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[m42364236k]

    Dears

 in some design practice company i see when they wanted to calculate the fire scenario for  liquid filled drums ,  they considered both wetted and unwetted fire case for  system and then thy e calculate the load based on wetted and unwetted  and  then select the orifice,

-when i refer to api521, 

in api indicated that unwetted fire  case just use for gas or vapor or super critical flow,

in each case that we have liquid generally we  calculate the fire case based on wetted surface/

 

any body have any suggestion

                                                     

[fallah]

 

 in some design practice company i see when they wanted to calculate the fire scenario for  liquid filled drums ,  they considered both wetted and unwetted fire case for  system and then thy e calculate the load based on wetted and unwetted  and  then select the orifice,

any body have any suggestion

                                                     

 

Hi,

 

They do so, because they want to know the wetted wall fire case would be the governing case or gas expansion case i.e. when last liquid droplet has been vaporized. Then the case which will result in greater relieving area would be selected as the case for relevant PSV sizing. Of course, in most cases the wetted wall fire case would be the case for PSV sizing in fire scenario...