38 replies to this topic

[JoeWong]

Dear Jaimin
Warm welcome to you...

Before get into your question, can you advise the following ?

i) Did you consider settle-out condition (mean system settle out to minimum ambient temperature prior to blowodnw) for low temp blowdown ? Probably this condition will give you worst MDT.

ii) Did you include the metal mass effect in blowdown ? How you define the "vessel" in Depressuing Module ? It may affect the calculated MDT.

iii) Do you consider minimum, normal, maximum level in the module ? Liquid level significantly affect MDT.

iv) Did you conduct cold blowdown by fixing the time e.g. 15 miniute ? if you did that, you will undersize you RO for fire blowdown.

v) What is the isentropic exponent you have considered ? 70% per HYSYS default ?



Dear Brian Lim.
I would like to invite you to drop some notes on the definition of Min. vessel fluid temp., Min inner wall temp. etc... to help us understand further. Thanks.

Note : I hope you are the Brian Lim in HYSYS Singapore. Otherwise forget about it and forgive me.

JoeWong

[JoeWong]

Dear Jaimin,

i) Did you consider settle-out condition (mean system settle out to minimum ambient temperature prior to blowodnw) for low temp blowdown ? Probably this condition will give you worst MDT.
-----> No. I have to fix the MDT based on blowdown starting at normal operating temperature.

You may try blowdown from Normal operating temperature. Please also conduct second check on settle out condition.

ii) Did you include the metal mass effect in blowdown ? How you define the "vessel" in Depressuing Module ? It may affect the calculated MDT.
-----> No. Does it require to include?

You may end-up a VERY conservative design without inclusion of metal mass. Of course there are more complication by inclusion of metal mass.

iii) Do you consider minimum, normal, maximum level in the module ? Liquid level significantly affect MDT.
-----> No. Fix level of liquid, 1 mtr.

Why fixed at 1m ? Any specific reason ? You may have to answer to your client why this level is taken.
Suggest you try run with minimum, normal, maximum level. You will see the impact of varying level.

iv) Did you conduct cold blowdown by fixing the time e.g. 15 miniute ? if you did that, you will undersize you RO for fire blowdown.
-----> I cant get this. I have to depressureing vessel to 50% of design pre. in 15 min.

I hope your 50% of design pressure is lower than 6.9 barg in compliance to API521 (If you have to compliy to this code]. If not, please read API Std 521, 2007, section 5.20 to see if you need to comply to minimum pressure of 6.9 barg.

v) What is the isentropic exponent you have considered ? 70% per HYSYS default ?
-----> 93%

Any specific rule guiding you to 93% ?

Above questions mainly to trigger you to think more on setting up you model. Peoples has said rubbish-in-rubbsih-out. Detail understanding of your problem and correct inputs to the model will yield a better results for interpretation.

Back to your question, generally liquid having better heat transfer efficiency as compare to vapor. Those you may experience lowest fluid temperature at the bottom of vessel. In most cases, the metal may see this temperature.



Hope this help
JoeWong

[JoeWong]

Jaimin,

Huh...it can form a long article...Let me know your email address. I will drop you some simple note.

JoeWong

[JoeWong]

Please check you mailbox.

JoeWong

[JoeWong]

Jaimin,

Any big differences between them? I believe you should base on MIN VESSEL FLUID TEMP. Please take note that the liquid temperature will be worst.

JoeWong

[JoeWong]

Without inputs, assumptions, basis, actual method used...it is almost impossible to judge if it is OK.
My feeling is the temperature on low side.

JoeWong

[Dtan76]

Hi Joe

Thanks for sharing, can sent me the dep article to me as well?
I can be reached at cheekuan76@yahoo.com

Thanks and regards

[JoeWong]

DTAN76,

Please check you mail box.

JoeWong

[suresh2]

Joe,

Acutally i posted a question about Depressuriztion by HYSYS in this forum before. However, could send me the depressurization procedure.

my e-mail id: sureshreddy325@gmail.com

Thanks

[Zack Adam]

Dear Joe Wong;

Cud u pls also drop me the procedure.... just wanna check wether its similar to my understanding... tq

[JoeWong]

Suresh & Zack,
I have drop some note in your mailbox.

JoeWong

[Dtan76]

Hi Joe

As promised early, I had sent you the depressuring guideline and you said you will come back to me with your valuable comment...

When can I received your feedback????

Thanks

[JoeWong]

DTAN76,

Please check you mail box.

JoeWong

[Zack Adam]

Joe Wong;

Sorry since I didn't get a copy of it.... could you please resend to me again. appreciate your help...tq

Joe,

I'd appreciate a copy of any DEP articles or materials or comments you have available.

My e-mail address is: n1pa@ghg.net

Thanks!

===========================

Do you have a guideline about terminology? For example, what is your definition of "blowdown" and what is your definition of "depressurizing"? They are related, but in my view, "blowdown" usually refers to plant-size units or vessels, whereas "depressurizing" can mean whole systems, such as an entire plant or a long feeder pipeline, etc.

Best,

Armentor

[benoyjohn]

Joe,


Can you please send me the article on depressurizing / blowdown.

Thanks and Regards
Benoy


My Email : benoy.john@mottmac.com.om

[Cheryl]

Joe

Can you forward the article to me as well.
Thanks

xiruo98@hotmail.com

[JoeWong]

Dear all,

I have sent some simple procedures to Jaimin instead of article... I know some of you would like to have a very comprehensive procedure... i am not sure this is available...I am in the process of compiling some information for those who are interested in depressuring...Hope you can wait...

Will only post them when it is properly done.

JoeWong

[Viney]

hi joe

Appreciate your efforts in helping us all with your experience. Would you be able to share those depressurising procedures (as sent to Jaimin/latest) with me. Ofcourse i shall be waiting for the detail procedures too.

regards