Siphon break query

[knapee]

Dear Sir


I got some trivial question about siphon break.
(Attached drawing).

Case 1. The line 1 ( no siphon break),
As delta P(B-A) < s.g.*h1, the liquid could flow down.
but as delta P(B-A) > s.g.*h1, the liquid will hold up and
not flow down, and gas in drum B may flush back to drum A.
Case 2. The line 2 (siphon beak).
As delta P(B-A) < s.g.*h1, the liquid could flow down.but as delta P(B-A) > s.g.*h2,
the liquid will hold up and
not flow down, and gas in drum B may flush back to drum A.

If s.g. * h1 < delta P (B-A) < s.g.*h2, the liquid won't flow down, and gas will not flush back.
Anyone can tell what is difference between case 1 and case 2 design.

Could any pro help me out?

Thank you very much.

 

[sshep]

A syphon break usually creates an air gap at the high point of the overflow connecting line. This air gap is to prevent liquid from flowing through discharge piping that runs above the source liquid level, which it can do in a liquid full piping system.

Neither of what you drew is what I would consider a syphon break and (because the piping is running liquid full), there is essentually no difference in the two configurations.

best wishes,
sshep