Failure of Electrical Submersible Pump

[sowhatso]

Dear All ,

Yesterday,I had a problem during the start up for one of the submersible pump in my water project .

Technical Inputs :

The electrical centrifugal submersible pump was installed at 450m setting , the static fluid level was at 250m above the pump , the pump capacity is 100m3/hr at 350m head .During the first start the amp on the soft starter were seen to increase to 85A.The soft start then tripped with an overload alarm,suspected locked shaft condition. after that attempt for second start with with the phasing changed to reverse the pump rotation, the amp climbed to a similar value as before then dropped down to 19 amps and remained at the same value. No production was seen at the surface,after speaking to the guys at the wellhead it was found that some air pressure was seen comming from the air relief valve from the top of the wellhead flowline, the fluid level was seen to drop 2m only.

Several starts attempts were done with the phase changing (each start after 30min stop) ,but we got the same results , the current is about 19 amp , no flow , and no drop in water level. THE 19 amp current value is about 66% from the normal operating current value ( 29 amp).

The suspected reasons for this failure are : blockage at the first stage or intake ,leakage , or broken shaft . but I know that broken shft should show 50% amp value or less as it is no load conditions !!!! .

We are now in the process of taking a decision to pull out the pump , any inputs from you regarding the expected failure cause or any recommendations are highly appreciated ,

Thanks in advance.

 

[Artisi]

Has the pump run ok before.
How long since it was last run.
Any signs of sand etc in the pumpage from prior operation.
Same current draw on all phases.

Looks like you will be pulling the pump out.

 

[sowhatso]

Artisi,

The pump has not been run before , it is a new pump.

Before one year ,after complete the construction of the well ,a pumping test was conducted for the well to determine its capacity and to do water quality test using differet pump , their was no sand or indication for any solids and sediments.

Artisi , If the flow was blocked, the amps would be high, or low ???

 

[Artisi]

assuming it is a radial flow impeller/s pump, low amps would indicate low flow which could be a blockage somewhere in the system.

 

[thewellguy]

I beleive that you had the pump phased correctly the first time. I think that the pump is currently running backwards. What you have discribed is a clasic description of a sub running backward. (It happened to me yesterday) A sub will pump water when running backward, it just will not make the head pressure.

I would guess that there was an incorrect setting in the softstart and that caused the problem. Maybe too long of ramp time or not enough torque boost.

 

[sowhatso]

Dear thewellguy ,

I just need to know one thing , if the settings of the softstart are not correct , can we have this problem , No flow and no pressure ??

If you can give me some more information about this issue it will be highly apprecuated , I am going to contact the pump manufacture , but in the mean while I wish you can send me more details about the effect of the softstart settings on the pump performance.

Best Regards,

Rami

 

[thewellguy]

A pump that had been sitting idle for 1 year could have developed corrosion that was "locking" the pump so that it would not spin.

When a deep set pump like this is run backward, at the well head you will see the following. The pump will turn on and start blowing air out like normal. Then the air volume will slow down and at some point stop because the pump will have reached the point at which it will no longer over come the head running backwards. The water level in the well will drop some. How much depends on the specific capacity of the well.

The amps in a situation like this will vary. Sometimes they will be high and other low. I have never been able to learn why this is.

As far as the soft start, I don't have enough info to answer your question. In general with a submersible well pump motor like a Franklin, Byron Jackson, or Pleuger, the bottom bearing (thrust bearing) is a water/oil lubed kingsbury type bearing. In order to get the thrust plate to "lift" off the thrust shoes you have to obtain a minimum speed, usually within 3 seconds per manufactuer. untill there is lift the baering faces will drag on each other, damage the bearing and pull high amps.

Without more info I can only guess.

 

[sowhatso]

Dear thewellguy / Artisi ,

We pulledout the well pump yesterday , and we found the shaft is broken above the coupling that connect the pump to the motor , I attached two photos to the broken shaft .

I need to know , from your experience , the possible causes to break the shaft ?????

Is it possible to braek the shaft if the check valve above the pump is blocked ??? or something stick inside the pump between the impleller and casing which cause the braek ????or we may have improper adjustment for the coupling beteen the motor and pump ????
These are the possibilities I'm thinking about but I still need to hear something from you ???

Regards ,

 

[sowhatso]

another photo ..

 

[Artisi]

the photo's do not show sufficient detail to even have a guess as to the mode of failure. My suggestion is to have a proper analysis undertaken by a metalurgist. For shaft failures I always used our state rail authority as they are involved constantly in rotating shaft failure / analysis.

 

[thewellguy]

I can't tell from the picture why it failed. What brand and HP motor and fluid end is it?