Intermediate strength bolts on B16.5 and B16.47 flanges

Anilkumar Panchal, CEng

Para. 5.3.3 of B16.5 and B16.7, states that intermediate strength bolts may be used on flanges provided user verified integrity. Is there any method or code or standard or procedure for verification of joint? Please advise.

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• Hugo Julien ASME PCC-1!

• Anilkumar Panchal, CEng Is it Appendix O in ASME PCC-1?

  
  
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• Jörg A. Anilkumar, there are a number of factors which contribute to the reliability of critical flanged joints and hence, which should be verified. These include material specs (flanges, studs, nuts, washers), seal specs (gaskets, rings), geometry (flange surface condition, perpendicularity), installation procedures and, the proverbial icing on the cake: bolt stress.
  It is important to note that the use of calibrated wrenches to apply increasing levels of torque in esoteric patterns does not verify bolt stress. It only verifies how much INPUT force was applied. The RESULT of this effort remains unknown. Likewise, neither does applied tensioner pressure guarantee specific residual bolt stress values. 
  Valid verification methods are, however, available. All have their own pros and cons: http://www.heviitech.com/verification/
  While not in every case (because such precision isn't always required), we find the use of ultrasonic bolt elongation measurement to be quite suitable.

• Warren Brown Anilkumar Panchal, CEng it is a bit open to interpretation as to what "verified" means. However, I would suggest that you interpret it as performing a PCC-1 Appendix O calculation with a view to determining if the joint integrity will be limited by maximum permissible bolt stress if a lower strength bolt is used. You will see that if the selected bolt stress must be reduced according to equation O-4.

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