Definition:
Process Safety Time (PST) is the time between the failure (or triggering event) occurring in the process to the occurrence of the hazardous event. It is a property of the process only. The SIF must be designed factoring this in.
Key Points:
- Defines response time requirements for SIFs.
- Calculated based on process dynamics and hazard escalation rates.
Example:
A component fails which causes reactor pressure to increase. Based on the process it would take 30 seconds for the reactor to reach MAWP (maximum allowed working pressure). Therefore, 30 sec is the PST. The protective action via a SIF must complete within that time (response time).
See also: Response Time for very similar term
Cited Source:
- IEC 61511-1:2016, Clause 11.2.7.