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Vacuum Dip Leg


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#1 Sridhar P

Sridhar P

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Posted 28 May 2009 - 12:34 AM

In Vacuum systems- say a seperator operating in vacuum to remove the condensate from air. The dry dip leg height of the leg to be above 10.33 m to avoid lifting of the water. What should be the height of the dip leg immesed inside the liquid. Is there any formulae for this.

Regards,
P.Sridhar

#2 ankur2061

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Posted 28 May 2009 - 04:31 AM

QUOTE (Sridhar P @ May 28 2009, 01:34 AM) <{POST_SNAPBACK}>
In Vacuum systems- say a seperator operating in vacuum to remove the condensate from air. The dry dip leg height of the leg to be above 10.33 m to avoid lifting of the water. What should be the height of the dip leg immesed inside the liquid. Is there any formulae for this.

Regards,
P.Sridhar


Sridhar,

It is rather quite simple. You need to convert the vacuum value to absolute pressure value and then it can be calculated. An example:

Vaccum in system = 500 Torr
= 0.66 atm(a)

Specific gravity of the condensing liquid: 1.1

Then minimum seal or barometric leg height

= 10.33 - (0.66*10.33/1.1) = 4.132 m

However if your operating levels of vacuum are fine say less than 200 Torr then the usual practice is to avoid any calculations and straight away provide a barometric leg of 10.33 m and leave it at that. This provides a conservative design preventing any liquid being sucked into the vacuum system in an upset scenaro of very fine vacuum being created by the vacuum generating device (vacuum pump/ejector).

Hope this helps.

Regards,
Ankur.



#3 Sridhar P

Sridhar P

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Posted 28 May 2009 - 10:05 PM

Dear Sir,

Thanks for your inputs. But my basic query is - what is the length of the leg that is to be immersed inside the liquid. Is it that the leg just immersing in the liquid is sufficient. or practically to avoid liquid dip break any specific requirements are there.

Regards,
P.Sridhar


#4 breizh

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Posted 28 May 2009 - 10:52 PM

Hello ,
Go to this link for more information :http://dekkerknowledge.com/questions.php?questionid=47

Basically the immersed pipe should be long enough to avoid air / gas entry which can jeopardize your vacuum .
Regards

Breizh

#5 ankur2061

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Posted 29 May 2009 - 11:19 AM

Sridhar,

Check out the below link for an earlier post by our esteemed member Doug on the`subject matter as well as by our very own Art Montemayor. Very inormative post on vacuum dip leg or barometric leg.

http://www.cheresour...?showtopic=2530

Regards,
Ankur.




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