Engagement of Studs in Tapped Holes
How to identify the length of bolt that is threaded
inside a component like 3-1/8'' 5M studded tee?
API Spec 6A requires that
Studs have a minimum of thread engagement equal to the nominal diameter
of the stud. In your case, 3-1/8" 5M studded flanges use 1-1/8" diameter
studs, these studs should have approximately 1-1/4" of measured threaded
end that screws into the tapped hole. This 1-1/4" of measured length
includes the chamfered end and is measured to the last scratch made by
the runout of the thread on the body of the stud, plus 1/8", minus 0."
The information above assumes the
equipment is assembled with what are called Tap End Studs, which have
full diameter bodies and threads cut on each end, as specified in the
document linked below. Should the equipment have
All Thread Studs
installed, they have probably been tightened against the bottom of the
tapped holes, and the depth of the tapped holes varies with the practice
of the manufacturer. WOODCO USA strongly recommends against the use of
All Thread Studs in tapped holes.
To get complete information on the
dimensions of studs used in API flange connections, see
Should you need any studs, nuts,
ring gaskets, or complete pieces of equipment, please