# Bolting Torque Calculations

In order to achieve required leak-proof tightening of bolted flange joint assembly, appropriate bolt tightening method is used. Proper tightening of flange joint assembly creates compressive forces on gasket and pre-tensioning in bolts. As per bolt tightening methods or guidelines, cross tightening sequence is followed. Several cross tightening methods are available such as hand torque, slug/hand wrench, hydraulic torque, hydraulic tensioner etc.

### Guidelines for bolt tightening:

As per guidelines are given in “ASME PCC-1 Guidelines for Pressure Boundary Bolted Flange Joint Assembly”, torque increments for bolt tightening are given as follows:

Target torque for bolt tightening is calculated as per ASME PCC-1, Appendix-K as follows:
Target torque, T = K*D*F
Where,
T = Target torque, N.mm (in.lb.)
K = Nut factor
D = Nominal bolt diameter, mm (in.)
F = Target bolt load, N (lb)
Example:
Let us consider 1’’ bolt of SA193 Gr. B7 is required for flange joint material with nut factor of 0.16. We will evaluate target bolt torque required for leak-proof tightening.