Low Pump Discharge As Compared To Rated

Decrease viscosity of fluid.

Increase diameter of plumbing.

Reduce the number of pipe bends.

It's the elbows that are killing you. Move the pump closer to the pickup point, or change the elbows to 'long sweep' elbows. Have the inlet 'trumpet' shaped, it makes a difference.

Make suction line of 200mm from tank bottom to almost pump suction and reduce number of bends to bare minimum and use reducer just at the pump suction connection. If using suction strainer, keep it clean and if required do clean it freuently enough.

This will definetly help.

how tall is the pump? I fear that you have not got the pump submerged enough! I take it this is a submersible pump.. or if not is that why you have 30foot (10M) of suction line?

Try reducing the length of the suction line! Yes the bends add to the problem as does the ID of the pipe.

You might also check the frequency of the supply voltage to that required by the motor. If the pump is rated at 30 c/m ph @ 60Hz and your supply is 50Hz that will also effect your flow rate (Laws of affinity)...

Also what size is the outlet pipe?

Just a thought!

Size of outlet pipe is 100 mm .

how long and how many bends?

mentioned in thread. bends - 16 / length - 10 mm

your thread said it was the suction line

Dear chandrakant31,

the rating of a standard centrifugal pump consists of two values, maximum pressure and maximum flow (as per the nameplate) and both are inversely related.

The pump is able to get (theoretically) each of these values, but not at the same time. Either you get the total flow, or the maximum pressure.

Normally an intermediate point, that you can find in the pump curves, within an area marked for optimum performance.

If your piping require more pressure to go trough, (i.e: presssure drop due to twisted piping, or other restriction) the flow will be smaller.

Said all that, I do not think the piping is the issue here, the speed is too slow (1,06m/s with 30m3/h, and you say the actual flow is even smaller)

I would say that, with such amount of elbows, you have air pockets. Just a guess.

16 elbows in 10 meters... it seems an experiment really. Would you mind to post a picture?

Best regards and, please, let us know the result.

Abel

What is discharge line diameter mm? Is this also 100mm? What is vertical height?

Good point... what is the static head of the discharge point?

chandrakant,

Was this problem observed since beginning? If yes then you have a problem of either piping (16 bends in suction) or pump selection. You can check the corrections of selection in the pump curves supplied by the manufacturer. Piping sizes seem OK for the flow mentioned.

If the problem is recent, there is choking of the strainer. Make a practice of cleaning the strainer frequently.

Temporary solution:- If you have selected the pump wrongly, I suggest you to check with the manufacturer if the impeller diameter can be increased. (manufacturers normally keep margin for increasing the diameter of the pump by some percentage.) If yes, then go for it, if the increased impeller dia. is meeting your required flow.

Mahesh