Sizing a seal pot that also acts as an overflow

[SSK1999]

Hi All,

I’m in the process of designing a seal pot and overflow tank for a slurry system and would appreciate some guidance.
I have a 6-inch pipe that connects the slurry tank to the seal pot. The maximum flow through this line is 34 m³/hr.
For the outlet of the seal pot, I’ve selected a 7-inch pipe.

My key concerns are:

1. How should go about sizing the seal pot to accommodate the expected flow.
2. What should the submersion depth of the pipe be inside the seal pot to ensure it maintains a proper seal while avoiding backpressure that could cause slurry to flow back into the slurry tank during overflow?
3. The liquid in the seal pot is water.
4. The density of the slurry is 1240kg/m3.

Any advice or insights on sizing and submersion depth would be greatly appreciated!

 

[georgeverghese]

At the outset, how do you expect this seal pot to work when it is in slurry service ? - solids will accumulate in the seal pot and eventually block up the dip leg.

 

[SSK1999]

It's meant to be for failure situations only. In the event of an overflow, production will need to pause. But we need the overflow to work, atleast temporarily, without creating a mess in the berm.

 

[katmar]

What is the design pressure for the main tank? How did you select 7" as the outlet line size from the seal pot? Where does this outlet line discharge? Is there some form of gas or vapor in the main tank that would be ejected via the seal pot before the slurry reaches it? At what elevation will the seal pot be installed relative to the main tank?

How have you approached this design so far, and where did you find difficulties in the design process?

 

[Latexman]

A P&ID would have been more informative. Why is this seal pot needed?

 

[georgeverghese]

You'll have to tell us much more. So far, we gather the following :
a)The seal pot is normally not flowing slurry, it is meant only for overflow scenarios. So there is a normal liquid level in the seal pot, meant to prevent backpressure from the somewhere in the exit line. Describe this backpressure source, how it varies and max possible backpressure
b)How is the normal liquid level in this seal pot maintained? What is the seal liquid ? You'll need instrumentation to monitor this liquid level to warn operators when normal liquid level is abnormal ( too high / too low). Materials of construction for this seal pot, dip leg must be corrosion resistant. Usually some inert liquid with high boiling point such as ethylene glycol is typically used, not water. Do you have plans to pipe up ethylene glycol to this seal pot with level control ?

In many Companies, for concerns related to (b), seal pots are not the preferred option.

As a side note, there is no such thing as a "7inch pipe". Go for 8inch.