Determination of the Required Reliability for Safety Instrumented Systems

2 Determination of the Required Reliability for Safety Instrumented Systems 

The design of a protection system against runaway comprises defining the nature of the system as well as its reliability. Let us consider that probability 

A diazotization is to be performed in aqueous phase, by slow addition of sodium nitrite in a 2.5 molkg-1 solution of an aniline derivative. The process temperature is 

5 °C and the reaction considered fast at this temperature. Nevertheless, for the safety analysis, an accumulation of 10% is considered realistic. The industrial charge is 4000 kg of final reaction mass in a 4 m3 glass-lined reactor. This vessel is protected against overpressure by a safety valve with a set pressure of 0.3 bar g. The total empty volume of the vessel is 5.5 m3. The vent line has an internal diameter of 50mm and the maximum allowed working pressure of the reactor is 0.3 bar (g). 

Estimate the gas release rate at MTSR (assess its controllability). 

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