ASTM A193 B7 and ASTM A320
L7 bolting, API recognizes both % of bolt
yield strength, and psi stress in bolts, as measures of flange
clamping force necessary to provide a secure connection. As a result
of API recognizing two methods of expression of clamping force, but also de-facto recognizing only torque as a means of achieving this
clamping force, this website tool will offer
two calculators. The first provides a torque value to achieve a % of
bolt yield strength, and the second provides a torque value to achieve a
tension in the bolt measured in psi.
Keep in mind that torque
provides a method of measurement that may vary a great deal
depending on conditions and the lubrication of bolts, nuts, and the
surface the nuts bear against. Everything should be clean, smooth
and well lubricated.
API recognizes two methods of bolt and nut
lubrication: bolts and nuts with bare metal or plated, lubricated
with thread compound tested in accordance with API RP 5A3 / ISO
13678, or bolts and nuts coated with
If you have chosen one of
these lubrication methods, you can have some confidence in choosing
the friction factors API has recognized for them. If you have chosen
another lubricant, you must obtain that manufacturer's friction
factor and use it to obtain meaningful torque values.
provide the torque necessary to achieve a % of bolt yield strength
tension in the bolt.
provide the torque necessary to achieve psi tension in