Shutoff valve reset in case of emergency scenarios

[nRGee]

Greetings,

I came across this design in one of the refineries handling Naphtha. Kindly refer to the schematic attached herewith.

Naphtha stripper column is provided with an ON/OFF valve on stripper bottom product rundown line. The purpose of this ON/OFF valve is to stop sending the OFF-SPEC product to storage tank in case of unit shutdown. On the other hand, there is one more line to OFF-SPEC PRODUCT TANK.

In case of Manual shutdown of Naphtha treating unit, this ON/OFF valve gets closed as per logic. Manual shutdown is used for emergency scenarios like fire.

Stripper column, usually, will have an inventory of 20m3 and the entire stripper bottom product system has a hold up volume of roughly 30 m3.

In case of fire, this valve will be closed and the entire system will be exposed to fire. There are several flanges and other instruments that get exposed to fire. Failure of flanges, instruments may dump all the Naphtha in that area and add FUEL TO THE FIRE.

My proposal is to provide a SOFT RESET button to the ON / OFF valve on DCS. So that operator can RESET the valve to OPEN it and push the Naphtha content to OFF-SPEC product tank.

Is it okay to push Naphtha out of the system so that fuel to the fire can be reduced? is it a recommended and good engineering practice? is there any specific guideline on this?

Thanks in advance. Don't miss to see the schematic for better understanding.

Best regards,
Raghu

 

[MortenA]

I think you are missing that i likely source for the fire will be a leak downstream the ESDV. So by allowing to open this valve you might also feed the fire with more fuel. Since your column should be protected from overpressure by blowdown and safety valve as well as deluge for avoiding boiling a leak from the column itself is not that likely? On the other hand, since your proposal is an operator activated system then the operator will be able to assess this before opening the valve.

--- Best regards, Morten Andersen