Short bolting continues to be apparent in site surveys, site audits are raising the issues on aged and new piping systems.

Check bolts for adequate length. This length should consider the presence of washers, nut height, and required thread protrusion. The requirements in the new construction codes are based on complete thread engagement for the full depth of the nut. However, it has been shown that the full strength in a threaded fastener can be developed with one thread less than complete thread engagement, a potential consideration in certain post-construction situations. The use of bolt tensioners requires that the threaded portion of the bolt extends to at least one bolt diameter beyond the outside nut face on the tensioner side of the joint. Galvanised or coated bolts may require special tensioner puller sleeves.  Excess thread protrusion can hinder joint disassembly due to corrosion, paint, or damage.

A practice that facilitates joint disassembly is to fully engage the nut on one end (no bolt projection beyond the nut so that all excess threads are located on the opposite end. Excess thread protrusion beyond the nut should be minimized)

See below for reference:

  • ASME PCC 1 – 2019 – Page 3 – Appendix 8.2 or contact the Academy for further information.
  • ASME B31.3 Process Piping Code
  • ASME Boiler Code – Section v111, Div 1

General Academy Courses promote the 2 > 3 threads protrusion above the height of the nut…..including hardened washer – consistent standard for all bolts in the flange.