Hi all,

From nozzle cal generate by PVelite, i've found PVelite using straight away the thickness from selected schedule.

Question: Should the thickness value must deduct undertolerance 1st?

Thanks..

Hello Auwis

Generally, when nozzle reinforcement is being considered, ASME Section VIII, Divisions 1 and 2 do not required that the mill under tolerance be deducted. In the case of a seamless tube, the tolerance is for the extrusion process. If you lose thickness on one side of the tube, you gain it on the other side. The nett effect is that you do not really lose any material thickness for this reason.

Hi Ray,

Thanks for your reply.

I'm not quite agree actually.

for Div.1.
Please refer to ASME VIII,Div.1, Ed 2007, Ad.2009, UG-16(d), UG-37(definition "t"), Appendix-L (Example. L-7.2)

For Div.2,
"3.2.10.2 Pipe and Tube
If pipe or tube is ordered by its nominal wall thickness, the manufacturing undertolerance on wall thickness shall be taken into account. After the minimum required wall thickness is determined, it shall be increased by an amount sufficient to provide the manufacturing undertolerance allowed in the pipe or tube specification."

Further explanation is welcome "Please"

Thanks..

Hello Auwis

There are two different issues here.

1 We have to ensure the nozzle wall is thick enough to withstand the pressure (internal or external). In this case, the undertolerance is important, and should be taken into account to ensure the thinned wall thickness still has enough metal to cope with the pressure.

2 When doing a nozzle reinforcement calculation in accordance with UG-37, the nomenclature for ‘tn’ states that the nominal wall thickness be used without regard for the mill undertolerance. This, as I explained, is because metal lost on one side of the pipe is gained on the other side.