Expansion Tank
Expansion Tank
(OP)
Hey guys,
Can someone please explain to me mathematically why should the expansion tank be connected to the suction side of the pump and not at the discharge.
I can't seem to understand the point of no pressure change. Doesn't the tank itself exert pressure on the water network?
Expansion tank doesn't have a water supply nor return it is connected to the network via one pipe.
What i know is this:
Entire system is filled thorough a fill valve and then this valve is shut. When the temperature changes in the chilled water network the air trapped in the tank is compressed. But if the tank is not connected how does it detect temperature change?
Can someone please clarify once and for all?
Can someone please explain to me mathematically why should the expansion tank be connected to the suction side of the pump and not at the discharge.
I can't seem to understand the point of no pressure change. Doesn't the tank itself exert pressure on the water network?
Expansion tank doesn't have a water supply nor return it is connected to the network via one pipe.
What i know is this:
Entire system is filled thorough a fill valve and then this valve is shut. When the temperature changes in the chilled water network the air trapped in the tank is compressed. But if the tank is not connected how does it detect temperature change?
Can someone please clarify once and for all?





RE: Expansion Tank
To work the expansion tank needs to be connected to the circuit. Water will flow in and out of the tank a it needs to so that the air pressure in the tank equals the pressure at the point where the tank is connected. The tank acts on pressure change caused by expansion or contraction of the water in a closed circuit.
There are many posts here with diagrams which might help.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Expansion Tank
http://bellgossett.com/literature-library/#categor...
RE: Expansion Tank
http://documentlibrary.xylemappliedwater.com/wp-co...
knowledge is power
RE: Expansion Tank
RE: Expansion Tank
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Expansion Tank
RE: Expansion Tank
The preassure on the inlet side will probably vary less than on the discharge side, so if you want to use numbers the I suppose you could look at static pressure at no flow compared to operating pressure which should be a smaller number than on the discharge side. Other than that I don't believe there is a "mathematical" solution.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Expansion Tank
RE: Expansion Tank
If so then i'm starting to get a better grisp on this matter if not then i have a lot more to read lol.
One more thing, only one pipe is connected to the expansion tank and this one pipe serves water going in (expansion) and water going out (pressure exerted by the tank), right?
RE: Expansion Tank
only one pipe to expansion pump since it either goes in or out, not both at the same time.
Get this book
RE: Expansion Tank
RE: Expansion Tank
For a low rise building, the expansion tank is always installed at the suction side of the pump because of NPSH.
If the expansion is installed at the discharge side, the pump NPSH need to be checked. This installation is normally for high rise building to reduce the system pressure.
Example: If the Expansion tank is charged at 40psig and the pump head is 30psi.
1. If the expansion tank is installed at the suction side of the pump. The suction pressure is 40psig and the discharge pressure is 40+30 = 70psig.
2. If the expansion tank is installed at the discharge side of the pump. The discharge pressure is 40psig and the suction pressure is 40-30 = 10psig. Therefore, you need to check if this 10psig is enough for pump NPSH.
RE: Expansion Tank
RE: Expansion Tank
RE: Expansion Tank
RE: Expansion Tank
RE: Expansion Tank
RE: Expansion Tank
RE: Expansion Tank
RE: Expansion Tank
1. If the expansion tank is installed at the suction side of the pump. The suction pressure is 40psig and the discharge pressure is 40+30 = 70psig.
2. If the expansion tank is installed at the discharge side of the pump. The discharge pressure is 40psig and the suction pressure is 40-30 = 10psig. Therefore, you need to check if this 10psig is enough for pump NPSH."
Nicole could you please explain why u added the pressures in the first part and subtracted them in the second?
Thanks!