8 replies to this topic

[Elí]

Hi Everyone,

I have a consult about an existing atmospheric tank (without nameplate), I want to know the MAWP/MAWV but I do not have any information about this tank. the only data that I have  is the  PV valve set point.

 

Tank Volumen = 300 BBL

 PV Valve Set point = 4 onz/inch2 and  -0.4 onz/inch

 

How Could I do know which standard is applicable in order to calculate the MAWP/MAWV (API 650, API 620, API 12D, API 12F)?

 

Thanks for your support.

 

[fallah]

EIi,

 

At the moment what can be claimed about this existing tank is: the MAWP/MAWV of the tank after construction had been greater/lower than those values you mentioned at above...

 

API 653 or API 579 might help you out for evaluation of this existing tank...

[Julien123456789]

Eli,

I had a similar project 2 years ago.

I remember that the tank design pressure = 25 mbarg

 

Hope this reference can give you an idea.

 

 

Julien

Edited by Julien123456789, 06 April 2016 - 11:00 AM.

[Elí]

Thanks Fallah, I'm going to review API 653 /API 579. Actually, the thickness of shell and roof are known too. I thought that the thickness plus tank dimensions were enough for MAWP/MAWV calculation.

 

Hi Julien:

Could you please tell me, how have you calculated the design pressure of the tanks that you mentioned?

[fallah]

 

EIi,

 

It could't be enough; some other info such as welding joint efficiency, corrosion allowance, material of constrution, local site conditions...are also required...
 

[Elí]

Hi Fallah:

I was reading API 653,  this standard shows how calculate the minimum thickness as a function of welding joint efficiency, corrosion allowance, material of construction, etc. So, I could calculate the minimum thickness, But this standard doesn't show how to calculate the MAWP/MAWV. 

However, API 653 refers to API 650, should I use API 650 in order to calculate the MAWP/MAWV?

 

Thanks

[Art Montemayor]

Eli:

 

You are getting confused about the definitions of the Design pressure, the MAWP, and MAWV.  You should study and familiarize yourself with these terms before trying to do any calculations.

 

Learn what the MAWP is and how it is obtained by using our SEARCH ENGINE.  You don't "calculate" the MAWP.  You have to BACK-CALCULATE it.

 

Follow the helpful advice that Fallah has given you and apply the definitions of the MAWP.  

[Julien123456789]

 

Dear Eli,

 

Honestly, I don't know how to calculate it.  It is just a data that i found when realizing the project.

 

I am not a mechanical engineer.

 

Julien.

[Pilesar]

Not all tanks are designed to an API or ASME tank standard. If this tank meets a design code or standard, then you can assign a pressure rating based on that standard. I would not use this tank to store anything flammable or otherwise hazardous without a pressure rating. For designing the vent for an atmospheric tank, the 4 oz/in2 max pressure is reasonable.