cyclic load on the agitator nozzle
cyclic load on the agitator nozzle
(OP)
Dear sirs,
I am doing pressure vessel design in that vessel one agitator nozzle is on the top head, in the data sheet
specifies Fatigue analysis to be done
I have no idea how to perform the fatigue analysis
i hope anyone will guide me to perform the calculation
thanking you
Babu Mathan
Pressure Vessel Engineer.





RE: cyclic load on the agitator nozzle
Once you have the loads, the stresses are calculated using WRC 107 methods, which you probably already know. To evaluate the fatigue, use either the Soderberg or Gerber criteria to evaluate the fatigue. If you are not familiar with these criteria, check just about any good machine design book.
Soderberg uses equation:
(Sm/Sy) + (Sa/Sn) = 1/N
Where Sm = mean stress
Sy = yield stress
Sa = alternating stress
Sn = endurance limit stress
N = Safety factor
Gerber uses the equation:
(Sm/Su)^2 + (Sa/Sn) = 1/N
Where Su = Ultimate tensile stress
and other variables defined as in the Soderberg equation.
I hope this is helpful.
RE: cyclic load on the agitator nozzle
Since you are dealing with a pressure vessel nozzle and head, I suggest you first look at Appendix 5 of the ASME Code Section VIII, Division 2. Appendix 5 contains fatigue analysis design criteria.
Vince Carucci