Centrifugal Borehole Pump

[TechnoZA]

Recently I was conducting tests on a centrifugal borehole pump. When the pump was started up under no head (i.e. the pump was run without any connections other than the riser pipe) it would run without problems. As soon as the delivery pipework was connected up, the pump would trip on over-current.

According to my knowledge of centrifugal pumps, the pump should have rather tripped with no pipework attached, as the connection of pipework would have increased the head, and thus decreased the current drawn.

Any suggestions as to why this happened?

 

[Artisi]

Is the pump fitted with radial (centrifugal) or axial flow impellers.

 

[Valvecrazy]

With a pump having axial flow impellers, the amperage will increase as the pressure increases. On a pump with a centrifugal impeller, the amperage should decrease as the pressure increases, unless you have a bad thrust bearing or the impeller clearance was set incorrectly.

 

[TechnoZA]

Thanks for the responses. I don't know offhand the impeller design, but I'll find out. I checked out some pump curves, and you're quite right. A likely cause.

 

[EdStainless]

How much back pressure was on the pump with no outlet piping attached? Are you sure that you haven't caused damage from running the pump too 'wide open'?

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Plymouth Tube

 

[crazytexacan]

GREETINGS; How long was the pump run with no , discharge piping attached?? If you operated it for more than a few seconds, the IMPELLER could have unseated itself from the wear/sealing ring, or even pulled the thrust bearing out of its housing and, not allowed it to "fall" back in place... I have seen up-thrust pull a bearing retainer out of place, I suggest checking the clearance(s)..., LAST NEVER start a large SUBMERSABLE pump up, across the line the first time... with out bumping.... the starter,,, to fill the DROP pipe, this pump has probably FAILED because of "UPTHRUST" , or the VERY high Velocity of running under no load pulled some trash into the intake, jamming the impeller. GOOD LUCK!!! I have run many multistage down hole pumps, and large Centrif. The basics are easy to over look.