×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

ESP underload question.

ESP underload question.

ESP underload question.

(OP)
Dear Experts;

 I have a question concerning ESP. I was told that operating the pump against a closed valve would cause the system to trip on underload. Is there any truth to this? If so, can you offer an explanation as to why this happens? It does make more sense that it trips on overload to me.

 Thank you.

RE: ESP underload question.

An ESP is a dynamic device.  If it has no flow it is doing no work. No work means minimal power draw or underload.  

David

RE: ESP underload question.

If it were to trip on anything it would be overheating, due to fluid not moving through the pump, which is used to cool the motor.

There could be a trip point set for power dropping below a certain point, say at anything below some percentage of rated power, but it is protecting against heat buildup, not "underload".  

RE: ESP underload question.

I'm not sure I buy the concept that windage losses will cause over heating before the underload trip.  As I understand it, the underload trip is there to guard against the over heating.

David

RE: ESP underload question.

It is true and a pro-active protection for ESP and also canned motor pumps to trip the motor when dry running or loss prime occurs in the pump.It has been around for some time.In the a case of ESP, to prevent the motor from over heating when insufficient or no liquid flowing across the motor for cooling.

It is an electronic devise wired into the motor control circuit and by measuring the motor current drawn.
When a centrifugal pump encounters shut valve or dry run situation, the power will decrease and hence the motor current. The device will trip the motor starter contactors when it sensed the motor line current is below the set value.

Below are some links to such devices.

http://www.benderrelay.com/datasheets_US/CSD25_new_LV.pdf

http://www.rototech.com.au/pdf/eucr_2c.pdf

RE: ESP underload question.

Base in my experience on ESP if is operating againts closed valve it might trip on overload.. if low production it will trip on underload  

RE: ESP underload question.

OilHunter,

I agree with you if the pump is progressive cavity type.

RE: ESP underload question.

Pumpsonly,
That is an odd statement.  A PCP is a positive displacement pump and if you dead end it you'll get really high pressure until something breaks or goes down of overcurrent.

The whole underload discusison is about dynamic pumps.

David

RE: ESP underload question.

David,
My response was in reply to oilhunter's statement.

"Base in my experience on ESP if is operating againts closed valve it might trip on overload."

And is correct for PCP. Dynmaic pump will not over load with shut valve except for axial flow pump.

RE: ESP underload question.

ahendawy85

In general the statement is true for ESP's.  This statement assumes the underlaod has been properly set.  At 0 flow (Closed Valve) the power required will be minimal.  The motor seal assembly, intake, pump and induction motor all have losses when operating at very low flows and loads.  The typical ESP induction motor will not go below 40% of its nameplate current when operating against a closed valve.

Our industry also has axial flow charge pumps used in gassy wells.  Axial flow stages require more power at low rates.  The combined load of an axial flow charge pump and the mixed or radial flow primary pump could prevent an underload device working as we would want.

If you would supply an equipment list of the installed equipment I could tell you the actual no flow motor current.  

I did make a quick search on the internet and found an explanation by Irrigation Craft on their site.  This shows three typical impellers, radial flow, Frances and Axial flow pump curves.  I am not aware of any Frances impellers in our industry, but the Frances does behave similar to the mixed flow designs we use.  

http://www.irrigationcraft.com/power_1.htm

D23

 

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources