by Bruce Kerr, Fluor Daniel
Why are refiners today installing safety interlocks and even fully automating the coke drum switch?
Delayed Cokers are very manpower intensive units that require a great deal of operator attention. Through the years refiners, that have Delayed Cokers, have seen and/or have read many incident reports where operators have inadvertently opened valves creating serious safety problems. Results from these incidents can be and have been devastating, not only to equipment loss and unit downtime but moreover serious injury to personnel and even death.
Operating Philosophies Differ
Operations personnel differ in as far as operating philosophy throughout the Delayed Coking industry. One refiner may want a fully automated system, this system would use the DCS to initiate valve movements for the drum switch. Sequencing programs can be installed in the DCS to allow for the drum switch from the air free step through the switch itself without outside operators doing the switch. This system could also have a complete Safety Interlock in place that would not only prevent catastrophic hot oil losses to the atmosphere but also prevent operational upsets. Another philosophy may have the outside operator monitoring valve movements from a safe location, on the switch deck, and setting steam seals between valve sequencing during the drum switch. Some refiners may prefer to have a basic interlock system that will prevent erroneous valve movements, which may cause catastrophic oil losses or blocked process flow to the coker heater. This type system could be operated by manual valves with proximity switches mounted to the valve or operated locally from a panel or push button station at either an air, electric, or hydraulic operated valve with no valve movements initiated from the DCS.
Many refiners are installing this technology in their facilities, whether it be retrofitted to an existing unit or on a grass roots unit. Installing simplified systems to the fully automated DCS control scheme and variations stages of automation in-between.