One nozzle tank!

[Habattack]

Hello all,
I’m looking for some opinions. I recently visited a plant that had tanks with a common inlet/outlet. These are cone bottom tanks, approx 2500 gallons. The nozzle was at the tip of the cone. It had a three-way valve connected to pumps on both sides: one pumped in and the other pumped out. They discovered that they wanted to fill while drawing from the tank, so ended up adding a top inlet.
I’d never seen such a thing. Strikes me as impractical. Does anyone know of a code, standard or documented best practice that addresses this? Any other thoughts?

Thanks!

 

[LittleInch]

Which bit strikes you as impractical? One nozzle or a new nozzle?

One nozzle for in and out, especially in such a small tank is far from unknown. Saves on nozzles and valves.

Also this tank is likely not made to any code and in any case, tank codes don't get into such things.

What they could do is make the inlet connected to a manifold with two valves and then they could open both at the same time. Saves another nozzle. Stick a non return valve on the one being pumped in and then open both if they need to. The tank will act as a balancing chamber / fixed pressure point and if more comes in than goes out then the tank fills and if the reverse then the tank empties - Simples.



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

 

[Habattack]

Thanks LittleInch,
I appreciate your perspective. I guess I prefer to pay for an extra nozzle than to mess around with manifolds and valves. But I see how you could work around it.
Cheers!

 

[LittleInch]

In your example be careful about a nozzle high up resulting in free fall liquid in the tank.

Depending on the fluid this might be no problem or create lots of vapour.

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

 

[MJCronin]

Lets see.... Cone bottom tank, single bottom nozzle tank .... flow going in and out ... right ?

Again, a few more questions for the third world....

1) With flow going sometimes in and sometimes out ... That must mean tank level goes up and down, right ?
2) With tank level going up and down, either the tank pressure changes or this is an atmospheric tank with vents, Which one is it ?
3) Cone bottom tanks are usually selected to gather sediments/debris etc on the bottom. But you cannot do this.... Why do you have a cone ?
4) Were these tanks used before for another service ? Is this yet another sad example of "junkyard" chemical engineering ?
5) What is the liquid and what is the design temperature and pressure for these tanks ? Any instrumentation on these tanks ?
6) Is this something real for which you have a pressing need or is it something you vaguely recollect .... something from a dream ?
7) Any pictures available ?

Looking forward to your response

MJCronin
Sr. Process Engineer

 

[LittleInch]

MJC - this guy is showing as PA, USA....

The single nozzle used for inflow and outflow is what seems to prompt the question.

Did you take your medication today??

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

 

[Habattack]

MJC,
Thanks for commenting. As per my original post, I saw these tanks during a visit; I am neither designing nor operating these tanks and so not looking for design advice. Rather, I was looking to understand how common this one nozzle setup (shared inlet/outlet) is as I personally had never seen it. Whenever building a tank, I looked for flexibility in operation and future re-purposing of tanks.

Nonethless, in response to your questions:

1) yes
2) atmospheric with vent
3) These are actually slurry tanks with agitators. Cone bottom is poor choice of design in my opinion
4) No, they were recently installed new
5) Minerals and water slurry, ambient temp & press. Level indicator I think is all they had
6) Not a dream: actual physical tanks that I touched recently (in past month)
7) No

 

[Compositepro]

"These are actually slurry tanks with agitators. Cone bottom is poor choice of design in my opinion."

Cone bottom is the best choice for slurries so you do not have any place for settling to accumulate. These tanks would be buffering the flow from upstream to downstream processes.

 

[Habattack]

Compo,
I disagree. It’s easy for the solids to accumulate in the cone even with agitation. A dish bottom tank is much better