Flange Bolt-Up Torque

Target preload, per-bolt torque, and the star tightening sequence for a bolted flange.

Run the calculator

Example

You enter

Bolt nominal diameter (in) 0.75
Thread series UNC
Bolt count 8
Target preload (% of yield) 50
Bolt yield (ksi, B7 = 105) 105
Nut factor K 0.18

You get

Preload per bolt (lb) 17535
Torque per bolt 197.27

Details, formula, and sources

Target preload and short-form torque (T = K*D*F) per bolt plus the cross/star tightening sequence for a bolted flange joint.

F = stress * A_tensile; short-form torque T = K * D * F (D nominal bolt diameter). Cross/star tightening sequence per the ASME PCC-1 legacy pattern for the bolt count.

Bolt-preload torque by the short-form T = K*D*F and the cross/star tightening sequence, per ASME PCC-1 Guidelines for Pressure Boundary Bolted Flange Joint Assembly and the ASME B16.5 flange classes, by name.

Public first-principles short-form torque. The nut factor K, gasket seating stress, and target preload are joint- and lubricant-specific and user-supplied.

Estimate. AHJ and licensed professional govern.

Field names used by the API: bolt_diameter_in, thread_series, bolt_count, target_percent_yield, yield_ksi, nut_factor_k, preload_lb, torque_ftlb

Nut factor K lubricated about 0.16-0.20, dry about 0.20-0.25; user-supplied, default flaggedASME PCC-1 / fastener data