Dear Friends
I really wonder to know why there is no CSO valve (Car sealed open) befor blow down valve but one is located after BDV , (is that a HAZOP point which is considered to avoid mistake ? )
Thanks and Regards

The BDV by itself is an isolation valve with actuator on it. You don't need another isolation valve upstream of isolation valve...

Dear Joe wong
thank you for anwering
would you please tell me why there is CSO valve after BDV (down stream of RO) ?

With permission from Mr. Joe Wong
Valve itself for maintenance and being CSO as a safeguard for avoiding operator error.
Regards

Dear Fallah
thanks for reply
would you please explain which kind of maintenance you mean ?
when we have only BDV and one CSO valve it seems no useful
and operator mistake cuold be more acceptable but please explain more
Thanks

You are free & welcome to comment...

The flare system will be online during maintanance...

You need an isolation valve downstream of BDV/RO to isolate upstream system i.e. BDV/RO/ separator for separator cleaning, RO inspection/replacement, BDV actuator/solenoid volve service, etc.

CSO of this isolation valve is to avoid inadvertently closure by operator.

Dear Campiloo,
Explanations submitted by Joe Wong are so complete i am not able to add.
Thanks

Dear Friends
thanks for good and complete reply