CGA G-6.7

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This publication provides techniques and information that allow owners and operators of bulk carbon dioxide containers to safely repressurize containers that have decreased below their design operating temperatures (typically 200 psig -20 degrees F).

Carbon dioxide auto-refrigerates as gas is removed from a container. This causes the remaining liquid to decrease in temperature until it is colder than the container design limits. Special techniques and considerations need to be used to safely repressurize and warm the dry ice or cold liquid that remains inside a bulk container before returning it to normal service. These procedures are based upon CGA-sponsored testing and the best available technical knowledge.

Improper repressurization of bulk carbon dioxide containers could lead to catastrophic failure due to the extreme cold temperatures of the liquid/solid carbon dioxide making the container walls brittle.

Containers can lose pressure due to a number of upset conditions such as failure of a pressure building vaporizer, failure of a safety relief device to close, excessive liquid or vapor withdrawal.

The 3rd edition includes new information on the low temperature ductility properties of typical container metals.