Spectacle Blind Flange

Product Description

1. Product Introduction

The Spectacle Blind Flange is named for its shape: when the assembled flange element is viewed from the side, the solid blind section and the open spacer section together resemble a pair of spectacles. In practice, the flange element consists of two parallel flanged plates joined at their inner diameter by a center web — one half is a solid blind plate, the other half is an open spacer with a bore matching the pipe. The assembled element is bolted between two flange faces in the pipeline. When the solid blind half is positioned against the downstream flange face, the line is completely blocked (isolated position). When the element is rotated 180° and the spacer half is against the flange face, the line is open and flow passes through the spacer bore (bypass or operating position). The key safety advantage is that the isolation status is immediately and unambiguously visible from the outside — anyone can see from a glance whether the line is blocked or open. This eliminates the ambiguity associated with valves, which may appear closed but could be partially open or have a leaking seat. Spectacle blinds are specified in ISA and IEC hazardous-area standards as a primary means of energy isolation for lockout-tagout procedures, and they are required by OSHA and ATEX regulations in classified areas. Manufactured to ASME B16.48 as the dimensional standard.

2. Product Features

- Sizes from 1/2" to 24" NPS — standard small to medium pipeline range

- Pressure ratings up to CL2500 (CL150–CL2500) for all process pressure requirements

- Clear visual indication of isolation status from outside — no guesswork

- Dual-function: blind for isolation + spacer for normal flow, in one element

- No bolt removal or pipe cutting needed to switch between open and isolated states

- Required in hazardous-area isolation procedures per ISA S82 and IEC 60364

- Standard: ASME B16.48 (with dimensions per ASME B16.5/16.47 flange tables)

3. Core Specifications

Parameter	Specification
Size Range	1/2" – 24" NPS
Pressure Rating	CL150 – CL2500
Facing	RF (Raised Face), FF (Flat Face), RTJ (Ring Type Joint)
Configuration	Blind half (solid plate) + Spacer half (bore) in one element
Visual Status	Unambiguous external indication: ISOLATED or OPEN at a glance
Materials	Carbon steel, alloy steel, stainless steel
Standards	ASME B16.48
Certifications	API, ISO 9001, ISO 14001, ISO 45001, CE

4. Materials

- Stainless steel: ASTM A182 F304, F304L, F316, F316L for corrosive media

5. Product Standards

- ASME B16.48 — Line Blanks (Spectacle Blind, Spade, and Spacer Flanges)

6. Applications

- Line isolation for pump and compressor isolation during maintenance in refineries

- Safety-critical isolation at heat exchanger inlets and outlets in chemical plants

- Power plant turbine and boiler isolation for safe maintenance access

- Oil and gas production wellhead and separator isolation during workover operations

- Hazardous area energy isolation for ISA S82 / IEC compliance in classified locations

- Process line bypass switching between isolation and operating positions

7. Packaging

8. Customization

Non-standard thicknesses for higher test pressures, spade-and-spacer combinations (without spectacle web) for flanges requiring insertion depth, and special alloys for H₂S and sour gas service. Custom orientation markings and color-coded safety labels available.

For detailed specifications and applications, explore this product page.

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