An Investigation of Modern Physics by Brian Williams
• ## Understanding Vacuum and Pressure.

Posted on September 12th, 2010

### Understanding mechanics is nothing to do with mathematics, it is the reality of what is actually happening and why it is happening.

A vacuum is the complete absence of any gas or any other substance that could exert a pressure. A diamond in a vacuum chamber would not effect the vacuum in any way. Most other substances and gases would. Note: Total absence of pressure has never been achieved.

Luckily we very rarely have to consider such a tight meaning, because we are usually only considering a partial vacuum and its effects. Note that intergalactic space is not a vacuum, it is just at a much lower pressure than we are used to. If it was a vacuum our atmosphere would disappear like dust up a vacuum cleaner hose.

Note:- The reason we retain our atmosphere is that although you would expect it to be sucked into the partial vacuum of space, this is balanced by the gravitational force of the Earth acting on the gases forming our atmosphere.

I have worked on the design of pressure systems operating up to 30.000 pounds per square inch, (including B.O.P s and other oil and gas equipment, to be topical.)  but the problems of designing vacuum systems is a lot more difficult, especially considering we are only dealing with a maximum pressure difference of about 14 pounds per square inch. This indicates that something strange happens at low pressures.

Very low pressure systems are difficult to make and costly to run. The difficulty is due to the problems of sealing against leaks. Joints that seal perfectly at pressures of 10,000 pounds per square inch may leak like a sieve under very low pressures. Materials of the vessels  themselves will leak under vacuum, meaning that special materials must be used. Even with the best materials there is some leakage, which means that the vacuum pumps must be run continually to sustain any vacuum attained.

At low pressures, atoms and molecules that retain their stability at normal atmospheric pressure, begin to act oddly. As the pressure reduces they expand. (They are a in compressed state whilst a normal pressure.) This expansion means that the they take up more space in the containing vessel and also weigh less,. (The mass decreases, but please note that the individual atoms/molecules still have the same mass, but there will now be less of them taking up the same space, therefore the weight for each cubic centimetre is less)

Note:- Removing the atoms/molecules is rather like removing a flock of sheep from a field. Initially you have no difficulty removing large groups of them, but as the numbers reduce you have difficulty in rounding up the few remaining ones.

Why does a partial vacuum work better than pressure in certain cases?

Normally you are taught that a suction pump operates due to the pressure difference, and that by removing the pressure on the suction side, the the atmospheric pressure forces the gas or liquid to move. In general, this is a working principle that includes most normal situations.

However, consider a pipe with a suction pump at one end, the other end lying in a tank of sludge. When you switch on the pump the partial vacuum at the pump end allows the liquid at that end to expand and become lighter, making it easier to move and it will start to move through the pump. This expansion of the fluid will in itself cause some of the fluid to pass through the pump.

The expansion effect will pass back through the pipe until the effect of the reduced pressure reaches the sludge tank, when atmospheric pressure takes over. Even if you close off the pipe at the sludge tank end, the liquid expansion will still continue until you stop the pump.

This is why, when attempting to unblock the sink, it is the upstroke that finally clears the blockage, the expansion of the water molecules effectively breaking up the blockage. The downwards pressure of the plunger in most cases applying far more force on the blockage than the differential pressure set up by suction, but in most cases without shifting it.

Another apparently strange thing is that a car tyre with 30 psi pressure in it will stay up for years  (Mine don,t). However, if you place it in a vacuum chamber at (say) 8psi absolute, it will leak. This not due to the increased pressure difference, (cars tyres can take a considerably higher pressure than that without leaking) but due to the atom/molecule changes under low pressures.

Note:- To be effective suction pumps should be of the positive displacement type. Vacuum cleaners, water pumps etcetera. are only capable of creating a relatively small vacuum effect.  A sink plunger creates a far more effective vacuum.
A problem with many pumping systems which use non-positive displacement pumps is cavitation, which has the same cause, creating vapour or gas within the pump, which ceases to run correctly or even not work at all.

—————————-

The old washing machines that used a central paddle arrangement that moved one way and then the other way, depended on vacuum for their cleaning efficiency. When the paddles reversed direction a partial vacuum was created which sucked water through the washing. Later washing machines are unable to do this and although the wet washing gets moved about, only a very small amount of water actually passes through the washing. Unfortunately the old system generally required top loading which is difficult to fit in modern kitchens.

Also read Dinosurs and the Expanding Earth – 2 -The Earth Mechanics

Author – Brian Williams

### 116 responses to “Understanding Vacuum and Pressure.”

1. Brooke Colaianni

normally cant find it in me to care enough to leaves a comment for articles on the internet but this was really pretty great, thanks and keep it up, Ill check back once again

2. Corey Sperry

Enjoyed looking at this, quite great stuff, thanks .

3. Kirk Sutphin

not really relevant but i waiting at the dumb air port the only website i can logon to is the one here regardless it was a good read

4. Orange County Lawyer

Certainly like your web site but you need to test the spelling on quite a few of your posts. Several of them are rife with spelling problems and I find it very bothersome to tell the truth however I’ll certainly come again again.
——————————————
I do find this type of comment mildly annoying. There are unlikely to be many spelling errors on my web site. A problem is that my website is an English site, and I am English therefore I write in the English language. There are thousands of spelling differences between the English and American languages. Also, many differences in the meaning and/or uses of particular words. In your above comments, in English you would check the spelling, NOT test it, and you would be looking for spelling mistakes not spelling problems.
It is refreshing to find a lawyer who admits to ” I find it very bothersome to tell the truth………”. Yes I know you didn’t mean that, but if you can’t correctly write in the English language I suggest you find more suitable employment.

Brian

5. Ermelinda

This is a message to the admin. Your website:Understanding Vacuum and Pressure. | Physics or Fantasy is missing out on at least 300 visitors per day. I discovered this page via Google but it was hard to find as you were not on the first page of search results. I have found a website which offers to dramatically increase your traffic to your website: http://*****seo.com/traffic/. I managed to get over 10,000 visitors per month using their services, you could also get lot more targeted visitors than you have now. Hope this helps 🙂 Take care.
—————————————————
The above comment from a SEO company. At this time (6/11/2012) the above posting is at number 6 on page 1 of the google listing out of 30,300,000 entries. It has been on page 1 for a number of months, (this is without any help from SEO companies or others.) I would suggest that she looks up entries for opticians in her area.
I checked under SEO companies and surprise, surprise, her company wasn’t on any of the first 10 pages out of 873,000,000 entries. (This figure would indicate that approximately 12.5% of the World’s population are SEO experts, I must admit that I find this a little surprising)
Brian

6. Lindsay Vallarta

Music began playing anytime I opened this web site, so irritating!
———————————
As there are neither music or video on my web site it must be your computer. Perhaps it gets excited at going to a good website for a change.

Brian

7. firma reklamowa

Very interesting and factual article, but in my opinion does not fully exhaust the subject.
—————————–
There are thousands of books and articles covering the subject of vacuum and pressure. However, knowing the technicalities of the subjects does not mean that you understand them. If you are involved in the subjects, keeping my article in mind should prevent you from making serious errors.
Brian

8. Malena Bucciarelli

Thank you a lot for giving everyone remarkably superb opportunity to read articles and blog posts from here. It is usually so useful and stuffed with a great time for me personally and my office colleagues to search your site not less than thrice per week to read through the newest secrets you have got. And of course, I’m actually amazed with the powerful suggestions you give. Some 2 tips in this posting are undeniably the finest I’ve ever had.

9. Irvin Bhakta

I am very happy to read this. This is the type of manual that needs to be given and not the accidental misinformation that is at the other blogs. Appreciate your sharing this best doc.

10. Emiko Graser

Hey there! I could have sworn I’ve been to this site before but after reading through some of the post I realized it’s new to me. Anyhow, I’m definitely glad I found it and I’ll be book-marking and checking back often!

11. Werner Schirrmacher

I’m so happy to read this. This is the type of manual that needs to be given and not the accidental misinformation that’s at the other blogs. Appreciate your sharing this greatest doc.

12. With havin so much written content do you ever run into any problems of plagorism or copyright infringement? My website has a lot of unique content I’ve either written myself or outsourced but it appears a lot of it is popping it up all over the web without my authorization. Do you know any ways to help reduce content from being stolen? I’d definitely appreciate it.
——————————-
Kelly, it is impossible to prevent it happening unless the search engine owners decide to do it. This is unlikely to happen I rely on my publication dates if I need to sue. Plus I have the advantage in my physics related posts (My main concern), in that I can supply full technical backup leading up to the publication of the post. Physicists would not be able to do this and would be subject to ridicule if they tried.
Brian

13. Demmer

Hello, your website has high bounce rate, that’s why it doesn’t rank in google and lose average 60% of traffic. You should install one useful wp plugin and you will see difference fast. Just search in google for**********Deleted ————————————————-
Demmer, This particular post has been at number 1 ( out of approximate 50,000,000)for most of the last two years. At present it is at number 55 (out of 66,000,000. I wonder where your web site stands. In the last 18 months my website has been severely hacked and there has been two attempts to take control of it. This has unfortunately affected some of my rankings. Note: My post “Newton’s Colour Wheel – The Reality” is at number 1 on Google, Bing and Yahoo and has been at number one for over 12 months.

14. This post is very informative. Thanks for putting it together. I have a much better understanding of the subject now.
————————-
Thanks Al. I checked your web site. Well designed, neat and well written and NO garbage. Well done.
Brian

15. Hurrah! In the end I got a web site from where I can in fact
get valuable information concerning my study and knowledge.

16. This article presents clear idea designed for the new viewers of blogging, that actually how to do blogging.