This topic contains 9 replies, has 4 voices, and was last updated by Anonymous 12 years, 3 months ago.
February 10, 2009 at 1:25 pm #3196
could anybody provide best practices for coke drum ovh lines cleanout facilities? if possible, provide some feedback on recommended sizing (full line size flange, 10″, etc) and best location for water/coke droppout connection (vertical or horizontal)?
February 11, 2009 at 3:27 pm #6262
Clean out facilities are typically full line size Blind Tees/Crosses or removable Ells.
Tees or crosses provide full access to the pipe and may facilitate and faster the cleaning process, but are also more costly. It is highly recommended in the first turn coming out of the drum, which requires frequent cleanout during normal operation. In the other hand, they also add extra turbulence in the lines, adding pressure drop, and possibly even areas where coke buildup is enhanced, which may make it necessary to clean out the lines more often, so its excessive use should avoided as possible. The pressure drop increase will have a long-term effect in the process, so every 1 psi increase reduces liquid yield. My recollection is that liquid yield is reduced about 0.15% per 1 psi increase; although it looks a small number, it becomes a significant loss opportunity.
Ells are cheaper and provides easy access in both directions; the rigging to handle an ell would be similar to that needed for a blind flange, but slightly more robust. The ells could have welded lifting lugs installed to make the rigging a snap. Ells provide lower pressure drop and avoid coke deposition areas. It can be considered for sections where the timeframe required to perform the cleaning will not have any effect in the normal operating cycle, because the pair of drum would have to be out of service to perform any work; like, sections of the pipe between the common valve (SP3) to the Fractionator.
February 12, 2009 at 2:07 pm #6257
February 12, 2009 at 5:13 pm #6256
In the DCU I worked some years ago, we had a full size flanged opening (tee) on top of the drum. This was a 24 ” line. Between this tee and the fractionator we had smaller flanged openings (maybe 8″, not sure) at every elbow, oriented in the direction of the flow.
Most of the coke buildup would occur right after exiting the drum.
February 12, 2009 at 7:54 pm #6254
was it an elbow or T connection? how about the drain connection?
February 14, 2009 at 4:26 pm #6244
antonio saura CebrianParticipant
Lucy are you talking about the drain between sp1&sp2 and sp6 & switch valve?,
These connections are typically 2 inches, in our designs We change the connection between valve switch & sp6 to 3 “, with connections for cleaning or removable spool
February 14, 2009 at 10:04 pm #6243
how often did you remove the coke and water, at every second change in direction or did you push the coke to the end at the fractionator? was the coke dropout location vertically down or horizontal and was it 10″ or full line size
Is there a limit of hydroblsting not being able to be done past two changes in direction because of the equipment or it can go for more direction changes?
February 16, 2009 at 8:10 am #6240
No. I mean, the size for drain connections to remove waste during clean-out, or you just push everything towards Fractionator.
February 18, 2009 at 9:11 am #6235
I wonder if anybody have experienced bad fouling downstream of SP3 up to Fractionator inlet?
February 28, 2009 at 12:12 pm #6215
there is not a general answer to your questions since it depends on fouling level; for design purposes my rule is that horizontal piping equivalent lenght should not belonger than 100 ft and turns should be minimized as possible; when required for stress or piping arrangement constrainsts, then long 120 degree ells should be used and cleaning connection located to the ell closest to the 100 ft; the connection size should be min 6 inches and max 10″, and located in horizontal position and tangential to bottom of the pipe.
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