×
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

Condenser water pumps - strainers
7

Condenser water pumps - strainers

Condenser water pumps - strainers

(OP)
I am attempting to solve a pump cavitation problem in a condenser water system with an open cooling tower.  The pumps are base mounted single suction with inlet strainers installed.  I am thinking that the additional pressure drop caused by the inlet strainers may be causing the pumps to cavitate, but have not tested the theory yet.  I wanted to throw out this general question to the audience:  Since cooling towers are normally equipped with sump strainers, is it really necessary to keep the pump inlet strainers installed beyond initial startup?  Yes, some minor junk like pine needles will get past the sump strainer and into the water loop, but I do not think that this kind of thing would cause any major pumping problems, and we do have a solids seperator in the loop.  I am thinking that pump inlet strainers installed in an on an open condenser water system could easily reduce the available NPSH below that required.

RE: Condenser water pumps - strainers

I am a big believer in the adage that "90% of pump problems are caused at the suction".  Removing them should help your situation.  

What kind of condenser do you have?  Can it readily by cleaned if by chance some solids did get by are are stuck?  Will your sump strainer remove solid particles larger than the maximum particle size of the pump?

Of the cooling towers that I am most familiar with, none had inlet strainers so I believe you should be OK.

RE: Condenser water pumps - strainers

Yes, this can be a problem and I have seen it a couple of times.  The typical pump in ths range will handle 3" solids, put the strainer on the downstream side if you need to.  Usually the CT just has an anti-vortex cross in the sump, you might want to consider a truly coarse (chainlink fence like) "filter" across the drain to keep plastic bags and other trash out of the system.

RE: Condenser water pumps - strainers

You could also clean the strainer regularly and the pressure drop and boiling would be minimized.

Also, if this is a variable-speed pump, the tangential solids separator will not work well.

RE: Condenser water pumps - strainers

I would suggest finding out if you have enough head on the suction side of the pumps.  Run a pressure loss calculation to figure out the pump's NPSHR compared to your available NPSHA.  Remember that you are typically dealing with absolute (vs. gage) pressures here.

Yes, a dirty strainer will choke the flow on the inlet side of the pump to the point where it can cavitate, especially if you have marginal elevation of the tower sump over the inlet of th e pump.  There are many other situations that lead to pump performance problems and each can be solved once you have diagnosed the problem.

I agree that a centrifugal separator can under perform in an installation with variable flow, whether it is a pump with VFD, a system with 2-way valves or if you have multiple chillers.  I would definitely leave the strainer in the piping.  You can move it to the discharge side if your inlet pressure is marginal.  You can add differential pressure sensors around the strainer to alarm a high pressure loss to the BMS and initialize service.

RE: Condenser water pumps - strainers

As you have inline strainers advised in your posting together with sump inlet strainers, I would check the inline strainers for clogging and or excessive head loss.

RE: Condenser water pumps - strainers

Geby,

Not sure if you are on the right path.Have a look at:

http://www.pressure-drop.com/Online-Calculator/pda/1107.html

Determine the pressure drop through the Y strainer.I am sure it would not be high enough to cause cavitation.If in doubt,take out the basket(w/o basket pressure drop~0) and see if there is a difference.

I would recommend focussing on other installation issues such as piping config,correct reducers,height of tower basin above pumps etc

RE: Condenser water pumps - strainers

Seems the gremlins got at my earlier posting and deleted some of it.

  
As you have inline strainers advised in your posting together with sump inlet strainers,I think it would be appropriate to remove them and rely on the sump strainers. Although I would check the inline strainers for clogging and or excessive head loss as a check if this is the problem.  

RE: Condenser water pumps - strainers

1) Open the Strainers

2) If the baskets are full of something organic or compounded, find out what it is and where it came from...Then pursue what can be done to eliminate it.

3) If the baskets are simply full of rust, slime and what have you; Throw these away and get something a little finer but about as solid as a rock sieve for a sump strainer...

4) If there's nothing in the baskets: Throw them away and investigate your pump levels...

5) If there's something in the baskets that you can't remove and can't avoid, but would not collect in an idle pump, move the strainers to the pump discharge...but buy them new baskets anyways.

Note that the baskets only survive in Case 5.

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