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!

*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.

Jobs

Hi, I have a pump which is going

Hi, I have a pump which is going

(OP)
Hi,

I have a pump which is going close to over load current for a prolonged period during start up when the pump is running at low flow. Other than flow, what can be causing the high current?

Thanks.

RE: Hi, I have a pump which is going

High pressure and poor efficiency at low flow.

Or maybe the pump is supposed to do this - what does your pump curve say / look like.

What other fault finding have you done?

How long is "a prolonged period during start up" 5 seconds, 5 minutes, 5 hours?

FGS give us something to bite on here.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Hi, I have a pump which is going

(OP)
Pump was run 30 secs then manually shutdown due to high amps.

Not relates to flow as minimum flow was met in recycle. Current at this flow would be significantly less than we seen.

RE: Hi, I have a pump which is going

Other than Flow? Pressure
What type of pumps is? How do you start the pump?

RE: Hi, I have a pump which is going

(OP)
Centrifugal pump started on min flow recycle with normal back pressure.

I'm more interested in things like motor problems - could a motor issue cause high amps?

RE: Hi, I have a pump which is going

Low voltage causes high amps assuming the motor is the right size.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Hi, I have a pump which is going

Details needed. Voltage, amps power , normal plus what you expected, pump curve, anything else you can think of.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Hi, I have a pump which is going

Single or 3 phase, 1 kw or 1000 kW, pump type etc.?

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

RE: Hi, I have a pump which is going

Don't discount friction. If something is causing the the impeller to rub against the housing, it will look like extra pressure to the motor causing the motor to draw more current to achieve the desired flow/pressure requirements.

Several years ago, had a small close-coupled circulator (1/4 hp) literally burn out the motor on two pumps. It isn't until I make a trip to see the pump first hand and open it up that we discover the impeller is destroyed. Fortunately enough of it is intact showing signs of contact with the housing along with shiny areas inside the housing that we determine the failure is due to contact between the impeller and housing. Review of the install manual it quickly becomes clear why; basically the pump was installed in an incorrect and non-manufacturer approved orientation. The orientation is fixed and viola no problems since.

RE: Hi, I have a pump which is going

Check the surface finish of the pump internals. Low flow/high head pumps such as Sunflo/Sundyne and other pumps with straight vane impellers will definitely draw high current even at lower than design flow if there are issues with the surface finish.

RE: Hi, I have a pump which is going

If it is in recycle, how is the pumps being controlled and ensure it is sitting on its curve ? We OFTEN get called to check pumps out to find that the recycle line has no restriction or orifice to make sure it is on its curve, being a recycle line too very rarely is there a pressure gauge to make sure its on its curve - if its not kept on its curve then it will end of curve which will be high current and leading to whole host of mechanical problems.

Ash Fenn

www.cdrpumps.co.uk

RE: Hi, I have a pump which is going

A regular centrifugal pump running at low flow should be drawing low amps. High pressure in the pump case causes amps to decrease, not increase. Now if the motor thrust bearing is bad the high pump pressure will cause the impeller to drag and the amps would increase.

RE: Hi, I have a pump which is going

If this is at startup, could just be pump overcoming inertia of the water. All pumps and fans need to do this and will draw more power during setup than when running at a steady state at design parameters.

You're shutting it down after 30 secs?
Is it reaching design flow in that time?
What is HP of pump and what is design flow?
Is there VFD on the motor? What is controling the VFD?
What is design startup time?

Let me echo LittleInch's sentiment:
More info, more info, more info.

RE: Hi, I have a pump which is going

The inertia of water in the pipes into and out of the pump does not lead to high amps, but rather lower amps. It is the flow through the pump that creates load. Having the pipes empty when the pump starts will cause high flow because there is no flow restriction while the pipe is filling. So pipes that drain out when the pump stops can cause an overload when starting.

RE: Hi, I have a pump which is going

The commutator bars on the pump motor may be fouled. Clean them up.

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


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close