Marc – I recommend steaming the drum for at least 12 hours with big steam, then cool with water. Given 45 minutes of feed and a long steam out, you will only need about 15% of your normal water total (since feed that entered is likely less than 10% of normal total; coke yield will be high since coking temperatures are low for first 45 minutes). Concern will be a plugged drain after water cooling- hopefully the extended steaming will reduce or eliminate risk of uncoked resid plugging the inlet distributor or drain line. Worst case you would have to partially open the bottom head (using remote unheading techniques) to drain the water. Hopefully that will not be needed and you will drain via your normal line-up.
Of course, you should not unhead if you cannot get water into the coke drum. In that case you need to try to get steam in and then add water simultaneously. There may be water-hammer issues, but that is acceptable if it allows water to enter the drum. Another option is to add water via the top water line, assuming you have such a connection. Cooling can be validated by determining if steam is being generated as water enters from the top (a rise, even a modest one, in top oulet temperature should be apparent).
We have had success with this technique at our Beaumont and Chalmette-2 Cokers. Best regards – Mitch Moloney