Hello Stressers!!!

My opinion regarding this topic is the Code sets minimum requirements only. A competent stress engineer who can identify those special situations such as high strain concentrations I think is a must to avoid pre mature cracking of welds. But as we all know welds have many uncertainties involved including the quality of weld.

Just my thoughts and subject to further opinion from other practicing stress engineers.

Anyway, so far all the calculations I have performed uses the normal ASME B31.3 primary sustained stress and secondary expansion stress even the Radiant Coil Piping which is operating at 600 deg C for 3 years now. But that calculation is taken from a licensor who has lots of experience in Radiant Coil Piping. I even tried using 1/3 of thermal expansion stress added to the sustained stress but it's failing for one existing furnace line that is currently operating.

I remember one of my senior stress engineer who doesn't like to weld pad on piping. I was confused then why he wants to avoid it because during that time I want some calculations to prove to me that it's not working. But during the course of my experience I have read that pad at high temperature creates high thermal stress locally due to heat transfer rates (large mass, small mass difference). So, Why perform a very detailed calculation if you can avoid it by just omitting it from design.

My statement is open for correction as I have seen operating plants with high temperatures (550 deg. C) with pad on the support. Maybe the insulation helps to reduce the thermal difference.

Cheers!!!