ASTM A182 F316L Spectacle Blind Flange, B16.48 spectacle blind Flange

ASTM A182 F316L spectacle blind flanges are figure-8 shaped pipeline components used to isolate or allow flow in piping systems. Manufactured according to ASME B16.48, they consist of a solid blind and a spacer connected by a metal section, enabling safe and reliable pipeline isolation during maintenance operations.

Click here to check ASME/ANSI B16.48 Class 150 Spectacle Blind Flange / Figure-8 Blank RF

We can manufacture Spectacle Blind with different type of joint face (RF, FF, RTJ) in series 150/300/600/900/1500/2500 in according to major dimensional standards ASME B16.48.

 Spectacle Blind Flange may have a different type of joint face (RF Raised Face, FF Flat Face, RTJ Ring Joint), depending the type of flange

What is a Spectacle Blind Flange?

A spectacle blind flange (figure 8 flange) is a combination of:

• A solid blind (to stop flow)
• A ring spacer (to allow flow)

These two parts are permanently connected and rotated during operation.

The shape resembles a pair of glasses, hence the name “spectacle blind”.

How Does a Spectacle Blind Work?

• When the blind side is installed → flow is blocked
• When the spacer side is installed → flow is allowed

Installed between two flanges with gaskets on both sides to ensure leak-tight sealing.

Spectacle Blind Flange  is usually used on the oil line with two different functions:

• If the spade is put in between the flanges, it stops the fluid’s passage;
• If the spacer is put in between the flanges, the passage of the fluid is allowed.

The Spectacle Blind is inserted between two flanges: in order to guarantee a perfect  waterlight two gaskets are normally mounted , one on each side of spectacle blind.

Product Specifications

• Material: ASTM A182 F316 / F316L
• Standard: ASME B16.48
• Type: Spectacle Blind (Figure 8)
• Connection: Flanged

Pressure Class

Available in full ASME pressure ratings:

• Class 150
• Class 300
• Class 600
• Class 900
• Class 1500
• Class 2500

Facing Types

• RF (Raised Face)
• FF (Flat Face)
• RTJ (Ring Type Joint)

👉 Selected based on piping system design

Material Advantages – F316L Stainless Steel

• Excellent corrosion resistance
• Resistant to chloride environments
• Good performance in chemical and marine applications
• Low carbon content (L grade) reduces risk of intergranular corrosion

Chemical Composition – ASTM A182 F316L (%)

Mechanical Properties

• Tensile Strength: ≥ 485 MPa
• Yield Strength: ≥ 170 MPa

Applications

ASTM A182 F316L spectacle blind flanges are widely used in:

• Oil & gas pipelines
• Petrochemical plants
• Chemical processing systems
• Offshore platforms
• Water treatment systems

👉 Ideal for corrosive and critical service environments

Installation Notes

• Always install with two gaskets (one on each side)
• Ensure proper bolt tightening
• Depressurize system before switching blind/spacer

Ensures safe operation and prevents leakage

Quick Summary of Spectacle Blind flanges

• Type: Spectacle Blind (Figure 8)
• Standard: ASME B16.48
• Material: ASTM A182 F316L
• Function: Flow isolation / flow passage
• Pressure: Class 150 – 2500
• Application: Oil, gas, chemical

FAQ: Spectacle Blind Flange

Q1: What is a spectacle blind flange used for?

It is used to isolate or allow flow in pipelines during operation and maintenance.

Q2: Why is it called a figure 8 flange?

Because its shape resembles the number 8 or a pair of spectacles.

Q3: What is the difference between blind and spacer?

The blind blocks flow, while the spacer allows flow.

Q4: Why use F316L material?

F316L offers excellent corrosion resistance, especially in chemical and marine environments.

We also produce high quality ASME B16.5 ASTM A182 F316L Flanges

ASME B16.5 ASTM A182 F316L Blind RF Flanges

ASME B16.5 ASTM A182 F316L Blind RTJ Flanges

ASME B16.5 ASTM A182 F316L Weld neck RF Flanges

ASME B16.5 ASTM A182 F316L Slip on  RF Flanges