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Toor
26-09-2016, 05:03 PM
Hi,
Please see attached level measurements on Deethanizer over head condenser, My concern is this much high level will trip compressor frequently because of liquid propane can go in compressor suction KOD.
Can any one please comment on this.
thanks
Toor

Josip
27-09-2016, 10:52 PM
Hi, Toor :)


Hi,
Please see attached level measurements on Deethanizer over head condenser, My concern is this much high level will trip compressor frequently because of liquid propane can go in compressor suction KOD.
Can any one please comment on this.
thanks
Toor

From attached scheme it is not clear (unfortunately some areas are not readable) what type of condenser you have (for sure it is S&T) ... it will be good if you can make a cross-section sketch of your condenser ... where we can see your tubes within condenser i.e. at what level is the last row of tubes within flooded vessel i.e. bottom vessel ...

Your LTT-9304 level transmitter is positioned good, but LTT-9370 very bad, both must be at the same level and with the same length plus level sight glass of the same length (but this is the same as in any petrochemical plant where refrigeration plant is designed by chemical engineers .. with my full respect to all of them, but this is not a good way ... I know one LTT is control unit and another LTT is for safety ... but installation at different levels has no sense ... why?!?

example: you want to empty your condenser i.e. drain all liquid propane to remain only gas ... assume your LTT-9304 is broken for some reason ... with LTT-9370 you cannot see if your condenser's bottom vessel is empty ... you have blind section ... on both sides ... what is there to see above upper vessel of condenser?:confused: ...

I'm mechanical engineer and I wouldn't try to design chemical plant ;) at least not without some good chemical engineer as my mentor) ... but that is another story ;)


Furthermore after condenser you have 1st stage suction KOD with hot oil heater as I remember from another post ... I believe if you have some liquid as propane drops entering into KOD (if not too much i.e. flood) it will evaporate .... at compressor suction port you should have only gas ... do you have some level transmitter within KOD ... probably not or not shown on your sketch ...


I believe you will not have any problem with liquid return ... but ...


Best regards, Josip :)

Toor
28-09-2016, 02:21 AM
Hi Josip,
Good Morning
Josip this plant design is very bad, LIT 9304 was not original, it is added on our request and even though LG was not original.
LIT 9371 was original design, we face lot of problems with this condenser but now ok, Regarding your query for condenser GA, yes bottom part is S&T and upper part is disengaging vessel with demister pad. in addition to this, 1st KOD is equiped with LG/LIT and Heating coil.
now some time liquid propane is going in KOD and causing tripping problem because of propane boiling in KOD and LIT is sensing hi level.
I appreciate you for your expertise and time to answer my questions.
Thanks
Toor

RANGER1
28-09-2016, 08:50 AM
Toor, From what I have seen, Usually only tube bundle is submerged in bottom S&T H/E.
Pipes of top of S&T only carry gas into top main "header'
gas has to be able to freely vent to top header.
Can you advise size of these lines & how many between bottom & top vessel!
Oil also has to be continually skimmed off or liquid stream from S&T through rectifier, otherwise oil concentration becomes to high.
This also includes any other heat exchangers like economiser if flooded.

Josip
28-09-2016, 11:10 AM
Hi, Toor :)


Hi Josip,Good MorningJosip this plant design is very bad, LIT 9304 was not original, it is added on our request and even though LG was not original.LIT 9371 was original design, we face lot of problems with this condenser but now ok, Regarding your query for condenser GA, yes bottom part is S&T and upper part is disengaging vessel with demister pad. in addition to this, 1st KOD is equiped with LG/LIT and Heating coil. now some time liquid propane is going in KOD and causing tripping problem because of propane boiling in KOD and LIT is sensing hi level.I appreciate you for your expertise and time to answer my questions.ThanksToor

OK ... according to your drawings your working level should be at level which you described as 0% or 271mm higher then central line of bottom vessel (RANGER1 described the reason "why") .... seems it is the top of the last pipes row within bottom vessel what is the best level for liquid propane above that level you can only have smaller COP and liquid return to 1st stage KOD ....

... maybe you'll need to recalibrate LIT-9304 using the bottom shell of bottom vessel as 0% level and this one which is now 0% should be 50% for you i.e. working level ... (instruments usually cannot read above 100% ... it is coming out like bad reading) and as 100% level (with alarm) you can put the level at the bottom of the upper vessel with demister .... of course you need to recalibrate LIT-9370 accordingly ...

Thinking out loud:

It will be good if you can shift your LIT-9370 at the same level as LIT-9304 ... then you'll have parallel reading and control ... with two identical spools you can lower LIT-9370 (not the best way ... there will be some pocket with liquid propane and maybe some oil at bottom spool, but with small drain valve not a big deal to check it from time to time) this can be done without any welding or stopping the plant ...



Permissible propane level within 1st stage KOD can be at the middle of hot oil coil i.e. heater ... in normal occasion you should never come to this level ... 100% level of your LIT-9304 should give you some alarm that something went wrong and you can act before your compressor trips on high level within 1st stage KOD (Knock Out Drum) refrigeration guys call that vessel - suction separator ... but ....

Hope this will give you some idea ...

Best regards, Josip :)

Toor
08-10-2016, 05:19 PM
Hi Josip
Level indicators problem has solved working with vega vendor.
Thanks for your suggestions.
Regards
Toor