Flange Bolt Chart (ASME B16.5)
Quick reference for flange bolt specifications. Find the number of bolts, bolt size, and bolt length for ASME B16.5 flanges by pressure class and pipe size.
Select Flange Specifications
Class 150 - 2" Flange Specifications
Per ASME B16.5
Number of Bolts
4
Bolt Size
5/8"
Bolt Length
2.75"
Bolt Circle Diameter
4.75"
Flange OD
6"
Flange Thickness
0.69"
Bolt Requirements Summary
You need 4 bolts, size 5/8", length 2.75" (with matching nuts and washers)
Class 150 Complete Bolt Chart
| Size | # Bolts | Bolt Size | Bolt Length | Bolt Circle | Flange OD |
|---|---|---|---|---|---|
| 1/2" | 4 | 1/2" | 2" | 2.38" | 3.5" |
| 3/4" | 4 | 1/2" | 2.25" | 2.75" | 3.88" |
| 1" | 4 | 1/2" | 2.25" | 3.12" | 4.25" |
| 1-1/4" | 4 | 1/2" | 2.5" | 3.5" | 4.62" |
| 1-1/2" | 4 | 1/2" | 2.5" | 3.88" | 5" |
| 2" | 4 | 5/8" | 2.75" | 4.75" | 6" |
| 2-1/2" | 4 | 5/8" | 3" | 5.5" | 7" |
| 3" | 4 | 5/8" | 3" | 6" | 7.5" |
| 4" | 8 | 5/8" | 3.25" | 7.5" | 9" |
| 6" | 8 | 3/4" | 3.5" | 9.5" | 11" |
| 8" | 8 | 3/4" | 4" | 11.75" | 13.5" |
| 10" | 12 | 7/8" | 4.25" | 14.25" | 16" |
| 12" | 12 | 7/8" | 4.5" | 17" | 19" |
* All dimensions in inches. Bolt lengths are for standard raised face flanges with one gasket.
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ASME B16.5 Standard
ASME B16.5 covers pipe flanges and flanged fittings for NPS 1/2 through NPS 24 in pressure classes 150, 300, 400, 600, 900, 1500, and 2500. This standard specifies dimensions, tolerances, marking, and material requirements.
Bolt Material Selection
Common bolt materials for flanged connections:
- •ASTM A193 B7: Most common, for temperatures up to 450°C
- •ASTM A193 B8: Stainless steel, for corrosive environments
- •ASTM A193 B16: For high-temperature service above 450°C
Bolt Length Calculation
The bolt lengths shown are for standard raised face (RF) flanges with one gasket. For ring-type joint (RTJ) flanges or special gaskets, adjust the length accordingly. Always ensure adequate thread engagement in the nut.
Frequently Asked Questions
What is the bolt circle diameter?
The bolt circle diameter (BCD) is the diameter of the circle that passes through the center of all bolt holes. It's used to locate the bolt holes on the flange face.
How do I determine the correct bolt length?
Bolt length = 2 × flange thickness + gasket thickness + nut height + washer thickness + thread protrusion. The values in this chart are standard lengths for RF flanges with standard gaskets.
Can I use studs instead of bolts?
Yes, stud bolts with two nuts are commonly used for flanged connections, especially in higher pressure classes. The stud length would be similar to the bolt length shown, but verify with your specific application requirements.
What torque should I use for flange bolts?
Bolt torque depends on bolt material, size, lubrication, and gasket type. Refer to ASME PCC-1 for recommended bolt-up procedures and torque values. Always use a cross-pattern tightening sequence.
Disclaimer: This chart provides reference data based on ASME B16.5. Always verify dimensions with the actual flange manufacturer's specifications. For critical applications, consult with a qualified engineer.