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It is 1 am Wednesday morning for me. This thing keep me wide awake - interesting stuff.
I will run the test in 7 hours time when I return to my office - I will take my video camera. If the results looks positive one way or the other, no need to do more. But if the result is murky, I will set up a test in a more controlled environment. Anyone is take bets? |
Originally Posted by dubbleugly01;
it's hard to tell what's what in the diagrams of the check valves posted.
Here are a couple of pics of a checkvalve in the water line to the intercooler sprayer on an 03 Evo. You can clearly see the ball on one side, and the spring on the other. I hooked up a little rig I have with a bicycle pump, vacuum tubing, tee and pressure gauge. The spring is a 3# spring. http://i124.photobucket.com/albums/p...Picture091.jpg I can see you point very clearly. the ball valve will create a flow paths relative to the upstream pressure. CV only applied to mega flow in relation to the ID. My original statement is balanced on a knife edge until tomorrow. :confused: |
uh, didnt you guys forget that there is a pressure on the downstream side of the checkvalve, generated by the turbo? i.e. Air pressure.
...or did you account for that already? I might have missed it in the throwing around of formulas...:rolleyes: (im still studying to be a mech. engineer :D) |
VIDEOS (Microsoft IE only):
Here are abner's Check valve test - please be patient, video files are about 5MB NO CHECK VALVE (see video) Download (1.78MB): Click here ONE CHECK VALVES (see video) Download (4.40MB): Click here TWO CHECK VALVES (see video) Download (3.86MB): Click here The final flow quantity should give you some clues on the effect of the CV. |
Originally Posted by SoCalRedLine
(Post 4710657)
uh, didnt you guys forget that there is a pressure on the downstream side of the checkvalve, generated by the turbo? i.e. Air pressure.
...or did you account for that already? I might have missed it in the throwing around of formulas...:rolleyes: (im still studying to be a mech. engineer :D) See post #3, a chart with CV accounted for turbo pressure. |
^yea, i saw that, but i didnt see it anywhere in the other guys formulas. im sure they prolly did get it, as they know more than me.
me = still in school them = out practicing what im learning...lol |
Originally Posted by Richard L
(Post 4710702)
VIDEOS (Microsoft IE only):
Here are abner's Check valve test - please be patient, video files are about 5MB NO CHECK VALVE (see video) Download (1.78MB): Click here ONE CHECK VALVES (see video) Download (4.40MB): Click here TWO CHECK VALVES (see video) Download (3.86MB): Click here The final flow quantity should give you some clues on the effect of the CV. although the starting volume with no checkvalve seems a bit low for an M5 at 125 psig, the drop in flow is what's significant. After looking at all the backup data Abner provided for the nozzle, and check valves, it's obvious that each check valve is adding close to 25#'s of pressure drop (and they have 25# springs, imagine that) between the pump and the nozzle. Just like Richard had originally stated. You can sleep well tonight Richard knowing your were spot on to begin with. :beer: Abner, thanks for going to the trouble of setting up the test and running it! |
I'm going to make this real simple for you...please go borrow someones Whitey/Swagelok catalog, page through the little tabs until you come to one that says "Check Valves" on it, go to page 3 for the inline CP Type valves and find the chart at the middle of the page. See where it has 4CP in the left column? Put your finger there and go across the columns until you come to the column that gives a value for Cv. See how the manufacturer of the valve provides you with this number so that you can determine...pressure drop through the valve!!!! Damn, ain't that sumpin'? Slap me naked and hide my clothes! The people that make the valves actually give you the tools you need to size the valve so that you can get the downstream pressure your system requires. Ain't America great?
Originally Posted by dubbleugly01
(Post 4710489)
it's hard to tell what's what in the diagrams of the check valves posted.
Here are a couple of pics of a checkvalve in the water line to the intercooler sprayer on an 03 Evo. You can clearly see the ball on one side, and the spring on the other. I hooked up a little rig I have with a bicycle pump, vacuum tubing, tee and pressure gauge. The spring is a 3# spring. This is the type check valve I see in Richards diagram in question with the 20# check valve. And I still say this type of check valve will cause a pressure drop equal to the spring pressure. The differential pressure across the ball and seat has to equal 3#'s to get check valve to crack open, and it maintains a 3# drop even after it's open, at various pumping rates. The differential has to equal 3#'s to keep it open. So if you have no pressure on the backside or downstream of the ball, it opens at 3#'s. If you had say 10#'s of pressure on the backside of the ball, I'd have to pump 13#'s of pressure with the bicycle pump to get it to crack open and stay open and flow. Are you guys trying to tell me once the seat is broken and the valve cracks open, the pressure drop will be dependent upon some Cv value alone????? Nope, it's going to be the pressure drop caused by the orifice (Cv) PLUS the spring pressure. At low flows, it'll be damn near 3#'s, at higher flows, it could be considerably more. But never less than 3#'s. If this is the type of check valve for the test, by all means run the test. |
So what causes the pressure drop, the spring or obstruction to flow? The latter would play more on dynamic pressure I think
A rod bolt may snap in two in either case - kinda like waiting for an earthquake |
Originally Posted by Whoosh
(Post 4711057)
I'm going to make this real simple for you...please go borrow someones Whitey/Swagelok catalog, page through the little tabs until you come to one that says "Check Valves" on it, go to page 3 for the inline CP Type valves and find the chart at the middle of the page. See where it has 4CP in the left column? Put your finger there and go across the columns until you come to the column that gives a value for Cv. See how the manufacturer of the valve provides you with this number so that you can determine...pressure drop through the valve!!!! Damn, ain't that sumpin'? Slap me naked and hide my clothes! The people that make the valves actually give you the tools you need to size the valve so that you can get the downstream pressure your system requires. Ain't America great?
The test Abner did shows the check valve adds a significant amount of pressure drop, and reduced flow at the nozzle. And it's not due to the Cv of the valve by itself. You have the flow measurements you requested, now go do your calculations and confirm this. It's the spring!!!!!!! lol Notice how the graph in the swagelock catalog starts at 25 psi pressure drop at 0 flow, and only goes up from there? Ain't it sumpin? The spring basically resets the starting point to 25 psi worht of pressure drop, and as flow increases from 0, so does the pressure drop. And the pressure drop increse as flow increases can be calculated by the Cv, but the spring resets the baseline to 25 psi pressure drop minimum to begin with. |
You failed to recognize in the video that the pump is also a demand pump so it cycles on and off so yes the check valves are closing and opening. The argument was never made on volume of flow, the check valve will restrict flow. The argument was will the check valve decrease pressure by the amount of the spring. Volume and pressure are 2 different things are not to be used in a comparison like this. The video did prove that check valves will restrict flow rate though..
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Originally Posted by cpoevo
(Post 4711345)
......The video did prove that check valves will restrict flow rate though..
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Originally Posted by cpoevo
(Post 4711345)
You failed to recognize in the video that the pump is also a demand pump so it cycles on and off so yes the check valves are closing and opening. The argument was never made on volume of flow, the check valve will restrict flow. The argument was will the check valve decrease pressure by the amount of the spring. Volume and pressure are 2 different things are not to be used in a comparison like this. The video did prove that check valves will restrict flow rate though..
if you look at the flow data Abner generated at the nozzle in the videos, and then compare that flow rate to the published data for that nozzle on flow vs. pressure, which Abner also posted, it's easy to see that each check valve accounts for about 25 psi or so of reduced pressure at the nozzle to account for the flow reduction recorded in the videos. The WHOLE argument is about volume of flow, and what impact will a check valve have on the volume of flow at the nozzle. The only way to reduce the flow at the nozzle is to decrease the pressure, and two of you say a check valve won't decrease the pressure onec open, but by about 1-4#'s or so, depending upon Cv of the valve.. Abner's test of check valves with 25# springs shows a corresponding flow reduction at the nozzle associated with about 25#'s less pressure. And this was at flow rates of 125 ml/min with two check valves, a very low flow that the Cv won't calculate out to be a 25# drop. With this style check valve, you most definitely have to add the spring pressure plus the pressure drop due to flow to get total pressure drop across the check valve. You can't simply say once the valve cracks open, the spring no longer matters and doesn't figure into the equation. Yes, flow and pressure are two different things, but intimately related to each other. Change one, and the other must change also. You can't separate the two. |
Originally Posted by SlowCar
(Post 4711402)
now imagine progressive pump speed system using a on-demand pump + checkvalve....:crap:
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Finally, you've caught ...some...snap. I absolutely agree with you that the spring is there to hold the initial pressure on the upstream side of the valve to whatever the spring value is. But that is not called pressure drop. The friction of the fluid as it travels through the orifice (i.e. the inside restrictions in the valve) for a specific flow rate is called pressure drop. The entire basis for my original disagreement with Richard was not flow, but the required pressure to maintain a 30# pressure at the nozzle for proper atomization. As flow (gpm if you will) increase so does the pressure drop across the valve. Just as it does for fluid traveling along the inside of some type of conduit (pipe, tubing, etc). Can you see that there is a greater pressure drop in a pipe that is 1 mile long as a opposed to a pipe 1 foot long? The spring in this case acts as a backpressure regulator to maintain a minimum of "X" amount of pressure. As soon as you overcome that resistance and the ball is unseated, the downstream side of the valve become pressurized to a value that is equal to the upstream side minus pressure losses due to valves, pipe and fittings. Now...go spank yourself you silly Chem E.!
Originally Posted by dubbleugly01
(Post 4711183)
I'll slap you silly, but I won't slap you naked {thumbup}
The test Abner did shows the check valve adds a significant amount of pressure drop, and reduced flow at the nozzle. And it's not due to the Cv of the valve by itself. You have the flow measurements you requested, now go do your calculations and confirm this. It's the spring!!!!!!! lol Notice how the graph in the swagelock catalog starts at 25 psi pressure drop at 0 flow, and only goes up from there? Ain't it sumpin? The spring basically resets the starting point to 25 psi worht of pressure drop, and as flow increases from 0, so does the pressure drop. And the pressure drop increse as flow increases can be calculated by the Cv, but the spring resets the baseline to 25 psi pressure drop minimum to begin with. |
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