Branched suction pipe foR a pump

  • Thread starter prasan_y2k
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  • #1

Main Question or Discussion Point

A PUMP OF 0.25HP IS CONNECTED IN THE ABOVE FASHION (REF ATTACHMENT) TO THREE TANKS BY MEANS OF A SINGLE SUCTION PIPE. THE SINGLE SUCTION PIPE IS FURTHER BRANCHED TO THREE SUCTION PIPES, ONE EACH FOR THREE TANKS.
THE DESIGN DISCHARGE CAPACITY OF THE PUMP IS APPROXIMATELY 45 LIT/MIN. BUT PRACTICALLY, AS PER THE ABOVE ARRANGEMENT, THE DISCHARGE RATE IS SHOWN TO BE VERY LOW (APPROX 8-10 LIT/MIN). HOW CAN WE INCREASE THE DISCHARGE RATE OF THE PUMP??
IF WE INTERCONNECT THE TANKS FROM BOTTOM AND KEEP A SINGLE SUCTION PIPE AND REMOVE THE BRANCHING, WILL THERE BE AN INCRESE IN DISCHARGE RATE OF THE PUMP???
Given: Height of the pump from tank base: 1.5m
 

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  • #2
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First, what type of pump is it? I'm assuming it's a centrifugal pump, and that's what the rest of this reply will be based on.

I don't believe that would help (connecting the tanks), especially since the reentrants would introduce more friction losses in your available suction head.

Can you increase the speed of the pump? It doesn't sound like you are having cavitation problems, or running the pump dry. Just sounds like you are getting low flow.

Do you hear any strange noises in the pump? Any vibration? Any pulsing in the discharge lines?

Generally we want to keep our suction lines large. When the three lines come together, do you increase the line size of the pump suction?
 
  • #3
The pump is a 12 Volt DC Rotary Vane Pump. The pump is running on a 12 volt battery, so I cannot figure a way out to increase the speed. There is no strange sound or vibration in the pump. When the three lines come together, the pipe dia remains same (1").

I am still confused as how the interconnection of tanks will introduce more frictional losses in suction head. The interconnection of tanks (by means of 1/2" pipes) will make the suction line without branches, and make the 3 tanks behave as one.

Also, I would like to add that the discharge hose is 100 feet long and is kept on a hose reel. Nevertheless, even if the entire hose is taken off the hose reel, there is hardly any noticable change in discharge rate.
 
  • #4
882
34
Yea, I don't see friction being your main concern here anyway. I don't think modifying that will change your system, it's a PD pump afterall.

I think speed here is your biggest concern. I would bet that your pump is not spinning fast enough.
 
  • #5
Thanks for your reply.

The pump is wired directly from a 12V auxillary car battery and the battery is fully charged. Battery charges itself from the car's alternator. I dont see any way how to increase voltage, as that may lead to increasing speed.

But wont the pump make less effort in suction from one pipe(later after interconnecting the tanks) rather than three (as in the present case)?
 
  • #6
882
34
It's a PD pump, suction isn't an issue, really. At a given speed, the pump will provide a certain capacity, basically no matter what. PD pumps are very good at suction head.

The only think I can think of is somehow the flow is being choked in the small diameter pipe when they all meet.

With that said, one suction pipe will probably make it more efficient, anyway. But not noticeably. If it isn't very expensive, go ahead and change the set up, and use a larger diameter pipe, reduce at the pump suction if you need 1 inch, just be sure to use the right type of reducer, or do it a few diameters upstream.

What type of drive is it from the motor to the pump? No room for a gear assembly or small sheaves?

What are the electrical requirements of the motor you are using for the pump? Do you have them available?
 

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