Storage Tank PVV and Liquid flow

[LoAnnie]

First I must say that I have read everything in this forum about storage tanks, but haven't found (or possibly just not understood) the answer to my question.

I have atmospheric storage tanks that fall under API 2000. They will have Pressure/Vacuum vents and Emergency vents installed. I understand about inbreathing and outbreathing with regards to pumping rate and thermal changes. I even understand the emergency vent for fire case. My problem is Liquid Overfilling. If my outlet is closed, the 2 level alarms and shutoff recommended by API 2000 are not present. If the liquid coming into the tank at 915 gpm, accidentally overfills the tank, how do I size relief capacity for this case? Am I going to need a third relief device for this tank that can handle liquid flow? Please walk me through this. I understand PSVs for pressure vessels much better than the low pressure storage tanks.

Thanks in advance,
LoAnnie

 

[Ashereng]

I am not a tank expert. Or API for that matter.

However, for most atmospheric tank that I have come across, there isn't a PSV for liquid overfill.

Typically, at the top of the tank, you have a upside down "U" tube vent, your PVRV and "thief" hatch (or personnel way) that is larger than your inlet piping.

The vent takes care of the pressure changes due to level going up and down.

The PVRV (pressure relieve and vacuum breaker) makes sure the vent tube is doing its job.

The theif hatch (usually a weighted hinged lid) takes care of the liquid. When you over fill the tank, the stuff goes out the top (pushes the hinged lid open), then onto the roof of the tank, and down the side of the tank, and onto the ground.

Perhaps a tank guy can give a better response.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

 

[LoAnnie]

I understand that it is going to spill out, but don't you have to make sure that the emergency vent (hatch, manway) can pass the liquid without the tank failing?

 

[Ashereng]

What is your inlet pipe size?

Thief hatches such as the Enardo come in 8" diamneter to 8" x 22" oblong.

http://www.enardo.com/products/prod_gh_a_110_200.htm

If your inlet pipe is even bigger, you can install 2 or more hatches.


"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?