Centrifugal Water Pumps

Dear Hari,

This sounds good, but there is terrific load over motor. Assume each individual pump needs a starting torque of 1N/m, then you have to provide a motor with starting torque of 2N/m. This is related to design aspects.

As you are providing pumps on both side, then there will no cooling to motor frame. hence, there will be considerable rise in temperature. This should be taken care while deciding the motor ratings.

Another important aspects is application. Both pumps must have the common application with same constant parabolic load curve. Both pumps must have common start time.

Suvek Kumar

i agree sir.. the aspect is where you can split the pumps into 2 halving the output.. i just wanna run a diagnosis and see if there is any improvement in the efficiency.. i'm also working on the cooling aspect.. please give your suggestions on this

Does not matter how many pumps you place on it. It is only going to do the amount of work designed. It would be better to match the correct pump to it. Leaving the fan to do its job. You can not expect to double the work the pump does by placing pumps at both ends. You will over load the motor. Even if you place two pumps designed for 1/2 hp motor on both ends. You wouldn't get better performance as the motor with out it's fan will over heat.

sir, i agree but i dont wanna double the motor load.. i can place 2 1/2 hp pumps on an 1hp motor.. and on submersible open-well pumps, its water-cooled.. on surface pumps i need ways to cool the motor...

a power shower has exactly that

why do you want this?

that is exactly what i'm talking about... can you give me more information on the pump in the picture?

Man,........mechanical efficiency will be squared because the no. of mechanical connections will double like bearings and couplings,etc if your motor is capable you might install one more impeller on the same side i.e two stage. It will increase efficiency as more work at less friction losses. understand or wait, some will clear you on this point.

Centrifugal pumps are not designed to be reversible. Just remember in your proposed setup that one pump will rotate clockwise, the other will rotate counter clockwise. Also remember that a centrifugal pump rotating in the opposite direction from what it was designed for will pump somewhat; but very inefficiently.

Most rotary pumps are reversible; but they don't work very well on water for reasons I won't go into here for the sake of brevity.

Ed Weldon

hmm... i get the point...

but how does the direction of rotation affect the performance? i can make the casing's volute for that direction of rotation and alter the second impeller for load sake...

but i firstly wanna know the advantages of having two pumps in 1 motor..

"As an idea i have a theory of mounting a pumps in the both ends of the motor shaft........ will this work? what are your suggestions?"; quote mechmerizer in oroginal post

"but i firstly wanna know the advantages of having two pumps in 1 motor.." quote mechmerizer in response #9

Mechmerizer: My suggestion to you is to get you act together. First you suggest this two pump one motor scheme, without any additional details, as if such an arrangement presents some advantage in solving whatever mysterious engineering problem you have. Then you turn around and state "i firstly wanna know the advantages of having two pumps in 1 motor" in response to my post.

Only you know that answer. I'm not sure why any of us are even bothering with you. I am certainly not going to write a treatise on the performance characteristics of centrifugal pumps running backwards. I'd suggest you go study the technology of centrifugal pump design with all the vector diagrams discussions of specific speed, etc. and learn the answers "on your own nickel" as we say here.

BTW the power shower illustrated by APD in response#3 looks like it has regenerative turbine pump liquid ends. Somewhat similar to centrifugal pumps they are high head low flow types and can be designed so that the same parts can be used in opposite rotation directions with a simple change to the venting of the seal cavity, and may not even need that for low pressure installations such as typify domestic water systems. They tend to be substantially less efficient then conventional volute type centrifugals.

Ed Weldon