Thread: Tanker venting

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    Default Tanker venting

    Trying to spec a new tanker for a rural department and I am looking for some input on the tank vent. We will probably end up going with 10 inch Newton dumps (one at the rear and one each side) and we would like to spec a tank vent that will allow for the fastest dumping operations. One rule of thumb that I have heard is that the vent should be one and a half times the size of the dump. In other words the 100 square inch dumps would require a 150 squad inch vent. This seams a little large, is it needed to optimize performance? Thanks.

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    We have a 3500 gal eliptical (3200 water/ 300 foam) With 10" chutes on each side at the rear and one extendable chute directly out the back. The over flow tower is about 24" x 24" (576" sq) and is open straight to the tank this also acts as our vent. It's a littleunsightly sticking off the top of the eliptical...but we've never had a "glub glub" problem.
    Think about a gas can.... if you keep the vent closed when you pour you get what I call the "glub...glub" effect. open the vent and whal-ah a nice smooth pour. Same Idea here.
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    Quote Originally Posted by car5 View Post
    Trying to spec a new tanker for a rural department and I am looking for some input on the tank vent. We will probably end up going with 10 inch Newton dumps (one at the rear and one each side) and we would like to spec a tank vent that will allow for the fastest dumping operations. One rule of thumb that I have heard is that the vent should be one and a half times the size of the dump. In other words the 100 square inch dumps would require a 150 squad inch vent. This seams a little large, is it needed to optimize performance? Thanks.
    If you have not had Newtons before they dump so fast you may damage your drop tank / folding tank if you are not careful. (Bent frames etc) The way to go but be careful...

    If you say you want the tank to dump at XXX gpm, you don't have to do the engineering for it, the builder does. Then you test that it dumps at XXX gpm at your acceptance inspection.
    Last edited by ChiefDog; 02-13-2010 at 06:57 PM. Reason: clarify folding tank getting damaged

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    Default Vent Size

    Air moves with less resistance than water, so your vent can be smaller in area than your dump valve. Our tankers that were built by A.H. Stock Mfg. who also make the Newton Kwik Dumps have 8x8 inch vents. This makes them 64 square inches and the dumps 100 square inches.
    Last edited by bendone; 02-13-2010 at 07:18 PM.

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    better to over vent then undervent. It's much easier to fix onces you practice and see how it works in real world applications. From my experience I would go atleast 150% of dumping hole area.

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    Quote Originally Posted by volfireman034 View Post
    better to over vent then undervent. It's much easier to fix onces you practice and see how it works in real world applications. From my experience I would go atleast 150% of dumping hole area.
    Correct. It's not just about letting air in quickly during dumping, it's to provide a relief when overfilling to avoid pressurizing the tank.
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    I work for a company that manufacturs fiberglass process vessels and our standard rule of thumb is to size the vent at least the same size or bigger that the largest inlet or outlet on the tank to prevent any vacuum or pressure from occuring. The truck builder should be talking with the tank builder about the proper vent size. I would just put in the spec that the vent size should be sized correctly for the size of dump you are wanting.
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