2 replies to this topic

[Nicholas]

Hi All

 

My name is Nicholas.

 

I have a tank design to the API Standard 650, low pressure application. However, in an emergency situation, I would like to route condensate at an average pressure of 150 psig to this tank (of design atmospheric pressure). The tank will act as a means of storage until the situation (of too much slugs from offshore) is brought under control.

 

I am evaluating the out breathing from the tank and comparing it to the capacities of the existing relief systems on the tank. 

 

I initially evaluated the out-breathing using a Flash simulation in Hysys. I would like to query if I should also perform a Volatile Liquids calculation and add the result of the Flash calculation to the result of the Volatile Liquids calculation. This seems to be the case in Section 3.3.2.2.1 c of API 2000. Did I interpret this section © correctly?

 

 

Also, for further clarification, I used Boyle's/Charles' Law to convert from the actual tank conditions to standard conditions:

 

Actual Conditions:

P1 = 14.69 psia (atmospheric tank)

V1 = 7074 ft3/hr (Section 3.3.2.2.1

T1 = 26 degC = 538.47 deg R (condensate)

 

Standard Conditions:

P2 = 14.69 psia

V2 = ?

T2 = 60 degF = 519.67 deg R

 

The V2 = 6827 ft3/hr

 

Is the above a reasonable estimation?

 

Thanks and Regards

 

[Mahdi1980]

Nicholas,

 

Normally to design a PSV for the atmospheric tank, you should calculate the in-breathing and out-breathing of the tank and get the bigger result as the basis to design and size the safety valve.

In such cases, you should consider the maximum flow rate into/out from the tank and also take into account the required air/ inert gas to compensate the volume decrease resulting from the ambient temperature reduction to avoid collapse of the tank or vessel.

Then take plus them and compare to each other.

 

If the liquid is volatile like Naphtha, you should consider the volume of volatile due to the maximum temperature and set an inert gas as blanket of the vessel.

[Nicholas]

Thank you Mr. Sharifian.

 

I just learned some more information on this tank.

 

The Tank is designed to API 650 and has a fixed roof in addition to a Floating Roof on the inside.

 

According to API 2000, the Standard is not applicable to external Floating Roof. 

 

I would like to confirm that the Standard is applicable to this design described here.

 

Thanks and Regards

 

Nicholas