Bolting – Do’s and Don’ts

Asked by philyanko 5 years, 5 months ago | 1 Answers

1 Answer

Normandy 5 years, 5 months ago



  • Ensure that the correct size and material of bolting is used. (Refer to the piping specification.)
  • Allow for two threads to be exposed outside the nut once tight­ened; this is good practice. The only exception is when a flange requires hydraulic bolt tensioning and the additional length of bolt to be exposed outside the nut will be specified.
  • Only use clean, rust-free nuts and studbolts.
  • Coat the stud, the nut thread, the nut and the flange bearing surfaces with the selected bolt thread lubricant.

  • Do not use damaged or worn studbolts, bolts or nuts.
  • Do not use nuts or bolts that do not fit correctly together.
  • Do not use bolting that cannot be correctly identified. 
  • Do not mix studbolts with different coatings on a particular flange. Different bolt coatings require different torques to achieve the same bolt tension, as some coatings are more lubri­cating than others.
  • Nuts should not be assembled with the hard stamp or pad against the flange. The machined face should always come into contact with the flange.
  • Do not use bolting which is not clearly marked with the correct material grade - a wrong assumption could have serious con­sequences.