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Knockout Drum Mist Extractor Not Permitted For Flare System Acc. To Ap

knockout drum flare mist

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#1 TNCX34

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Posted 13 September 2017 - 06:08 AM

Hello

 

One of our client mention that  "Mist Extractor for knock out drum of the Flare system is not permitted as per API or International standards."

 

Do you have any information regarding to this subjected limitation also we are trying to find such limitation however till now there is no chance to understand this limitation or what we need to use instead of this system if the limitation issue is true?

 

Thanks in advance.



#2 Bobby Strain

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Posted 13 September 2017 - 02:42 PM

That is correct. No potential obstruction should be installed in an emergency relief system. So the vessel must be open, without internals that may obstruct flow. And, if this is a new knockout drum, be careful in sizing it. The procedure in the API recommended practice is not correct. And the API committee has not figured it out yet.

 

Bobby



#3 TNCX34

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Posted 14 September 2017 - 01:11 AM

Dear Bobby,

 

In the light of the given information including molar flow rates, I modeled it on software basis and and also check some documentation such API 12J, accordingly regarding diameter seems not problematic considering lenght appr. 6 times more than diameter! However as for internals, in DS provided there are several internals for that system such as, inlet diverter, mist eliminator and it is not given explanation on it but maybe one baffle, coalescer or foam breaker shown as just dashed line as one line I am not sure what is these internals. System is working such 2 phase diverter and gas is on going to flare and liquid is transfering to recycle tanks. At that moment what is your recommendation, not putting any internals to drum, and how can I provide reference about that issue because I need to give certain explanation and references, unless I am using internals? 

 

Thanks for your kind replies.



#4 Pan Nainggolan

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Posted 14 September 2017 - 03:33 AM

TNCX34,

 

Refer to API 521 for KO Drum of Flare or Vent System.



#5 TNCX34

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Posted 15 September 2017 - 01:20 AM

Dear Pan,
 
I think that I checked the important parts of the documentation and I found one possible reference please look at that;
 
Although horizontal and vertical knockout drums are available in many designs, the differences are mainly in how the path of the vapor is directed. The various designs include the following:
 
a. A horizontal drum with the vapor entering one end of the vessel and exiting at the top of the opposite end (no internal baffling).
 
 
What do you think is it a reference of no internal parts?


#6 Bobby Strain

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Posted 15 September 2017 - 02:31 PM

API 12J is applicable to a process separator, not a flare system KO drum.

 

Bobby



#7 Pan Nainggolan

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Posted 18 September 2017 - 01:03 AM

TNCX34,

 

Mist eliminator/extractor is different with baffle. You are talking about mist extractor, aren't you?



#8 TNCX34

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Posted 18 September 2017 - 03:42 AM

Pan,

 

Main problem is that what do I need to put inside of the vessel I am not sure actually. Client DS show that some internals inside of the vessel however definition is not given, just dashed line shown upper inlet shell to near bottom(horizontal vessel). But client also mentioned that first message of mine as internals do not permitted by API and other standarts. I need to understand what do I need to put inside certainly or nothing. Because this vessel will be ASME U-Stamped project and very strict rules to be followed in next schedule and performing changes will be very difficult at that period. I need to clear all the things as internals that is the case. Main concerns that whether there will be any mist eliminator or baffles or another parts which can be determined as internals? Hopefully you can assist me in this regards. Thanks.



#9 Pan Nainggolan

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Posted 19 September 2017 - 12:56 AM

TNCX34,

 

Could you please upload any drawing of your KO Drum (General Arrangement is better)? to make it clear what exactly internal in your Drum. I've ever designed and commissioned Flare KO Drum as per API 521 and stamped with ASME.






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