2 replies to this topic

[bmicky]

Hi,

We design a Vapor Recovery Unit, which its main part is a screw vacuum pump. The system will be located at a site in South America (elevation is about 2,000 m above sea level. The required vacuum level is 0.069 bara.

Based on the pump's operation curve, which was received from a vendor, the maximum vacuum level which can be achieved at sea level by this pump is 29 in HgV (0.03 bara).

I try to evaluate, whether the required vacuum level of 0.069 bara can be achieved at 2000 m above sea level by this pump. I used the following methodology:

This vacuum pump with a maximum capability of 29 in HgV at sea level is rated of 97%.

(29 in HgV/29.92 in HgV)= 0.97

Then, I assumed the 97% rating can be used to the vacuum pump to determine its performance at 2000 m above sea level. The ambient pressure at 2000 m above sea level is about 0.763 bara.

Therefore, the pump’s performance at 2000 m is 0.763 bara X 0.97= 0.74 bara.

Based on this, the vacuum pump can only achieve a maximum absolute pressure of 0.273 bara (1.013 bara-0.74 bara). It means the required vacuum level of 0.069 bara [u]can’t be achieved at 2000 m above sea level.

I asked this question a pump’s vendor. Based on his evaluation, the maximum vacuum level which can be achieved with the pump is 0.023 bara (0.763 bara- 0.74 bara), and therefore he don’t see any problem to achieve the vacuum required level of 0.069 bara.

I'm a little confused. Who is right?

 

Thanks in advance, Mike

[juuichi]

hi mike

 

I think the vendor is right, if the principles of your calculations stand it means the vacuum pump can pump down to 3% of the ambient absolute pressure.

 

If the ambient at 2000m above sea level is 0.763bara then the vacuum pressure is 0.023 bara.

[breizh]

Hi ,
Consider reading the document attached (first pages) .

Breizh