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Automatic Air Vents 2

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mechanical3010

Mechanical
Dec 10, 2010
43
The closed loop piping network, such as that of chilled water system usually has an Air Separator in the Pump Room. Furthermore, Automatic Air Vents are provided at the highest points (Pipe Risers) to expel air before it even reaches the Air Separator. Sometimes the horizontal piping must be offset upwards to avoid other services and installations. Are Automatic Air Vents essential at these small (one foot high) offsets, or can the water push the air towards the Air Seperator (like it does in open to atmosphere systems such as domestic water supply)?
 
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Put the air vents in to avoid getting airlocked. The water may not be able to push through the trapped section of pipe, then you're stuck.
 
I wouldn't recommend Automatic Air Vents anywhere but a mechanical room or service space (they spit). We call for manual air vents at the offsets as noted, and they are essential.
 
In a closed chilled water loop it is very unlikely you need more than one air vent. The water velocity should be enough to sweep air to the air separator.
 
Use manual air vents at any vertical offset.....it's all good til it's not.

I've seen air binding in a 6" riser and a 500-ton system had to be shut down to get it out. Vents are inexpensive.
 
By manual air vent do you mean just a valve that you open to release the air? If that is the case, water is likely to come out of it when operated to see if there was any air. Manually opening AAVs at each offset would be quite a task. Even if the air vents spit they would do so only when there is air, and this should not happen every day. I guess the air would be found only when the network is first filled or when it is refilled after completely draining it.
 
Manual air vents are like schraeder valves on a tire. You can push the middle part to release air. Push it until a bit of water flows out.
 
Air vents everywhere. Air is less dense than water, so it doesn't want to be pushed down, ever, laws of physics and all. Manual air vents are great, and if you don't know what they are, contact a hydronic rep. You will see water shoot out, but these are small openings, and that means the air is gone and it's time to close the vent (this is a good indicator).
 
You can use thermostatic steam traps as automatic air vents in chilled water systems. Clean them once in a while and there shouldn't be any problem.

 
I have never heard about using a steam trap as an auto-air vent. I'm going to look into that more quark.
 
I thought air vents were something that management wore in their ears, but it might only have been ticks.



 
Many steam traps incorporate an air vent function, but they will all be much more expensive than a simple float type air vent. A thermostatic steam trap won't work. It has to get hot to close. Float type steam traps will often have a thermostatic air vent inside
 
Chris,

I have been using them for 10 years now and works well as long as there is no debris inside. I made similar comments to that of Compositepro, when I was suggested the first time. You can try and there is no harm[wink]

Only thing I don't know is that the traps are expensive than a good automatic air vent valve, atleast not in India.

 
I wouldn't install an auto air vent anywhere else in the system other than on the air separator. A good coin vent can cost about $6.00-$10.00 each. The manual vent should only be needed at start-up and helping with problems that may arise in the future. Spending a lot of money for auto vents is a waste.

Plus a manual vent would be a lot smaller and easier to install than the steam trap. Still not sold on the whole idea that using a steam trap in place of an air vent is a good idea.
 
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