UG-36 (c)(3)(a) exemption

My input as below:
Design Internal pressure = 480 KPa
Temperature for internal pressure = 100 deg. c
Head material = SA-516 60
Wall actual thickness = 12mm
nozzle material = SA-106 B
Diameter basic for nozzle (OD)
Outside diameter of nozzle = 88.91 mm
Actual thickness of nozzle = 5.49mm
Corrosion allowance for nozzle = 0 mm
joint efficiency = 1
outward projection of nozzle = 423.01mm

PVelite result taking exemption UG-36(c)(3)(a)for this nozzle calculation.
Question : Why this UG-36(c)(3)(a) is exempted from this case?

Hello klchong

Firstly, let us look at UG-36(c)(3)(a). The nozzle has in inside diameter of 77,93 mm. The head thickness is 12 mm. According to the paragraph you do not have exemption. I am not sure why you got the exemption. When I ran the calculation, the reinforcement calculation was performed.

Perhaps you could send me the file, and I can have a look at it.