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roonathankam
Participant

Join Date: Nov 2009
Posts: 3

Selecting Valve Setpoints

12/02/2009 4:56 AM

Hello all

Can somebody help me with the subj?? Is there any Criteria for selecting the setpoints for the Dep-pad Valve and Breather Valves. I have a tank with a working capacity of 100m3 , Design Pressure 255 mmWC(g) ; Pump in rate- 400000 GPH . Calculated Nitrogen Vent Rate 1470 Nm3/hr . Setpoint considered for De-pad valve is 140 mm WC(g).Set point for Breather Valve - 180 mm WC(g). Setpoint for the blanketing valve is 20 mm WC(g) . With the given parameters, are these sepoints okay> or is there any criteria for deciding this based on pump in rate?
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naveen_menon
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India - Member - Naveen Menon Engineering Fields - Instrumentation Engineering - Naveen Menon

Join Date: Oct 2007
Location: India
Posts: 92
Good Answers: 2
#1

Re: Selecting Valve Setpoints

12/03/2009 7:58 AM

What is the process fluid ??
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roonathankam
Participant

Join Date: Nov 2009
Posts: 3
#2
In reply to #1

Re: Selecting Valve Setpoints

12/03/2009 8:10 AM

Hi naveen, its nitrogen blanketing for Heavy Aromatics Storage Tank .
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AKsrey
Active Contributor

Join Date: Nov 2009
Posts: 15
#3

Re: Selecting Valve Setpoints

12/03/2009 9:04 AM

I would make sure the Depad valve can handle the total flow rate before the breather vent opens. Than make sure the breather valve can handle the total relief rate of any upset before the tank can rupture. The blanket valve must be able to handle any pump out rate. I assume you have some way to protect against a vacuum should the pad valve fail.
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josej
Power-User

Join Date: Mar 2008
Location: Mumbai
Posts: 250
Good Answers: 2
#4

Re: Selecting Valve Setpoints

12/05/2009 6:28 AM

Set Point shall be 10 % of MAWP For Positive pressure and For Negative gauge pressure make sure its less than Design pressure --vaccum side( Ref API 650 /620)

Just curious why you didnt considered single Pressure Vaccum safety valve PVSV

Regards

Jose John
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Anonymous Poster
#5
In reply to #4

Re: Selecting Valve Setpoints

12/06/2009 11:44 PM

We have a PVRV for emergency Venting & setpoint for that is -60/200 mmWC . This depad valve is for normal outbreathing.My concern is on the setpooint of the De-pad valve . How close can it be to the PVRV Setpoint? currently we have considered 140mm WC.
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roonathankam
Participant

Join Date: Nov 2009
Posts: 3
#6

Re: Selecting Valve Setpoints

12/06/2009 11:49 PM

We already have a PVRV for emergency Venting & setpoint for that is -60/200 mmWC . This depad valve is for normal outbreathing.My concern is on the setpoint of the De-pad valve . How close can it be to the PVRV Setpoint? currently we have considered 140mm WC.
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AKsrey
Active Contributor

Join Date: Nov 2009
Posts: 15
#7

Re: Selecting Valve Setpoints

12/07/2009 8:44 AM

It depends on size of depad valve. Make sure depad valve can pass the required flow before the over pressure gets within 10% of the breather vent. You may want to increase the breather vent set point to the design of the tank (225) if it can pass its required flow at a 10% overpressure.
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Users who posted comments:

AKsrey (2); Anonymous Poster (1); josej (1); naveen_menon (1); roonathankam (2)

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