Drip Irrigation Emitters

The topic of drip irrigation emitters came up during a discussion of pressure regulators on a combat email forum. These are light, cheap doodads that may have promise for fuel systems, although after seeing how they work, I can't imagine how. I got some from the following source:

http://www.yardsupply.com/cgi-bin/SoftCart.exe/star/prodpages/drip/944120.htm?E+star

Preston and I dissected a couple to see how they work. Looks like a rubber diaphragm pushes on a labyrinth to hold flow rate sorta constant, assuming that output pressure is low.

I love that description - rubber diaphragm pushes on labyrinth. What was the name of the King of Crete again?

Yeah, I suspect this won't work the way we want them to work (regulate pressure) because they are meant to supply a constant volume per unit time. If you restrict the flow rate via the needle valve to less than the regulated flow rate, the needle valve will likely see the same pressure as if the emitter wasn't there.

Konosis, I think was the kingdom or the king of Crete, not sure of the spelling. I was stationed on Crete in the 50's. CRS has set in since then.....

Yes, CRS. I believe I am having a 'drip' of the same thing!
Interesting cutaway, don't you think?

> What was the name of the King of Crete again?

Minos. His palace was Knossos.

It looks as tho these could regulate flow rate and somewhat peressure. I guess that the rubber varies the flow thru the maze system. The maze system disperses pressure/flow by bouncing the liquid off of all the corners in there... resulting in a fairly steady exit rate. Thats my guess. Its use for model planes might be for an easier needle on pressure. IMHO. MM

Unless there is something there that we can't see in the pictures, it looks like the flow passage is open from one end to the other. Hard to see how the inlet pressure wouldn't transfer right through to the outlet.

It looks like the gizmo works like the more usual .018 solder orfice in a tube, dual needle valves, or coiled tube restrictor. The diaphragm gets pressed into the "labyrinth"(neat word)by that star-shaped backing plate and restricts the flow. I suspect they use different thicknesses of gasket to get different flow rates easily. the passages look to be fairly large in xsection so they won't plug up easily.

Putting some sort of restrictor between the bladder and the needle valve works pretty well. If the restricted flow is about twice what the engine needs to 4 cycle the needle valve will have a nice, wide adjustment range.

Rubber diaphram is on the preasure/inlet side of the hose. The more preasure, the more squeaze on the labrynith making a tighter passage so more restriction. Less preasure, less restriction.

Yes, the pressure comes in on one side of the diaphragm and then flows across the diaphragm to the notch in the side, and then through the passage on the other side of the diaphragm. The pressure drop across the diaphragm, from one side to the other, would be pretty small. It looks like the star-shaped backing plate is designed to compress the gasket over the passage, giving 6 restrictions, in addition to the overall flow restriction of a small passage.

Howard and Preston are engineers. What gives fellas? I don't have one to look at right now.

Another question, of course, is it fuelproof?

I think Phil's explanation is right.
The housing looks fuelproof; I'm less certain about the diaphragm.

But why do we care? Having bought a few and cut 'em open,
we can't think of how they would help.