why does a check valve not work as a vent during filling
why does a check valve not work as a vent during filling
(OP)
We have a 5000 US gal tank for aqua ammonia storage. In addition to inlet and outlet( these two are closed most of the time) a 2" PVC with a ball check valve is connected at the top of tank as a vent. We utilize this 5000 gal ammonia over a period of 5 months without loosing any ammonia. However, it takes only 30 minutes to refill this tank from bulk trailer, and onone wants to stay inside the facility due to ammonia smell. Why the check valve with PVC vent is not functioning as a vent during this fill up? Should we have to have additional-independent vent( with regular ball valve) in addition to the one we have so that we can manually keep it open and close only for fillup purpose?





RE: why does a check valve not work as a vent during filling
It appears to me that the check valve spring is too strong and will not allow the seal plate/ball to lift. It also appears to me that the venting is occuring at the fill port. Do you seal the fill port when filling? Vapor will take the path of least resistance.
Maybe you could add a ball valve that would only be used during filling.
Try removing the spring in the check valve at next filling and see if it opens. If it a ball check and oriented in a vertical line you may not need the spring.
A new thought is the ball check there to pervent a vacuum or an overpressure situation. Which direction is its flow arrow. I should have asked this first!
pennpoint
RE: why does a check valve not work as a vent during filling
RE: why does a check valve not work as a vent during filling
The check valve, we have, is a ball check valve, and it is oriented in vertical line. The direction of its flow arrow is upwards towards sky. Therefore, it will definitely help for overpressure situations.
Chicopee,
In fact we have two 5000 US gal tanks. One is for FRESH and the other is for SPENT. The bulk trailer brings fresh in, and takes the spent back. Thersfore, if we use return vapour line, then we will end up keeping the ammonia vapour in our spent tank everytime we fill up the fresh. This is one of the options which I am thinking about.
Saumian
RE: why does a check valve not work as a vent during filling
RE: why does a check valve not work as a vent during filling
when you use your aqua amonia and when you take liquid out, it fills with amonia gas evaporated by the vacuum you created.
when you fills probably the pressure of the tank increases making a release.
My first word of caution: check that the tanks can resist the vacuum created when emptying, I already have seen some colapsed tanks.
The second: check that the pressure created by the check valve during the unloading is lower than what the vessel can resist.
Even better than this: use a properly designed and constructed conservation vent (like Protego). A check valve has not a very exact release pressure.
if you can not return the Amonia vapors to the delivery truck they can be easily captured with water (scrubber).
Rgs
RE: why does a check valve not work as a vent during filling
I believe that you mean that A conservation vent should have been used as the breather, not as an apparatus which can get rid of the ammonia vapours in our situation. Do We need an exhaust even with a conservation vent(valve)?
Saumian
RE: why does a check valve not work as a vent during filling
Roy Gariepy
Maintenance and Reliability Dept.
Bayer Corporation Dorlastan Fibers Div.
Goose Creek, South Carolina USA
RE: why does a check valve not work as a vent during filling
RE: why does a check valve not work as a vent during filling
Many facilities exchange the vapor with the supply tank truck to minimize venting losses. The conservation vent is the vent. If you have a vent and a conservation vent then the conservation vent function is defeated.
I suggest you contact a reputable supplier of conservation vents.
RE: why does a check valve not work as a vent during filling
The conservation vent can release the overpressure to the atmosphere (if this is allowed, safe or enviromentally sound) or to a pipe for further treatment. in other cases (vacuum) to suck air from the atmosphere or from other systems.
As rbcoulter mentioned there are valves that have something like a big plate and a defined weight for each application. they can be configured to open by pressure or vacuum or both.
A variation of this exists with a membrane that is loaded by a liquid.
Other systems (older) uses a pipe that is dip in a liquid at a defined height, this requires a lot of work to keep the liquid level (usually water).
You can find futher information and profesional advice by companies like protego (www.protego.com) or protectoseal (http://www.protectoseal.com/pvcvents.html)
Kind regards
RE: why does a check valve not work as a vent during filling
It appears that the check valve is there, in the original design, for over-pressure situations. The logic is there since a tanker truck with air-compressor have been used to tranfer aqua ammonia from tanker to FRESH tank.
It also appears that if we use a transfer pump to transfer AA from tanker to FRESH tank, then we may not end up having this much ammonia smell. A tranfer pump along with vapour return line would have fixed most of our concern.
We shall really need a check valve in addition to the Coservation valve if we have one, in case this Conservation valve fails.
Therefore, we now need a system with ducts, a pump, a cleaner ( scrubber) for fill up purpose of FRESH tank, to get rid of ammonia vapours in addition to the check valve system.
Thanks for all again.
Saumian