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Unbalanced Heat Method And Api 521


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#1 invssse

invssse

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Posted 17 July 2016 - 06:58 PM

Dear Members,

I have a question that make me confused a little bit. 

 

As known, as a widely accepted method,  "unbalanced heat load" is used by many (or most) designers to estimate relief load for distillation column, particularly for scenarios like general electric failure, reflux failure and so on.

 

While I cannot find any definite message in API 521 to support this method.

Can anybody of you shed some lights on this? thanks.

 

Invssse



#2 Bobby Strain

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Posted 17 July 2016 - 07:52 PM

The phrase somehow stuck. But the method is actually "heat balance", which is performed to estimate the relief load. You must surely have a description of how to proceed with this estimation, since you have a phrase. But be careful what you use for a reference method.

 

Bobby



#3 colt16

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Posted 18 July 2016 - 01:56 PM

Dear Members,

I have a question that make me confused a little bit. 

 

As known, as a widely accepted method,  "unbalanced heat load" is used by many (or most) designers to estimate relief load for distillation column, particularly for scenarios like general electric failure, reflux failure and so on.

 

While I cannot find any definite message in API 521 to support this method.

Can anybody of you shed some lights on this? thanks.

 

Invssse

 

Yes you can. I don't know which version you have but using API STD 521 (2013 - 5th Ed) you can read section 5.6



#4 invssse

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Posted 18 July 2016 - 06:50 PM

@Colt16

 

Thank you for the reply.

Yes, at the latest edition 6, the phrase you mentioned is described at section 4.4.3.2.

I can only find the following messages that can support unbalanced heat method while it's too general/vague.

 

"The required relieving rate is determined by a heat and material balance on the system at the relieving pressure."

"Because of the difficulty in calculating detailed heat and material balances, the simplified....through 4.4.3.2.9 have generally been accepted for determining relieving rates."






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