4 replies to this topic

[Faustini]

Dear community and fellows,

 

I'd like to clear a doubt along with my companions.

 

Supposing I have an ethanol storage tank (fixed roof). The following data is related to ethanol vapor pressure:

 

@ 20°C = 6 kPa

@ 25°C = 8 kPa

@ 78,3° C = 101,325 kPa (760mm Hg)

 

Supposing I have to install a PVR valve set to 3 kPa and the ambient temperature is ALWAYS 25°C (no variation),

 

My questions are:

 

1. Will the product always evaporate as the vapor pressure at 25°C is 6 8kPa?

2. If I set the PVR to 6 8kPa, then the valve won't open, will it?

3. Will the product temperature decrease to 20°C as the pressure inside the tank will always be 3 kPa? (sorry for the awful question, but I needed to ask)

4. Is the PVR valve set up correct? Or set it to 6 8kPa was the best option?

 

Thanks in advance,

Faustini

Edited by Faustini, 14 August 2013 - 06:09 AM.

[Pingue2008]

Faustini,

 

I am not an expert in designing PRV but I noticed a couple of things:

1- Why did you provide the Vapor pressure at different Temp? is that suppose to help?

2- what is the temperature of interest? (temperature of the vapor space in the tank)

3- if you have ethanol in the tank it means that the tank has been design for a certain temp & Pressure & MAWP conditions. provide these details.

4-what are the  sizes of the storage tank? (we are trying to prevent the tank to fail).

5- the business of relief calculations is not a game of guessing.

Maybe what I am trying to say is that the information provided is not sufficient to answer your query. what product are talking about in your

first question?

[breizh]

Faustini,

Consider this handbook  about ethanol , you will get some information and reference ,

Other resources for protections of tanks and emission .

 

Hope this helps.

 

Breizh

Edited by breizh, 13 August 2013 - 11:22 PM.

[fallah]

 

My questions are:

 

1. Will the product always evaporate as the vapor pressure at 25°C is 6 (8 as per your assumptions) Kpa? Yes

2. If I set the PVR to 6 (8 as per your assumptions) kPa, then the valve won't open, will it? Won't open but might has leakage due to getting start to open

3. Will the product temperature decrease to 20°C as the pressure inside the tank will always be 3 kPa? (sorry for the awful question, but I needed to ask) No

4. Is the PVR valve set up correct? Or set it to 6 kPa was the best option? It should be set in accordance with other safety devices and tank design pressure/vacuum

 

Faustini,

 

With lack of adequate information my answers are as red in above...

Edited by fallah, 14 August 2013 - 01:38 AM.

[Faustini]

Of course, gentlemen, I'm assuming that the tank will support the pressure/vacuum and all calculations are already done. The subject I'd want to discuss here is vapor pressure x pressure relief valve, not ethanol or the tank itself. (Breizh, your material was of great value, thank you very much).

 

 

Pingue2008

 

2- what is the temperature of interest? (temperature of the vapor space in the tank) Are you saying liquid and vapor have different temperatures even if the ambient temperature is constant 25°C? (there is no process inside the tank)

 

Mr. Fallah

 

I appreciate your direct answers and thank you for correcting me (first post already edited). My predictions were correct, but now it's far clearer.