6 replies to this topic

[black friday]

Hi all,

I'm just trying to size a PSV downstream of a low pressure gas regulator. I don't have a Cv or orifice size, only a nominal flow and flow curves. Can these be used to determine failure flowrates?

The regulator in question is fed at 4 barg and will be relieved by the PSV at .1 barg.

See the attached pdf for the data I have on the regulator.

Any help is much appreciated. Cheers.

 

Attached Files

•  EquipA_EU_LGB_BS20-0_1-0_51.pdf   103.03KB   61 downloads

[Rodscott]

Black friday,
 
to try to find maximum flow rate whether a failure occurs, you can use Aspen Plus or Hysys, spacifying inlet pressure, outlet pressure and pipe diameter. The maximum flowrate through the pipe will be the chocked flow, that meams flow velocity equals to sound velocity.
 
Hope this help.
 
Rodscott

Edited by Rodscott, 18 March 2013 - 06:21 AM.

[shan]

No. When the regulator fails, its performance will not fit the normal flow curve.

[PaoloPemi]

for a low pressure, low flow regulator the port diameter is usually only a small fraction of inlet / oulet diameters,

since PSV set is well below 50% inlet pressure (for PRV) you can presume critical flow,

at low pressures you can estimate the speed of sound for nitrogen with the formula

 

ss = SQRT(kRt/M) where k = cp/cv about 1.4 for nitrogen (1 Bar, 25 C)

 

 

to give a reference, Prode Properties with SRK model calculates these values

P 2 Bar T 300K (about 25C) ss = 353 m/s

 

presuming a port of 1/4" or below (you can ask the manufacturer for the exact value) you can see that only a small PSV is required

[black friday]

Thanks for the feedback guys, I'll have a stab at it with PaoloPemi's method for a rough estimate. I thought there was no correlation between normal performance and failure behaviour but nice to have it confirmed.

Cheers everyone.

[latexman]

Call Air Liquide and ask for technical support.  They have the data you need.

[fallah]

Black Friday,

 

Ltexman is on right track. Vendor is best reference can provide the data you need. In fact, they provide the maximum flowrate through PCV while it is in wide open position due to filure...