2 replies to this topic

[William.K]

Hi, I need your advice. 

I am doing PSV sizing of liquid phase and almost done.

But as you know, almost is never enough.

 

depending on API 520, I used SI Unit formula like A=((11.78 x Q) / (Kd x Kw x Kc x Kv)) x ((G / (p1 - p2))^0.5

 

Kd is 0.65 without rupture disk, rated coefficient of discharge

Kc is 1 without rupture disk, combination correction factor

Kv is 1 (first time assume), correction factor due to viscosity

Kw is 1 (refer to the API 520 table, back pressure 3 barg and set pressure 10 barg), correction factor due to back pressure

P1 is 1000kPag, upstream relieving pressure

P2 is 300kPag (back pressure depend on the tank maximum pressure because the relief fluid will return to the tank), back pressure

Q is 3333.4 litter/min, flow rate

G is 0.554 (Fluid is LNG), specific gravity

 

As a result, I got A is 1699.52mm2. So I chose orifice size L (1841mm2)

 

is it right? please check my result.

 

and I wanted to get Reynold's number, so I also used SI Unit formula like R = (Q x (18800 x G)) / (μ x (A)^0.5)

 

I already knew the A is 1841mm2, Q, G, but the thing is μ.

 

μ is absolute viscosity at the following temperature, centi-poise and I know LNG cP is 0.126. But if you put the all values in the formula,

 

result will be 6.4 x 10^6. is it right? If the result will be 6.4 x 10^6, Kv = (0.9935 + (2.878 / R^0.5) + (342.75 / R^1.5))^-1.0 = 1.01

 

So 1.01 is wrong result I think.

 

What is the problem with my calculation? I am not sure μ is 0.126. please clarify this point, too.

 

Please let me get this over with.

 

Thank you.

 

 

 

[breizh]

http://www.leser.com...ngineering.html

 

Consider this resource to support your work , examples are included in the document .

 

Good luck,

 

Breizh

[William.K]

Thank you breizh. In fact, I also have the leser's documents and also software program trial version.

I will try to consider the resource again. 

 

Thanks