6 replies to this topic

[jordan1111]

Hello guys,

 

Background Infor: We have a two stage air ejectors where 2nd stage maximum discharge pressure is 760mmHgA =29.9 inHgA and it is designed for sea level.

Our facility usually has an atmospheric pressure (barometer reading) of 27.8 inHg. 

 

My question is that at our facility's elevation, the 2nd stage maximum discharge pressure should be our atmospheric pressure (27.8 inHg) + (29.9-27.8=2.1 inHg gauge). 

Is this a correct statement?

 

Thanks in advance.

Jordan

[breizh]

Hi,

Consider this resource to support your query.

https://www.dekkerva...g-vacuum-pumps/

 

Breizh 

[jordan1111]

Thank you for your help Breizh. 

I do understand vacuum performance is related with barometric/atmosphere pressure. 

But my question is for the last stage maximum discharge pressure. On the Spec. sheet, the last stage discharge pressure is rated at 760 mmHgA at sea level. I would like to know that if our atmohsphere pressure is at 27.8 inHg, the last stage discharge pressure is then at 760 mmHgA x (27.8/29.9 inHg) = 706 inHgA. 

 

Thank you. 

[gegio1960]

i don't understand the scope of your question but the (obvious) answer is: YES (the last stage discharge pressure is imposed by your atmospheric pressure).

[jordan1111]

We are trying to find out why we cannnot discharge from the last stage to hotwell (26" submerged into the water level = 2 inHg liquid head). Based on spec sheet, it's max discharge pressure is at 760 mmHgA and sea level which means it can sustain a back pressure of 29.9 inHg without breaking operation, but our local atmospheric pressure is around 27.8 inHg + 2 inHg liquid head in the hotwell plus some pressure drop on the piping, it is exceeding the 29.9 inHg back pressure. 

We can simply cut some pipe off going down to the hotwell. But I would like to know if my analysis is on the right track?

Thanks again. 

[breizh]

Hi,

Before cutting pipes, tell us more about the background. Is it a new problem or from the start? 

What is the feedback from the manufacturer?

I've attached a doc about trouble shooting Steam ejectors.

A sketch of your system will be helpful.

Breizh

 

[Bobby Strain]

The problem may be elsewhere. The liquid seal is aerated, so it is less than the static liquid seal.

 

Bobby