What is a spectacle blind flange?

 
A spectacle blind – also known as a figure-8 blind – is generally a piece of metal that is cut to fit between two pipe flanges and usually sandwiched between two gaskets. A spectacle blind is often made from two metal discs that are attached to each other by a small section of steel.

The shape is similar to a pair of glasses or “spectacles” – hence the name spectacle blind. One end of the blind will have an opening to allow flow through the pipe during operation and the other end is solid to block flow during maintenance. They are generally installed as a permanent device to separate process piping systems.

The whole idea of a spectacle blind is so that one can be absolutely sure that an item of equipment is properly and securely blanked off with no possibility of any flow or leakage through a valve during maintenance. The flow can be diverted to other items of equipment but not just bypassed around the blank as this would compromise the safety function of the spectacle blind. The flow has to valved off and pressure relieved prior to loosening flange bolts and swinging the blind.

All Dims Per ASME B16.48

1. For use with Flat or Raised Face Flanges
2. Specify Surface in Microinch ASA 500, 250, 125, 63 or 32. If Not Specified Mill Finish Supplied.
3. Available with Phonographic Serrated Surface or Ground Finish. Available with Ring Type Joint
4. Normally Supplied in A285 Gr. C, A515 Gr 70, A516 Gr. 70, 304SS, 316SS. Other Materials Available

A figure-8 blank (also called a Spectacle Blind Flange) is+ a pressure-retaining plate with one solid end and one open end connected with a web or tie bar.

Size range:

• Size: 1/2” to 60”, DN 12mm to DN 1500mm
• Pressure class: Class 150 to Class 2,500, PN 2.5 to PN 250
• Facing: RF / RTJ

A spectacle flange is a specialty flange made of two metal discs attached in the middle by a small section of steel. Spectable flanges get their name because they look like a pair of reading glasses, or spectacles. Spectacle flanges, also known as spectacle blind flanges, are most commonly used on piping systems that need to be separated regularly or where the flow through the systems is regularly stopped. One end of the spectacle flange is solid, while the other end has a hole in the center. The spectacle flange can be rotated to place either the solid or hollow end within the pipe system, thereby opening or closing the flow.

For pipe Flanges-regularly seperated for isolation, maintenance or reasons, a spectacle extrudes Solution. Typically, spec blinds was mounted in the open position so-your flow pipe operates and is normally. Blinds is mounted onto one of the $number so is need to isolate a, it ' s easy!

Advantages of Spectacle Flanges

• Spectacle flanges require no welding for installation
• Spectacle flanges from Sunny Steel Flange have a wide range of pressure tolerances
• Sunny Steel will manufacture spectacle flanges to your specifications

Dimensions of spectacle blinds according to ASME B16.48

1. Spectacle blind 2.Flanges 3.Gaskets 4.Stud bolts

Spectical blind flange classes

• 150# RF Flange Rating
• 300# RF Flange Rating
• 600# RF Flange Rating
• 900# RF Flange Rating

Keywrods: Spectacle Blind Flanges, Spectacle Blind Flange, Spectacle Flanges, Spectacle Blind Flanges manufactory

Spectacle blind flange Usage

A spectacle blind is a safety device used to isolate a section of line or piece of equipment when the line or equipment needs to be inspected or removed from service. It is different than a valve in that the blind is a permanent or long term isolation device.

A spectacle blind is machined from a single piece of metal that is cut to match the pipe size, fit between two pipe flanges and requires an additional gasket when it is installed. Also, the bolts will need to be lengthened depending on what piping class and size blind is used. The thickness of the spectacle blind is specified based on the line pressure and pipe size.

The specification that determines the dimensions of a spectacle blinds is ASME B16.48 - Line Blanks. A line blank conforming to this standard will be marked in the following way:

• B16
• Nominal Pipe Size (NPS)
• Nominal Pressure Class
• Material
• Manufacturer's Name
• If RTJ, the ring number

One end of the blind will have an opening to allow flow through the pipe during operation and the other end is solid to block flow during maintenance.

Spec blind flange - line closed

Spec blind flange - line open

A spec blind is a combination of a ring spacer and single blind. They are usually permanently installed in a piping system and rotated as needed.

A figure-8 blank

A figure-8 blank (also called a Spectacle Blind Flange) is a pressure-retaining plate with one solid end and one open end connected with a web or tie bar.

Specifications:

• Size: 1/2” to 60”, DN 12mm to DN 1500mm
• Pressure class: Class 150 to Class 2,500, PN 2.5 to PN 250
• Facing: RF / RTJ

Material: 

• Cabon steel: A105, A350 LF2
• Stainless steel: A182 F304/F304L/F316/F316L/F321
• Alloy steel: F11, F12

Packing: plywood case and plywood pallet

Keywrods: Spectacle Blind Flanges, Spectacle Blind Flange, Spectacle Flanges, Spectacle Blind Flanges manufactory




Standards, Dimensions & Weight ASME B16.48 Class 150 ASME B16.48 Class 300 ASME B16.48 Class 600 ASME B16.48 Class 900 ASME B16.48 Class 1500 ASME B16.48 Class 2500

Key Features:
Can be attached to the pipe without welding (sometimes an additional seal weld is used as well)
Ideal for higher pressure and temperature applications for small pipe sizes
Not recommended for larger loads, especially when subjected to higher torque

Uses of threaded flanges:
Threaded flanges can be fitted to pipes of various sizes without welding and this is one chief benefit for which these flanges are highly demanded. They can be used in extremely high pressure applications, particularly at or near atmospheric temperature, where the necessary post weld heat treatment is not possible.

They are ideal for small diameter piping applications.
They are economical and time saving devices.
These threaded flanges are normally designed for non-cyclic applications.
The flanges are suitable to be used in applications where welding is hazardous.
They can be used in highly explosive areas.
These types of flanges are made from plate, and come in 3 different types.

The first and most widely used type are spec blinds – short for spectacle: these are flanges with two equal outside diameter (OD) parts welded together by way of a ‘bridge’. One of the parts also contains an inside diameter (ID), while the other is a blank, or blind. A whole is put at the halfway mark of the bridge. These are also called spectacles, figure 8’s, and figure 8 blanks, because of their resemblance to reading glasses (spectacles) and figure 8’s. These are referred to as ‘Line Blanks’ in the ASME/ANSI standards.

The second and third types are quite similar: both have longer bridges, referred to as ‘paddles’, which resemble longer handles. One type has only an OD, and so is a blind plate – similar in appearance to a large pizza oven peel. These are referred to as paddle blinds. The other type is exactly the same but comes with an ID as well, enabling flow-through when installed in a piping system. These pieces have holes in the paddle which enables field personnel to determine by sight which piece is installed in a system. These are referred to as paddle spacers, and are often supplied in sets together with the paddle blinds.

All 3 types of these flanges are used in piping systems or pressure vessels where the flow needs to be interrupted from time to time. They are installed between two pipe flanges (as specified above), and by way of a screw inserted into the hole in the bridge or paddle, they are able to rotate or ‘swing’ into and out of position to interrupt or allow the flow, as the user sees fit. Our spec blind flanges are available with raised, flat, or RTJ faces.