Breather Valve

[gkandy]

Demineralised Water ( for Boiler Feed Service ) Tank and Sulfuric Acid ( 98% ) Tank are normally provided with Silica gel absorbers in their vent for moisture absorption ? Do we require any breather valves for prevention of vaccum? Is there any other option other than using inert gas to fill up the vapor space ?

 

[TD2K]

If the silica gel absorbers can pass enough air for the maximum pump-out rate without exceeding the tank's vacuum rating, then you could argue you have provided vacuum breaking capacity. My concern would be whether the flow capacity of those driers could significantly change as the dessiccant ages and it won't pass as much gas as initially sized for. In which case, your tank is not long for this world which is annoying, expensive and with concentrated sulphuric acid, potentially very dangerous.

If the driers don't have enough capacity or you don't want to depend on them, you'll need to install additional vacuum breaking capacity (and you should also look at the outbreathing capacity as well). Whether it has to be inert gas is up to you, if the silica driers should handle the 'bulk' of the inbreathing requirements and only a relatively rare situation should require the new breather valves to operate (say, a pump run-out condition or a failure of the driers such as the beds compacting to where they won't pass enough air), then I'd likely look at just using atmospheric air. The amount of water that you'd introduce into the tank would be pretty small.

Depending on the reliability of your istrument air system and the situation that causes the new valves to operate, instrument air might be another backup fluid to look at. And N2 is also fine, just make sure you have proper warning signs that the tank could contain inert gas. We used to post placards at N2 potential vent points also.

 

[sewerguy]

If you put something in that can plug as part of the primary breathing device, I would commonly put in independant over/under pressure protection.

I have never heard of inert gas blanketing being required for sulfuric or demin water storage.

 

[gkandy]

TD2K

Thanks a lot.