Sorry, more context is necessary. For example please tell us the refining process it is related to. Normally, in refinery, a drum is just a vessel. In this case it might refer to a vessel where one stream is mixed again with other(s).

Es posible que haga referencia a algún tipo especial de recipiente. Tal vez con mayor contexto podría comprender mejor a qué hace referencia.

Gracias, Clarisa