel Pipe Flanges specification. (Retrieved: 3 September 2026)