5 replies to this topic

[J_Leo]

Hello,

 

What are the rules of thump for the low liquid level and vapor space in the bullets and spheres to store propane or butane?

 

I don't have much experience in sizing these storage vessels. Your advice is greatly appreciated.

 

Thank you,

 

Leo

[Bobby Strain]

Spheres often come equipped with a boot on the bottom to allow easy water draining. On a bullet, with clean contents, it can also be equipped with a boot. So you can set the lowest level wherever you wish. Leave enough vapor space so you don't release liquid in the event of a relief valve discharge. Also, the liquid contents will be at different temperature from day to night, or weather. So leave enough room for liquid swell.

 

Bobby

[J_Leo]

Bobby,

Thank you very much for your advice.
Regarding the vapor space, do you think it is ok if it is 5% of the total vessel volume at max operating temperature? The temperature of the flow to the vessel is higher than max ambient temperature. Can I assume the volume will only shrink because it is designed for max operating temperature?
Or should I design the vessel at lowest storage temperature with much bigger vapor space and assume it will expand to leave 5% volume as the temperature rises to the highest operating temperature?

Thank you,
Leo

[farid.k]

can refer NFPA 58 (2001) for details of the maximum liquid level including the liquid volume correction factors and equations concerning capacity temperature. refer NFPA 58 para 4-4 and appendix F. other regulation specify shall have 10% that must be secured. For minimum level, should consider pump NPSHa. when NPSHa - NPSHr is less then 1 meter, should consider that level as low low. otherwise risk for pump cavitation will be high.

[J_Leo]

Farid, thank you very much! I round API 2510 as guidelines for the vapor space. I am specifying a can pump for this service, so LL liquid level don't have to as high.

 

Regarding the low design temperature, if I flash propane to atm I got -45°F. I saw this was specified as the lower design temperature for propane bullets, so low temperature carbon steel has to be used. However, it was not specified for propane sphere. Any comments on this?

 

Regards,

Leo

[farid.k]

Farid, thank you very much! I round API 2510 as guidelines for the vapor space. I am specifying a can pump for this service, so LL liquid level don't have to as high.

Regarding the low design temperature, if I flash propane to atm I got -45°F. I saw this was specified as the lower design temperature for propane bullets, so low temperature carbon steel has to be used. However, it was not specified for propane sphere. Any comments on this?

Regards,
Leo

Yes.you use can pump and if I not mistaken we call it as vs6 pump. Let say you want to have lower ll level, then can have to be longer in order to gain the static head and increased the npsha. But the longer the can the expensive the pump.so this is your task to do sizing the tank and pump, set the minimum level so that the pump never cavitate.

Regarding the material, just refer the material spec design temperature. If it can be operate at ambient and flushing temperature it should be OK. Same goes to piping. Because flushing to flare at pipe line also possible.

Edited by farid.k, 09 April 2015 - 05:45 PM.