Leak scenario for preventing escalation

DEP 80001010 

The separation distances have in general been arrived at through consequence modelling of relevant failure scenarios (e.g., tank top fire, or loss of containment via a 25 mm (1 inch) hole in a pressurized system), giving distances to blast
overpressures and radiation levels.

 

GS EP SAF 253 Fire zone

20 mm (1) leak diameter 

- Corresponds to ¾ inch fitting rupture scenario (rounded to the nearest upper natural number)

 

SP-1258 QRA & PEM

Generally 22mm hole size covers about 90% of the leak frequency of an isolatable segment/equipment. It had been a practice in PDO to apply 22mm as credible hole size for different PEM calculations.