4 replies to this topic

[Mirul1996]

Hi,

 

 I am currently doing my internship in the oil and gas industry (contractor) as process engineer. My supervisor give me a task to do some reverse engineering where i need to study how a spreadsheet (calculation) construct by other process engineer was been constructed.

 

Ok the situation is the natural gas source is coming from NPS 18 and flow through NPS 8. The problem is i stuck at the early stage to calculate density of the natural gas at respective T and P. Based on the equation ρ = P.Mw/RTZ i got 19.52 but he got 20.17. Does anyone can help me? Thank you.

 

As in the attachment are the spreasheet and the gas composition

Attached Files

•  spreadsheet.PNG   22.95KB   4 downloads
•  speadsheet 1.PNG   27.25KB   2 downloads
•  Gas Composition.PNG   30.65KB   2 downloads

[breizh]

Hi,

The spreadsheet is correct , make sure your pressure is expressed in absolute !

Good luck

Breizh

Edited by breizh, 03 July 2020 - 06:08 AM.

[Bobby Strain]

Mirul,

      Your spreadsheet lacks any equations to show what the spreadsheet is doing. Spreadsheets are a lousy way to work. At the least, if an engineer is going to use spreadsheets repeatedly for design calculations, they should be well documented. And Excel formulas should be shunned. For professional work you should only use a compiled program. Or at least use Excel VBA which should be well documented with comments. Why? You demonstrated why with your question. You couldn't find a proper formula within the spreadsheet to check. So, start your career right and only use appropriate tools. And Excel formulas are not quality professional tools. Now, Breizh didn't do you a great service when he poked a few numbers on a spreadsheet for you. But, he is a very experienced and helpful engineer who gave you an answer to show your error, not to correct your method. What would you have done without his help? You need to develop good habits whenever you are young, so that you may grow old and wise.

 

Good luck,

Bobby

[breizh]

Hi,

Agree with Bobby about the method !

I've added calculators to support your work , each of them has references to consult 

https://checalc.com/index.html

Another great resource is GPSA ( Gas processors suppliers association)  engineering data book . Ask your supervisor , he should have a copy of this reference !

 

Good luck 

Breizh 

Edited by breizh, 04 July 2020 - 04:27 AM.

[Mirul1996]

Hi,

 

Thank you sir Breizh and Bobby. I didnt think the pressure in absolute and think the equation was wrong.