ASME B16.48 Flange Standard

Line Blank Dimensions & Tolerances

ASME B16.48 Flange Standard

ASME B16.48 Standard Flanges: Dimensions | Specifications | Material Grade | Standards | About ANSI B16.48 | All Product Types

ASME B16.48 is a key standard issued by the American Society of Mechanical Engineers that governs the design, dimensions, tolerances, and pressure class ratings of line blanks, including spades, spacers, and spectacle blinds used in piping systems. This standard ensures proper isolation, flow control, and safe shutdown capability in critical process lines.

The B16.48 standard provides detailed guidance on flange thicknesses, outer diameters, handle dimensions, gasket contact surfaces, and tolerances to ensure compatibility with ASME B16.5 and B16.47 flanges. It covers nominal pipe sizes (NPS) from ½″ to 24″ and pressure ratings of Class 150, 300, 600, and 900.

Unlike typical pressure-retaining flanges, line blanks per ASME B16.48 are not bolted components themselves but rather designed to be sandwiched between two flanges for system isolation or maintenance. They are widely used in industries like oil and gas, refineries, petrochemical plants, and offshore piping systems.

This standard also mandates identification markings for size, rating, material, and heat number, and defines surface finish requirements such as stock finish or serrated finish, depending on sealing performance needs. ASME B16.48 is essential for ensuring dimensional interchangeability, safe operation under pressure, and standardized fabrication of line blank components across global piping networks.

Comprehensive Overview of ASME B16.48 Standard for Line Blanks: Design Requirements, Dimensional Tolerances, Face Finishes, and Pressure Class Ratings

For complete technical details, including dimensions, pressure rating classes, weight charts, sizes, tolerances, and material specifications of our ANSI B16.48 Standard Flanges, please download the full Catalog PDF below.

Technical Role of ASME B16.48 in High-Pressure Isolation: Use of Spades, Spacers, and Spectacle Blanks in Compliance with Facing and Marking Requirements

Technical Specifications of ASME / ANSI B16.48

Specification Details
Standard ASME B16.48 – Line Blanks (Spades, Spacers, Spectacle Blinds)
Size Range ½″ to 24″ NPS (DN15 to DN600)
Pressure Ratings Class 150, 300, 600, 900
Type of Blanks Spectacle Blind, Paddle Blank (Spade), Paddle Spacer
Face Types Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ) – if applicable
Facing Finish Stock Finish (125–250 AARH), Serrated Finish, Smooth Finish
Thickness Tolerance ±0.25 mm (as per ASME B16.48 standard requirements)
Material Compatibility To match the companion flanges per B16.5 / B16.47 materials
Marking Requirements Marked with NPS, Class, Material Grade, Heat Number, Manufacturer’s ID
Interchangeability Designed for compatibility with ASME B16.5 and B16.47 flanges
Applications Flow isolation, line maintenance, system shutdown, safety blocking
Documentation EN 10204 3.1 / 3.2, NACE MR0175, ISO 9001, PED 2014/68/EU
Application Industries Oil & Gas, Petrochemical, Power Generation, Water Treatment, Food & Beverage, Fire Protection Systems, Pulp & Paper, Shipbuilding, HVAC, Offshore
Origin Made in India (by Nutech Overseas)
Export Network USA, Europe, and Middle East

Complete Material Grade Chart - Class 150 ANSI B16.48

Material Category B16.48 Flange Grades
Stainless Steel B16.48 Flange ASTM A182 F304 / F304L / F304H, F316 / F316L / F316Ti, F310, F309S, F317 / F317L, F321 / F321H, F347 / F347H, F904L, ASTM A351 CF3 / CF3M / CF8 / CF8M / CF8C, DIN 1.4301, 1.4306, 1.4307, 1.4311, 1.4401, 1.4404, 1.4408, 1.4409, 1.4541, 1.4571, 1.4550, 1.4435, 1.4539
Duplex Steel B16.48 Flange ASTM A182 F51 / F52 / F53 / F54 / F55 / F57 / F59 / F60 / F61, UNS S31803 / S32205
Super Duplex Steel B16.48 Flange ASTM A182 F53 / F55 / F57 / F59 / F60 / F61, UNS S32750 / S32760
Carbon Steel B16.48 Flange ASTM A105 / A105N, ASTM A350 LF2, ASTM A694 F52 / F56 / F60 / F65 / F70 / F80, ASTM A216 WCB, DIN 1.0460 / 1.0402 / 1.0619, Die Steel, Mild Steel
Alloy Steel B16.48 Flange ASTM A182 F5 / F9 / F11 / F12 / F22 / F91, AISI 4130 / 4140
Nickel Alloy B16.48 Flange Nickel 200 / 201, ASTM B564
Monel B16.48 Flange Monel 400 (UNS N04400), Monel K500 (UNS N05500), ASTM B564
Inconel B16.48 Flange Inconel 600 / 601 / 625 / 690 / 718 / 783 / X750, ASTM B564
Incoloy B16.48 Flange Incoloy 800 / 800H / 800HT (UNS N08800), Incoloy 825 (UNS N08825), Incoloy 925, ASTM B564
Hastelloy B16.48 Flange Hastelloy C276 (UNS N10276), C22 (UNS N06022), C4, C2000, B2, B3, X, ASTM B564
Alloy 20 B16.48 Flange Alloy 20 / 20Cb-3, Carpenter® 20, ASTM B462
254 SMO B16.48 Flange SMO 254 / 6Mo, UNS S31254, DIN 1.4547, ASTM A182
Copper Nickel B16.48 Flange Copper Nickel 90/10 (C70600), 70/30 (C71500), UNS C71640, ASTM B61 / B62 / B151 / B152
Copper B16.48 Flange TP1, TP2, T1, T2, C10100–C12300, C14200–C17200, C21000–C71520, including C10930, C11000, C11400, C12000, C12200, C26000, C28000, C33000, C44300, C70600, etc.
Brass B16.48 Flange Grades 3602, 2604, H59, H62, etc.
Aluminium B16.48 Flange Aluminium Grades 5052, 6061, 6063, 2017, 7075, etc.
Titanium B16.48 Flange ASTM B381 Gr.1 / Gr.2 / Gr.4 / Gr.5 / Gr.7, UNS R50250 / R50400 / R50550 / R50700 / R52400 / R53400 / R56320 / R56400
Other Special Grades Al6XN, Tin Bronze, Aluminium Bronze, Lead Bronze, Nimonic 75 / 80A / 90

International Flange Standards We Manufacture & Supply

What is ASME B16.48 and when is it used in piping systems?

ASME B16.48 is a standard developed by the American Society of Mechanical Engineers that covers the design, dimensions, tolerances, and marking requirements for line blanks such as spectacle blinds, paddle blanks (spades), and paddle spacers. These components are not used to join two pipes, but rather to block or isolate flow in a pipeline, particularly during maintenance or inspection.

They are commonly installed between two ASME B16.5 or B16.47 flanges and are used in critical piping systems found in:

  • Oil and gas refineries
  • Chemical and petrochemical plants
  • Offshore platforms
  • High-pressure and high-temperature process lines
  • Systems requiring routine isolation for inspection

Line blanks per B16.48 are essential for ensuring safe shutdowns, preventing backflow, and maintaining process integrity.

What are the dimensional tolerances specified in ASME B16.48 for line blanks?

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.

What is the difference between ASME B16.48 and ASME B16.5 flange standards?

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

Feature ASME B16.48 ASME B16.5
Purpose Line blanks (spades, spacers, spectacle blinds) for flow isolation Pressure-retaining flanges for connecting pipes, valves, equipment
Component Type Non-pressure retaining components Pressure-retaining flange components
Size Range ½″ to 24″ NPS ½″ to 24″ NPS
Pressure Classes Class 150, 300, 600, 900 Class 150, 300, 600, 900, 1500, 2500
Use Cases Isolation, shutdown, maintenance operations Permanent pipe-to-pipe or pipe-to-equipment connections
Facing Finish Stock, serrated, smooth Stock, serrated, smooth (based on flange type)

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.

What are the key installation considerations for ASME B16.48 spectacle blinds and line blanks?

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.

How to choose the right material for ASME B16.48 line blanks in different industrial environments?

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.

Does Nutech export ASME B16.48 flange blanks internationally?

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.

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