In most of the Hydro-cracker Units (Depending Upon Capacity), From the stripper’s bottom, the reactor liquid product is fed through stripper bottoms-kerosene product exchanger, stripper bottoms-diesel product exchanger, stripper bottoms-diesel pump around exchanger, and product fractionator feed heater to product fractionator by stripper bottoms pumps. The design operation feed temperature to product fractionator is ~385 oC.
The Stripper Bottom Level controller (Primary) controls flow (Feed) rate (Secondary) of feed to Fractionator Heater.
During startup of stripper bottom pump, initially pump flow above minimum flow is achieved using spill back controller. After that passes flow controllers are taken on manual mode and their MV/opening adjusted such that each pass has the same flow rate & amp; MV/opening as others. After achieving a flow rate above the minimum permissible flow rate of the heater, controllers are put on cascade mode with a stripper bottom level controller.
Since Stripper are fed with Stripping Steam, water condensate problem is face during startup or changeover of pumps. This problem can cause fluctuation in Heater Pass Flow and eventually initiate Tripping Sequence of Heater. So condensate from standby pump suction & discharge lines and casing drain points should be removed prior to startup of Pump.