Which Is Good Centrifugal Or Piston Pump

It depends upon what is downstream of the pump, for a centrifugal pump will approach a pressure limit whereas a piston pump will not. In the absence of any information it is not possible to make a choice between them.

What does the HazOp Study report for this plant have to say on the topic (rhetorical question - NNTR)?

There are thousands of pump suppliers across the globe. Please feel gree to use an internet search engine outside the forum to find appropriate ones.

sir i am little confused with downstream please tell me about it and in general if you had to pick between these two which one would you have chosen . (for 100 m height )

Whichever is appropriate for the rest of the installation, of course. Don't expect the forum to be able to see the proposed plant or even the design drawings. The best that can be done here is to respond on the basis of a detailed description, which is conspicuously absent.

Flowrates?

Line sizes?

Line materials?

Temperatures?

Get the idea?

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It's homework.

Consider multistage centrifugal.

Then consider a regenerative turbine pump.

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The performance curve of any particular pump may be found by asking its manufacturer directly during enquiry for quotation. These documents are vital during the process of selecting the individual pump for the duty required.

The duty point (pressure v flowrate) has not been revealed to the forum, therefore any excursion along this path is of mere academic interest only at present.

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100 meter suction lift--no way, neither will. Centrifugal is NOT self priming, but piston is. Piston needs a relief valve of some sort; assuming you have enough power driving it, if the pumped fluid has no place to go, you will either stall the pump or break something. Centrifugal is more forgiving and flexible. Piston is more mechanically complex. Have you calculated the pressure needed to get to 100 meters? (Plus some working pressure of course.) Volume needed is important as someone said. Centrifugal will be a high speed pump; piston is not.

Get a fire engine! You need 142psi just to get up to the 100m level plus whatever flow you want. Used ones are available. I can get you one real cheap if you don't tell anyone. All transactions are cash in an envelope left at a pay phone.

Good Luck, Old Salt

After carefully studying all of the supplied information, and consulting the local requirements, I have determined that the absolute best pump for you to use is a Waterous CR series pump. Ask your local Waterous distributer for a demonstrator to try in your operation. Good luck as always.

Dear Mr.sparshaaa,

Go for centrifugal pump. Operation will be smooth, Piston Pump maintanance will be high. But single stage centrifugal pump has limitation for the delivery head.

100 Metres is equal to 9.302 Kg/cm^2 and a single stage Centrifugal Pump will work provided suction head is below 7.92 Metres or Less.

Only thing is that the Dia. of the impeller of the pump will be bigger in the sense the dia. of the impeller will be bigger, since the Head developed by the pump is governed by the Equation H = (V1^2-V2^2)/2 X g.,

where H = Head in Metres, V1 is the Velocity of the Vane tip at the O.D. of the Impeller, V2 is the Velocity of the Vane at the eye of the Impeller, g is the acceleration due to gravity.

You have not mentioned what will be the Suction Head and you referred "i've to lift the water to a height say 100m or more" hence it is to taken as SUCTION HEAD + DELIVERY HEAD = TOTAL LIFT (Frictional Head Loss Ignored) and this 100 Metre to be reckoned from the water surface.

DHAYANANDHAN.S

The best designed piston pump will be more efficient than the centrifugal, but I am not aware of any manufacturer of stock piston pumps that will match your head requirements.

Also, of consideration is the suspended matter in the liquid to be pumped.

"Ans suppose i've to lift the water to a height say 100m or more which pump should i use piston or centrifugal ( which would be better to use)."

Not exactly sure what this means....... mastery of English and diction is certainly rare on this forum.

However, pump suction lift of water is only practical to about 22 ft. and the theoretical maximum lift is about 34 ft.

100m suction lift of a pump of a pump is not possible

http://en.wikipedia.org/wiki/Drafting_water

A lift over a 100 m high ridge then back down to a pool the other side of the ridge that is a few meters below where one started will not require a pump at all.

Only after the hose is filled. You have to lift the water over the top. Maybe suck REALLY hard on the down hill side.

Priming this siphon would certainly be a royal.... {you get the idea}

Let's not forget, over two thousand years ago the Roman Empire moved water much farther and over higher ridges. The electric induction motor, internal combustion motor and centrifugal pumps did not exist.

True. I wonder if the ancients had to deal with ignorance as it is manifested here today?

Or would the Darwin Principal, under another name, have eliminated the hopeless for the betterment of the gene pool?

This thread really sucks.

I hope this is homework because this installation, making some unstated assumptions, would be very expensive and probably much more equipment than you were planning on. One of the other contributors, #13, suggested a Waterous CR centrifugal pump. This is very suited for your application although the majority of them are used for fire engines as I noted in #12.

Based on the following estimated criteria:

Elevation 100m = 328 ft

Discharge flow 200 gpm = 757 liters/min

Discharge piping size 3"

Friction loss for 200 gpm through 3" pipe = 60psi

Pressure necessary to raise water (no flow) water 100m/328ft= 142psi

Discharge pressure of 200 psi total for elevation and friction

? discharge flow of 200gpm @ 50 psi at end of piping (assumed)

Net pressure required 250 psi

Taking these assumed figures, since incomplete data was stated, and the manufacturers pump curve you will need a 120 hp motor/engine @ 2,900 rpm just to get the water up to the top with no flow.

At 200 gpm flow it will require a 170 hp motor/engine @ 3,300 rpm.

The basic pump, gear box, motor/engine, controls, piping and numerous other needed items are going to cost big money. You could expect to pay at least $50,000 for a bare basic installation (very rough estimate) if not much more. These figures are based on either an electric motor or a diesel engine and just the equipment with no installation labor or freight considered.

A piston pump at the estimated criteria would be a nightmare!

Are you interested in that used fire engine that suddenly appeared in the guys garage? A 2,000 year unit would probably hit the used market for $60-80,000, but I could get it for you from this guy for about a third that price. Just remember cash only and all lettering has to be removed.

Good Luck, Old Salt

Centrifugal Pumps are good for selection for higher flow rates and lower pressures, whereas piston pumps are more useful for pumping low volumes at higher pressures.

In your case it depends on the flow rate which you have not specified. But I would say except for very low volumes, centrifugal pump is far far better for your application. You may only need a multi-stage pump which are available in plenty for a head of 100 M which is approx. 10 Kg/cm2g pressure. Multi-stage centrifulgal pumps can be easily procured from Pump Suppliers such as KSB pumps Ltd., Sulzer pumps, Kirloskar Brothers and a score of others. They also will not cost exhorbitantly. A rough guess for the cost will be less than Rs.200,000/-($3500) for a pump of 10000 liters/hr and 100 M head in India. Assuming your requirement of pumping is 3000 liters/hr the motor required for your purpose will be 2.2 KW standard motor.

The myth of piston pumps being only suited to low volumes at high pressures pervades because no other type of pump can match the efficiency of pistons for this application. But the Chicago Sanitation District, among others found out decades ago in tests that throughout the range of all pressures and volumes, a properly designed (bore, stroke, aperature sizes and locations, etc.) reciprocating piston pump is the most efficient of all pumping methods for liquids that are free of fouling solids.

It is no accident that the most efficient method of utilizing carbon/hydrogen liquid/gas combustion is the IC engine, perhaps apart from a complex staging of combined cycle processes.

If anyone knows of a manufacturer of low pressure (under 100 m, or better, 50 m of head), high volume piston pumps I have a need.

Piston pumps deliver non-uniform pressure during the cycle of moving piston and are far costlier than centrifugal for the same volume. The foundation is exposed to more vibration due to non-uniform force. The shaft and impellers of centrifugal pumps are dynamically balanced and gives very little vibration. I have installed umpteen no. of centrifugal pumps for much higher pressures than 10 kg/cm2g. there are hardly any maintenance issues. There are more maintenance problems in piston pumps. There are many more small parts that can go wrong. Centrifulgal pumps can easily take care of solid particles more efficiently than piston pumps. Overall capital, operation and maintenance costs of centrifugal are much lower.

I stand by my assertion. If suspended solids are not an issue, a properly designed piston pump over its lifetime will consume far less energy than the most efficient centrifugal, even for the same constant head/volume lifetime performance. By properly designed: Ganged in a bank of at least 4 pistons (each cycled to offset by 90 degrees from the next piston), all flywheel balanced with surge chambers .

Again, I assume we are talking about rather unvarying discharge conditions of head and volume for comparison. The piston pump can perform at 85 per cent mechanical to water efficiency. The max you can get with a centrifugal is about 70 per cent for a very narrow operating range. When you run the capital cost to lifetime energy costs, the 15 per cent difference balances the capital cost difference in about ten years for the max stated efficiency of each. If the head/volume operating conditions change, the centrifugal efficiency drops quickly; the piston pump does not, requiring only minor adjustments, which can be done automatically, in the surge chamber.

I predict a re-birth of piston pumps for applications other than very high pressures, for which they are exclusively used today. Any manufacturer who is interested in making this happen will lead the re-birth.

I have seen centrifugal pump efficiencies as high as 91%.

The present high capacity centrifugal pumps will give you 85% (hydraulic + mechanical) efficiency. If anyone used Energy efficient motors of EB1 / EB2 you will get more than 95% for motor efficiency.

Give me an example of a true centrifugal that has an 85 (or 91) per cent efficiency. I agree with the motor efficiency. The Chicsan piston pumps had at least 85 per cent over a broad range of operating conditions.

High performance fire pumps with labyrinth sealing between impeller and housing would seem to have an advantage over the sealing issues of a piston pump. Can you explain how a piston pump has higher efficiency with piston drag and check valves over a centrifugal pump with no drag other than a mechanical rotation seal?

The centrifugal pumps expend consider entropy in casing and fitting turbulence, considerably more than is the case with a piston pump, even with its check valves, which check valve(s) by the way, is (are) almost always also a feature on either the suction or discharge or both side(s) of centrifugal installations.

If no part of a piston and cylinder were to be exposed to high temperatures and one had the opportunity to choose among all lubricants for the interface, water would be better than any version of petroleum lubricants presently in use...strictly from the standpoint of lubrication.

Centrifugal pumps have more "slip" (leakage within the pump) than piston pumps. Don't know if this is the same as entropy, because I never did understand thermo and never had a class in it! My interests are antique fire apparatus; some of the very early pump comparisons showed that it takes more power for the same flow in a centrifugal pump as compared to a piston pump. That is, centrifugal pumps are less efficient. But the centrifugal pump survived because it is simpler to operate and considerably less expensive to build.

Contact Kirloskar Brothers Ltd. through website. A few months back we had obtained quotes for 2W+1S pumps of 500 m3/hr and 60 m head, that had efficiency of 85%. By changing impeller sizes with the same casing one can get different curves for different capacities for optimum efficiency at less or more flow rates within available range. This was a single stage pump. There are several others too at international level.

Thanks. Never heard of Kirloskar. Their catalogs do not show anything other than the max. efficiency points for case and impeller sizes. I have emailed them with a request for the info.

I have dealt with many types of pumps and compressors for just about every conceivable liquid/gas and have yet to find a centrifugal at 85 per cent efficiency regardless of impeller shape, casing clearance, RPM, etc.

Hmm... This is sort of like asking for the best chess move... Or the best medicine...

People,

sparshaaa is a STUDENT.

This is homework!

He has no clue of the real world uses for pumps.

Then this is a lousy homework question. Which engineering design is better without a clear task to engineer is a lousy homework question.

Yes, it is.

One can only hope.............................................

If he is a student then he should start with the basics, no long confusing formulas, pump curves, friction losses, etc. Use an Archimedes Pump. The simplest you can get therefore the best match for a new student.

An Archimedes Pump

Good Luck, Old Salt

The best pump to use (like Solar Eagle mentioned) is the one that matches all of your requirements for pressure, flow, and the driving force and speed available. That is all I have to say on the matter.