4 replies to this topic

[Ali Z]

Let's say you have a 3"J4" PSV with a 10" discharge line to a collector system. And let's suppose that you are doing your back-pressure hydraulic calculations either with HYSYS or FlareNet. In order to accommodate the 4"to10" reducer, in the outlet, into your calcs, would you add a 4" line with an enlargement into your model or you will just consider that reducer in your 10" line (probably as enlargement or contraction)? because it makes a large difference: if you do consider a 4" line in your hydraulic calcs, in most cases, it would be your major pressure drop if you have a large flow.

 

I appreciate your help, but please answer ONLY my question and right to the point...thanks

[shan]

It you attach 10"x4" reducer on the PSV outlet flange face directly, no 4" line should be included in the hydraulic calculation.  However, if you attaché a 4" piping section on the PSV outlet, then 10"x4" reduce, you have to include the 4" piping section into your hydraulic calculation.

[flarenuf]

hello Ali

an answer to the point  from me ;-)  even if you are only playing ..
firstly if you have access to FNT and HYSYS  you should use FNT as HYSYS isnt really designed to do flare systems
when you build the  network in FNT the program automatically puts a swage ( reducer or expander) between differing pipe sizes so you dont have to do it . So a 4 " to 10" expansion will be placed between the PSV exit flange and the inlet to the 10" pipe .
Correct Back pressure calcs will then be done to the exit flange.

once you have done this you may find that a 10" line isnt needed ( if its a new design)

flarenuf

[Ali Z]

it seems you're only playing....

you must simply consider the reality and the physical constraints.

often the reality of engineering is Cost Minimization: ie you won't put 10" pipe where you can 6" or 8"...

good luck!

 

If you knew in detail that how much the dynamic of the small section of PSV orifice to your outlet line affects your cost, you would have not thought that I am playing...it is often ignored by engineers, but it is important.

[Ali Z]

It you attach 10"x4" reducer on the PSV outlet flange face directly, no 4" line should be included in the hydraulic calculation.  However, if you attaché a 4" piping section on the PSV outlet, then 10"x4" reduce, you have to include the 4" piping section into your hydraulic calculation.

 

 

hello Ali

an answer to the point  from me ;-)  even if you are only playing ..
firstly if you have access to FNT and HYSYS  you should use FNT as HYSYS isnt really designed to do flare systems
when you build the  network in FNT the program automatically puts a swage ( reducer or expander) between differing pipe sizes so you dont have to do it . So a 4 " to 10" expansion will be placed between the PSV exit flange and the inlet to the 10" pipe .
Correct Back pressure calcs will then be done to the exit flange.

once you have done this you may find that a 10" line isnt needed ( if its a new design)

flarenuf

 

Thank you guys, yes I use flarenet very very often, but we didn't want to use it for the sake of this project as we are in a rush.