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This topic contains 3 replies, has 3 voices, and was last updated by Anonymous 12 years, 2 months ago.
January 5, 2011 at 1:59 pm #2419
Has anyone chosen to not shutdown their heaters on low flow from a single pass? We use conventional orifice plates and have frequent spurious trips due to plugged taps. We are considering going to a 2 out of 4 voting scheme and would like to know if others have ventured into this territory.
January 6, 2011 at 7:45 am #5351
If you have facilities to isolate single pass, then you do not have to shutdown the whole heater; most cokers i’ve been are moving towards having independent pass trip by providing such facilities to process and burner management. I still think wedge meters continue leading as best meters out there for the service, even though there have been few successful cokers running ultrasonic. Regarding logic, 2oo3 voting is my preference.
Back to your question, the answer is NO, and I’d not try staying running above cracking temperatures, so the least would be going on circulation at lower temperature while keeping good steam velocities.
January 6, 2011 at 7:51 am #5350
sorry, i did not realize wast signed as guess.
Craig, one more thing may help avoiding plugging and spurious trips is getting bigger taps (like 2″) well wrapped with good 600# steam tracing.
Hope this helps,
January 12, 2011 at 3:40 am #5341
When I worked at a Coker for several years we evolved from orifices to wedge meters. Until we had the wedge meeters installed, we would run with the individual pass controllers bypass valves cracked open to help avoid low flow trips. Also, you really need to check your upstream temperatures and be sure that you are not too hot or have built up too much coke as the hard little balls of coke that get pumped to the heater have got to go through the orifice. If they are too big, they will result in low flow heater pass tripping. After the wedge meters were installed, they just about did away with the low flow tripping except when a big enough ball of coke would plug the actual control valve. Under no circumstances do you want to run the heater with the pass flow blocked. You’ll ruin that pass flow and pipes of chrome metalurgies are very expensive and the down time would be astronomical in cost. Better to bypass the heater and clean it out, then resume. We had a procedure for not having to come all the way down and would run the coker like a crude unit while we cleaned out the heater. It can be done, but when you put hot charge back to the heater and into the system you have to be darn sure the pipes are dry. Hot charge hitting a condensate build up will blow things apart, it’s not pretty. Hope this helps you.
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