Spectacle Blind Flange (Figure-8 Blind Flange)

What is a spectacle blind flange (figure-8 blind flange)?

A spectacle blind flange is also known as a figure-8 blind flange,it is made of two pieces metal discs which are joint together by a part of steel handle in the middle.One disk is a solid plate( just like blind flange) and the other is a ring.Its shape is similar to a pair of glasses,so it is celled  the spectacle blind flange.The spectacle blind flange(figure-8 blind flange) is a safety device used to isolate piping or equipment that needs to be inspected or removed from a piping system.Its end of the ring that connects to the pipe to allow flow throgh the pipe during operation,similar to the end of the blind flange that connect to the pipe to prevent flow during maintenance.Unlike valves,spectacle blind flanges are permanent or long term isolation block.It can be rotated to place the blind or hollew end into the ductwork so that the system can be opened or closed.

Spectacle Blind Flanges

What is a spade and ring spacer?

A spade and ring spacer is basically the same as spectacle blind flange, except that both are not attached to each other.

A flange spade, also known as a steel “blanking spade”, or “single-blind”, “blank” or “paddle blind”, is a metallic ring used to isolate a pipe (it has the same scope as a spectacle blind). To close the pipe, the spade is inserted between the flanges; to open the pipe, the spade is removed, and the ring spacer takes its place.

Field staff understands if a pipe is open or closed, as blanking spades have one single signaling hole on the device holder, and ring spacers have instead two holes.

Ring spacer and spade

A spectacle blind combines a flange spade and a ring spacer in a single device (this is the reason why flange spades are called “single-blinds” or “blanks”). The difference is that spectacle blinds may need some space to be rotated, and this space is not always available due to the routing of the piping system. This is when two separate devices are used, as they do not require rotation to be installed.

Flange spades and ring spacers are manufactured according to the ASME B16.48 specification and belong to the family of pipeline isolation devices. Spades, ring spacers, and spectacle blinds are available in multiple sizes (from 1/2 inch to 24 inches, and pressure rating from 150 to 2500#) and material grades (the same available for standard flanges) depending on the fluid conveyed by the pipeline.

The difference between spade,ring spacer and spectacle blind flange is shown in the image:

Spectacle blind flange and spade and ring spacer

Specifications of spectacle blind flange(Figure-8 blind flange)

Size: 1/2″(15NB) to 24″(600NB)

Pressure class: CLASS 150, CLASS 300,CLASS 600, CLASS 900, CLASS 1500, CLASS 2500,

PN 2.5 to PN 250

Flange Face Type: Raised Face (RF),Flat Face (FF),Ring Type Joint (RTJ)

Spectacel blind flange material gardes:

Carbon steel:

• ASTM/ASME A105 Specatacle Blind Flange
• ASTM/ ASME A 350 LF 2 Specatacle Blind Flange
• 20# Specatacle Blind Flange
• Q235 Specatacle Blind Flange
• 16Mn Specatacle Blind Flange

Stainless steel:

• ASTM A182 Gr F304 Spectacle Blind Flange
• ASTM A182 Gr F304L Spectacle Blind Flange
• ASTM A182 Gr F310 Spectacle Blind Flange
• ASTM A182 Gr F316 Spectacle Blind Flange
• ASTM A182 Gr F316L Spectacle Blind Flange
• ASTM A182 Gr F317 Spectacle Blind Flange
• ASTM A182 Gr F317L Spectacle Blind Flange
• ASTM A182 Gr F321 Spectacle Blind Flange
• ASTM A182 Gr F347 Spectacle Blind Flange

Alloy steel:

• A350 Gr LF2 Spectacle Blind Flange
• A350 Gr LF3 Spectacle Blind Flange
• A182 Gr F1 Spectacle Blind Flange
• A182 Gr F5 Spectacle Blind Flange
• A182 Gr F9 Spectacle Blind Flange
• A182 Gr F11 Spectacle Blind Flange
• A182 Gr F12 Spectacle Blind Flange
• A182 Gr F22 Spectacle Blind Flange

Nickel alloy steel:

Haihao Group can provide a variety spectacle blind flange,as follows:

• ANSI/ASME B16.48 class 150 spectacle blind flange
• ANSI/ASME B16.48 class 300 spectacle blind flange
• ANSI/ASME B16.48 class 600 spectacle blind flange
• ANSI/ASME B16.48 class 900 spectacle blind flange
• ANSI/ASME B16.48 class 1500 spectacle blind flange
• ANSI/ASME B16.48 class 2500 spectacle blind flange

Haihao Group is committed to providing high quality flanges and service with on–time shipments to customer. Our products are mainly for Petroleum, natural gas, petrochemical, shipbuilding, power generation, pulp and paper industries.Haihao Group is produced strictly in accordance with the international standard of ASME/ANSI,BS,DIN,EN,JIS,GOST,UNI,ISO and specifications.We do many specials and will help you design and specify the flange that best fits your needs.Email:sales@haihaogroup.com