3 replies to this topic

[274@P6]

Hi to all,

 

1. How to calculate the relief load for the Instrument air failure case? 

 

2.How this Instrument air failure scenario will differ from blocked outlet case?

[fallah]

 

1. How to calculate the relief load for the Instrument air failure case? 

 

2.How this Instrument air failure scenario will differ from blocked outlet case?

 

Hi,

 

1-The loss of IA will normally lead to total shutdown; hence due to the limited flare capacity simultaneous depressurization of the total units isn't possible then a sequential depressurizing is inevitable. You can estimate the relief load of each sequence depressurization and select the highest value as the relief load of IA failure.

2-IA failure is a common failure leading to several relief toward the flare while BO is a local failure with normally a single relief to the flare.

[Technical Bard]

For instrument air failure, you need to consider what position every air-driven control valve actuator will move to.  Valves that are spring-to-close or spring-to-open will move to their "failure position".  Then you look at how accumulation of material or heat in the process could cause overpressure.  

[274@P6]

thank for the clarification @fallah and @Bard.

 

1. During the blocked outlet scenario in group header (Two phase), the outlet line of PSV connected to either flare header or closed drain?

 

2. For Indirect bath heater and Heat exchanger TSV is connected to closed drain but sometimes its connected to flare header. which one is correct? 

Edited by 274@P6, 10 December 2020 - 04:46 AM.