ASME B16.48 Flange Standard

ASME B16.48 provides specific tolerances for the dimensions of line blanks to ensure proper fit and safe installation. These tolerances help maintain gasket alignment, bolt hole compatibility, and system pressure integrity.

Key dimensional tolerances include:

1. Thickness Tolerance: Typically ±0.25 mm for spades, spacers, and spectacle blinds
2. Bolt Hole Alignment: Holes must match the bolt circle of the mating flange (as per ASME B16.5 or B16.47)
3. Outer Diameter Tolerance: Varies by pressure class and size, but kept minimal to avoid misalignment
4. Facing Surface Finish: Controlled between 125–250 AARH for standard gasket compatibility
5. Handle Length and Width (if applicable): Must meet minimum requirements for identification and safety

These tolerances are critical in high-pressure and high-temperature systems where precision is essential to avoid leaks or flange damage.

While both ASME B16.48 and B16.5 are essential flange-related standards, they serve different functions in a piping system:

In summary, ASME B16.48 is used for temporary flow control and safety, whereas ASME B16.5 is used for permanent flange connections in piping systems.

Proper installation of ASME B16.48 spectacle blinds, spades, and spacers is essential to ensure pressure integrity and operational safety. These components are typically installed between flanges in critical isolation points of a pipeline system.

Key installation guidelines include:

1. Orientation: Spectacle blinds must be installed with the open or closed end aligned according to system operation — typically, the blank end is used during shutdown or testing.
2. Flange Compatibility: The line blank thickness, outer diameter, and bolt circle must match the mating ASME B16.5 or B16.47 flange standards.
3. Gasket Selection: Use a compatible gasket material and type (spiral wound, full face, ring-type) based on the flange facing and media conditions.
4. Bolt Torque: Apply uniform bolt torque in a crisscross pattern to ensure proper compression without overloading the line blank.
5. Pre-Installation Check: Ensure surface finish, markings, and dimensions are verified before installation, especially for sour service or NACE-compliant projects.
6. Spacer or Spade Use: For systems requiring frequent maintenance, use paddle spacers and spades with handles for quick switch-over without full disassembly.

These precautions help maintain seal integrity, prevent leaks, and extend the lifespan of isolation components under high-pressure service conditions.

Material selection for ASME B16.48 line blanks — including spectacle blinds, spades, and spacers — is crucial for ensuring long-term performance, corrosion resistance, and compliance with project specifications. The right material depends on several technical factors:

Key Considerations:

• Corrosive Environment:
  • For highly corrosive systems, use Duplex (UNS S32205), Super Duplex (UNS S32750), or Hastelloy C276
  • For seawater or marine exposure, Copper Nickel (Cu-Ni 90/10 or 70/30) is recommended
• High-Temperature Service:
  • Incoloy 800H, Alloy 20, and Inconel 625 offer excellent performance above 600°C
  • Avoid carbon steel in high-temp cycling systems due to oxidation risk
• Low-Temperature or Cryogenic Systems:
  • Use LTCS (Low-Temperature Carbon Steel ASTM A350 LF2) or Stainless Steel 304/316 with impact-tested certification
• Sour Service / H2S Exposure:
  • Ensure NACE MR0175 / ISO 15156 compliance, typically using SS316L, Duplex, or Nickel Alloys
• General Utility Lines:
  • Carbon Steel (ASTM A105) or Stainless Steel (ASTM A182 F304/F316) are economical and commonly used in non-corrosive conditions

By selecting the appropriate material, end users can avoid failures due to corrosion, erosion, or thermal stress — ensuring compliance with international standards and increasing system longevity.

Yes, Nutech is a trusted manufacturer and exporter of ASME B16.48 line blanks, including spectacle blinds, spades, and spacers, to a wide range of global markets. We serve various industries such as oil & gas, power generation, marine, and petrochemical sectors with timely delivery and customized specifications.

We regularly export to key regions including:

• Middle East: UAE, Saudi Arabia, Qatar, Oman, Bahrain, Kuwait
• Southeast Asia: Singapore, Indonesia, Malaysia, Philippines, Vietnam
• North & South America: USA, Canada, Brazil, Mexico
• Europe: Germany, Italy, France, Netherlands, Spain, UK
• Africa: South Africa, Egypt, Nigeria
• South Asia: Sri Lanka, Bangladesh, Nepal

Our export-grade flange blanks conform to ASME, EN, and PED standards, and are supplied with complete test certifications, inspection reports, and traceability. With strong logistics and compliance experience, we ensure reliable global support for EPC projects, OEMs, and end users.