If the drum is not draining properly, the decoking crew should proceed as follows:
- Wait as long as possible without jeopardizing the cycle.
- Set the bottom carriage—which is used to slide the bottom head out from under the coke drum—up against the head.
- Remove all but four bolts. Then loosen the remaining four bolts so that the bottom head is cracked open.
- As the drum drains, continue to loosen the bolts to facilitate drainage.
In defense of this unorthodox procedure, the author can only say that he has seen it done repeatedly and that it is the only way to get a drum with a plugged drain line rapidly drained. Before applying this remedy, the decoking crew should ascertain that the drum is completely depressured and that the water level is well below the lowest radiation-level detection point. One way to improve drainage is to install a distributor at the feed nozzle to prevent the nozzle from plugging.
Draining can also be re-established by blowing steam back into the bottom head for a few minutes. Make sure to block in the drain line prior to re-initiating steam flow.
Categories: Process Troubleshooting | Tags: decoking crew | Leave a comment