Horizontal and Vertical Conventional Pressure Tanks in same plant? 1

[TXPE_MED]

I have a client who contacted me wanting to replace a smaller (<1,000 gal) vertical conventional (air over water) pressure tank with a larger (>5,000 gal) horizontal tank.

My first thought is, why replace when you can just add? Then I started thinking about the hydraulics and how a pressure tank works. Note, both tanks would have their own air charge system (i.e. Air Rite).

Questions:[ol 1]
[li]If both tanks have their own tap to the main line (not manifolded) together, will they act independently of each other and water levels in each tank are not relevant? If true, then the horizontal tank can be installed almost anywhere within the plant boundary.[/li]
[li]If it is relevant, can you install the horizontal tank such that the vertical center aligns with the vertical center of the vertical tank? (Though, the vertical movement of the water in each tank will not be the same.)[/li]
[li]Would manifolding the tanks together change anything?[/li]
[/ol]

Thanks,
TXPE_MED

 

[LittleInch]

1) I think so. The only difference will be the sttic height might be a little different, but they are not the same volume any way.
What's the amount of pressure here?
2)You could, but the level is going to be different any way
3) You would have a common pressure node. Depends on the sizing and relative height of each tank and whether the pressure above them is also manifolded together?

A sketch might help you and us figure this out better, with elevation, heights and pressure all listed

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

 

[1503-44]

Nothing in a connected hydraulic system ever acts independently. Nothing. At least without specifying some very special conditions with a long list of "if statements".

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[bimr]

Who knows why the client wants replacement? Is the existing tank corroded? Is there adequate space in the building for a larger tank? Is the pump cycle time too short?

You can install two pressure tanks on the same part of the booster system. Since these are pressure tanks on a pressure network, the water elevations in the tanks shouldn't matter. The smaller tank is only 20% of the total volume so the smaller tank is probably not necessary.

With a larger tank volume, you will have a longer time between pump starts/stops.

 

[1503-44]

If they share a common connection, the tank water levels will equalise whenever the air pressure in both tanks are equal. If the tank pressures were not equal, then their difference in water level in feet would be [&Delta;]P x 144/62.4, as required to have a pressure balance at the common connection point.

Assuming round tank shells and filling begins at equal tank pressures ....

If both tanks start out at equal air pressures, flow to each tank will be what is necessary to keep those pressures equal, so both tanks will fill at the rate necessary to keep their levels equal too.

If filling begins at different tank pressures, then flow will go to the tank with the lowest pressure until pressures in both tanks are equal. That flow may be from the common connection point, or from the higher pressure tank. Then flow will proportion from the connection as necessary to keep equal pressures in both tanks thereafter, also implying maintaining equal levels.

If the vertical tank tops out first, then its air pressure will rise accordingly to equal the pressure of the horizontal tank. Additional flow into that vertical tank will be only enough to keep up with the pressure of the horizontal tank. If the horizontal tank tops out first, then the reverse is true.

I think that's how it works.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."