Is a connection design OK, if make-up torque loads the pin end against a shoulder?
If torque is closely controlled such that the makeup stress on the pin end is well below the yield stress of the metal, and no compression or bending loads are expected on the connection, then pin end loads are acceptable. However should makeup be too loose or too tight, or should bending or compression loads occur, then the potential for the pin end to fail plastically exists, which will cause loosening and leakage because the compressive axial stress due to makeup, plus compression loads plus bending loads are all additive, which compound the compressive stress on the pin ends so as to cause plastic failure, loosening and leakage.
