Tank outbreathing with compressed air

[Zyzz123]

Is there any way to calculate the required venting capacity for outbreathing if my fluid is coming from a tank trailer.
The tank trailer uses compressed air to push out the liquid into my tank. My problem is that as the tank trailer is running out of liquid, it might be pushing compressed air into the tank, and Im not sure how to account for this in my outbreathing calculations. Currently I'm using formulas from API 2000.

 

[chicopee]

Work out the details needed for solving Bernoulli's equation. You know the air pressures in the tanker truck and storage tanks, differences in elevation of the fluid in each tank, size of line between tanks, air pump characteristic curve, and the estimated time to fill the storage tanks. With estimated transfer rates between tanks, you should be able to satisfy Bernoulli's equation. Since you are looking at the maximum air displacement which should occur when the storage tank is nearly empty, whatever transfer rate you get, you can calculate the rate of liquid rise in the storage tank which can be equated to some venting units such as CFM.

 

[MJCronin]

Zyzz...

Most chemical delivery wagons using compressed air will push air into the customer's tank.

This method, although simple and cheap for the chemical vendor, has repeatedly caused customer tank failure..... commonly when delivery is to FRP or plastic tanks.

The most typical failure is delivery of hydrochloric acid to a customer with an FRP tank equipped with a scrubber on the vent.

While there is no problem under normal operating conditions, an emergency relief valve is truly required when the final "whoosh" occurs at delivery.

I have been involved in two legal cases involving tank failure under this scenario...... it seems to happen over and over.

As so well stated in 1993 by the late Trevor Kletz... "Organisations Have No Memory and Accidents (will) Recur"

http://www.epa.gov/oem/docs/chem/surpass.pdf

http://en.wikipedia.org/wiki/Trevor_Kletz

MJCronin
Sr. Process Engineer