6 replies to this topic

[fallah]

Dear all,
In which cases we have to consider "syphon break" on liquid flow lines?

Regards
Fallah

[JoeWong]

Dear all,
In which cases we have to consider "syphon break" on liquid flow lines?

Regards
Fallah

Two out of many...
i) Gravity transfer line
ii) RISK of vacuum due to liquid column

JoeWong

[Art Montemayor]

There is one more, important application, Joe.

It is the introduction of a liquid into a storage tank via a Dip Pipe - a method that Fallah is adverse to, as witnessed in another prior thread.

Nevertheless, it is used throughout industry to avoid the generation of static electricity and requires a syphon break in the form of a small hole drilled into the upper part of the Dip Pipe, directly under the roof of the tank. This avoids a back-syphon effect taking place after flow is stopped during filling of the tank.

As you state, there are many more applications - most of them take place during the gravity flow (or "drain") of fluids from one process into another.

[JoeWong]

Mr. Montemayor,
Yeap...you are right. In the skimmer, we apply dip pipe (liquid feeding line) to minimise turbulence on the HC layer. Small hole on the upper part of dip pipe act as "syphon breaker".

JoeWong

[Alawi]

How small is the hole? Is there a certain standard to calculate its diameter, will liquid jet from the hole while the tank is filling, or is it like a check valve?

Thanks

[JoeWong]

Alawi,

It purely a small hole drilled on upper part (vapor section) of the inlet pipe. The size typically a few mm i.e. 6mm.

JoeWong

[trilok_sontakke]

You have to consider siphon break if you are venting out some gas (say Hydrogen) from
process equipment (say reactor) to atmosphere via catch pot (It is simply a vessel filled with liquid (say water) to reduce the gas velocity.

In this case there is a chance of liquid flow from catch pot to process equipment due to siphoning
effect.

This problem can be easily addressed by putting a non return valve (NRV) in the line.

As per Mr. Art for the dip pipe we can easily break the siphon by having a small pinhole
at some upper distance above liquid level. But in case where the feed is entering through the bottom
of the tank (for example in scrubbers), there is a chance of reverse flow if feed line pressure drops below the pressure produced by liquid level in the tank.(worst case senario is feed pump failure)

The simple solution in those cases is introduction of NRV in the line.