First of all, thank all of you for your answers.

I must say I am not agreeing with your opinions and I will say why:

I calculate my seismic cases as it follows:

Seism 1 = OPE 1 + Seism 1 - OPE 1(Case T high)

Seism 2 = OPE2 + Seism 2 - OPE 2 (Case Environment temperature)

In the case of piping and its butts for seism, those two are with enough gap for a good work in occasional cases.

By this way, the seism 1, will be the obtained load for from the dilatation point of the pipe till the millimetres that rest to arrive to the butt.

Meanwhile, in the seism 2 that won’t have dilatations, it will have a seism 2 bigger due to the butt is very far and the espace run should be bigger.

According to that, the stress caused by a seism for the case 2 is much bigger than in the case 1. On comparing with the Sh smaller, the pipe will fail for such situation.

For all of that, I think that for the stress Sh, it should be the correspondent for each case of operation, since I do not see that the Code indicates what Sh be the higher T of operation of the line, but THE OPERATING TEMPERATURE, that in the case 2 will be the environment temperature.

Best Regards.