PST meaning in oil and gas

Process Safety Time

“The time period between a failure occurring in the process or the basic process control system (with the potential to give rise to a hazardous event) and the occurrence of the hazardous event if the safety instrumented function is not performed.” I.e., the time period between a high pressure envelope is exceeded and a vessel rupture. PST is important because it determines the maximum amount of time that can be allowed for the SIS to perform all of these actions: o Sense the out-of-control condition o Filter the input signal o Process the input, including any scan time o PLC scan time o Time out any trip delay timer (to remove process noise) o Output process scan time I.e., the time period between a high pressure envelope is exceeded and a vessel rupture. o Digital filter of output signal o And finally, fully actuate the output device