Spectacle Blind Flange Manufacturer, Supplier & Exporter
A spectacle blind flange, also known as a figure-8 blind, combines a solid blind disc and an open spacer ring joined by a web, so it looks like a pair of spectacles. Raaj Fittings manufactures and exports spectacle blinds to ASME B16.48 in stainless steel, duplex, nickel alloys, carbon steel and alloy steel, with raised face or ring type joint faces.
The spectacle blind is installed permanently between two pipe flanges. With the spacer ring in the line the pipe is open; to isolate it, the bolts are slackened, the plate is rotated and the solid disc is brought into the line. Because one half is always visible outside the flanges, operators can see at a glance whether the line is open or closed.
All spectacle blinds are supplied with EN 10204 3.1 mill test certificates, with 3.2 certification and third-party inspection on request.
We export spectacle blind flanges to EPC contractors, refineries and stockists across the Middle East and GCC, Europe and the Americas, made to the ASME, EN or DIN standard your project specifies, with PED-compliant supply for European projects on request.
Spectacle Blind Flange Specifications
½" NPS to 24" NPS to ASME B16.48 (larger sizes are normally supplied as separate paddle blinds and spacers)
ASME Class 150, 300, 600, 900, 1500 and 2500
ASME B16.48 (line blanks); legacy API 590 dimensions on request
Raised Face (RF) / flat finish for RF flanges; Ring Type Joint (RTJ) with octagonal or oval ring ends
To ASME B16.48 for the size, class and facing, or as calculated for the design conditions
Cut from plate or forged, and CNC machined
EN 10204 3.1 mill test certificate as standard; EN 10204 3.2 on request
Materials & Grades
We supply spectacle blind flanges in the following materials and grades. All grades are supplied with EN 10204 3.1 / 3.2 Mill Test Certificates.
Stainless Steel Spectacle Blind Flanges
Stainless steel flanges offer excellent corrosion resistance and are essential in chemical, pharmaceutical, food processing, and marine environments.
(ASTM A182 F304 / F304L) General corrosion resistance
(ASTM A182 F316 / F316L) Superior resistance to chlorides, acids; marine & pharmaceutical service
(ASTM A182 F316H) High-temperature elevated creep strength
(ASTM A182 F321) Titanium-stabilized; suitable for sustained elevated temperatures
(ASTM A182 F347) Columbium-stabilized; used in heat exchangers and high-temperature piping
High alloy; exceptional resistance to strong acids
Duplex & Super Duplex Stainless Steel Spectacle Blind Flanges
Duplex and super duplex grades offer approximately twice the yield strength of standard austenitic stainless steel, combined with excellent resistance to stress corrosion cracking and pitting — making them ideal for offshore, subsea, and chemical processing.
(UNS S31803 / S32205) Used in offshore platforms and chemical processing plants
(UNS S32750) Ideal for seawater handling and desalination systems
(UNS S32760) Designed for high-chloride offshore service applications
Nickel Alloy Spectacle Blind Flanges
For the most aggressive corrosive environments — including concentrated acids, caustic solutions, sour gas service, and extreme temperatures — we offer flanges in a full range of nickel alloys.
(UNS N06600) High-temperature oxidation resistance
(UNS N06625) Outstanding corrosion resistance for offshore and subsea service
(UNS N08825) Excellent resistance to phosphoric and sulfuric acids
(UNS N10276) Broad-spectrum corrosion resistance in acids and chlorides
(UNS N06022) Superior resistance to oxidizing acids
(UNS N04400) Suitable for seawater, hydrofluoric acid, and marine environments
(UNS N08020) Engineered for sulfuric acid service
Exceptional corrosion resistance with low weight
(C70600 / C71500) Preferred for marine and seawater piping systems
Carbon Steel Spectacle Blind Flanges
Carbon steel is the standard choice for general-purpose, non-corrosive, and elevated-temperature services. The primary grade for forged carbon steel flanges is ASTM A105, and for low-temperature service, ASTM A350 LF2.
Primary grade for forged carbon steel fittings and flanges — covers ambient and elevated-temperature service in pressurised piping systems.
Low-temperature carbon steel, impact-tested for service down to -46°C (-50°F) — LNG, cold climate, and cryogenic piping applications.
Alloy Steel Spectacle Blind Flanges
Alloy steel flanges are specified for high-temperature, high-pressure service in power generation, petrochemical, and refinery applications.
(5% Cr, ½% Mo) Designed for elevated temperature refinery service
(9% Cr, 1% Mo) Suitable for high-temperature steam and hydrogen service
(1¼% Cr, ½% Mo) Widely used in thermal power plant piping systems
(2¼% Cr, 1% Mo) Used in high-temperature pressure vessels and reactors
(9% Cr, 1% Mo, V, Nb) Engineered for ultra-high-temperature power plant steam lines
Why Use a Spectacle Blind?
Valves alone are not considered a positive isolation for maintenance, because they can leak or be opened by mistake. A spectacle blind provides a physical barrier: once the solid disc is in the line, nothing can pass. Leaving the blind permanently in place between the flanges means isolation can be applied quickly and safely, and the visible spacer or blind half shows the line status to everyone on site.
- Positive isolation — a solid steel barrier for maintenance, inspection and confined-space entry.
- Visible status — the half outside the flanges shows whether the line is open or blinded.
- Always on hand — the blind and spacer are one piece, so neither can be lost or mixed up.
- Same bolting — fits between standard ASME B16.5 flanges using longer stud bolts.
Spectacle Blind or Paddle Blind?
Spectacle blinds are convenient up to medium sizes. In large diameters and high pressure classes the combined plate becomes heavy and awkward to turn, so separate paddle blinds and ring spacers are used instead and swapped when required. To close the end of a line rather than isolate it mid-run, a blind flange is used.
Matching the Flange Facing
For raised face flanges, the spectacle blind has flat faces that sit on two gaskets. For ring type joint flanges, the blind has machined ring ends that engage the grooves of the weld neck flanges on either side, so the facing must be specified when ordering.
Applications & Industries
- Isolation points at equipment such as pumps, compressors, vessels and heat exchangers
- Battery-limit isolation in refineries, petrochemical and gas plants
- Hydrocarbon and toxic-gas lines where positive isolation is mandatory
- Steam and feedwater systems in power plants
- Offshore process and utility systems in duplex and super duplex
- Chemical, fertiliser and LNG plants
See all flange types we manufacture.
Testing, Inspection, Marking & Packing
Spectacle blinds are produced under our quality assurance process:
- Incoming material verification with PMI testing
- Chemical and mechanical testing to the applicable ASTM plate or forging specification
- Dimensional inspection of thickness, outside diameters, spacer bore and web
- Surface finish check on the gasket faces, and ring-end dimensions on RTJ blinds
- Marking with grade, size, class, facing and heat number on the web
Supplied with EN 10204 3.1 mill test certificates; EN 10204 3.2 certificates and third-party inspection are available on request.
Flanges are packed for export with gasket faces protected by covers, rust-preventive coating on carbon and alloy steel, and seaworthy wooden cases; marking, tagging and packing to your specification are available on request.
Why Choose Raaj Fittings for Spectacle Blind Flanges?
Raaj Sagar Steels has supplied piping components since 2003 and today manufactures flanges at two plants in India for buyers in the Middle East, Europe and the Americas.
- Manufactured in-house — Spectacle blind flanges are made in our own plants, so material, dimensions and delivery stay under our control.
- Ready stock, short lead times — common sizes and grades are held in stock for prompt dispatch; other sizes, grades and specials are manufactured to order.
- Certified quality — ISO 9001:2015, ISO 14001:2015 and ISO 45001:2018 certified; PED 2014/68/EU and IBR supply available, and NACE MR0175 / ISO 15156 material on request.
- 100% material verification — PMI testing on incoming material and EN 10204 3.1 mill test certificates with every order; 3.2 certificates on request.
- Third-party inspection ready — we regularly work with SGS, Bureau Veritas, TÜV and DNV.
- Export documentation — MTCs, certificates of origin, packing lists and inspection reports to suit projects in the GCC, Europe and the Americas.
- Export packing — seaworthy packing with end and face protection, and packing to your specification on request.
- Fast response — our team replies to enquiries within one business day.
Spectacle Blind Flanges — FAQs
A spectacle blind is a steel plate with a solid blind disc at one end and an open ring at the other, joined by a web. Installed between two flanges, it can be turned to either block the line or let fluid flow through the ring.
ASME B16.48 covers spectacle blinds, paddle blanks and paddle spacers for use between ASME B16.5 and B16.47 flanges. It replaced the earlier API 590 standard.
A closed valve can leak or be opened by mistake. A spectacle blind places a solid metal barrier in the line, and the visible half outside the flanges shows its position, so it is accepted as positive isolation for maintenance.
In large sizes and high pressure classes a one-piece spectacle blind becomes very heavy. Separate paddle blinds and ring spacers are then used and exchanged as needed.
Give the size, pressure class, flange facing (RF or RTJ), material grade and the mating flange standard. For RTJ blinds, state the ring number as well.
Yes. We supply spectacle blind flanges for projects under the European Pressure Equipment Directive (PED 2014/68/EU), and with IBR certification for Indian boiler applications. NACE MR0175 / ISO 15156 compliant material is also available on request for sour service in the Middle East and the Americas.
