Nozzle wall thickness UG-45 1

[lcatg]

DATA: Int Pres P=.03 kg/mm2.g
Ext Pres Pe=0.046 kg/mm2.g
Nozzle 4in SCH 40 ID 102.26 mm, thickness 6.02 mm
Design Temp = 100 deg celcius.
Allowable stress for both shell and nozzle = 11.64 kg/mm2.g

Now as per UG-45 ASME,

ta=0.1319 mm
tb1=1.57mm
tb2=8.6 mm
tb3=5.27mm (from TABLE UG-45, for NPS 4)

now, tb=min[tb3, max(tb1,tb2)]
=min[5.27,max(1.57,8.6)]
tb=5.27 mm

tUG-45 = max(ta,tb)
=max(0.1319,5.27)
=5.27mm

But,as in appendix L-7.2.3.4,

This thickness should be less than the minimum thickness provided of 0.875*6.02 = 5.2675.

Since tUG-45 is slightly larger than 5.2675mm, is the thickness considered 6.02mm is passing the code or not? is it necessary to follow the last step given in red color? Please tell me if any mistakes in procedure?

 

[Jano6924]

If corrosion allowance is zero then yes, I think the 6.02mm thickness is OK, if corrosion is larger than zero then you shall use a larger thickness.

Take a look into thicknesses shown on Table UG-45 you will see that all correspond to SCH Std. times 0.875 the mill tolerance for pipe. Hence for 4in pipe nominal thickness is 6.02mm then 6.02*0.875=5.2675mm and rounded to 2 decimals will give 5.27mm.

You shall make sure about the value of allowable corrosion.

Hope this helps.

 

[lcatg]

Thanks @Jano6924..