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ASME SECTION VIII Sizing of bursting disc

ASME SECTION VIII Sizing of bursting disc

ASME SECTION VIII Sizing of bursting disc

(OP)
Hi, I am trying to size the correct burst disc and calculate required discharge area according to ASME VIII.
Here's the specification.
-Burst design pressure(Po): 21.34PSIG
-Burst pressure(Pb) : 23.47PSIG
-Absolute bursting pressure(P1) : 38.17PSIA
-Flow required(W) : 92,395.72lb/hr

And I am wondering whether this calculation fomular is correct.

Required discharge area(A)= W / 51.5 x Kd x Kr x P1 x Kn
I don't know what is 51.5 is for..
Anyway, if I calculate the required discharge area,it is
92,395.72 / 51.5 x 0.62 x 0.88 x 38.17 x 1 = 86.15 Sq.in

The fomular for sizing the burst disc is I think..
Burst disc size = √(root)4A / π
And, if I size the burst disc according to this formular, it is,

√(root)4 x 86.15 Sq.in / π = 10.47inch
So, the size of burst disc has to be 12inch.
Does my calculation correct?
Please help~!
 

RE: ASME SECTION VIII Sizing of bursting disc

At a glance, this looks to be a proper diameter.  Very low pressure and very high slow rate gives a HUGE Rubture Disk diameter.

Try recalcing your system using a little thicker metal.  If you can give the system a doubled Max Allowable Working Pressure, you cut the area of the Rupture Disk in half.  Just because you only need a small pressure for the Operating Pressure, there is no reason that the system cannot be rated at a much higher pressure, and relieved based on that higher Design Pressure.

RE: ASME SECTION VIII Sizing of bursting disc

(OP)
Thank you very much.
I appreciate your answer.
I just realized that there is another fomular to calculate required discharge area(A) as below.

A = W X √(root)(T X Z)/M / C X Kd X Kr X P1

Where,
W = required flow
T = Absolute temperature in Degree. Rankine
Z = (I don't know)
M = Molecular weight
C = 326(Is this a coefficient?)
Kd = Coefficient of discharge(Where can I find coefficient chart?)
Kr = Measure of the flow resistance through the rupture disc and accounts for the holder and the bursting characteristics of the disc
P1 = Absolute bursting pressure

I tried to find the fomular I have in ASME code section VIII division 1, 2 to find out how these calculation formulars are used but I couldn't find them.
Where can I find the ASME fomulars related with bursting disc?
I'm desperate, please help me~!

RE: ASME SECTION VIII Sizing of bursting disc

If the disc is in piping and the inlet exceeds 8-pipe diameters and the discharge 5-pipe diameters you'll need to use the line loss method vs. a Ko of 0.62 you would use the Kr value.

RE: ASME SECTION VIII Sizing of bursting disc

(OP)
Thank you for your reply.
Could you tell me more about the line loss method and what Ko does mean? Please help me. I am totally lost and I have no idea how to size my burst disc properly.

RE: ASME SECTION VIII Sizing of bursting disc

Ko is the orifice coefficient of 0.62 in your first post. The disc is sized more as an orifice.  

As I stated the conditions previously depend on if the discharge is piped.  Then a Kr value from the manufacturer will be used in your line loss (assume compressible) calculation.

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