Submersible Pump Oddities.

[jraef]

Had some problems starting up a submersible pump today. It's late and I'm too tired to repeat this, so please check it out here:

http://www.lmpforum.com/viewthread.php?tid=671&page=1#pid1876

Please feel free to post replys to either site.

Thanks in advance.

"Venditori de oleum-vipera non vigere excordis populi"

 

[itsmoked]

jraef; Yuk. Sorry the train jumped the track.

I agree with you, with respect to, centrifical + no flow = no load. The motor should spin. In fact it should have little load when starting.

I don't believe that it is jamming because of power being applied. It is jamming for mechanical reasons. Cut to the chase. Pull it.

It may have rotated a few times on that first try but that was it. There's a rock in it or some debrie from the last blowout, maybe a piece of wire, insulation or??

Good luck!

 

[jraef]

Thanks for the support. Yes, they are pulling it, but they were reluctant because it is a major operation for them (small mountain community with few resources and low budjets for hiring outside contractors). I failed to mention it, but the rotation pnenomenon was repeated 3 times for various engineers that kept showing up, which puzzles me.

"Venditori de oleum-vipera non vigere excordis populi"

 

[quark]

Pump might be jammed. But it is not always centrifugal pump+no flow = no load. The case is different for axial and mixed flow pumps. If it is a radial multistage pump then only possibility would be a jammed pump.

Regards,

 

[dpc]

Sure sounds like a mechanical issue with the pump - I assume the phase sequence is correct?

 

[jraef]

Actually we don't know about the phase sequence, because the only way to tell is to start it and see if you get rated flow, which hasn't happened yet. It does not have a backspin ratchet however.

"Venditori de oleum-vipera non vigere excordis populi"

 

[jraef]

Well, they managed to pull the pump today after all, and I am vindicated! There are 2 x 2" IPT service openings at the crown coupling from the motor to the pump shaft. These openings provide access for making the final connection of the coupling set screws, and are to be sealed afterwards with 2" threaded pipe plugs. Apparently, after the pump technician did his spin test of the motor by hand, they made up the coupling and installed the plugs. But they must have gone out and purchased the plugs at Home Depot or from an electrical supplier, so they were not tapered threads. Consequently they were tightened into the holes so far that they were jammed against the coupling. When the VFD was giving excess tourque it was making the coupling scrape along slowly against these plugs, but when we went accross-the-line with the soft startrer, they just dug in deep.

Someone has some explaining to do... but not me

 

[itsmoked]

jraef: Ah that sounds pretty amateur! Glad it's solved thanks for the report.

 

[mc5w]

Please do not forget to adjust the motor overload relay for the smaller motor. I also hope that it is hooked up to disable both the VFD and the soft start when it trips.

SquareDs pamphlet on variable frequency drives HIGHLY recommends that you use a motor overload relay between the drive and the motor even if the drive has an internal software overload relay. Software overload relays are not foolproof and an external relay also will serve to protect mechanical components. Any motor thermostat should only be used to confirm that motor cooling works. In 1 VFD application on 5 steel coil straightneners I had to set the overload relay for 2.5 HP even though the motors and gearboxes were rated 3 HP. The problem was that in the high ambient inside of a large closed box the gearbox would overheat and pop the output shaft bearing and seal When operated at 3 HP. ONe steel coil straightener somehow had high internal friction because of component tolerances that were somehow unlucky.

Turns out that all of the VFD people over at General Electric use SquareD's VFD pamphlet.

 

[jraef]

Yes, there is a Multilin 269 relay that protects the motor in either mode. That was in the original post on the other site.

"Venditori de oleum-vipera non vigere excordis populi"