My Thread Pooped Out...

Hi stolisma

a 1/2" nozzle on an irrigation sprinkler will discharge

37 USGPM at 30PSI and 57 at 70 psi

This will not solve your problem because the opening of the disk above the hole and the riser will have a big effect'

Maybe you should look at a 1/2 " orifice with abnout 1/2 the pressure as back pressure.

I can certainly regulate the pressure down. Having pondered a little longer on the setup, I might need to reduce the size of the hole through and weaken the spring pressure considerably. I dont need to have near that kind of flow, this is a kitchen sink faucet. What is typical flow on that, maybe 1.5-2 gpm?? I just need to balance the flow of roughly 2gpm with the hole size being determined here and pressure being variable before my mixing valve. I can also increase my piston diam if needed in order to achieve the effect, which is making the spigot pop up when the water is turned on. I will do some reading on the sprinkler heads also.

Is there a chart outlining the pressure flow comparisons that you mentioned?

Think 7 gpm don't want keep lazy bastards waiting for H2O

Conference Room 4

Sorry,

Having a problem seeing the benefit of your design. Not to be negative, but can you explain the benefit of your design over conventional valves? I'm too old to see the drawing very well.

Glad to try to help, but I'm not sure what the objective is. I assume we're mixing hot and cold water somewhere in here.

Indeed we are mixing the water in a different apparatus (canabalized faucet).

After the on/off/mixing valve, the flow comes into the bottom of this cylinder. It hits the piston, which has the faucet head tapped into it. when the pressure is applied, it needs to raise the faucet head. When the water is turned off, the compression spring returns the faucet head to the retracted position. This sink and faucet are in a bar top that has wooden leaves on soss invisible hinges which close over the sink to render a clear bar surface (purpose is because the client said they want it done that way). I am trying to achieve roughly 2gpm flow into this chamber with a piston that is at this point 2.75" diameter. I need to have a hole through the piston that is larger enough to let the water flow at this rate but restrict it sufficiently to exert enough pressure on the piston to overcome the spring easily yet return easily via spring pressure when the water is turned off.

If i stumbled on the wording, i apologize. let me know if it is still unclear.

"making the spigot pop up when the water is turned on." is all I needed.

Thanks! Now I understand some of your questions. I'll look at the sketch again.

^{_{Can't the lazy bastards pull the faucet up into place?}}

Perhaps an electric lift, triggered by flow? Maybe the client would get off hearing little motors and gears turn when he/she turns on the water?

You could make it voice activated!

Or, like my '72 Vette wipers: pull electric dash switch which activates vacuum motor which opens wiper door which closes electrical switch which turns on wipers.

Sorry, of course it was clear to me. it was in my head. I think that was outlined somewhere earlier in the thread.

That much $ does tend to make lazy bastards out of them. oh well, just glad i found them in time to spend it. Yeah, originally there was a vertical drawer that contained the faucet connected with flexlines but was a poorly designed foot actuator. They asked me to fix the issue last year and so, of course they were in a hurry and so I simply addressed their then current malfunction. I retrofitted the drawer with drawer glides and a 12volt linear actuator and power supply. the noise, was of course, far too loud but hey, that's what i could do in a pinch and they were willing to suffer with it. well, the kids did not have the presence of mind to fold the faucet back into its drawer before touching my elegantly crafted patinaed brass inset rocker switch. so when it went down, it disengaged from its push point (as designed to if there was an obstruction) and stopped working. **this just in, what if they go to close the leaves without turning the water off** maybe a proximity switch so that when the leaves close, it shuts a solenoid. well, one step at a time.

what do you think about hole size, flow and pressures?

I think you should make a number of restrictor plates and try them. Pressure should be below 50PSI.

My criteria for success would be having enough pressure to keep the spigot deployed, even if a drunken sailor falls on it.

Have you seen, "Overboard"?

To be very sincere I did not understand the reasons for your design and was not able to give any hint. Now it is clear.

1- Use only 1 O-ring as seal and a guide ring (if possible teflon or an other plastic with anti friction quality so that the o-ring will glide with low resistance) to avoid a sticking of the piston.

The design has to be low friction since you have a spring return the higher the friction the stronger the spring and the higher the pressure drop to lift the piston. The water flow is variable so that the pressure should actuate at the lowest possible flow.

2- If you have a thin plate with the hole in it then you can assume a flow coefficient of 0.59...0.64 (mean value 0.605) In an other thread a similar question was presented with respect to the change of an orifice in order to obtain an different pressure drop. Same flow equation is valid: look at the thread "orifice sizing" and you have every thing you need to solve your problem!

If you have questions then please ask.

3- remark: if the orifice is near as diameter to the tube Di then you have to change some parameters since a good ration should be do/Di<1/3. If you cannot then you should also compute the pressure drop in the tube and consider it in your spring/piston design.

Thank you nickname. this is what i am looking for. I am currently enrolled in the school of hard knocks (have been for 20 years now). unfortunately, this is the first encounter with this type of situation for me and i am spotty in principal and math. the mechanical is second nature.

agreed on the one o ring and teflon tube to reduce drag.

I will take a look at that thread and get back.

Keep an eye on this thread if you would, I am pretty sure that i will have more questions. Thanks again.

Alright, I had a guy explain the delta p, coefficient of velocity, inlet pressure etc to me.

I now have a tenuous grasp on the principals at hand in those terms. previously, i was working on dead reckoning. i wasnt too awfully far off, i just need to reduce the orifice size because i am looking for 3-5 gpm.

nickname, you mentioned 'a thin plate' and reducing to one o ring in your last response. does the thickness of the piston/plate have an effect here? also, i am a little nervous about reducing to one o ring. ultimately, i cannot have a leaky faucet. if i take my inlet pressure at say 30psi acting on the piston that is just under 6 sq inches, orifice size .25" rendering around 4gpm that gives me roughly 175# of force on the piston. My spring rates are 41# and 51# (again, dead reckoning). I feel like that will be enough force to return the faucet even with two o rings on the piston and one at the top end where the faucet exits the cylinder.

This seems like a decent balance to me. anyone agree or disagree?

Thin plate means the orifice length << its diameter, for 1/4" the length should be about 1/16 or even less.

The o-rings are quite sensitive to wear so that you are obliged to have a high preload to compensate it but so the friction is also high! Look at other seals too, a lip seal will give you some advantages : low preload thus low friction without pressure and the higher the pressure the better the sealing.

Think to have enough pressure force at the MINIMAL flow possible at which the system should react!

multiseal low friction X-ring seals

Good stuff guys, thanks.

nickname, at 30 psi over 6 sq inches, i have three times the force needed to overcome the spring. right? I felt like a 40-50# spring would overcome the return friction of the o rings. flawed logic??

from what i learned earlier in the day, the orifice, though it does play into the equation, it seemed to me not to effect the pressure exerted on the piston terribly. that seemed to have more effect on the gpm than loss of pressure on the piston.

good point on the drag of the orings and the load pressure, I have fought that one before. now that you bring it up, i did see and replace a lip ring once and i remember considering the benefits at the time. that brings the question, now that we are talking friction, what surface finish should i be shooting for on the cylinder wall keeping in mind that i am using uhmw for the cylinder (prototype will be acrylic tube for all to see how it works). material recommendations welcome!

bwire, that xring rocks. i will call them in the morning.

thanks again guys.

comments??