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#1 Guest_mohammadreza piri_*

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Posted 20 April 2010 - 03:11 AM

Hi dear all,

In in-breathing/out-breathing calculation If we deal with the big pump capacity and huge storage tank, the value of in-breathing and out-breathing will be significant and the result is big size of PVRV. To reduce the size we need to add the number of PVRV, How to estimate/calculate the number of PVRV required?Is there any standard basis for that?

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#2 kkala

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Posted 24 April 2010 - 10:41 AM

The question is understood to be whether we can install more than one operating pressure vacuum vents (PVVs) to cover operation of large tanks with high ingoing or outgoing liquid flows.
Looking at http://www.opw-fcs.i...file.axd?id=558 '> http://www.opw-fcs.i...file.axd?id=558 , we can note that:
1. Multiple PVVs may be installed on a single side.
2. Vent pipes may be manifolded to produce single PVV line.
Thus the answer is YES.
It is also noted that:
-PVV sizes found in WWW are limited to 2" and 3" (rarely 4").
-the API RP2000 has increased (2009) venting requirements, as understood from recent threads in cheresources forum.
- compliance to NFPA 30 (2008) 21.4.3 can be required (read in WWW).

Edited by kkala, 24 April 2010 - 10:56 AM.


#3 Guest_mohammadreza piri_*

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Posted 26 April 2010 - 12:47 AM

Dear KKala,

Thanks for your explanation. Just I wanted to know if we can divide the required ingoing/outgoing flowrates to number of PVRVs and avoid of a PRV with big size.

Regards-MPI

#4 kkala

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Posted 26 April 2010 - 03:16 AM

Yes, you can, as post of 24-Apr-10 supports, based on vendor's info. And probably there are not PVVs of big size in the market, which makes obligatory to install multiple PVVs of small size.
By the way, in the post of 24-Apr-10 please read "site", not "side" (apparent error).
Regards - Kostas

#5 Guest_mohammadreza piri_*

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Posted 04 May 2010 - 07:03 PM

Thanks a lot again for your clarification.
Regards-MPI

#6 Guest_Nish_*

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Posted 05 May 2010 - 07:51 AM

Thanks a lot again for your clarification.
Regards-MPI


FYI

I have seen some big tanks fitted with 4 to 8 breather valves with nozzle size 12".

#7 fallah

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Posted 05 May 2010 - 01:16 PM

FYI
I have seen some big tanks fitted with 4 to 8 breather valves with nozzle size 12".


Each valve's nozzle size was 12"?

What was the pump capacity?

#8 proinwv

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Posted 13 May 2010 - 07:51 PM

I'll jump in a little late, but I want to add that I recommend that when multiple vents are used, that the set points be staggered or stagged to provide a more uniform opening and prevent chattering as the vents (may) fight each other. Of course you need to have enough MAWP to accommodate this strategy.

Also, be very careful when manifolding vent discharges. The back-pressures may surprise you and will effect vent opening pressures, unless piloted vents are used.




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