Dear All ,

I need valve Opening ,closing and Overall event duration time profile of the PSV during Pop up condition. I talked to PSV-(Crosby-Tyco) vendor and he gave me the generalized value of opening and closing time mentioned in the catelogue and he told me that they do not provide Specific Time history profile according to different type or Size of the PSV .As per crosby catalogue the generalized valve opening and closing time is 80 ms and 250 ms respectively. The same is mentioned in COADE- MEN December 1998 newsletter. In the newsletter the 1000ms is assumed for the valve at full open condition while valve vendor told me that this value may be approx 200-300 ms .I think 1000 ms is considered as a conservative value so that lower modes of vibration can also attain the higher DLF.

Experienced user please tell how do you decide the value of valve Opening ,closing and Overall event duration for the more accurate definition of Force time profile.

Opening time affects high frequency response and duration affects low frequency response. Closing time is not part of this "equation". A long duration is conservative and, for piping system low frequencies, one second is long enough. Opening time is the key here. See also B31.1 Nonmandatory Appendix II.
I'm talking about a single impulse load.