pump models

[cfboiler]

Could anyone please explain if pump manufacturers design and manufacture pump models to run on both 50/60Hz or do they have specific pumps models that run on 50Hz and a separate set for 60Hz. what are the implications if say we use a pump designed to run on 50Hz and use it for 60Hz application? thanks in advance.

 

[Artisi]

Assume you are talking about process type pumps and not large custom designed units, although for large custom pumps the hydraulic design may well be suitable for and give acceptable performance at any number of speeds.

Normally a manufacturer would design for the frequency of the country US/Cdn 60Hz, the rest of the world 50Hz.
Generally there would be no real implications of designing at 50 and then running the pump at 60Hz unless you are really pushing the envelope for hydraulic performance or mechanical integrity at 50Hz, if hydraulic performance is marginal at 50Hz this might require testing at 60Hz to ensure there are no hydraulic impediments and a design check for shaft strength, deflection, bearing life etc. etc.

You need to be more specific with your question, you will then get specific answers.



It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[rotw]

yes they have a separate set of curves. Basically at 60 Hz the pump will spin faster so for the same impeller diameter the pump develop more head. we can put it also differently and say that for the same duty (Q-H) you need a smaller casing frame /impeller size to do the job at constant speed and without throttle device.

The pump designed for 50 Hz has a motor designed for this frequency so you cannot use it on 60 Hz in my opinion. So the motor is your main limitation. Suppose you could overcome this issue then it is like I wrote above and you might need to trim the impeller or need a VSDS or throttle to achieve same duty (Q-H) compared to 50 Hz.

In my opinion for the pump itself, if you run it at 60 Hz while it is designed for 50 Hz the main parameter to verify (with OEM or/and competent consultant) is that the pump rotor dynamics / vibration analysis is still acceptable and sound when operating at 20% higher speed than design.

 

[LittleInch]

Pump manufacturers design pumps to operate at different speeds. For many pump vendors websites etc, they have a variety of curves for the standard fixed speed you can get from different motors and different frequencies which are generally 2 pol, 4 pole and 6 pole motors. A 50 htz electric two pole motor runs at around 2990 rpm, a 60 htz machine about 20% faster at around 3580 rpm, four pole is half of this, six pole slower still. As the pump will run faster at 60 htz than 50, then like for like the 60 htz pumpo will generate a higher head for the same flow and hence demand more shaft power from the motor.

Hence your question is really about the motor. The implications for running a motor at 60 rather than 50 are that it will consume about 20% more power due to its load increasing by that amount and the head of the pump will increase by somewhere between 10 to 20% for the same flow which could exceed the pump casing design pressure or your downstream piping pressure. There may be other electrical issues I'm not familiar with which cause an issue, but normally it's due to overheating.

As artisi and rotary say, you would need to check with both the motor vendor and the pump vendor to see if there are any issues, but if your motor had some space capacity and your pump is actually designed to run at a variety of speeds you may not need to change it, but each vendor is different.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[Artisi]

Come on LittleInch, you're slipping .

Lets assume the speed change at BEP from 50 to 60 Hz.
Power, Head, Flow will change as follows:
power is N1/N2^3 = (60/50)^3 = 72.8% increase
Head N1/N2^2 = (60/50)^2 = 44% increase
Flow N1/N2 = 20% increase.

That is why hydraulic as well as mechanical capabilities need reviewing.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[LittleInch]

I was never really a pump guy - I just look at the pump curves. I didn't think head increased as much as that, but will bow to your greater knowledge. So the impact of 50 to 60 htz if you don't change anything else is actually quite significant. That's why I was a little surprised by your statement "Generally there would be no real implications of designing at 50 and then running the pump at 60Hz "... Although the OP hasn't said it the implication is that he has a 50htz motor and pump and wants to use it somewhere where the supply is 60 htz....

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[TenPenny]

It somewhat depends on what you mean by 'designed'. Do you mean 'designed' as in, the impeller geometry, vane shape, etc? Or do you mean 'selected', as in, configured for a particular application?

Technically, the pump is 'designed' for one particular speed and flow/head point. That's how the impeller and volute are designed, the geometry selected, vane thickness determined, etc. Bearings, shafts, frames are then selected to be able to handle the loads imposed, most manufacturers have a certain set of frame sizes that they will use, so the power end components are selected from those options. It's rare that a new pump is designed, most manufacturers have well-established catalog offerings already.

From that, the pump curves for different impeller trims and speeds are developed. It is from there, the pump is selected for an application. There are cases where a pump may not be configurable with a full size impeller at 2Pole speeds (3600 rpm / 3000 rpm) due to the vane tip speed or bearing loads, or, in the case of say rubber lined impellers, they are limited in tip speed so that the rubber does not disintegrate.

 

[cfboiler]

Thanks for all your comments.

 

[Artisi]

At this point I think we need a bit more input from the OP as to what he is really asking.
I believe he has a 50Hz designed pump and wishes to run it at 60Hz - but then that's my understanding of his question. Pump application, pump manufacturer, model etc would help.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[DubMac]

From Tenpenny: "the pump is 'designed' for one particular speed and flow/head point"

One of the most basic truisms in the pump world.

 

[rotw]

This topic reminds me a quote from a pumps sales man who told me once that pumps manufacturers do not like 60 Hz markets comparatively to 50Hz. 60 Hz makes the pumps smaller for a given duty respective to their 50 Hz counterpart, so this is less steel and therefore less sales/profit. Sales people don't like 60 Hz markets...

 

[BigInch]

Artisi,
Rest of the world, except for Guyana, Liberia, Philippines, Taiwan & Korea: 60 Hz
Cuba, Cayman Islands, most of the islands in the West Indies & South America use 60 Hz, except for Bolivia and Barbados, French Guiana, Paraguay, Argentina & Malvina Islands, St. Lucia, St. Vincent which use 50. The British Virgin Islands use 60 Hz.
Peru is 60 Hz except for the city of Arequipa.
Many south Pacific islands use 60, Tahiti is one.
Saudi Arabia uses 60 Hz, although in some refineries and other specific sites you may find a local 50 Hz system.
The strangest of all is Japan which has 60 Hz from Tokyo NE; 50 Hz to the south and west.




I hate Windowz 8!!!!

 

[rotw]

You can also add Mexico to the 60Hz list...

http://www.controlledpwr.com/help-international-voltages.php

 

[BigInch]

I was thinking Mexico was in North America. I guess technically it is Central America. In which case all of North and Central America (down to and including Panama) uses 60 Hz.
Colombia, Ecuador, Venezuela, Brazil, Surinam, Guyana, 60.
Uruguay & Paraguay.. 50
Even though all formerly Dutch, Aruba is 60 Hz but Curacao and Bonaire are on 50 Hz.

So, now found the list. As it turns out, frequency isn't the problem. Look at the voltages.

http://www.worldstandards.eu/electricity/three-phase-electric-power/

I hate Windowz 8!!!!

 

[Artisi]

When I said 60Hz US/Cdn and 50Hz for the rest I was thinking of major design centres / manufacturing as opposed to end users.
The world is certainly a mixed bag of frequency and voltages.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[BigInch]

Count Brazil within that lot.

I hate Windowz 8!!!!

 

[TenPenny]

We have one client here in Canada who still (as of yesterday) has some parts of the plant with 50Hz power; they used to have some 25Hz and some 50Hz, but have converted most (but not all) of the mill to 60Hz.

 

[shreyds9]

Pump manufacturers do have different pump family curves for 50 Hz and 60Hz. As some members said hydrauic as well as mechanical aspects for pump design are to be checked.

But then how do OEMs do testing for pumps which are manufactured for say Singapore with 50Hz frequency but the pumps being built in USA with 60Hz frequency.

Normally OEM have a deviation/ clarification that pump performance will be extrapolated for rated speed. How do OEMs suggest to carryout testing in this case?

 

[DubMac]

As Tenpenny said above: pumps are initially designed around one point, and only one point. That is, one capacity and TDH at one speed. Every deviation moving away from that design point creates flow instabilities; very minimal near the point and increasing the farther away you get. Unless otherwise stated in the contract (very seldom), manufacturers will only guarantee the pump to operate at ONE POINT. It may not be the same point the pump was designed for, but they will only guarantee ONE POINT.

Most manufacturers do not test individual pumps at the actual point they are sold for, the "rated", or guarantee point, unless requested by purchaser. Typically they will be tested at full impeller trim at 3-5 points on the curve, and speed many times is dictated by whatever test stand motor is most easily accessible. The affinity laws are then applied to test data and necessary corrections applied to impeller and/or case, such as trimming, backfiling, cutwater adjustments, etc.

In most cases (standard services), pumps are not even retested after these adjustments are made; just reassembled, painted and shipped. For 90% of pumps sold, this is satisfactory. For critical service pumps, however, most will be retested until test data is "jam up".

Of course the purchaser can require any testing parameters he wants; up to being witnessed, with the actual job motor, and also can call out spec at rated Conditions of Service, and as many other points/speeds as he desires to pay for.

 

[cfboiler]

Hi All,

Thanks for all your comments. I have another question: is it acceptable if say a pump would be tested in 50Hz but the final destination of the pump would be in a 60Hz power application? How would they do this setup? (just test the pump with 50Hz and then apply correction factors for 6oHz?)