Vacuum Breaker 3

[asv80]

Are vacuum breakers required according to any code for a heat exchanger condensing steam in the shell side?

We want to install a vacuum breaker as it would protect the shell, however others say there is no requirements per code and hence not needed.

Thanks in advance.


Excuse for posting in two places!

 

[Yorkman]

I've never seen any code that requires a vacuum but it's good piping practice to include one. With out one condensate is not going to be able to leave the heat exchanger when the supply steam is shut off. As the steam begins to condense the pressure in the vessel will begin to drop and eventualy go into a vacuum, not allowing the condensate to freely drain, where the damage can occur is as steam reenters the vessel water hammer can occur, you've also lost capacity of the HX while the steam is trying to drive the condensate out.

I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI

 

[asv80]

Thanks Yorkman. That is the primary reason we were suggesting its use.

 

[JimCasey]

And then there is the pragmatic consideration: A HX shell is basically a steel balloon, and tolerates pressure well. But one can crumple like a toothpaste tube with vacuum loads.

 

[Yorkman]

Along with the vacuum breaker might I suggest an air vent rated for steam. Think of a steam heat exchanger as a breathing vessel you need a vacuum breaker so air can be drawn in to let the condensate out and then it needs an air vent to expell the air to let the steam back in.

I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI

 

[asv80]

Thanks for the good point Yorkman.

We are going to installing a vacuum breaker and air vent connections on the shell.

 

[quark]

Thermostatic traps are excellent air vents.

 

[lugnuts67]

Thermostatic traps are excellent air vents - both Watson McDaniel and Spirax Sarco make a couple different flavors designed specifically for use as air vents. As far as vacuum breakers go, determine the CFM requirements and then the cheapest solution is to install a light seat pressure spring check valve backwards.

 

[abcmex]

Dear Sirs,
steam and air should be kept apart. I recommend you to google "heat exchanger stall steam" or simply visit

http://www.spiraxsarco.com/learn/modules/13_1_01.asp.

To install a vacuum breaker is a cheap solution but you should be aware of the concequences.

rgs

 

[sailoday28]

IF the operating or design GAUGE pressure of the shell side is relatively high,- Then the shell may be capable of withstanding vacuum conditions.

IF vessel collapse or failure due to vacuum is the concern, I would check with the vendor,

Regards