Cooling Tower Basin / Sump design 2

[Bill3752]

We are installing a cross flow CT and need to design the basis and sump. Are there any rules of thumb that I should apply?

 

[nickelkid]

What type of pumps are you using?

Also,

http://www.cti.org/tech_papers.shtml

 

[katmar]

Slope the basin floor towards the drain for easy sludge removal during shutdowns.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[Bill3752]

Leaning towards horizontal Goulds pumps.

On basin, roughly would like an idea of how deep to make. Is there a rule of thumb?

On sump, is there a rule of thumb like so many minutes of holdup?

Will be running at 9000 - 10000 gpm.

 

[nickelkid]

Confirm what you need for NPSHr,it may make a lot of decisions for you.

 

[MJCronin]

Bill..

Cooling tower basin design and pump selection is something that must be taken very seriously.

Like most of the posts to this forum, I am going to assume that you have never done this before.

The selection of the sump design, operating level, pump type and NPSHa of the sump must be done together !!!

Cooling tower pumps are notorious for caviation and operating problems based on a bad sump design.

I suggest that you review the sump design suggestions conatined in the "Pump handbook" ( Karrassic et.al.) and the information in the Hydraulic Institute standards

Cooling Tower pumps require an additional NPSH margin, above the NPSH Required. Hydraulic Institute Standard (ANSI/HI 9.6.1) suggests NPSH margin ratios of from 1.2 to 2.5 times.

Also see:

http://www.bellgossett.com/Press/BG-mystery.asp

http://goliath.ecnext.com/coms2/gi_0198-121812/The-NPSH-debate-on-cooling.html

http://books.google.com/books?id=cH...hl=en&sa=X&oi=book_result&resnum=14&ct=result

http://www.pumps.org/content_detail.aspx?id=2180

My opinion only..

-MJC

 

[nickelkid]

"Cooling tower basin design and pump selection is something that must be taken very seriously."

And rarely is!

MJC has done an excellent job of articulating this issue, thanks.

 

[toothless]

Will you be incorporating screens between the basin and sump to catch debris before it gets to the pump? I'd recommend it.

 

[longeron]

Amen to MJCronin's post.

Please make sure that if you install a horizontal pump as you mentioned above that the water level in the sump is above the NPSHR for the pump selected and that it is higher than the top of the pump casing when the pump is installed in the field. Otherwise priming the pump will be extraordinarily difficult.

 

[786392]

Dear Bill,
Although I am sure that MJC has conveyed Excellently all about the issue.I would add that lots of foreign materials, process systems leakages find their way into this basin and effective space availability for utilization decreases over a period of time.
Thus ensure easy clean-out and sludge/ filth removal capablities in design.
Moreover the Cooling Water; As I understand is really heart of Process safety catering for most of the system's cooling ,controling the temperatures& pressures.We must give this top priority.

Best Regards
Qalander(Chem)