9 replies to this topic

[R.Ahmadi]

Dear all
why is a spool installed upstream of PSVs flange to flange of the relevant vessel

[fallah]

Hi Ahmadi,

 

That pipe spool actually is to be installed there as a "positive isolation" facility; hence, in maintenance cases this spool will be removed and the vessel flange will be blinded.  Then, as the blind has to be removed before spool re-installation, there would be no safety issue due to forgetting to change the spectacle blind status from close to open by operator in the case without a spool installation.

[R.Ahmadi]

Dear Fallah
thank you for your attention to my questionquestion and your comprehensive answer.
In conclusion,using an end blind flange instead of spectacle blind is the reason, isn't it?

[fallah]

Hi Ahmadi,

 

The spool will be equipped with a flange at both ends and would be installed inline between the PSV and related vessel.  Then, for creating isolation during maintenance, there would be no need for a spectacle blind and it's adequate to remove the spool and isolate the vessel with a blind.

[R.Ahmadi]

thank you
I am dealing with a spool equipped vessel, there's a spacer upstream of the spool between the vessel and psv.
anyway, thanks a lot.

Edited by R.Ahmadi, 18 May 2018 - 12:27 PM.

[fallah]

Hi,

 

If there is a both ends flaged spool between the PSV and relevant vessel there is no need to having any spacer upstream/downstream of the spool...

[R.Ahmadi]

great,

what's the meaning of positive isolation precisely?

[fallah]

Hi,

 

Positive isolation is simply a type of isolation in which no leakage is tolerated.  Then isolation with a valve isn't a positive isolation and isolation with a blind either by inserting it between two inline flanges or after removing a pipe spool is considered as a positive isolation.

[Nasreddine]

Hi

 

Please there are any docs talk about isolation process and positive in design phase?

[breizh]

Hi ,

you may find some interest reading the document attached.

 

Breizh