3 replies to this topic

[ahyong]

Dear All,

I am reviewing a calculation sheet by cross checking with SHELL DEP on GAS/LIQUID/LIQUID Separator. The specific 3 phase separator has weir as the internal. I was stuck at the part when reviewing the calculation formula for control time in both light liquid phase and heavy liquid phase. The control time provided in SHELL DEP I believe is generally for "normal" situation such as separator with boot or without internal. (hope you understand what I mean). Is there any documents or materials that I can refer to find out the control time formulae in both light liquid compartment and heavy liquid compartment when using weir as internal?

Thank you very much

[AlertO]

Hi Ahyong

Control time you mention means the hold-up time between the interval level(e.g.high, high-high, low, low-low) in the vessel, doedn't it?

If yes, the control time should be from the actual requirement from the operation even though it's boot seperator or weir separator. For example, if we follow DEP to set the level for 5 min for L>>L-L,but the operation can not make a action in time. The control time we set will be useless.

Hope this may help you.

[ahyong]

Hi Ahyong

Control time you mention means the hold-up time between the interval level(e.g.high, high-high, low, low-low) in the vessel, doedn't it?

If yes, the control time should be from the actual requirement from the operation even though it's boot seperator or weir separator. For example, if we follow DEP to set the level for 5 min for L>>L-L,but the operation can not make a action in time. The control time we set will be useless.

Hope this may help you.

Hi, Alert O

 

Yes, I mean the hold-up time between the interval level. In the DEP, they mentioned how to calculate (provided formula) the control time in the boot where the heavy liquid is collected (DEP 31.22.05.12 pg79) and also the light liquid phasee at pg.80. But I believe that this formulae cannot be used when you are verifying a 3 phase vessel with weir. SO here i refer to the formulae provided in th same document at page 88. There are 2 kinds of formula here, which means based on the Qlight/Qheavy ration, the formulae to count the control time in liquid compartment/heavyliquid compartment will be different.

Shell DEP did not mention how to decide on "large ratio" or "small ratio".

If someone has any idea on this please kindly provide your opinion. Thank you very much!

[AlertO]

Hi Ahyong

OK i got your point. your question is about the formula shown in the calculation for boot separator, but you want to know the formula for weir separator, right?

Surely, the formula is totally different due to the shapes. The boot separator is calculated based on the vertical cylender while the weir separator is calculated based on partial volume of horizontal cylender which more difficult to calculate.

you can use the attached spreedsheet for calculating the partial volume in each interval level.

Attached Files

•  Vessel_Volumes.xls   1.39MB   78 downloads