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From: ATC/NC CAT
Category: Safety
Date: 22 Dec 2004
Your question surprised me and make me think twice before I respond. Bear in mind that prior to switching, the empty coke drum shall be as a minimum in "Warm to BDC" but ideally it must be in "Warm to Fractionator cycle" before we switch. After the switch from the filled drum to the empty warmed up drum (i.e., normally drum metal temp ~ 750 deg F), we normally do steam sweeping of the feed line for extended time before we closed the feed charge inlet valve. This process is called feed line steam sweeping of residue which can essentially be called pre-stripping cycle. Stripping is the initial cooling step using small steam for a filled and newly isolated coke drum. The size of the stripping steam and the size sweeping steam is almost the same in our case except the stripping steam is tapped after the feed inlet isolation valve while the sweeping is tapped before the feed inlet isolation valve. Please revisit your plant SOP or clarify your question to the coker community.