Hi...

Could someone please explain to me something regarding bolt root area in pvelite..

When you have girth flange connection those flanges are checked acc. tema table D-5..most of the time... When you want to choose bolt thread series, you can choose UNC, TEMA, TEMA Metric..etc... Now, if you choose TEMA then for every bolt size root area is like in table D-5 from TEMA... But if you choose UNC thread series, root area is matching D-5 table only up to 1" size of bolt... So, if you choose bolt size 1.25" with thread series UNC and TEMA you'll get different root areas...and that is directly affecting the size of flange..

Could someone explain to me why is it like this?

Thanks in advance.

I think the thread series is different, hence the root area is also different. Refer to an engineering handbook for more details.

bolt root area =0.785*(d-1.0825*P)^2
d- norminal bolt diameter
P- thread picth