Anonymous
there are so many interlocks provided with top and bottom delta valves. which i mention below
1) drum must show off line by swich valve
2) sp1 & sp2 are closed ( valve used for isolation vapor from coke drum to fractionator)
3) sp4 & sp8 are closed ( valve used for isolation vapor from coke drum to blowdown)
4) both vent valve are in open condition
5) drum top pressure is either 0.05kg/ cm2 or below 0.05
6) drum top before quanche temperature is 150 c
when this all condition are satisfied then only we can open the top delta valve of that drum
i dont understand how did accident occured in cnrl ?