Bolt Torque Calculator
ASME PCC-1 based bolt torque estimation
Carbon steel, high strength, high temp
T = K × D × F | K = 0.15
Common Bolt Material Properties
| Grade | Yield Strength (MPa) | Yield Strength (ksi) | Notes |
|---|---|---|---|
| A193 B7 | 724 | 105 | Carbon steel, high strength, high temp |
| A193 B8 | 207 | 30 | Stainless steel 304/316, lower strength |
| A193 B16 | 724 | 105 | Cr-Mo-V, high temp creep resistance |
| A320 L7 | 724 | 105 | Low temp carbon steel, -100°F service |
Note
K-factor varies significantly with thread condition, coating, and lubrication. ASME PCC-1 recommends field calibration via hydraulic tensioning or torque-turn methods for critical flange joints, following Appendix O qualified procedures.
About Bolt Torque Calculation
Proper bolt torque is critical for achieving reliable flange joint sealing in industrial valve installations. The ASME PCC-1 guideline provides the standard methodology for determining assembly torque based on bolt material yield strength, nominal bolt diameter, thread friction coefficient (K-factor), and target prestress percentage. Under-torquing leads to joint leakage under operating pressure, while over-torquing can cause bolt yielding, flange damage, or gasket crushing.
This calculator uses the fundamental torque equation T = K × F × D, where T is the applied torque, K is the nut factor (friction coefficient), F is the target bolt preload, and D is the nominal bolt diameter. The default K-factor of 0.16 applies to lubricated bolts with anti-seize compound; dry bolts typically require K = 0.20. For PTFE-coated bolts, K may range from 0.10 to 0.14. Always consult the gasket manufacturer's recommended seating stress and the flange design pressure to determine the appropriate preload percentage.
Common bolt grades for valve flange joints include ASTM A193 B7 (low-temperature carbon steel, yield 105 ksi), A193 B8 Class 2 (strain-hardened 304 stainless, yield 100 ksi), A193 B16 (elevated temperature Cr-Mo-V, yield 105 ksi), and A320 L7 (low-temperature carbon steel for cryogenic service, yield 105 ksi). Selecting the correct bolt grade depends on service temperature, corrosion environment, and pressure rating class (ASME B16.5 Class 150 through Class 2500).
For critical applications such as high-pressure hydrogen service, sour gas (NACE MR0175), or seismic piping systems, ASME PCC-1 Appendix O recommends hydraulic bolt tensioning with ultrasonic elongation verification rather than manual torque wrenching. FLOWKS Valve provides torque charts and installation guidelines with all flanged valve products compliant with API 6D and ASME B16.34 requirements.