Hi everyone,I am new here and I am a novice to ASME. I am confused by
the discription in UG-36 (C)(3)(c) which is as followed:
Openings in vessels not subject to rapid fluctuations
in pressure do not require reinforcement other than
that inherent in the construction under the following conditions:
(a) welded, brazed, and flued connections meeting
the applicable rules and with a finished opening not
larger than:31⁄2 in. (89 mm) diameter — in vessel shells or heads
with a required minimum thickness of 3⁄8 in. (10 mm)
or less;
23⁄8 in. (60 mm) diameter — in vessel shells or heads
over a required minimum thickness of 3⁄8 in. (10 mm);
It seems that a larger opening require a thinner shell or head while a smaller opening require a thicker shell or head plate.Could anyone give me a explanation? Thanks very much!

I have given the following interpretation as per my understanding.

1. The primary condition is there should be no rapid pressure fluctuation.

2. If the required minimum thickness is 10 mm or less, no reinforcement checks for openings up to 89 mm

3. If the required thickness exceed 10 mm, no reinforcement check required for opening up to 60 mm

Is it OK? somebody can comment

R.SRINIVASAN
VICE PRESIDENT, DESIGN
PVD, ISGEC

_________________
R.SRINIVASAN
Sr. VICE PRESIDENT
Head, Design and Engineering
PED,ISGEC,
YAMUNANAGAR
HARYANA -135001
INDIA