Pump strainer

Hello AUREL MARES

from me

Kind Regards....

Hello PennPiper

from me

Kind Regards....

hi Sparky,

I have been watching our comments on many of your comments on different forum threads with a lot of interest, specially the animations contained therein.

Can you share your secret how you do it for the benefit of the rest of us, may be starting with a separate forum thread?

Regards/Sisira

Hello Sisira

I did that requested topic 30th December 2007, please refer here: http://cr4.globalspec.com/thread/15743/How-to-insert-Graphics-into-your-Post-to-make-it-more-readable-or-interesting

Have fun.

Kind Regards....

Cute picture! Is this an appetizer for MOBI?

(Sorry, I'm being bad again!)

I have left enough clues on this site to my state of semi-ignorance on the metric system. Your deduction that I am a citizen of the US of A is right on. I think Australia is remote enough that any of my activities will not affect you directly.

From a 2nd law of thermo view, you are technically correct. Matter or energy is not pulled toward a lower state, it is pushed from a higher state. However, for the majority of people I run across the visual aid of "suction" and "sucking" make it easier to understand.

Yes I was trying to be a smart a** by pointing out your description of low pressure pulling in a fluid from higher pressure sounded a lot like sucking. I apologize if my remarks caused offense.

No offence taken at all my friend, no need to apologise, why not air ones views...........I think an interchange of thoughts and ideas, is good for the mind..........and how others see things as well. I too can be a smart a*^# some times.

I run across the visual aid of "suction" and "sucking" make it easier to understand.

When I have a new class of students, one of the first sketches I draw on the white board is the straw and can...............after that I tell them that in all pumping systems a pump replaces their mouth........basic principles.........and pumps create flow.

It is interesting when you see the term NPSH in formulae. My story is, that probably some where between 40-50 years ago it was decided by the worlds leading pump manufacturers that they should, among other things, standardise pump terminology.

Of courese most manufacturers where American, hence these meetings were held in the States and US numbers far outweighed those from other countries..............to cut a long story short (hahaha).........the low pressure, low side or inlet side of the pump was to be called the "SUCTION" side of the pump...........however wrong it may appear to those of us that think,............ sorry,............... know we are right.

I used to be conceited once.............BUT............now I am perfect.

Cheers, my friend.

The problem with written communication is it is sometimes difficult to pick up on the sarcasm. I wasn't exactly sure where we stood, and am glad to clear the air.

It is great to see the different viewpoints on this site, and to get glimpses of why we do things the way we do. Even if it is wrong!

"I used to be conceited once.............BUT............now I am perfect."

To misquote a dead philosopher "I used to think, therefore I probably was."

is it free of charge or i have to pay

i m ready for that but dont know procedure

Hello again sandeep lokhande

Just click on that hyperlink in my earlier Post Topic: http://cr4.globalspec.com/thread/15743/How-to-insert-Graphics-into-your-Post-to-make-it-more-readable-or-interesting

It is free, gratis, without any charge to you.

Kind Regards....

MOBI,

I debated whether or not to get into this discussion since it has been several days since it began, but I couldn't let your misinformation stand without a challange.

Twice in your challenge demonstration you instruct the reader to "SUCK". Then, further along in the piece, you state "...because you create a pressure drop in your lungs and mouth..." Interesting. The "New World Dictionary" defines SUCK as "To draw in water, air etc. by creating a vacuum." That sounds very much like "...because you create a pressure drop in your lungs and mouth." doesn't it?

In your own demonstration you have instructed the reader to SUCK and you state that there would be no beverage delivered to the mouth of the participant. That doesn't diminish the fact that he is still "sucking". It only demonstrates that, while sucking from a closed vessel, there may be no movement of product. The mouth (or suction of a centrifugal pump) is still sucking.

Your demonstration proves three things: 1) - that sucking is not the only component that must be present to cause the flow of liquid 2) - that flow is not necessarily a result of SUCKING and 3) - that there is another definition of the word SUCK and it could very aptly be applied to the dissertation that you have presented in your reply.

In summary, I would leave you with this final statement: "Pumps DO suck."

Why is it that for practical purposes your dynamic suction head is generally regarded as being 26'................can't you "suck" any more?

If you recall I made the point that in engineering terms one does not "suck" anything, in biological terms ............that is different.

New World Dictionary" defines SUCK as "To draw in water, air etc. by creating a vacuum."

May I draw your attention to the word......vacuum.........an absence of pressure or matter..........not really true. As I said the Americans have a different view on many things concerning the Queen's English..............not only cant they spell, or in many cases pronunce words correctly.............they even misconstrue their meanings. Please do not take offense at this.............. it is not meant to be offensive. It is basically Americanisation of the English language.

I also explained how we ended up with the word "suction" applying to pump terminology.

Some time ago I read a couple of articles on pumps from European manufacturers and I thought it was interesting that they referred to the low side of the pump.............the only time suction was mentioned was in the formulae.

You're sounding kind of defensive. Yes we talk differently, and since we tossed out the "redcoats" a couple of centuries ago, we ain't been too particular about speaking either the King' or the Queen's English. Sometimes we seem to be provincial and talk funny, but I have noticed other parts of the world are the same way (provincial and talking funny, I mean). Be careful where and how you throw stones.

Anyway, from a technical view, no I can't "suck" more than 25-26'. Laws of nature and properties of water keep us from doing it.

And using your terminology, biological life does not "suck", it creates low pressure zones that cause various reactions and flows in the various fluid environments they live in.

Let's call a truce. My brain hurts. This argument is serving little useful purpose, other than highlighting the differing styles and methods of communication.

MOBI:

The reason the suction head is generally taken to be around 26' is simply physics. That is the extent of the atmospheric pressure that you so strongly refer to in your discussions. As to whether or not that is all I can suck, therein lies the problem. You are mistakingly assuming that the word "suck" and the word vacuum are synonimous. They are not.

Vacuum, as defined by the Collins English Dictionary and Thesaurus, definition #2 "a region where gas is present at a low pressure." The same source defines a vacuum pump as 1 - "a pump for producing a low gas pressure." And, of course "suck" is the act of producing that "...low pressure...". The question is not whether I can suck any more, the question is "How much negative pressure can I produce by sucking." I can suck until the cows come in (an American euphemism). There is nothing to stop the sucking. There is a point where sucking produces no further drop in the pressure in the vessel from which I am sucking.

So, in engineering terms, one does, indeed suck. The Collins dictionary I cited above defines "suck" as 7 - (of a pump) to draw in air..." That sounds more like an engineering term than you may be willing to give credit, but it does specifically refer to a pump. A pump is definitely NOT a biological term, although the heart is sometimes refered to as a pump. That same dictionary gives another definition of vacuum as 1 - "a region containing no matter, free space." This is a "British" definition as the Collins dictionary I cite is printed in Jolly Old England. For clarification, the dictionary I cited earlier is more completely named The New World Dictionary of the American Language. I just shortened it.

And, finally, I do not take offense to anything that I read here. I consider the replies to be the opinions of those respondents. The fact that sometimes they are completely wrong or don't have a clue as to what they are talking about is incidental. It is the free flow of ideas and, yes, opinions that helps make this forum the success that it is. Ignorance of a topic or subject is not offensive, ever.

I will look forward to seeing your responses in other threads in this forum. I have seen you here before, and, frankly, I have been impressed with some of your responses. I am sure there will be that again.

I agree let us call a truce..............and...............agree to disagree.

Very well said my friend.

I start work again next week, for twelve weeks...............this will mean that my postings will take a sharp decline for a while.............6 of those weeks I will be in Port Lincoln...............but they do fly me home weekends.

Thank you too Commoner for your interaction as well.

Thank you, my friend. I will anticipate your return.

The reason the suction head is generally taken to be around 26' is simply physics.

is it negative suction head?

we cant go more than this?

you said its simply physics. please let me know about it.

Sandeep:

Thank you for asking.

Atmospheric pressure is generally equal to 34 feet of water. Therefore, that would be a "perfect" vacuum.

The physics of the problem is that when a vacuum is created within a pipe that is positioned with one end submerged in water, the water will rise in the pipe to the point where the vacuum created equals the height to which the level of the water has risen. That is the physics. The atmospeheric pressure forces the water in the pipe up to that level. It is simply the pressure on top of the water forcing it up the pipe.

The reason MOBI has stated that the pressure is generally equal to around 26' is because of the various ulterior forces such as friction, miscalculation, etc that can affect the outcome of any calculations one might do to find the answer to the problem of how high the column might rise.

This is a measure of "safety" that is normally only used by those in the pump industry. For instance, there are manufacturers who make a self-priming pump capable of effecting that vacuum in the suction pipe. However, even though the perfect vacuum would be 34 feet of water, one never assumes that a self-priming pump will actually lift a column of water 34 feet. Generally, we use 26 feet as the absolute highest number just for safety factor.

I suspect that you know the "physics" of how this works, but you were querrying me about the 26 feet. My reply was directed to MOBI without taking into consideration that there were countless others who would see the message and wonder, as you obviously did, "Where does the 26 feet come from?" Well, now you know, I hope. I knew what MOBI was saying when he wrote that, but I failed to consider the audience.

If this doesn't answer your question, let me know and I'll give it another try.

yes still there is perplexity,

this 26' considering the losses of 34'

is it same for any quantity of liquid

any size of pipe

or any capacity of pump

please inform

The law applies to any size pipe, any quantity of liquid and any pump capacity. The limiting factor for the pump capacity is the time it takes the pump to evacuate the air from the pipe. The size of the pipe would impact that, too.

Let me try to illustrate how this works. Say you have a vessel of water that has a water level that is at sea level. There would be an atmospheric pressure of 34' of water (about 14.7 psi) pushing down on that total water surface. If you then set a pipe in that water standing vertically, you would see that the water in the pipe would have the same elevation as the surface of the water in the vessel. There would also be 34' of head (pressure) on the water inside the pipe.

Now, if you evacuate the air in the pipe above the water level, the water will rise in the pipe to a level that corresponds with the reduction in the pressure in the pipe. If, by evacuating the water in the pipe, you reduce the pressure (by creating a vacuum) in the pipe by 10 feet resulting in a pressure of only 24' inside the pipe, the level will rise in the pipe 10 feet.

Now, to create this vacuum, you must evacuate the air inside the pipe. The size of the pipe would dictate the amount of air that has to be removed and the capacity the pump has to remove the air would determine the time it takes to bring the level up that 10 feet.

As I said earlier, theoretically, the total reemoval of the air would lift the level 34 feet. However, extraneous factors such as friction, even the atmospheric pressure at that given time and human errors in calculation can all affect the ability of the pump to remove the air from the pipe. For that reason, it is good practice to never assume that the pump can evacuate all the air. For the purposes of pump selections, it is rarely assumed to be more than 26'.

I hope that is more informative. There will be those who will take issue with my reply, but this is a very loose inferpretation and explanation of what I meant in my rply. Hope you have a better grasp on it now.

yes i am very much convinced.

is it means i can not suck water more than 26' (considering losses)negative suction head.

please clear this doubt.