I have a separator, It is having ESD valve on feed intlet, vapor outlet, liquid outlet lines. These ESD valves are initiated by LIZA (1oo2)-high high (During LIZA trip feed inlet ESD valve closes, Liquid outlet ESD open, vapor outlet ESD closes) . Now there is a LCV on liquid outlet line which is controlled by an independent Level transmitter.
My first question whether I need to size the relief valve for liquid blocked outlet.??
My assumption is During LICA malfunction, vessel is having independent LIZA(1oo2) which will close the feed inlet ESD and will stop the feed, hence liquid blocked outlet case is not a valid scenario. Plus the time required for reaching the level from High High trip to vessel top is more than 30 mts so this scenario is not valid.
My second question is whether I have to consider the malfunction of IPF, say during high high level is the LIZA(1oo2) initiates the ESD valve, it fails to close. And the level in the separator rises which will pressurize the vessel and the liquid relief occurs through the relief valve. Is it a valid scenario. Whether we need to consider the failure of IPF.
Regards
Umesh
Full Version: Liquid Blocked Outlet For Ipf Failure
umeshr,
Some inputs for you. Hope it helps...
1oo2 level trips with single FEED SDV (not ESD) will only slightly increase the SIL level (may be not as you only have single FEED SDV) but it definitely increase the spurious trip (1oo2). SIL study can prove if you are meeting SIL requirement. I doubt.
The good point here is you have 30 minutes (i hope mts mean minutes) residence time before level reach the vessel top. BUT, i have a question, how you calculate this 30 minutes ? Do you base on normal maximum flowrate or upstream control valve failed open flowrate ?
Do you have any separator (vessel) located upstream which potentially feeding liquid to this vessel ? What is the liquid volume ? Can this vessel volume (above High-High trip) take all liquid from upstream separator or vessel ?
If this separator can not take the liquid volume from upstream separator, i really doubt you can ignore the liquid (flashing liquid) relief case.
What do yo mean by "failure of IPF" ? Do you mean failure on demand of trips ?
JoeWong
Some inputs for you. Hope it helps...
QUOTE (umeshr @ Oct 22 2007, 12:52 AM) 
My first question whether I need to size the relief valve for liquid blocked outlet.??
My assumption is During LICA malfunction, vessel is having independent LIZA(1oo2) which will close the feed inlet ESD and will stop the feed, hence liquid blocked outlet case is not a valid scenario. Plus the time required for reaching the level from High High trip to vessel top is more than 30 mts so this scenario is not valid.
My assumption is During LICA malfunction, vessel is having independent LIZA(1oo2) which will close the feed inlet ESD and will stop the feed, hence liquid blocked outlet case is not a valid scenario. Plus the time required for reaching the level from High High trip to vessel top is more than 30 mts so this scenario is not valid.
1oo2 level trips with single FEED SDV (not ESD) will only slightly increase the SIL level (may be not as you only have single FEED SDV) but it definitely increase the spurious trip (1oo2). SIL study can prove if you are meeting SIL requirement. I doubt.
The good point here is you have 30 minutes (i hope mts mean minutes) residence time before level reach the vessel top. BUT, i have a question, how you calculate this 30 minutes ? Do you base on normal maximum flowrate or upstream control valve failed open flowrate ?
Do you have any separator (vessel) located upstream which potentially feeding liquid to this vessel ? What is the liquid volume ? Can this vessel volume (above High-High trip) take all liquid from upstream separator or vessel ?
If this separator can not take the liquid volume from upstream separator, i really doubt you can ignore the liquid (flashing liquid) relief case.
QUOTE
My second question is whether I have to consider the malfunction of IPF, say during high high level is the LIZA(1oo2) initiates the ESD valve, it fails to close. And the level in the separator rises which will pressurize the vessel and the liquid relief occurs through the relief valve. Is it a valid scenario. Whether we need to consider the failure of IPF.
What do yo mean by "failure of IPF" ? Do you mean failure on demand of trips ?
JoeWong
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