Orifice sizing for External Fire - Wetted Surface 2

[michaelha]

I was given the project at work to set up an excel program in which we could determine the size of rupture disks/ pressure relief valves we would need for our vessel.

I am currently doing calculations for a vessel that uses acetone, but I am unsure which Temp to use when finding the area. Can I use the T1=To(P1/Po)?

To and Po being standard operating conditions
P1 = relieving pressure

Thank you for the help!
Mike

 

[Latexman]

What are the credible scenarios?

Good luck,
Latexman

Technically, the glass is always full - 1/2 air and 1/2 water.

 

[PaoloPemi]

as said by Latexman as first step you should evaluate the possible scenarios to investigate,
for fire case you can calculate the temperature at P.discharge solving a flash operation,
for an Excel example see

'

http://prodesoftwareapplications.blogspot.it/'

the same library has Excel macros to design / rate a PSV or a rupture disk in Excel.

 

[michaelha]

For this one, I'm looking at fire cases for wetted walls.

PaoloPemi: I can't open the link because of internet restrictions at work, but solving Temp at P.discharge can be done using the ideal since the relieving Temp will be much higher than the boiling point of the liquid inside, correct?

Thank you for the responses!
Mike

 

[PaoloPemi]

if you mean ideal gas (Z = 1) P1*V1/T1=P2*V2/T2
for the case V1 = V2 (vessel)
probably you did P1/T1 = P2/T2 and T2 = T1*(P2/P1)

but this may give only a rough estimate for the case of ideal gas in a vessel,
for the case of vaporizing liquid mixture you should follow a procedure
as that described in the above link,
for a pure fluid (below critical temperature) you may consider the vapor pressure correlation,
Paolo

 

[Latexman]

I get the feeling you are not on a technically sound path yet. For example, for fire case I would have expected to hear that the vessel MAWP would influence the choice of burst/set pressure of RD/PSV. Then, sizing pressure = 1.21 x Pset. Then, the sizing temperature is the boiling temperature of the liquid (acetone) at the sizing pressure., which would require a vapor pressure equation of some sort.

I recommend you obtain and study API 520 and API 521 Parts 1 and 2. Those are a good start. They will refer to other standards that will help you. You'll also need bits and pieces from chemistry, physics, basic chemical engineering, NFPA standards, thermodynamics, fluid flow, etc.

Good luck,
Latexman

Technically, the glass is always full - 1/2 air and 1/2 water.

 

[Latexman]

You owe it to yourself to access the link PaoloPemi gave, even if you have to call your IT and request it. The first paragraph says,

"Prode Properties includes a procedure to design/rate pressure safety valves with critical or two-phase flow with the most accurate models
-HEM (Homogeneous Equilibrium Model)
-HNE (Homogeneous Non-Equilibrium) with boiling delay and gas-liquid split contributes
-HNE-DS (Homogeneous Non-Equilibrium)
-NHNE (Non-Homogeneous Non-Equilibrium)
With Prode Properties you can size / rate a PSV directly in Excel (see the following application example)"

Sounds exactly like what you need, huh? Why re-invent the wheel? There are several sources of software that will already do what you want. This is one of them. Use Google and look around.


Good luck,
Latexman

Technically, the glass is always full - 1/2 air and 1/2 water.

 

[michaelha]

I will definitely check out the link/example. I've been reading API 520 and 521, and I think I know just enough to keep myself confused!

I appreciate the all the help. I'm sure I'll be posting more questions in the future to try and understand it all better.

Thanks Latexman and Paolo

Mike

 

[Latexman]

The rupture disk/safety valve "programs" that the companies I have work for over the last 35 years has taken considerable man-years of effort to develop and maintain. Multiple people and multiple years. Being asked to "set up an excel program" to do this sounds like the tip of an immense iceberg of an effort to me.

Good luck,
Latexman

Technically, the glass is always full - 1/2 air and 1/2 water.

 

[Duwe6]

"The rupture disk/safety valve "programs" that the companies I have work for over the last 35 years has taken considerable man-years of effort to develop and maintain. Multiple people and multiple years"

What he said. If you get done in less than 200 working days [loooong ones] I can guarantee that you have missed some necessary items.

"You owe it to yourself to access the link PaoloPemi gave, even if you have to call your IT and request it. . . . . . Sounds exactly like what you need, huh? Why re-invent the wheel? There are several sources of software that will already do what you want. This is one of them."

Ask the person paying you if they want to devote your next 1-5 years of time to reinventing something commercially available?

 

[rense]

I think that before to start a new project one must consider resources, capabilities and competences available,
for this case I agree that a ready to use solution can be the best option.