Recommended bolt torque for ANSI/ASME B16.5 Class 150 flanges, by facing and gasket type, for ASTM A193 Grade B7 studs.
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Dimensions and weights
Dimensional tolerances
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Select a facing and gasket type to view the recommended torque per bolt, including gasket contact area, number of bolts, bolt size, and minimum and preferred torque.
| Nominal Pipe Size (in) | Raised Face Contact I.D. (in) | Raised Face Contact O.D. (in) | Gasket Contact Area (sq.in.) | No. Bolts | Bolt Size (in) | Min. Rec'd Gasket Stress (psi) | Bolt Stress @ Min. Torque (psi) | Min. Rec'd Torque/Bolt (ft.lbs) | Max. Rec'd/Avail. Gasket Stress (psi) | Bolt Stress @ Max. Torque (psi) | Preferred Torque/Bolt (ft.lbs) |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 0.5 | 0.84 | 1.38 | 0.94 | 4 | 0.50 | 600 | 1120 | 1 | 900 | 1680 | 2 |
| 0.75 | 1.06 | 1.69 | 1.36 | 4 | 0.50 | 600 | 1619 | 2 | 900 | 2429 | 2 |
| 1 | 1.31 | 2.00 | 1.79 | 4 | 0.50 | 600 | 2134 | 2 | 900 | 3202 | 3 |
| 1.25 | 1.66 | 2.50 | 2.74 | 4 | 0.50 | 600 | 3266 | 3 | 900 | 4898 | 5 |
| 1.5 | 1.91 | 2.88 | 3.65 | 4 | 0.50 | 600 | 4342 | 4 | 900 | 6513 | 7 |
| 2 | 2.38 | 3.62 | 5.84 | 4 | 0.63 | 600 | 4337 | 9 | 900 | 6505 | 13 |
| 2.5 | 2.88 | 4.12 | 6.81 | 4 | 0.63 | 600 | 5060 | 10 | 900 | 7590 | 15 |
| 3 | 3.50 | 5.00 | 10.01 | 4 | 0.63 | 600 | 7432 | 15 | 900 | 11148 | 22 |
| 3.5 | 4.00 | 5.50 | 11.19 | 8 | 0.63 | 600 | 4153 | 8 | 900 | 6230 | 12 |
| 4 | 4.50 | 6.19 | 14.18 | 8 | 0.63 | 600 | 5266 | 11 | 900 | 7898 | 16 |
| 5 | 5.56 | 7.31 | 17.68 | 8 | 0.75 | 600 | 4391 | 15 | 900 | 6586 | 22 |
| 6 | 6.62 | 8.50 | 22.31 | 8 | 0.75 | 600 | 5542 | 18 | 900 | 8312 | 28 |
| 8 | 8.62 | 10.62 | 30.21 | 8 | 0.75 | 600 | 7502 | 25 | 900 | 11253 | 38 |
| 10 | 10.75 | 12.75 | 36.90 | 12 | 0.88 | 600 | 4403 | 23 | 900 | 6604 | 35 |
| 12 | 12.75 | 15.00 | 49.01 | 12 | 0.88 | 600 | 5849 | 31 | 900 | 8773 | 47 |
| 14 | 14.00 | 16.25 | 53.43 | 12 | 1.00 | 600 | 4848 | 40 | 900 | 7273 | 59 |
| 16 | 16.00 | 18.50 | 67.71 | 16 | 1.00 | 600 | 4608 | 38 | 900 | 6912 | 56 |
| 18 | 18.00 | 21.00 | 91.85 | 16 | 1.13 | 600 | 4731 | 56 | 900 | 7097 | 84 |
| 20 | 20.00 | 23.00 | 101.27 | 20 | 1.13 | 600 | 4173 | 49 | 900 | 6260 | 74 |
| 24 | 24.00 | 27.25 | 130.75 | 20 | 1.25 | 600 | 4222 | 70 | 900 | 6333 | 106 |
Each table lists, per nominal size: gasket contact area, number of bolts, bolt size, and torque per bolt, a minimum to reach a safe seal and a preferred (maximum) value not to exceed. Bolts are typically brought to a snug fit, then tightened in the numbered cross pattern shown in the example image, in two or three passes, ending within the min/preferred range. This even sequence helps the gasket compress uniformly rather than over-stressing one side of the flange. Re-check torque once the system reaches operating temperature.
We manufacture to your specifications and stock domestic AIS/Buy America and imported materials, with galvanized, epoxy, and additional coatings available. Rubber expansion joints and gaskets are also supplied on request.
The bolt circle, also called the bolt hole circle (B.H.C.) or bolt circle diameter, is the diameter of the imaginary circle that passes through the centers of all the bolt holes. It sets where the bolts sit and must match the mating flange exactly, even when two flanges share the same outside diameter. Every dimension table lists the bolt circle along with the number and size of the bolt holes.
Bolt count and bolt size are set by the flange standard and class alone, but torque is a joint calculation: it depends on the gasket's contact area, its minimum and maximum recommended compressive stress, and the bolt's own stress limit. Two different gaskets on the identical flange can call for very different torque, which is why this chart is organized by gasket type first. For bolt count and size by class, see the ANSI/ASME B16.5 Bolt & Stud Chart; for Class 300, see the Class 300 Torque Chart. For bolt count and size by class, see the ANSI/ASME B16.5 Bolt & Stud Chart; for Class 300, see the Class 300 Torque Chart.
Unless noted otherwise, the torque values on this page are for ASTM A193 Grade B7 studs at 60,000 psi bolt stress. If your project specifies a different bolt grade, confirm the correct torque with your bolting or gasket manufacturer before assembly.
These values are engineering data for rubber and compressed sheet gaskets. A different manufacturer's gasket can have a different recommended stress range, so treat these numbers as a starting reference and confirm torque with that gasket manufacturer before assembly.
Thin homogeneous rubber gaskets crush and seal at very low bolt stress, so the safe torque range on the small sizes is genuinely narrow, sometimes just a few foot-pounds. Overtightening past the maximum can extrude the gasket past the flange O.D.; vibration or thermal cycling at the low end can loosen the joint and cause gasket failure. Apply torque in increments and stop once the gasket reaches the flange edge.
API International stocks the flanges you need for your project, and our machine shop can modify stock products for special requirements. Contact API International’s experienced sales team, and we will help you select the right flange for your application.
