35 replies to this topic

[PaoloPemi]

I see the point,

however if you are not more than familiar with the software and its limits do not understimate the risk to obtain some "strange" results,

the advantage of simplified procedures (for example with columns it could be a binary or multicomponent short cut method) is that in many cases they allow to validate the values calculated with rigorous procedures (which are complex and require additional parameters not easy to manage).

I have a different software (PRODE) which I utilize mainly from Excel so I like the idea to use (where possible) a formula instead of a coded procedure (which is available),

Paolo

[sima-f]

hi

thanks for your help, i want to check my case with proII software for check the result and if the result is so different with hysys i check it with formula that is mentioned in API521.

[fallah]

hi

yes

 

sima-f,

 

If you select operating mode of "fire", you should select "None" for heat loss model because during fire case the vessel is engulfed in pool fire and the vessel's surrounding temperature is very high then there would be no heat loss to surrounding atmosphere...

[sima-f]

dear mr fallah

hi

i really appreciate your help, you'v been very helpful.thanks a lot

[fallah]

 

 whether hysys depressuring dynamic can determine RO size or not?

 

 

PN,

 

IMO, HYSYS depressuring dynamic nothing to do with RO sizing and merely provide Maximum Cv of the blowdown vlave along with the peak flowrate passing through it...

[Asset]

Has anyone come across BDVs for liquid filled systems (with BDV ..I mean depressuring valve with downstream RO)

 

These are part of offshore facility.

 

I was wondering how to go about with its adequacy check ( existing depressuring rate is 50% of design in 15 mins).

[fallah]

Asset,

 

If the system is filled with a liquid HC other than LPG and can be isolated in a fire case, with having a PSV no need to be equipped with a BDV for depressuring... 

[flarenuf]

hi
 

interesting to read all the different comments on this thread

having been involved with the hysys  DP utility since the beginning  perhaps i can clarify a few things  for you

the DP utility is there to allow users to design or rate existing blowdown installations or  PSV's

normally a DP station will comprise an ESD valve on teh process lines and a full bore ball valve with RO downstream to control the flowrate to Flare.

 

API recommends that you DP  HP vessels/pipes down to 50% of P or 6.9barg  in 15 mins ( based on a 1" thick vessel wall), different wall thicknesses require diff times
hysys will calculate the required orifice area / diam required in order to do this

as mention above by others it doesnt categorically say RO size as a lot of the forms are used in common with PSV sizing, so the word valve is used. it is however the required RO size that you finally end up with.

 

i have attached 3 files from my vast library :-) on this subject, i acknowledge credit to the other authors  of these

hopefully these will help some of you

 

flarenuf

 

Attached Files

•  DEP 007 - Validation of Hysys Depressuring Utility.pdf   85.94KB   182 downloads
•  DEP 009 - Effect of diff parameters on DP Calcs .pdf   262.74KB   149 downloads
•  DEP 012 - Vapor DP Concept and Implemenation.pdf   226.94KB   137 downloads

[marchem]

for a detailed description of algorithms I would look for A.Wong thesis (Blowsim) or similar works,

there are many papers discussing rigorous procedures as well as simplified models, as mentioned in previous posts,

I have the depressuring module in PRODE but it wouldn't be too difficult to create a simple model in Excel (or some other tool) as suggested by Paolo and (perhaps) requested by rkvizag04 on first post of this thread,
of course a simulator such as PROII, HYSYS, CHEMCAD etc. when available, can solve the problem.

[Asset]

Asset,

 

If the system is filled with a liquid HC other than LPG and can be isolated in a fire case, with having a PSV no need to be equipped with a BDV for depressuring... 

 Thanks Fallah,

 

I am actually looking for approach to tackle these "Liquid EDVs".

 

You are right that in case PSV (for fire case) if installed, there is not need of depressuring valve.

I might add, only high vapor pressure HCs (Propane, LPG, NGL etc) with substantial inventory are typically proposed with EDVs on offshore platform I came across (at times in addition to PSVs).

 

Coming back to approach on RO sizing (or the relief rate to be precise) ,  lets assume that the bulk of HC above its boiling point is stored and is provided with EDV ( & no PSV), one of the possible solution could be to consider liquid at its bubble point and calculate the vaporization rate based on average latent heat and decide on the release rate and alternately the RO size?? and can arguably debate on the depressurizing time. (15 minutes depressurizing apparently will be harsh).

 

One more point, this is actually validation work, so I can't go back and tell client that something looks fishy (well...unless absolutely sure)!!!

 

Thanks

[fallah]

Asset,

 

Your query isn't so clear...please clarify about the code based on which the relevant vessel has been designed (on which there is no PSV) and if the depressurizing is automatically actuated...a simple sketch can help much more to submit proper response...