Further to Vannella's point number 1. As per B31.3, 2010 edition, para 302.3.6 (a), wind and earthquake forces need not be considered acting together.
Wind at few geographical locations (areas near ocean) blow continuously. There, it is prudent to take wind as NON occasional case. However, earthquake is considered as occasional case.
We have all sorts of protection systems before PSV. Popping PSV is the last phenomenon that can occur. In other words PSV pops up occasionally. Analyzing it as SUS case could be really conservative. Also, it will not result in the gross distortion of the piping system.
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Rajinder