Pulling a vacuum on the coke drum should be a concern. However, we have witnessed operations draining coke drums using the Delta Valve at the Premcor (Valero) refinery in Port Arthur. They had their top heads off and top vent open during draining activities. Once their soak was complete, they just opened the Delta Valve and out came, coke & water, it emptied the entire contents in 7 minutes. To answer the other question, the Delta Valve must be cracked open to remove condensate prior to warming up to remove condensate unless limited by interlock.