8 replies to this topic

[shan]

I am working on a 3 phase separator with a go-by drawing. I am unable to explain why vapor line SDV is located downstream of flow meter and PCV but liquid line SDVs are located upstream flow meters of LCVs. Please help me on the issue.

[fallah]

shan,

 

Would you please upload a simple sketch of the system...

[shan]

Hi Fallah,

Please see the attachment for the sketch.

Attached Files

•  SDV Question.xlsx   16KB   74 downloads

[fallah]

shan,

 

With lack of adequate information not seeing a clear reason for that, might it is due to difference in flow meters type...

 

If you add the PSV connection and BDV route/location (if there is) to the sketch it might the reason would be clarified...

 

Would all SDVs be closed in fire case in order to separator isolation? Please also clarify this point...

[shan]

Hi Fallah,

As indicated in the updated attachment, I have included PSV and BDV in the sketch. I omitted them in the previous sketch because they are just typical.

I did think the SDVs should be downstream of flow meters to avoid the turbulence that may impact the accuracies of flow meters. This is true for the vapor line SDV. However, in term of avoiding turbulence, the liquid line SDVs should be downstream the flow meters too. I also agree the SDVs should be located as close to the vessel as possible to reduce the vessel blowdown volume. The liquid line SDVs follow this rule but why vapor line SDV not.

I have checked a few drawings from different sources. It seems to me the SDV arrangement is a common practice and does not alternate with the flow meter types.

Please anybody offer me an explanation.

[fallah]

shan,

 

Nothing updated attachment...

 

Anyway, when i mentioned in my previous post about the difference in flow meter type as possible reason for different SDV configuration i was thinking about possible impacts on accuracies of flow meters due to SDVs locations, just as your thought in this regard...

 

Also i did want to clarify about the PSV and BDV location on the sketch because i did think it might have impacts on SDV location in vapor line.

Indeed, if the vapor line is to be connected to flare network appears considering a SDV in that line shouldn't be necessary ... 

[shan]

I forgot press "Attach This File" button last post. Hopefully, it is OK this time.

Attached Files

•  SDV Question.xlsx   18.35KB   42 downloads

[fallah]

shan,

 

As per the updated sketch PSV/BDV configuration has no effect on SDV configuration. Then the fact that the SDV should be located as close to the vessel as possible to reduce the volume of the inventory might be applicable to this case. Obviously, locating the SDV in vapor line downstream of the flowelement hasn't so contradiction with this fact because most of blowdown rate would be related to liquid inventory for wuich relevant SDVs were already located at proper points...

 

I don't think a SDV as a full bore ball valve can be able to have considerable impact on passing fluid behavior and then accuracy of the downstream flow element...

Edited by fallah, 26 July 2013 - 01:35 PM.

[fallah]

shan,

 

One more thing:

 

It might SDV in vapor line be located downstream of the flow element because mentioned SDV is reduced bore type (contrary to other SDVs)...If so it is there not to affect the flow meter accuracy...

 

Would you please check this matter in SDVs data sheets and come back here to inform...