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Spool Installation Upstream Of Psvs


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#1 R.Ahmadi

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Posted 18 May 2018 - 09:36 AM

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

#2 fallah

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Posted 18 May 2018 - 10:20 AM

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.



#3 R.Ahmadi

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Posted 18 May 2018 - 11:24 AM

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?

#4 fallah

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Posted 18 May 2018 - 12:08 PM

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.



#5 R.Ahmadi

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Posted 18 May 2018 - 12:24 PM

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.


#6 fallah

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Posted 18 May 2018 - 12:33 PM

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...



#7 R.Ahmadi

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Posted 18 May 2018 - 12:41 PM

great,

what's the meaning of positive isolation precisely?



#8 fallah

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Posted 18 May 2018 - 12:52 PM

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.



#9 Nasreddine

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Posted 22 May 2018 - 06:56 AM

Hi

 

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



#10 breizh

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Posted 22 May 2018 - 05:46 PM

Hi ,

you may find some interest reading the document attached.

 

Breizh

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