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Spectacle Blinds |
Updated May 2026
Spectacle blinds, also known as line blanks, are safety devices used in industrial piping systems to reliably shut off sections of pipes during maintenance, inspections, or downtime.
Unlike a raised face (RF) flange connection, an RTJ flange connection is a metal⁃to⁃metal seal where a metal ring is placed between two RTJ flanges and this ring is compressed during the tightening of the flanges. This guarantees exceptional reliability under extreme pressure and temperature conditions.
Spectacle blinds are essential safety features in piping systems for reliably shutting off process fluids during maintenance, inspection, or system changes. The RTJ (Ring Type Joint) design offers a superior sealing solution for high-pressure applications, particularly in the oil, gas, and petrochemical industries.
RTJ-pectacle blind flanges according to ASME B16.48 are available in pressure classes from 150 to 2500, with sizes from NPS 1/2 to NPS 24, and intended for installation between ASME B16.5 flanges
Each RTJ gasket consists of a solid metal ring that can be mounted in specified flanges. These rings are manufactured according to the ASME B16.20 standard and meet precise dimensional requirements.
Both standards cover both oval and octagonal ring seals, with specific dimensional requirements for centerline distance, outer diameter, thickness, and web width etc.
OVAL
OCTAGONAL
Spades and Ring Spacers
As with an RF flange connection, separate spades and ring spacers are also available for the RTJ version, with both types featuring a handle, whereas a spectacle blind is a single unit. For RTJ blind flanges, the metal rings are also available in a customized, special form.
Spade RTJ type
Ring spacer RTJ type
Remark(s) of the Author...
Is it necessary to use Spectacle Blinds?
- I don't think so when it comes to large connections, because in practice they're often not
feasible. On paper, it looks simple: loosen a few screws, rotate the spectacle blind, and close
the flange connection. In practice, that's certainly not the case....
I am in favor of two separate flanges (ring and solid plate)
Spade handles
ASME B16.48 says.. spade handles may have no openings.
For spades that can be lifted by people, this is not a problem, but for a spade weighing hundreds of kilograms, a lifting device is required. Therefore, from a certain weight and size, a hole is usually made at the top of the handle to facilitate lifting. Many companies have their own rules for the construction of a spade handle, resulting in many different types and designs.
Related Post(s)
Dimensions NPS 1/2 to NPS 24, Pressure classes 150⁃2500 suitable for ASME B16.5 RTJ flanges...