GNEE manufactures aluminum flanges in standard sizes up to DN350, with custom sizes available above DN350. This page provides the actual dimension tables you need to order the right flange-including OD, bore, PCD, bolt hole size, and thickness per ASME B16.5.
If you need a quote, send us the flange type, alloy, size, standard, pressure class, facing, and quantity. For custom sizes, send a drawing.
Flange Dimension Terms
|
Dimension |
Term |
Meaning |
|
Outside Diameter |
OD / D |
Max diameter across flange edge |
|
Bore |
ID / B |
Center opening of flange |
|
Bolt Circle Diameter |
PCD / BCD / K |
Diameter through bolt-hole centers |
|
Bolt Hole Diameter |
d |
Diameter of each bolt hole |
|
Number of Bolt Holes |
n |
Total bolt holes |
|
Flange Thickness |
T |
Axial thickness of flange |
|
Facing |
FF / RF |
Sealing surface configuration |
Important: DN is a nominal size only. It does not determine OD, bore, PCD, or thickness. Always confirm the full dimensions from the applicable standard.
ASME B16.5 Class 150 Flange Dimensions
Standard dimensions for Slip-On, Weld Neck, and Blind flanges (Class 150):
|
DN |
NPS |
OD (mm) |
Bore* (mm) |
Thickness (mm) |
PCD (mm) |
Bolt Holes |
|
15 |
1/2" |
89 |
21.3 |
11.2 |
60.3 |
4 × Ø16 |
|
20 |
3/4" |
98 |
26.7 |
12.7 |
70.0 |
4 × Ø16 |
|
25 |
1" |
108 |
33.4 |
14.2 |
79.2 |
4 × Ø16 |
|
32 |
1-1/4" |
117 |
42.2 |
15.7 |
88.9 |
4 × Ø16 |
|
40 |
1-1/2" |
127 |
48.3 |
17.5 |
98.4 |
4 × Ø16 |
|
50 |
2" |
152 |
60.3 |
19.0 |
120.7 |
4 × Ø19 |
|
65 |
2-1/2" |
178 |
73.0 |
22.4 |
139.7 |
4 × Ø19 |
|
80 |
3" |
190 |
88.9 |
23.9 |
152.4 |
4 × Ø19 |
|
100 |
4" |
229 |
114.3 |
24.6 |
190.5 |
8 × Ø19 |
|
125 |
5" |
254 |
141.3 |
24.6 |
215.9 |
8 × Ø22 |
|
150 |
6" |
279 |
168.3 |
25.4 |
241.3 |
8 × Ø22 |
|
200 |
8" |
343 |
219.1 |
28.4 |
298.5 |
8 × Ø22 |
|
250 |
10" |
406 |
273.0 |
30.2 |
362.0 |
12 × Ø25 |
|
300 |
12" |
483 |
323.9 |
31.8 |
431.8 |
12 × Ø25 |
|
350 |
14" |
533 |
355.6 |
35.0 |
476.3 |
12 × Ø29 |
Notes:
*Bore = pipe OD for Slip-On flanges. For Weld Neck, bore depends on pipe schedule. For Blind flanges, there is no bore.
Dimensions per ASME B16.5. Tolerance: OD ±1.6mm for sizes up to DN100, ±3.2mm for larger.
Above DN350: Custom production per drawing.
Class 150 vs Class 300 Thickness
For the same nominal size, higher pressure class means thicker flange - but the OD and PCD stay the same for most sizes.
|
DN |
NPS |
Class 150 T (mm) |
Class 300 T (mm) |
OD (same) |
PCD (same) |
|
150 |
6" |
25.4 |
31.8 |
279 |
241.3 |
|
200 |
8" |
28.4 |
38.1 |
343 |
298.5 |
|
250 |
10" |
30.2 |
44.5 |
406 |
362.0 |
|
300 |
12" |
31.8 |
47.8 |
483 |
431.8 |
Note: For NPS ≤ 2-1/2", Class 300 also has a larger OD than Class 150. For NPS ≥ 3", only thickness (and hub geometry) changes. The full dimensional and pressure-temperature system is defined by ASME B16.5 - do not select thickness independently.
Flange Facing: Flat Face vs Raised Face
|
Facing |
Description |
Use |
|
Flat Face (FF) |
Flush sealing surface |
Low-pressure systems, cast iron equipment, older installations |
|
Raised Face (RF) |
Gasket seat raised above flange face |
Most common; general industrial piping |
RF raised height (ASME B16.5): 1.6mm for DN ≤ 300, 6.4mm for DN ≥ 350.
Note: FF and RF flanges are NOT directly interchangeable - the gasket and mating flange facing must match. Specify facing in every order.
Key Dimensions by Flange Type
|
Flange Type |
Must Specify |
|
Slip-On (SO) |
OD, bore (= pipe OD), T, PCD, bolt holes, facing |
|
Weld Neck (WN) |
OD, bore, T, PCD, hub OD, hub length, weld-end dimensions, facing |
|
Blind (BL) |
OD, T, PCD, bolt holes, facing (no bore) |
|
Threaded (TH) |
OD, threaded bore, T, PCD, bolt holes |
|
Socket Weld (SW) |
OD, socket diameter, socket depth, T, PCD, bolt holes |
|
Lap Joint (LJ) |
Flange OD, bore, T, PCD + Stub End dimensions |
|
Plate (PL) |
OD, bore, T, PCD, bolt holes, custom dimensions |
A Weld Neck flange cannot be made from a Slip-On drawing - the hub and weld-end dimensions are different.
Aluminum Alloys for Flanges
|
Alloy |
Tensile (MPa) |
Yield (MPa) |
Notes |
|
1060 |
60–95 |
≥ 28 |
Low strength, high purity, good corrosion resistance. Light-duty only. |
|
3003 |
140–180 |
≥ 125 |
Better strength than 1060, good formability. General use. |
|
5083 |
275–350 |
≥ 195 |
High strength, marine corrosion resistance. Offshore/marine. |
|
6061 |
290–310 (T6) |
≥ 255 |
Good strength + machinability. Most common flange alloy. |
|
6063 |
215–240 |
≥ 170 |
Good extrusion. Less common for flanges. |
|
6082 |
290–340 |
≥ 240 |
Higher strength. Engineering applications. |
Recommendation: 6061-T6 is the default for most aluminum flanges (good strength-to-weight, machinable, weldable). Use 5083 for marine. Use 1060/3003 only for low-pressure, non-critical service. Select alloy by actual pressure, temperature, and media - not by strength alone.
Standard vs Custom Flange
Standard flange: Specify alloy, type, DN/NPS, standard (ASME B16.5 / EN 1092-1 / JIS B2220), pressure class (Class 150 / PN16), and facing (FF/RF). We use the standard dimensional table.
Custom flange: If you need non-standard OD, bore, PCD, bolt pattern, thickness, or facing - send a drawing with all dimensions. We manufacture per your spec.
Important: EN 1092-1 (PN series) and ASME B16.5 (Class series) have different dimensions for the same DN. For example, DN150 PN16 has OD 285mm / PCD 240mm / 8×Ø22mm - close to but not identical with ASME B16.5 Class 150 (OD 279mm / PCD 241.3mm). Always confirm the standard system before ordering.
How to Measure an Existing Flange
If you don't know the standard, measure the existing flange:
OD - Largest diameter across the flange
Bore - Center opening diameter
Thickness - Flange face to face
Bolt holes - Count them, measure one hole diameter
PCD - Measure center-to-center distance between bolt holes (or across the pattern)
Facing - Flat Face or Raised Face?
Type - SO / WN / BL / TH / SW / LJ / PL?
Photo with a ruler or caliper next to the flange helps us identify it quickly.
How to Order
Send the following for a quote:
|
Item |
Example |
|
Flange Type |
Slip-On / Weld Neck / Blind |
|
Alloy |
6061-T6 |
|
Size |
DN150 / 6" |
|
Standard |
ASME B16.5 |
|
Pressure Class |
Class 150 |
|
Facing |
RF |
|
Quantity |
100 pcs |
|
Drawing |
If custom |
Lead time: 15–35 days for standard sizes, 25–45 days for custom orders.
MOQ: Depends on size and type. Contact us with your requirements.
If you only know part of the spec: Send pipe OD, alloy, type, and application. We will confirm the rest.
Quality Inspection
Dimensions: OD, bore, thickness, PCD, bolt-hole diameter, count - per ASME B16.5 tolerances
Material: Alloy verification per mill test certificate (EN 10204 3.1/3.2)
Surface: No cracks, dents, deep scratches
Third-party inspection: SGS, BV, TUV available
FAQ
What are the most important flange dimensions?
OD, bore, thickness, PCD, bolt-hole diameter, and number of bolt holes. Plus flange type, facing, standard, and pressure class. See the ASME B16.5 table above for actual values.
Is flange bore the same as pipe ID?
No. For Slip-On flanges, the bore matches pipe OD (not ID). For Weld Neck, bore matches pipe ID per schedule. For Blind flanges, there is no bore.
Does DN tell me the flange dimensions?
No. DN is nominal only. A DN150 Class 150 flange has OD 279mm, PCD 241.3mm, 8×Ø22mm holes, thickness 25.4mm - none of which equals "150".
What is the difference between FF and RF facing?
FF is flush; RF has a raised gasket seat (1.6mm for DN≤300). They are not interchangeable - the mating flange facing must match.
Can you make flanges above DN350?
Yes, as custom production. Send a drawing with OD, bore, thickness, PCD, bolt pattern, and facing.
What alloy should I use for a pressure flange?
6061-T6 is standard for most applications. Use 5083 for marine. Use 1060/3003 only for low-pressure, non-critical service.
Request a Quote
Send us your flange specifications - type, alloy, size, standard, pressure class, facing, and quantity. For custom sizes above DN350, send a drawing.
GNEE is an aluminum flange manufacturer supplying standard and custom flanges to industrial customers worldwide. Quote within 24 hours.
