Hi Michael,

Thanks for sharing your experience. This is really a subject matter that is complicated. I will try to see if I can dig deeper into CFD world and maybe understand more the cold liquid being injected hot gas stream phenomena.

And this is exactly same scenario I experience 2 years ago, a 6" cold liquid stream (130 deg C) & 12" hot gas receiving stream (400 deg. C). The system experiences cracks near the tee at the main pipe after 2 years operation. Anyway, I think the licensor did some detailed analysis which I haven't seen and they are the one who recommended to use thermal sleeve.

My task is just to update the stress analysis, and I was surprised why the original design have installed a diagonal bracing on the vertical tee connection (at the mixing point itself). And when I check the CII model, the diagonal bracing was modelled as rigid with temperature of 400 deg C. Obviously you know what's next if you correct the temperature of the bracing. And I think, everybody will agree to un-install this diagonal bracing. Just correct me if there are some reason for this bracing (vibration?). I'm not sure if this is what they call elastic follow-up, where the system is highly constrained locally. Or maybe this a combination of creep & low cycle fatigue which is both time dependent phenomenon.

Another one I observed is the tee is near the elbow which may also add to the effect on higher thermal gradients.

Just correct any wrong statement I've made.

Any other experience is greatly appreciated.

Cheers!!