[Lucibar Davalillo]

Here is my 2 cents on this…
That kind of failure is typical in cokers, but it becomes part of the most difficult decission as well.. what would i do? here are my rule of thombs: 1) if you were not more than 20 minutes with  cold material (less than 750 DegF) and still far away (less than 2/3 of coking cycle) before switching, i’d go back into the coke drum and cook it as hard i can; 2) if you were over 20 min with cold feed, but less than 1 hr, now you need to be very early in coking cycle (less than 1/3 of coking cycle), before you attemp a crazy comeback to that drum.  3) if you already passed 2/3 of coking cycle, do not even try going back and get prepared for the worst.

[Lucibar Davalillo]

Agree. If auto switch available, back and forth should be the first attempt. Floating the drum with water should be next, but preferably if having bottom slide valves.  

[Lucibar Davalillo]

Jimbo.. It is not for sure, but in general fouled heaters may contribute to poor coking factors; watch your coke drum inlet temperature to be over 900 deg.F
  

[Lucibar Davalillo]

 
As per U.S. EPA Refinery New Source Performance Standard 40 CFR 60, Subpart Ja, Federal Register May 14, 2007, all new, modified, or reconstructed Cokers after May 14, 2007, 
require complying with a minimum of 5 psig before venting coke drums.
 

[Lucibar Davalillo]

Ok GUEST,
It’d be better if you sign on and become a member, and provide a little more info about your situation.
However, we are here to help each other, so eventhough you can read many old replys regarding the topic, following is my best shot on your inquiry:
– first at all, you should determine the right amount of water needed to satisfy a good water quench; it is normally estimated considering a coke bed with 0.5 porosity and 55 bulk density; so, if water reach coke bed level before total expected water make, it is a sign of potential hot spot, or in other words, water went up too fast and most likely did not cool coke bed as suppossed to be.
– Another good indicator, and is the one most coker use first, is the coke drum pressure; even if your coke drum temps tells you is cold enough, but your ovh pressure is higher than 5 psig, then it is an indication of a hot spot.
– One last, but not the least, is how your water looks like when draining; it should be as dark as possible; if yellow, means lot of hydrocarbon still embedded and possibly creating hot spots; if steam coming out, rather than water, then it is the best indication of hot spot.
Well, good luck, and let me know if this helped at all.
Lucky 

[Lucibar Davalillo]

Marc, any feedback on this?
Hope it went all well
 
 

[Lucibar Davalillo]

Forgot to mention being prepared for manual unheading since most likely steam blowout will damage your H&C cylinders and won’t be able to get the head down

[Lucibar Davalillo]

Marc,
You had already got best advices from Mitch and Coked; at this point try all you can, even holding water and blowing steam through; if you can get steam/water through and able draining through the pipe, then you are in good shape, especially if your is a bottom entry drum without distributor? Normally bottom entry are easily plugged, especially when draining.
ultimately what you are looking for is making sure what ever is in that gets properly cooldown to avoid any hot tar material igniting and causing more damages.
It could be a very serious situation considering the drum may still be full of resid due to very short time into coking; also, you have H&C, which requires further safety precautions during unheading; just be prepared for the worst and hope for the best. Good luck and lets know how did it go
Lucky 
 
 

[Lucibar Davalillo]

The main advantage is that you know where you at into your the drum at any time; during coking process, either coke or foam, which let you be prepared for worse case scenario. Back-scatter is good to differentiate between coke or foam, but you won’t know how are you doing on either one until being close enough (+/- 3 ft) from the source. The best is a combination of both technologies.  

[Lucibar Davalillo]

Has anybody installed minimum flow bypass for any pump arrangement? If so, does it work? It’d take lot of pressure drop and possibly piping vibration issues with potential leaks; no to mention dealing with preventing plugging issues.
 
Any feedback is highly appreciated
Lucky

[Lucibar Davalillo]

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,
Lucky

[Lucibar Davalillo]

No way; you do not want chlorides over 200 ppmw in your cutting water since it will cause severe damage to expensive and critical decoking equipments. Solids is less a problem, as long as keeping them moving.

[Lucibar Davalillo]

You should have at least one lean sponge oil pump (unstripped LCGO) which could serve as back-up for LCGO product pumps; definitely you need some sort of carrier available; some cokers have HCGO as backup, which is cheaper than having to bypass coke drums due to lack of antifoam; now, if happen that none liquid carrier is available, this may sound wird, but I’ve used steam as last resource. 

[Lucibar Davalillo]

Sir,
For such critical system, all commands should be through hard wired system; Id not recommend using Modbus or any other kind of communication to operate the valves around the coke drums.
Rotork is Ok for all actuators on isolation valves and switch valves, while using “release relay” to disable the main contactor. Thus any move from the motor cannot occur. When the drum switch is done, the operator “release” the valve. Then it will not move until the “release” switch is switched back to his position.
 
However, no matter what, the human factor will always be there, since everything should be handled from local panel. Even, the release relay could be activated/deactivated from local panel by a local bypass maintenance switch.
 

[Lucibar Davalillo]

No. I have seem it installed in surface of a high temperature loses, like heaters chamber or between the mat and heater wall; I mean, over 1400 Deg,F operating temperatures and over 10% energy lost to ambient.
Who knows? it may still save some energy lost in transfer line, although loses there are below 5%, so may no be cost-effective.  

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