ASME B16.48

Applies to: Process piping systems requiring positive flow isolation using spectacle blinds, spades, or spacer rings installed between flanges; pressure Classes 150–2500; NPS ½–24.

Does NOT cover: Equipment nozzle blanks governed by ASME BPVC; pipeline isolation plugs; blind flanges (ASME B16.5/B16.47).

• Material selection compatible with process fluid and temperature
• Pressure rating matches the connected flange class
• Handle orientation marking (OPEN/CLOSED) per B16.48
• Ring-groove finish dimensions for RTJ face service
• Thickness calculated per flange design rules to withstand full differential pressure
• Hydrostatic test pressure per governing code if required

ASME B16.48 standardizes the geometry and pressure ratings of line blanks — spectacle blinds (oval plates with blind and open sections joined by a handle), spades (solid isolation discs), and spacer rings — used to achieve positive isolation in process piping. The standard ensures dimensional interchangeability within each pressure class (150–2500) for NPS ½–24.

Engineering note: A spectacle blind is the preferred isolation device when frequent line switching is needed, since it eliminates the need to break a flanged joint. The spade/spacer pair is used when less frequent isolation is acceptable. Engineers should verify that the handle strength and marking convention comply with B16.48 to prevent mis-alignment errors during maintenance.