3 replies to this topic

[bt.0303]

Dear Members,

 

Greetings!

 

I have to design an emergency vent & vacuum relief valve for a conical roof tank that is designed to take pressure limited to the weight of its roof.

 

 

In order to proceed with sizing calculation I want to first find out how much Internal positive & negative pressure this tank can withstand.

 

Would appreciate any suggestions, lead or references from the members. 

 

Please find below process details for your reference:

 

Tank Dimensions:

 

• Design Code- API 650, 11th Edition
• Type- Supported Conical Roof (Roof Thickness is 6mm). Roof is welded from outside (Single Welded Fillet of 5 mm).
• Inside Diameter- 10000 mm
• Height- 10000 mm
• Maximum Design Liquid Level- 10000 mm
• Design Pressure: ATM + Full of Liquid
• Insulation: Nil
• Specific Gravity of storage medium: 1000 kg/m3

Thanks & Regards!

 

 

 

 

 

[fallah]

Hi,

 

If you are finding the maximum internal pressure for a API 650 tank; it's 18 kpag.  If you are going to specify the internal pressure for the tank you described you should refer to the relevant edition of API 650 standard.
 

[Sagednabil]

Hi Falah,
 

I have read many threads about the (Max and Min) internal pressure of atmospheric storage tank. I am still not quite sure how the process engineers are able to evaluate the tank internal pressure.

 

For example, I  want to provide the process data for a tank to store water at 40 deg C, what code or standard, or equation shall i use to calculate the internal pressure?.

 

I have evaluated the required (in/out)breathing requirement according to API 2000, what is the next step, should i do pressured drop calc across the tank vent to calculate the internal pressure, but at this time the tank vent size is only assumptions?

 

Can you please advice what should be the next step after evaluating the breathing (in/out) requirements to calculate the tank internal pressure ?

 

Regards,
Saged

[Chemitofreak]

Hi,

 

Generally API 650 or API 620 are used, following is the basic difference between the two standards

 

API 650:

• API-650 is a general specification for designing welded steel storage tank for oil storage
• Large size storage tank
• Temperature: -40F to 500F
• Pressure: up to 2.5 psig

API 620:

• Design and Construction of large welded low pressure storage tank
• Large size storage tank
• Temperature: -325F to 250F
• Pressure: up to 15 psig
•  

​In API 650 tanks the pressure in the tanks should never exceed MAWP of the tank.

 

Regards,