Crude Unit Start-up: Consequences of High Liqiud Level



Following a crude unit revamp high liquid level during start-up caused the heavy diesel product to turn black. Yet because the internals were designed for severe uplift, no damage occurred.


National Petroleum Refiners of South Africa Ltd. (Natref) revamped their crude unit in 2002 to increase capacity. Natref revised the start-up and operating procedures to reflect the extensive flow scheme changes, which included many new pieces of equipment. Nonetheless, even after careful planning abnormal events can take place during start-up. Experienced operators often talk about high liquid level that can occur during start-up as a normal event, not an unusual occurrence. Relying on level instrumentation alone is not sufficient to
avoid high level and its consequences during start-up. Pressure is a very simple, yet often overlooked measurement that operators and start-up personnel can use to help avoid high column levels and the resultant problems (Photo 1).

Start-up can be a very dangerous time.Flow rates and levels are changing rapidly. Many things are occurring all at one time. Many crude units experience internalsdamage during start-up...


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Tags: CDU, VDU