Overflow tank control question 1

[delf]

Dear fourm members:

I have an overflow tank. There is a overflow pipe
connected on top of the tank, and through gravity
flow to a seal pot.
The service water will flow through a solenoid valve(XV-A) with
level control(LIT-B) to the seal pot.

It is confused me that the interlock in this solenoid vlave
write as LAL-B, LAH-B actuated, the XV-A will open.

But it doesn't make any sense to me that
LAH-B ( the seal pot at high liquid level),
the inelt valve (XV-A) should be closed instead of opened.


By the way the seal pot outlet will discharge to containment basin underground.


I appreciate your help and your comment if any.

 

[ajs1972]

Do you have a drawing in order to clarify your question? Thanks.

 

[delf]

Dear Sir

Sorry to bother this question twice.
I hope this attached drawing is clear.

It make much more senes to me as level of the tank is high,the inlet valve XV-A should close to stop more water into the tank.

Not sure my sense is right cause the licencer interlock description says that the XV-A should open to let more water in.




Thank you so much.

 

[sshep]

Isn't the seal pot just to keep vapors from coming out the overflow line by providing a water seal? The control of the seal level is to open service water via a level switch low, and close again on level switch high. This is what I see to be the operation- for whatever it is worth.

best wishes always,
sshep

 

[delf]

Thank you for your advise.

But I don't understand your point that overflow line is for keeping
vapors from coming out the overflow line. Istead, I think this overflow line provide a good solution for that tank water level
is overflow to tank high high level.

 

[eleccontract]

It could be possible that the high level switch is wired for normally closed operation. Meaning that it is activated (electrically) when it does not sense liquid at that level. Then in fact the operation of the system is how you suspect.

 

[sshep]

The overflow line itself is for overflow of liquid from the tank, but the WATER SEAL on the line is to keep vapors (or N2 blanket) from coming out the pipe which is connected to the vapor space. That was my interpretation.

 

[ash9144]

SShep is exactly right. The pot is the liquid seal for the vapor space. Water adds when level goes low, water closes when it hits the high level. The overflow pipe goes into seal pot below the liquid level in the seal pot which maintains X inches of water seal on your tank. If your tank pressures up it will blow through the seal pot out the liquid. If you overfill the tank it will flow out to the seal pot and most likely to the ground.