Did you know that caustic cleaners will chemically react with CO2?
Sodium hydroxide (NaOH) + CO2 = Sodium Bicarbonate (NaHCO3)
If this chemical reaction happens in a closed tank, pressure will drop and potentially become vacuum which can result in a tank implosion. The video below demonstrates this in a very easy way.
So, why is this important and what can I do to prevent this from happening?
A Unitank or a Brite tank contains huge amounts of CO2 after it has been emptied. A natural next step would be to add a caustic based cleaner as example PBW and water through the top 4" opening and mount the CIP. Remember that CO2 is heavier than air and will during this process remain in the tank. Now the tank is sealed off with a chemical reaction inside. In this case having the valve on the blow-off tube open will prevent vacuum as air will move freely into the tank as the pressure drops.
Always make sure free air can move into the tank during the washing process. Our recommendation is to use the blow-off tube as the air inlet.
Remember that powerful centrifugal pumps and vacuum pumps can cause vacuum in a closed tank. So, if using either of these pumps for transfer or similar, remember to either add CO2 to hold the positive pressure or let free air into the tank while pumping out.