'Anti-siphon valve' - Please explain

[HT32BSX115]

Re: 'Anti-siphon valve' - Please explain

50 feet?

I never said 50'....... I said 10 feet!

even 10 feet is hypothetical......

Someone want to tell me the name of a boat that is powered with gas engines that has over a 6' rise or drop from the gas tank to the engine?
Or is all this 50' garbage done on that stupid looking boat from Hypothetical Marine?

 

[Outsider]

Re: 'Anti-siphon valve' - Please explain

An "anti-siphon valve" could also be confused with an "anti-siphon vent" in the fill vent line. Eliminates the necessity for a vent hose loop, keeps water (and critters) from entering the tank through the external vent fitting. Most people don't really care how or why the valve works, only that it does. It's like computer problems, save the geek-speak, just tell me how to make it do what it's supposed to do ...

 

[Don S]

Re: 'Anti-siphon valve' - Please explain

No outsider, it's not being confused with the vent AS.
It's now not even being considered part of a fuel system. This thread has now wondered off into never-never land where nothing has anything to do with reality and how things actually works on a boat.
But we may get a math lesson out of it. Something to put in that shoebox in the back of your closet. You know, the one you never look at

 

[starsnstripers]

Re: 'Anti-siphon valve' - Please explain

HAHAHA! Man you guys get all carried away with your math stuff and figures. I'm getting a brain cramp here. All in all it seems like a safe good idea to my simple mind. Here's a thought on the clogging thing. What if you like angled the antisiphon valve at an upward angle from the tank so if any debris that got to it would drain back to the tank. Might work to a point unless it jams the valve. It would be almost self cleaning,HUH? OR, A screen/filter close to tank before the valve? Is there such thing as a fittinf screen? You know just like the antisiphon valve but with a fine screen? Like in some gm carbs? Oh thanks for those figures Chris, you enjoyed it.

what about this

 

[qystan]

Re: 'Anti-siphon valve' - Please explain

Its just another winter thing...... hang on a little more, spring is just round the corner.

 

[SgtMaj]

Re: 'Anti-siphon valve' - Please explain

I'm not trying to argue with you Rod, just running the maths....

SG of mercury is 13.57, SG of gas is 0.737. That makes Hg 18.41 times heavy than gas. So to draw the same vacuum as 1.5" of Hg, the gas column would have to be 18.41 times longer. 1.5" times 18.41 is 27.615 inches....

Running the same with a full vacuum, the gas column would have to be 18.41 times 30"... that's 46 ft... for a full 30" vacuum.

Running it for water, a full vacuum (the longest you can draw water, ask anyone who has set a bore) is 34 feet.

It doesn't matter if you are siphoning or lifting the liquid. It's all to do with the weight of the liquid column at the head.... and the atmospheric pressure...

Maybe someone could do a test for us... I'm not anywhere I can do this, but I'll try it when I get home... See how far a hose has to be lowered to crack open an anti-siphon valve....

If my maths is wrong can someone please point out exactly where....

Chris.............
(Line diameter will have absolutley no effect on the head height, merely the volume transferred)

Ok, but since head height is effected by weight, what is the difference in the gas column length to draw a 1.5" vacuum between someone in Denver, and someone in northern Brazil at sea level? Ooohh this is a good one... I can see at least three ways this question is tricky... Good luck Chris!

Ok, I already have the answer... how about you Chris?

 

[HT32BSX115]

Re: 'Anti-siphon valve' - Please explain

You know,

All this talk about head pressure is giving me a headache!!!

I'm going to leave this one alone from now on and go back to using Laplace Transforms to do network analysis...


jeeze.....

 

[Silvertip]

Re: 'Anti-siphon valve' - Please explain

I actually tried this to see if the anti-siphon valve did what it was supposed to do. I took the connector off the fuel line and extended the hose to shop floor level inside a portable tank. Sqeezing the primer bulb gets the flow going and although a siphon does occur through the anti siphon valve, flow is very slow and weak at that height which is about 3-1/2 feet. As you pull the hose upward flow stops when the end of the hose is about at keel level so in this simple test, they do work (at least mine does).

 

[achris]

Re: 'Anti-siphon valve' - Please explain

I actually tried this to see if the anti-siphon valve did what it was supposed to do. I took the connector off the fuel line and extended the hose to shop floor level inside a portable tank. Squeezing the primer bulb gets the flow going and although a siphon does occur through the anti siphon valve, flow is very slow and weak at that height which is about 3-1/2 feet. As you pull the hose upward flow stops when the end of the hose is about at keel level so in this simple test, they do work (at least mine does).

Not quite 50 feet.....

Chris............

 

[Silvertip]

Re: 'Anti-siphon valve' - Please explain

Yes, I know the test was not at 50 feet. Had a little trouble getting the boat up on the roof (it's 10 below zero here tonight). But we do know the valve begins to allow fuel flow (actually just a dribble) any time the end of the fuel line is below the keel and at 50 feet it would certainly flow well.

 

[achris]

Re: 'Anti-siphon valve' - Please explain

Yes, I know the test was not at 50 feet. Had a little trouble getting the boat up on the roof (it's 10 below zero here tonight).

Where's your ingenuity man????

But we do know the valve begins to allow fuel flow (actually just a dribble) any time the end of the fuel line is below the keel and at 50 feet it would certainly flow well.

I think the 'difference of opinion' was that someone said that the fuel wouldn't flow until the fuel line was 50 feet below the fuel level in the tank....

Did you manage to get an accurate figure of exactly what level difference stopped the fuel flowing?

Chris............

 

[SgtMaj]

Re: 'Anti-siphon valve' - Please explain

achris has replied, and yet he hasn't risen to my challenge? He probably hasn't seen it yet. I'll give him another post...

 

[achris]

Re: 'Anti-siphon valve' - Please explain

Ok, but since head height is effected by weight, what is the difference in the gas column length to draw a 1.5" vacuum between someone in Denver, and someone in northern Brazil at sea level? Ooohh this is a good one... I can see at least three ways this question is tricky... Good luck Chris!

Ok, I already have the answer... how about you Chris?

Ok, 3 ways.. First you have me on geography... What's Denver's altitude?

Northern Brazil.. They probably don't care, or use anti-siphon valves...

The answer could depend on the atmospheric pressure at the time. If we assume that the sea level pressure (we would then correct for altitude) is the same at both sites (and while we are at it we'll call the air temperature the same too). I will also assume at Denver is not at sea level (or you wouldn't have asked the question) and that it is higher than sea level (or it would be called Lake Denver), and yes I do know there are places that are lower than sea level and they aren't lakes.

The answer is..... both the same..... 1.5" of Hg is 1.5" regardless of altitude (or planet for that matter)!!!

Chris.............

P.s. Just arrived home (been flying for over 30 hours) so sorry for not seeing it earlier....