Vacuum defination in process industry

An absolute vacuum is difficult to achieve, but that's pretty irrelevant.

The common missconception is that you can 'suck' harder and harder and get more vacuum.
Of course you can't you can only get to zero absolute pressure, or -1 atmosphere relative to atmospheric. A simple peristaltic pump will suck down to a pretty good vacuum, but it depends what you are trying to evacuate, how big a volume it has and how leaky it is.
If you are processing semiconductor wafers then you don't want odd molecules messing up your silicon so you need a good 'hard' vacuum...
Most applications just need enough negative pressure to lift, hold or move something.(And that can be calculated by mass area etc)
Hopefully someone else can fill in more detail about actual definitions....

My work here is done...
Del

An absolute vacuum is difficult to achieve, but that's pretty irrelevant.

The common missconception is that you can 'suck' harder and harder and get more vacuum.
Of course you can't you can only get to zero absolute pressure, or -1 atmosphere relative to atmospheric. A simple peristaltic pump will suck down to a pretty good vacuum, but it depends what you are trying to evacuate, how big a volume it has and how leaky it is.
If you are processing semiconductor wafers then you don't want odd molecules messing up your silicon so you need a good 'hard' vacuum...
Most applications just need enough negative pressure to lift, hold or move something.(And that can be calculated by mass area etc)
Hopefully someone else can fill in more detail about actual definitions....

My work here is done...
Del

In industrial use, 0 to 29 inches of mercury is called rough vacuum. When you go to high vacuum, most of the time it is measured in tors. In the industrial world, there is no such thing as a perfect vacuum, 30 inches HG. (inches of mercury).

In vacuum, think of a positive pressure in a vessel as being little pebbles of sand. The name of the game is to pull out as many pebbles as you can, over a prescribed period of time. Most of the time, in most of the applications you will see, the range is from 14 inches HG to about 28 inches HG. It then becomes an issue of evacuation time to keep up with your work load, measured in SCFM. Vacuum is a mirror image of air. The inlet will be very cold, and the exhaust will be very warm, the reverse of a compressor.

One of the best places to get a general primer on vacuum is a company called GAST, or a company called PIAB. The booklet used to be free for the asking.

Low vacuum can be achieved with a mechanical pump. High vacuum (HV) is generally regarded as 10e-5 torr or less and ultra high vacuum (UHV) is in the 10e-9 pressure region. HV usually involves diffusion or cryo pumps and O ring seals, whereas UHV involves ion pumps, etc. and all stainless construction with all metal seals.

I'd like to add because the soft seals and lubrication out-gas,and this limits the vacuum.

I've been out of the chip fabs for ten years but last I knew the moon normally has a better vacuum than we can create. Space even more so.

I think of Vacuum like I think of Cold. They don't exist. Heat or a lack of heat and pressure or a lack of pressure. You will not likely ever have a lack of either even in deep space where the pressure is estimated at one molecule per cubic meter at a cool 3⁰K or was that Rankin? Been too long.

Brad

Respected sir,

Please give me some data of vacuum

1> 1 torr = how many vacuum ( with chart)

2> short defination of vacuum ( with chemical lang )

3> What is absolute vacuum?

4> What is gauge pressure?