Monitoring level and maximizing throughput
On the outside, coke drums are large dimeter vessels, often with thick walls. And on the inside, it’s a hot, sticky, violent environment. These factors make it exceptionally difficult for operators to measure level using traditional measurement instrumentation. Radiometric sensors are a refinery’s best option because these instruments are completely external and immune to thermal expansion and aggressive process conditions.
VEGA’s coke drum continuous level solution has evolved since it was first introduced. VEGA recommends tracking continuous level throughout the top half to one-third of the vessel while monitoring the top of the vessel for any unwanted particulate matter that may escape through the vapor overhead nozzle. In addition, VEGA recommends using a point switch at the bottom of the level system to ensure a good zero starting point between cycles.
VEGA uses the FIBERTRAC 31, a MINITRAC 31, and a POINTRAC 31 to give operators a full picture of what’s happening inside the delayed coking units. The FIBERTRAC 31 allows operators to monitor the level as the coke drum fills, giving them more control over the filling process and providing a better idea when to add antifoam agent. The MINITRAC 31, placed on the top of the vessel, operates as a vapor compensation gauge, which will begin to spike near the end of the fill cycle as particulate matter begins to carry over more due to the overall level in the drum. And the POINTRAC 31, placed near the bottom of the vessel, is the auto-zero gauge, which zeroes the entire system after the coke drum has been emptied and cleaned. This provides more accurate measurements to operators cycle after cycle.