5 replies to this topic

[vr1]

Hi All,

 

 One has calculated normal out breathing of a tank as,

 

Volume of liq in in am3/h = volume of air out in am3/h

 

and then converted am3/h to Nm3/h.

 

The other one has calculated as;

 

Volume of liq in in am3/h = volume of blanketing gas out in Nm3/h

and using Annex D (Eq 37) of API 2000, to convert he volumetric flow of blanketing gas in to that of air.

 

1. Which way is correct.

 

I am confused because, previously, I always used,

Volume of liq in in am3/h = volume of air out in Nm3/h - plain and simple.

 

2. Is this a conservative approach?

 

Thank you for replying

Vr

 

[shan]

The blanketing gas is under pressure and with different temperature with standard conditions.  Therefore, Volume of Liq in (am3/h) = Volume of Blanket Gas (am3/h).  Then convert the blanketing gas (am3/h) to (Nm3/h) based on the tank operating conditions.

[vr1]

Hi Shan,

 

 Thank you for the reply. But when you give the total outbreathing or inbreathing volumes for PVSV sizing or VRU vendor, we have to provide them in terms of Nm3/h of air or Sm3/h of air.

 

So as per your above statement, we have to convert this volume in Nm3/h of air again?.

 

Vr

[AlertO]

Hi Vr

 

Normally, we use the unit of Nm3/h for the PVSV accordingly with API2000. All vendors are familiar with this unit. If not too much work, use this unit is more clear and will not lead vendor to misunderstand.

[vr1]

Hi AlertO,

Units of Nm3/h is ok with me but it has to be provided in terms of Nm3/h of air, right?

 

I don't know if I am making myself clear,

 

My question is, as per API 2000 (new edition) while calculating normal outbreathing,

Volume of liq in (am3/h) = ? (what)

 

Thanks for the replies,

Vr

[shan]

Actually, there is not much difference between the volumes of air and blanket gas at the near ambient condition.