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Pump strainer

09/10/2008 3:21 AM

Hello to all

Please, is need a strainer on centrifugal pump suction? What is the best one?

Thanks

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#1

Re: Pump strainer

09/10/2008 3:32 AM

Yes, all pumps need a strainer or filter on suction line. The problem of unwanted material in pipelines is a never ending one. Whether the flowing material I seawater, oil, paint or a variety of food or chemical products, there is often something present that can cause trouble. Dirt, foreign matter, or even clumps of the product itself can clog or damage pumps, spray nozzles, condensers, and similar equipment. Sometime a finished product has to be rejected because of the presence of undesirable solid matter.

Basket strainers remove unwanted particles from pipeline flow. Furthermore they are relatively inexpensive compared to the equipment they protect or compared to the down time, inferior products, or loss of production if they were not doing their job in the piping system.

What is a Basket Strainer?

An official definition adopted is "A closed vessel with cleanable screen element designed to remove and retain foreign particles down to 0.001 inch diameter from various flowing fluids." Note the term "foreign particles". Strainers do not necessarily remove only dirt. They take out material which is not wanted in the fluid and this can sometime be a valuable product which may be saved.

The Difference Between Strainers and Filters

What is the difference between a strainer and a filter? Actually there isn't any since a strainer is, in reality, a coarse filter. The question is then one of semantics. Generally it is assumed that if the particle to be removed is not visible to the naked eye, the unit is filtering, and if the particle is visible, the unit is straining. The average human eye can detect a specific particle between 50 and 70 micros. Most people cannot see anything smaller than 325 mesh, or 44 microns. Since 200 mesh is equivalent to 74 microns, a general rule would be that if the screening device is coarser than 200 mesh, it is a strainer and if it is finer than 200 mesh it is a filter.

One of the best uses for a strainer is in conjunction with a filter. By installing a strainer directly ahead of a filter, the large heavy pieces which would quickly clog the filter are removed. The filter is then free to do its major job of fine particle removal and does not have to be cleaned so often.

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#2

Re: Pump strainer

09/10/2008 3:34 AM

Not knowing anything about the pump or the system can only generalise. The answer is yes, a strainer is required. Normally simple bucket or better Y type strainer is OK. Free area of the strainer should be roughly double the area of the pump inlet. Remember it is a strainer, not a filter. 6 mm holes could be good enough to catch large objects that could damage a reasonable sized pump.

If you need to filter the pumped medium that is a different question.

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#3
In reply to #1

Re: Pump strainer

09/10/2008 7:20 AM

Hello AUREL MARES

from me

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#4

Re: Pump strainer

09/10/2008 3:52 PM

Pump Suction Strainers, Which is best?
That is a very good question. The selection of a strainer depends on many factors. These include purpose, operating philosophy, maintenance philosophy, commodity, entrainments, space and cost.
There are four basic configurations (types) and they each have positive and negative points. The common types are listed below in alphabetical order along with some comments about selection.

Basket Strainers
http://www.fabrotech.com/std_bk.htm (Simplex)
http://www.fabrotech.com/duplx.htm (Duplex)
The Basket Strainer is normally fabricated and can be found in a wide range of sizes and materials. The larger sizes will come with legs for support (reduces loading on pump nozzles). The larger sizes require davits or monorails to remove the basket. Depending on the commodity they should also be located in a paved, curbed well drained area for removal and cleaning. Removal and re-installation of the basket does not normally effect the pump alignment. The available "cross-sectional area" choices depend on the screen selected. The Duplex Strainer allows for full operation on one strainer chamber while the other side is in full operation.
Cost: Highest total installed cost.

Cone Strainers
http://www.weamco.com/cone.htm
The Cone Strainer is normally a prefabricated, off-the-shelf piping item. They come in two basic configurations: the pointed cone and the truncated cone. They are available in various materials and open cross-sectional area. The Cone strainer may be used as a permanent strainer but is normally used only during start-up and in then removed. The minimum recommended cross-sectional area is 150% to 200%. This means that if you choose a 150% strainer and it gets one third plugged you still have 100% of your pump suction line cross section area open. With the 200% it gets one third plugged you still have 100% of your pump suction line cross section area open. With the 200% strainer if it gets one half plugged you still have 100% of your pump suction line cross section area open. It all depends on how dirty the product is and how you intend to maintain the strainers. Removal and/or installation will normally require the services of a Millwright to check or realign the pump. A critical piping layout issue is the space requirements (example: 12" pump suction line, pointed cone, 200% open area = 33" long)
Cost: Lowest total installed cost.

TEE Strainers
http://www.fabrotech.com/teestr.htm
The TEE Strainer is a strainer fabricated from a standard piping TEE. The end-to-end dimensions are the same as a standard TEE. They are available with butt-weld ends or with flanged ends. The screen removal cover can be flanged or quick release toggles. TEE strainers also come with the "flow" in one end and out the other (screen removal from the branch) or in one end and out the branch (screen removal from the end). The removal or installation of the screen does not affect the pump alignment. The available "cross-sectional area" choices depend on the screen selected.
Cost: Higher than Cone but lower than Basket

"Y" Strainers
http://www.fabrotech.com/c_carb.htm
The "Y" Strainer may be cast steel or fabricated. The "Y" Strainer is designed to allow for in place "blow-down" cleaning. Depending on the commodity and the "blow-down" piping this strainer can be cleaned while in full service. The "Y" Strainer is available in various end connection choices including screwed, socket-welded, butt-welded, flanged and mechanical-joint. The "Y" Strainer also comes in a wide range of sizes from very small to 24". The "Y" Strainer only comes with the flow in one end and out the other.
Cost: Higher than Cone but lower than Basket

All of the above: http://www.pelmareng.com/pdf/Filters/Fabricated_Strainers.pdf

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#5
In reply to #4

Re: Pump strainer

09/10/2008 6:36 PM

Hello PennPiper

from me

Kind Regards....

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#6
In reply to #5

Re: Pump strainer

09/11/2008 1:54 AM

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

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#7

Re: Pump strainer

09/11/2008 3:38 AM

REPLY:-strainer should install in suction of pump,because unwanted material should not suck by pump ,it may damage the pump,it protect the pump impeller,

thanks

R.C.MANDAL

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#8

Re: Pump strainer

09/11/2008 5:45 AM

I'm a pipeliner typically designing in flow rates of 500,000 ~ 1.3 MM bbls/day, so flows might be a bit different than your situation.

There are temporary strainers (cone type) we put just upstream of each pump to catch construction debris. I've seen hard hats, bolts, dogs, rats, welding rods, rags, cleaning pig parts, etc. Then there are permanent basket strainers installed in the main suction manifold. They can be in front of each pump also. But as a minimum ALWAYS use a temporary strainer during startup of a new situation.

What ever strainer you use, ask the pump supplier to approve it for traceability (not blame, just to get them involved up front). The real risk of strainers is that finer is not better. A pump is designed to handle certain sizes of debris. If you use a fine strainer, it will block quickly and starve the pump and the pump will die in 5 minutes.

ALWAYS put differential pressure instrumentation across every strainer, even temporary strainers. ALWAYS!

So the pump guy can help suggest surface area required for the flow rates, fouling service factor (if blocked 25% it still has enough flow), and most importantly the size of openings (mesh). I use 3 mm for large pumps pumps (20" to 48" flanges). The idea is to allow large particles that cannot get into the clearances to just pass through the pump, but limit too large of items that can mechanically break something, and yet not get too small so the strainer starves the suction flow.

I've only seen one pump in 34 years destroyed from debris (no strainer). I've seen hundreds with blocked strainers destroyed from low suction conditions caused by the strainer, and the particles trapped by the strainer would not have harmed the pump to begin with.

Strainers cause more risk than they solve is misapplied !

This is the practical true situation.

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#9
In reply to #3

Re: Pump strainer

09/11/2008 6:17 AM

Why can't I rate you for a good answer anymore???

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#10
In reply to #6

Post Graphics the Easy Way

09/11/2008 7:48 AM

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....

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#11

Re: Pump strainer

09/11/2008 8:46 AM

I actually have a very similar project so maybe I can tag along and get some help with mine as well.

Currently, we have a pump set up to transport product from one tank to another. The problem is that our storage tank (the one that product is coming from) has foreign, solid materials in it that should not be there.

I have been tasked with filtering the product before it reaches the second vessel (suction or discharge side of pump doesn't matter to the group in charge). I believe I have sized the filter correct for the project and I plan on putting it on the suction side of the pump, but my problem is the location of the plant that the filter will be.

This section of the plant is very isolated so I want to make sure that the filter bags are changed before they plug and cavitate the pump.

I plan on putting pressure gauges on each side of the filter and making the pressure check routine but I am not confident that this will be carried out, so I was wandering if anyone has any suggestions on how I can have my filters and minimize the chance of cavitating the pump (or if anyone has any suggestions on other methods outside of filters that will accomplish the same goal).

As a side note, I've thought about setting up a pressure transmitter and running it to the control room but this looks too costly to justify the project.

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#12
In reply to #11

Re: Pump strainer

09/11/2008 11:24 AM

In this case, I would advise a strainer ahead of the pump to protect it from debris and a filter before the tank for final filtering. The strainer should be coasre enough to prevent frequent plugging and starving the pump, but fine enough not to allow pump damage. The filter can be set to final product specifications for particle size. DP transmitters to alert or shutdown pump if filter and strainer need cleaning should not be that expensive to install. If it is too far to a monitoring point, set the DPs to shutdown the pump.

I have seen an 8" piece of 3/4" PVC pipe stop up an 8" water meter off of a 10" city potable water main. It goes to show that debris can show up anytime, anywhere, any system.

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#13
In reply to #7

Re: Pump strainer

09/11/2008 12:38 PM

My friend..........pumps do not "suck," pumps create flow.

In their action, pumps create a low pressure, lower than atmospheric pressure, on the inlet side of the pump.

Atmospheric pressure will then in turn force the fluid into the inlet pipe to the suction side of the pump. The pumping element will then trasfer the fluid to the outlet or discharge of the pump.

Any pressure created will be caused by a resistance in the discharge circuit.

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#14
In reply to #13

Re: Pump strainer

09/11/2008 4:17 PM

I hate to pick nits, but if something "create(s) a low presssure" doesn't it "suck"?

Sometimes a pump connected to the bottom of the tank will never see a pressure lower than atmospheric pressure.

Sorry, I will stop being anal now.

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#15
In reply to #14

Re: Pump strainer

09/11/2008 5:26 PM
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#16
In reply to #15

Re: Pump strainer

09/11/2008 5:45 PM

Cute picture! Is this an appetizer for MOBI?

(Sorry, I'm being bad again!)

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#17
In reply to #14

Re: Pump strainer

09/11/2008 11:48 PM

You would have to be American.............or taught in America, my friend.

Here's a little exercise for you to carry out:-

Take a steel can and half fill it with your favourite beverage, through a small hole in the top of the can, i

insert a thin walled metal straw into the small hole and push it to the bottom of the can. Now seal the straw in the can with silicon, silastic, etc.

Now put your mouth over the straw and "SUCK"..........how much of your favourite beverage will you get into your mouth??????.............Answer..........none.

Now vent the can to atmosphere...........and "SUCK".........astonishing..........you get liquid into your mouth.

Why?........because you create a pressure drop in your lungs and mouth..............atmospheric pressure does the rest.

When describing the first stroke of an engine that operates on the four stroke cycle I suppose you call it the "suction" stroke".............it is actually the inlet or induction stroke...............air is induced into the cylinder by the low pressure created in the cylinder as the piston moves down the bore fromT.D.C. to B.D.C............atmospheric pressure does the rest.

You may "suck"...........but, in engineering terms pumps do not suck...........but whatever you do in your extra-curricular activities has nothing to do with me.

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#18
In reply to #11

Re: Pump strainer and pumps that 'suck'

09/12/2008 3:19 AM

Too costly to monitor? Do a life cycle cost of downtime, destroyed pump, your time to solve, etc. Monitoring is cheap. If your put filtration on the suction side there must be enough 'pressure' to flow through the filters over to the pump suction flange. As pointed out above, pumps don't "suck" as such (certain brands of pumps do, but I digress). Pumps create pressure differential and the pressure being higher on one side of the first stage impeller eye causes flow to enter that impeller eye (or cavity of some sort). But there must be pressure forcing it in. Atmospheric pressure or boost pressure, but 'pressure' is required. Ex: Drink milk with a straw >> It is not your suction drawing milk up a straw, but atmospheric pressure pushing down on the surface of the milk in the glass causing it to rise up the straw when you removed the equalising pressure inside the top of the straw by drawing that pressure up into your mouth. Now you know why my ex-wife dumped me as even breakfast was a science project !!!

So if the product tank is gravity flow to the transfer pump, and vented, then you only have atmospheric pressure and fluid weight pushing fluid through your filter bank. So you will need to know what is the pressure drop across each filter, and get the curve of the pump, and see how it all fits together when the product tank is at very low volume (low head pressure) and your transfer tank is also low making the flow highest on the pump (to the right of the curve).

You should have redundant banks of filters (change on the fly) and oversize them by a good factor. Nobody will change them, so put a double redundant low suction pressure alarm and shutoff on the pump inlet, and a high filter differential pressure alarm on the filter banks. If you fail to do this you WILL destroy your pump. So, your new budget for instruments is the cost of a pump and lost product, and environmental impacts (fines), plus your time to solve, paperwork, shipping, installation, lost sales of product, unhappy customers of that product, etc. Add all that up and see if you can buy 3 - 4 instruments. Now factor in being professional and teaching colleagues a different way to avoid risks.

If you put the filters on the discharge side, they must be rated for full pressure differential your pump can produce WHEN they are fully blocked + 1.5 times safety, at full suction pressure of the pump and at maximum impeller diameter, maximum speed of pump, maximum density ever utilised. Then use a PSV (safety valve) to protect them from bursting.

For contaminated tanks we normal put a continuous filtration loop: basket strainer > coarse then fine filter.

Cheers

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#19
In reply to #17

Re: Pump strainer

09/12/2008 8:59 AM

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.

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#20
In reply to #19

Re: Pump strainer

09/12/2008 11:44 AM

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.

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#21
In reply to #20

Re: Pump strainer

09/12/2008 12:14 PM

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."

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#22
In reply to #10

Re: Post Graphics the Easy Way

09/14/2008 4:04 PM

is it free of charge or i have to pay

i m ready for that but dont know procedure

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#23
In reply to #22

Re: Post Graphics the Easy Way

09/14/2008 7:53 PM

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.

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#24
In reply to #17

Re: Pump strainer

09/16/2008 8:24 AM

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."

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#25
In reply to #24

Re: Pump strainer

09/16/2008 1:37 PM

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.

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#26
In reply to #25

Re: Pump strainer

09/16/2008 11:59 PM

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.

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#27
In reply to #25

Re: Pump strainer

09/17/2008 11:01 AM

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.

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#28
In reply to #26

Re: Pump strainer

09/17/2008 11:41 AM

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.

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#29
In reply to #28

Re: Pump strainer

09/17/2008 11:56 AM

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

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#30
In reply to #27

Re: Pump strainer

09/17/2008 3:13 PM

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.

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#31
In reply to #30

Re: Pump strainer

09/17/2008 4:03 PM

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.

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#32
In reply to #31

Re: Pump strainer

09/17/2008 4:32 PM

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

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#33
In reply to #32

Re: Pump strainer

09/17/2008 5:25 PM

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.

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#34
In reply to #33

Re: Pump strainer

09/17/2008 5:41 PM

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.

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#35
In reply to #32

Re: Pump strainer

09/17/2008 8:33 PM

this 26' considering the losses of 34'

is it same for any quantity of liquid - No, for Mercury the lift will only be about 28 inches, for oils it will be around 32-33 feet. Suction lift will vary with density of liquid.

any size of pipe - Approximately true. A smaller diameter or longer suction pipe will have more friction loss which will lower the lift capability.

or any capacity of pump - Different pumps will have different capabilities.

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#36
In reply to #33

Re: Pump strainer

09/17/2008 8:36 PM

Vapor pressure of water, which is temperature dependant. That is why condensate pumps have trouble with loss of suction.

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