Standard Bolt Torque

1. Tightening torque values from the formula T=KDP, where T = tightening torque, lb. ft. K - torque friction coefficient, D = nominal bolt diameter, in.; and P = bolt clamping load developed by tightening, lb.

   Note: Dry K = 0.22, Lubed K = 0.17

2. No proof load has been established by ASTM. Value shown in table are assumed at 95% of yield strength.
3. Proof load is the published number that full size headed bolts are tested to. The bolt is stressed up to the proof load value, and if there is no deformation, elongation, or fracture, then the bolt is deemed to have passed. For bolting specifications that do not have a published proof load, it is usually calculated at 92% of ultimate yield strength.
4. Clamp load is also known as preload or initial load in tension on bolt. Clamp load (lb.) is calculated by arbitrarily assuming useable bolt strength is 75% of bolt proof load (PSI) times the stress area (sq. in.) of threaded section of each bolt size. Higher or lower values of clamp load can be used depending on the application requirements and the judgment of the designer. The Maximum Bolt Torque chart is based on these values.
5. It is not generally recommend that bolt stress be above 60,000 psi (60ksi). Extreme operating conditions such as high temperature may reduce bolt yield strength. Caution should be used in these applications.

Gasket Bolt Torque

Gasket Bolt Charts are suggested torque values using ASTM A193 B7 bolting or equal yield strength bolt material and ASME B16.5 raised face flanges.

Charts are based on Friction Factor (K) of 0.17

Use correct size and new bolts, studs, nuts, washers. Multiply torques values by 0.70 for PTFE coated bolting. Lubricate on bolt threads and nut faces with compatible anti-seize. The charts give the torque value for the final pass. After hand tightening, torqueing must follow a cross bolting sequence. There shall be 3 complete passes (30%, 60%, 100% of final pass torque). Once final torque is achieved, a minimum of 2 clockwise passes to be applied until there is no further nut rotation.

ASME B16.20-2017 states that inward bucking of spiral wound gaskets has been identified as a potential problem. It is recommended that inner rings be used.

Your specific application should not be undertaken without independent study and evaluation for suitability. For specific application recommendations consult QUEST. Failure to select proper sealing products could result in property damage and/or serious personal injury.

Ring Type Joint Gasket Bolt Torque

The torque values reprinted in these tables are guidelines only and are the exclusive property of API. Note: Calculations based on K = 0.07 for PTFE (Teflon/Xylan) coatings and K = 0.13 for commonly available anti-seize lubricants. All values are approximate. No assumption of liability by API or Quest is implied or assumed for the use of this information.