Blind Flange RFQ Guide: RF, RTJ, FF & Class

Summary

Blind flange RFQs look simple because the part closes a line or vessel nozzle, but quotation accuracy depends on standard route, pressure class, facing, no-bore or custom-bore wording, material, inspection documents and whether the buyer actually needs a blind flange, spectacle blind or spacer.

Choose the governing route: ASME B16.5, ASME B16.47, MSS SP-44, EN/DIN, GOST or project drawing

State RF, FF, RTJ or special facing before price comparison

Confirm no-bore supply or show any tapped hole, center bore, hub or drawing-controlled detail

List MTC 3.1, dimensional report, NDT, PMI, marking and packing requirements in the first RFQ

Engineering Selection Notes

Blind flanges are often treated as commodity closures, but the engineering load path is different from a weld neck or slip-on flange. There is no pipe bore through the center in a standard blind flange, so internal pressure and bolt loading act across a solid plate. That makes thickness, facing, material route and dimensional standard more important than the short product name.

The first tradeoff is standard route. ASME B16.5 is the normal ASME route through NPS 24, while ASME B16.47 takes over for large-diameter steel flanges from NPS 26 to NPS 60. Pipeline projects may specify MSS SP-44, and European or CIS projects may use EN/DIN or GOST wording. A supplier should not guess between those routes because bolt pattern, pressure class language, facing and document habits can change.

The second tradeoff is whether the buyer really wants a plain blind, an RTJ blind, a flat-face blind, a tapped blind or a spectacle blind / spacer assembly. RFQ text such as blind flange Class 600 A105 is not enough when a mating valve requires FF, an RTJ gasket is specified, a center NPT tapping is needed for testing, or a spectacle blind is required for positive isolation. Put those details in the first message so offers are comparable.

Source Basis

The tables below use public standard-scope notes and buyer document rules, not copied proprietary dimension tables.

ASME B16.5 2025 scope - Used for B16.5 size, class and scope statements covering pressure-temperature ratings, materials, dimensions, tolerances, marking and testing.
ASME B16.47 large-diameter flange scope - Used for large-diameter NPS 26 through NPS 60 and Class 75 through 900 scope statements.
ANSI note on ANSI/MSS SP-44-2026 - Used for current MSS SP-44 pipeline-flange scope, class coverage and forged-steel or steel-plate blind-flange material note.
ISO 9712:2021 NDT personnel scope - Used for NDT method and personnel-qualification context when buyers specify UT, MT, PT or RT requirements.
EN 10204 Type 3.1 explanation - Used for the practical explanation that Type 3.1 certificates report actual test results from the supplied lot and are endorsed by the manufacturer's independent representative.
Texas Flange blind flange and facing notes - Used only for practical blind-flange application notes: no central opening, custom tapping / bore possibilities and RF / FF / RTJ face choices.

Blind Flange Standard Route Check

Route	Published scope used in this guide	Blind-flange RFQ implication	What not to assume
ASME B16.5	Pipe flanges and flanged fittings NPS 1/2 through NPS 24; Class 150, 300, 400, 600, 900 and 1500 through NPS 24; Class 2500 through NPS 12	Use for most ASME blind flange RFQs in the NPS 1/2 to NPS 24 range; state NPS, Class, facing, material and document scope	Do not treat Class 2500 above NPS 12 as automatically covered by B16.5 without project review
ASME B16.47	Large-diameter steel flanges NPS 26 through NPS 60 with Class 75, 150, 300, 400, 600 and 900	Use when the blind flange is a large-diameter steel item; state series / drawing route where the project distinguishes it	Do not extend B16.5 dimensions above NPS 24 by habit
ANSI/MSS SP-44	Steel pipeline flanges NPS 12 through NPS 60 with Class 150, 300, 400, 600 and 900; ANSI notes that blind flanges can be forged steel or steel plate	Use only when the pipeline specification calls MSS SP-44; state whether forged supply is required or plate material is accepted	Do not replace ASME B16.5 or B16.47 with MSS SP-44 unless the project permits it
EN / DIN / GOST / project drawing	Controlled by the project standard, legacy drawing or purchaser specification rather than the ASME route	Send DN, PN, type, facing, material and drawing revision; do not quote from a translated product name alone	Do not assume PN, DN, bore, facing or drilling can be converted directly to ASME wording

Blind Flange Facing and Closure Decisions

Detail	Technical basis	RFQ data to send	Risk if missing
Plain blind / no bore	A standard blind flange is a solid closure without a central opening	Say blind flange, no bore unless a tapped hole, center opening or drawing detail is required	Supplier may quote a catalogue blind while the buyer expects a custom testing or drain connection
RF - raised face	RF uses a raised sealing area and is common in many ASME flange orders	State RF, standard, class, material, gasket or surface-finish note, and mating flange route	Offer may assume the wrong face or omit surface-finish requirements
FF - flat face	FF provides a flat gasket contact surface and is often used where the mating equipment requires flat-face contact	State FF, full-face gasket requirement, mating valve / equipment note and bolt-up restrictions if the project has them	Raised-face supply can be incompatible with the mating equipment
RTJ - ring type joint	RTJ uses a ring groove for a metal ring gasket and is often selected for higher-pressure or severe-service sealing	State RTJ, ring number or groove requirement, Class, material, hardness / NDT notes and inspection hold points	Groove machining, inspection time and document scope may be missed
Tapped, center-bored or custom blind	Practical blind flange supply can include custom NPT tapping, center bore, high hub or drawing-controlled machining	Attach drawing with thread, bore, hub, thickness and tolerance notes	The price comparison will mix standard blinds with custom machined parts

Inspection and Document Checklist for Blind Flanges

Control	When it matters	Evidence to request	RFQ note
MTC 3.1	Most EPC, oil and gas, petrochemical, marine and pressure-equipment RFQs	Material grade, heat number, chemical / mechanical test results and authorized inspection representative validation	Ask for EN 10204 3.1 or project certificate wording in the first RFQ
Dimensional report	Any standard blind where bolt circle, thickness, OD, facing or RTJ groove must be accepted before shipment	Measured dimensions against ASME, EN/DIN, GOST or drawing basis	List the critical dimensions instead of asking only for photos
NDT	High-pressure, large-diameter, heavy forged, RTJ or project-critical blind flanges	UT, MT, PT, RT or other method per project acceptance criteria and qualified personnel route	Specify method, acceptance level, report language and witness need
PMI / hardness	Stainless, duplex, alloy, NACE or material-mix orders	PMI report, hardness record or project-specific material verification	Do not wait until pre-shipment inspection to add alloy verification
Marking and packing	Export shipments, mixed line-item orders and project receiving checks	Heat number, material, size, class / PN, face, item number, packing list and case mark	Match product marks with MTC, dimensional report and packing list

Practical Checklist

Use this list before sending drawings or line items for quotation review.

Governing route: ASME B16.5, ASME B16.47, MSS SP-44, EN 1092-1, DIN, GOST or project drawing

Size and pressure designation: NPS / DN plus Class / PN exactly as written in the specification

Blind style: standard no-bore blind, tapped blind, center-bored blind, high-hub blind or drawing-controlled custom blind

Facing: RF, FF, RTJ or special face, plus gasket / ring groove / surface-finish note where applicable

Material: ASTM A105 / A105N, A350 LF2, A182 stainless, duplex, alloy or project material wording

Forging route: state forged supply if plate material is not acceptable for the project

Inspection: MTC 3.1, dimensional report, PMI, UT, MT, PT, hardness or third-party inspection

Commercial and logistics: quantity, delivery destination, packing, marking language and required delivery window

Common RFQ Mistakes

These points often cause repeated clarification, price revisions or document mismatch.

Asking for a blind flange with bore when the requirement is actually a custom tapped or center-bored blind
Leaving RF, FF or RTJ facing unspecified even though the blind must match a mating flange or gasket
Confusing a blind flange with a spectacle blind, spacer or line blank assembly
Requesting ASME B16.5 Class 2500 in sizes beyond the published B16.5 Class 2500 scope without drawing review
Using MSS SP-44 wording on a non-pipeline ASME RFQ without end-user approval
Assuming plate material is acceptable for a blind flange when the purchase specification requires forged supply
Adding RTJ groove inspection, NDT, PMI or third-party witness points only after price comparison
Omitting heat-number marking, packing list references or document language for mixed export shipments

FAQ

Short answers for buyers preparing this RFQ topic.

Does a blind flange normally have a bore?

A standard blind flange is a solid closure with no central bore. If the buyer needs NPT tapping, a center hole, drain connection or special boss, the RFQ should call it out as a custom detail with a drawing.

Is a blind flange the same as a spectacle blind?

No. A blind flange closes a flanged end or nozzle. A spectacle blind, spacer or line blank is an isolation assembly used between flanges, so it should be quoted from the correct product route or drawing.

Which facing should a blind flange RFQ specify?

Specify RF, FF, RTJ or the drawing-controlled face. The blind must match the mating flange, gasket and project standard; RTJ or FF wording should be visible before price comparison.

What inspection documents should be requested for blind flanges?

Common requests include MTC 3.1, dimensional report, marking photos, PMI for alloy grades, UT / MT / PT where specified and third-party inspection documents if the project has hold points.

PDF Datasheets for RFQ Review

Use these direct PDF links with the article before sending line items. The PDFs are generated from published product-page RFQ scope tables and do not invent standard dimensions.

Blind Flanges RFQ Datasheet

Use this PDF when blind flange standard, facing, material, no-bore or custom-bore detail and inspection scope must be aligned before quotation.

Download PDF

ASME B16.5 Flanges RFQ Datasheet

Use this PDF when the RFQ is controlled by ASME B16.5, NPS, Class, facing, material and document requirements.