4 replies to this topic

[shahidulislam48]

Hi,

 

What could be the possible over pressure scenario for a PSV protecting vessel apart from Fire Case and Blocked outlet?

 

I have gone through other scenarios but above mentioned two seems to be more appropriate for sizing basis.

 

Am I missing anything important? Please let me know.

 

It would be very helpful.

 

Thanks in advance.

Shahidul

[fallah]

shahidul,

 

You shall extract all over pressure scenarios for a vessel according to relevant PFD, PID, cause & effect diagram, control loops, specified fire zones, operating conditions,.... Hence, a PSV on a vessel can be subject to single case over pressures such as blocked outlet, control valve failure,...or to common cases such as instrument air failure, cooling water failure,...

 

 Please look at the matter in much wider perspective as it would relate to the safety of the plant and involved operators... 

[shahidulislam48]

shahidul,

 

You shall extract all over pressure scenarios for a vessel according to relevant PFD, PID, cause & effect diagram, control loops, specified fire zones, operating conditions,.... Hence, a PSV on a vessel can be subject to single case over pressures such as blocked outlet, control valve failure,...or to common cases such as instrument air failure, cooling water failure,...

 

 Please look at the matter in much wider perspective as it would relate to the safety of the plant and involved operators... 

I get it.

 

If the control valve or any automated valve is "fail to close" and any power or air failure occur that will lead to valve to get closed. In that case, could we consider there is no effect of control valve failure on over pressure of vessel? 

[fallah]

shahidul,

 

It depends on the conditions as I mentioned, it may has effects or may not...!

[latexman]

Automated valves and control valves can get stuck in a certain position.  Binding of the valve stem, binding of the actuator, coupling failure, etc.  FTC or FTO does not stop this.