What Is an ASME B16.48 Fig. 8 Blank?
A Fig. 8 (spectacle) blank is a one-piece combination of a solid blank and an open spacer, joined at the center and rotated between two flanges. Rotating the unit 180° switches the line between open and closed without removing the assembly. ASME B16.48 covers steel line blanks for piping isolation, NPS 1/2 through NPS 24, Classes 150 through 2500.
Facing Types & Dimensions
- Raised-face (RF) Fig. 8 blanks — dimensions per B16.48 Tables 4.3.1-1 through 4.3.1-6 (Classes 150/300/600/900/1500/2500); the gasket-seating surface follows ASME B16.5.
- Female ring-joint facing Fig. 8 blanks — dimensions per B16.48 Tables 5.1-1 through 5.1-6 (Classes 150–2500).
- Male ring-joint facing Fig. 8 blanks — dimensions per B16.48 Tables 5.1-7 through 5.1-12.
Specific thicknesses and diameters: consult the referenced B16.48 tables — send us your NPS, class and facing and we will manufacture to the standard.
Size & Class Range
| Parameter | Range |
|---|---|
| Size | NPS 1/2 – NPS 24 |
| Pressure class | Class 150 / 300 / 600 / 900 / 1500 / 2500 |
| Typical materials | A105, A182 F304/F316/F321, A350 LF2 |
Related Standards
- ASME B16.48 — Steel Line Blanks (Parent Standard)
- ASME B16.48 Flat Blanks & Paddles
- ASME B16.5 — Pipe Flanges (NPS 1/2–24)
- ASME B16.20 — Gaskets for Blank Joints
- Our Flange Range
- ASTM A105 Carbon Steel
FAQ
How does a Fig. 8 blank work?
The solid half closes the line; the open half is a spacer that keeps the flange gap open. Unbolt, flip 180°, re-bolt — the line is isolated or opened without removing the unit.
What sizes and classes does B16.48 cover?
NPS 1/2 through NPS 24, Classes 150 through 2500, in raised-face and ring-joint facing.
RF or RTJ Fig. 8 blank?
Match the flange face of your system: raised-face blanks per B16.48 Tables 4.3.1-1–6, female/male RTJ blanks per Tables 5.1-1–12.
What material are spectacle blanks made from?
Carbon steel A105, stainless F304/F316/F321, low-temperature LF2 — matched to the line material and service temperature.
Need This Standard for Your Project?
We manufacture and export flanges, fittings and gaskets to ASME standards. Send your standard, size, material, and quantity — we reply within 24 hours.