Steam Ejector versus Vacuum Pump
Steam Ejector versus Vacuum Pump
(OP)
Why do different people prefer one or the other? What are the advantages and disadvantages of both. ALso, If you are to design a vacuum pump, what/how do you go about it (any helpful online or physical resources?) Please help!!





RE: Steam Ejector versus Vacuum Pump
David
RE: Steam Ejector versus Vacuum Pump
IN addition to what David has stated, other issues deal with how deep a vacuum you need to reach. If you use a water based LRVP, your vacuum is dictated by your ability to cool the water in the pump. If you use oil or other fluids you have the same consideration and your vacuum is limited by the vapor pressure of the fluid at that temperature.
You have the separator and pump and cooling systems for the LRVP fluid to deal with and that is moving parts and pieces. And the electricity bill to go with it.
With steam, you can stage the jets (I've never seen more than 5 stages) and pull some really deep vacuums if the process will allow it. You still have to have the cooling water or fluid for the inter and after condensers in the jet train.
And, you say vacuum pump which I immediately launched off on a disertation about LRVP's but there are non-liquid vacuum pumps that will get into really deep vacuums as well. But they are spendy and special purpose.
So what you need and what your resources are as to which method you choose to pull a vacuum on whatever process it is that you have.
rmw
RE: Steam Ejector versus Vacuum Pump
If you have all your data the application engineers at both links are very knowledgeable about their products. Fox has some good graphs and schematics.
http
http://www.s-k.com/pages/pro_06_00.html
A size too big is not problem, but an undersized system doesn't work.
RE: Steam Ejector versus Vacuum Pump
http://www.youtube.com/watch?v=0z1zIug6m3M
Here is a site that will give information on both jets and LRVP's. They used to have a connection to a H&C but I don't see it there now.
http://www.graham-mfg.com/
Enjoy.
rmw
RE: Steam Ejector versus Vacuum Pump
RE: Steam Ejector versus Vacuum Pump
Any compressor, therefore has a design flow rate, a design fluid (or combination of fluids if air/water vapor/other non-condensibles for example) and a design starting and ending point.
The pipe sizing is then a function of the fluid flow and pressure losses along the loop.
You haven't been specific about your application, but as an exapmple, for surface condensers for power plant applications, HEI has design parameters that help with vacuum pump sizing.
If you already have a steam ejector, then someone has already done the pipe sizing calculations. If on the other hand you are replacing the steam jets because they are now undersized (in-leakage exceeds original design) then your piping may be as well.
If you don't know your non condensibe rate or air in-leakage rate, you are going to have to put a measuring device on the non condensible exhaust of your current jet system and measure it.
Can you state why you are considering replacing a steam jet system with a vacuum pump? If I had a similar choice, and no limitations, I probably try to do the opposite.
rmw
RE: Steam Ejector versus Vacuum Pump
We are trying to run our crystallizer condenser more efficiently and have a payback in steam savings/energy. So I need to perform some equipment specifications to meet the process design requirements...
I know that steam injector is a safer bet (operators think so too). But im the intern and thats why im here, to replace it and not ask why (you know). Thats why I need help and the steps to take, what to do first? and so on....
RE: Steam Ejector versus Vacuum Pump
If you can get hold of Process Design and Engineering Practice by Donald R. Woods, PTR Prentice Hall, you"ll find good information. For example, Figure 2-20 gives the general applicability for "vacuum" gas moving equipment, as function of non condensible gas exhausted at steady state, (kg/h) vs absolute pressure, (kPa); plus worked examples.
RE: Steam Ejector versus Vacuum Pump
Pisa, www.vacuum-guide.com