Lessons Learned: Unheading Injury and Furnace Tube Thinning
The original delayed coking process was extremely high risk, especially top and bottom unheading. Lower cycle times and different resid qualities may have introduced new issues and risks. Top and bottom unheading risks are greatly mitigated with slide gate valves. However, two different refineries have experienced three “Line of fire” incidents, one very serious, even with Delta Valves. This incident will be discussed in the hopes of preventing personnel exposure and injuries through awareness of the risks.
The delayed coker furnace is the heart of the unit. The process itself and decoking methods can cause erosion to the tubes and especially the u-bends. This part of the presentation will explore a refinery’s experience with Coker furnace tube thinning that was “unusual” compared to typical damage profile. Their inspection findings will be shared with the coking community to make everyone aware of this new damage mechanism. This refinery is also seeking feedback through this presentation from other sites to determine if this has been seen in other furnaces.
Lessons Learned: Transfer Line Erosion and Coke Ignition
On a delayed coker, the pipe between the outlet of the furnace and the switch valve is called the Transfer Line. Over time, coke will accumulate in this pipe. Removal of the coke is typically done using hydroblasting from the cleanout flanges at various points in the transfer line. Porous coke can retain unconverted hydrocarbons and can remain hot due to its insulating properties. The presentation will share an incident where coke ignited during the cleaning process. The goal of the presentation is the provide awareness of this risk and share prevention measures that were put in place following the incident.
On a delayed coker, the pipe between the outlet of the furnace and the switch valve is called the Transfer Line. Over time, coke will accumulate in this pipe. The accumulation reduces the flow area thereby increasing the velocity at a given flow rate. Higher velocity increases the erosion of the pipe especially at the elbows. The presentation will share recent inspection results where accelerated erosion was found. The goal of the presentation will be the share the findings so that other refiners can ensure their inspection programs cover this scenario, reducing the risk of loss of containment.