FLANGE STANDARD LIBRARYAX FORGE · SPEC SHEET
SPEC SHEETNo. 372
ASME B16.5 · ASME B16.5-2025

B16.5 Class 300 12″ Weld Neck

DN300Weld NeckDimensions mmWeight kg
ASME B16.5 · 12″ (DN300) · Class 300 · Weld Neck FlangeASME B16.5 · 12″ (DN300) · Class 300 · Weld Neck Flange O.D. D 520.7 Bolt circle K 450.9 16ר31.8 Raised face Ø 381.0 Thickness C 49.3 RF height f 1.5 Length H 128.5 Hub Ø A 374.7 Weld end Ø 323.9 Both views share one scale (1:8.2); schematic only Unit: mm

Schematic — drawn from the table, not to scale for inspection.

SymbolItemValue
DOutside diameter520.7mm
CFlange thickness / blind thickness49.3mm
D2Raised face diameter381mm
fRaised face height1.5mm
KBolt circle diameter450.9mm
nNumber of bolt holes16pcs
dBolt hole diameter31.8mm
AHub diameter374.7mm
HHub length / overall length128.5mm
BWelding-end diameter323.9mm
—Approximate weight63.5kg

Pressure–temperature ratings · Class 300 · Group 1.1

≤ 38 °C51.0 bar50 °C49.8 bar100 °C46.7 bar150 °C45.1 bar200 °C43.8 bar250 °C42.0 bar300 °C39.9 bar325 °C38.7 bar350 °C37.6 bar375 °C36.4 bar400 °C34.6 bar425 °C28.7 bar450 °C23.0 bar475 °C17.5 bar500 °C11.5 bar538 °C5.8 bar

Source: Table 2-1.1 (printed p. 25) — pressure–temperature ratings for Group 1.1 materials, SI units; Group 1.1.

Material and notes

Base material: ASTM A105 (North America, Middle East, South-East Asia)

Rating: ASME classes are not fixed pressures. For ASTM A105 (material group 1.1) the ASME B16.5-2025 ambient rating is 285 psi (19.6 bar) at Class 150, 740 psi (51.0 bar) at Class 300, 985 psi (68.0 bar) at Class 400, 1,480 psi (102.0 bar) at Class 600, 2,2…

Tolerances / marking: Tolerances, facing finish, material and marking requirements: ASME B16.5-2025 Sections 6 and 7.

Notes / special requirements

Work order Inspector Date Travels with the part; file after inspection