4 replies to this topic

[Pikeslayer]

Hello all,

 

In our plant we have two open to atmosphere tanks that we store sodium silicate in.  One tank is used in our process, and when it is empty we switch to the other and vice versa.  Right now the tanks have open tops.  When one is over filled it runs down the sides and is wasted.  What I would like to do is connect the the two tanks near the top with a single horizontal pipe so that when an overflow condition occurs in one tank the overflow would gravity flow to the other tank.  The desity of our material is .05 lbs/in^3, the viscosity is 800CPS.  My overflow pipe would be about 5 ft. long.  When we fill the tank the material is delivered at 166 gal/min.

 

I want to determine the minimum pipe size to accomplish this.

 

After looking at Manning's equation, two things are puzzling me:

 

      1.)  I see no consideration of viscosity

      2.)  I can't input zero slope

 

Is it safe to input a minimal slope, and then upsize the pipe slightly?

 

Thanks in advance,

 

Don

 

[latexman]

Assume the horizontal pipe is installed below the top edge such that there is some straight side above the top of the pipe.  To start lets assume there is 1 foot of straight side above the pipe.  Find the diameter that allows 166 gpm with 1 foot of head using the appropriate flow equation for full pipe flow.  Check N_Re for the proper flow regime.  Then just make the pipe one or two pipe sizes larger.  You can use whatever convenient head you want.

[Pikeslayer]

Why in the heck didn't I think of that.  Couldn't see the forest for the trees.

[latexman]

Don't beat yourself up too bad.  I've been doing ChE jobs for over 35 years.  Sometimes when you are stuck you have to ask yourself, how can I make this simple and easy to calculate.  When you do, the uncertainty/risk is reduced.  This is a good thing!

Edited by latexman, 15 January 2015 - 07:39 AM.

[breizh]

Hi ,

 

Additional input about open channel flow and partially filled pipe , for water , Manning's equation,....

 

Hope this helps

 

Breizh