I'm just trying to understand the system you're designing.

Me too.

It seems like we are arriving at a high-flow shut-off. So if a head or two is severed by the landscapers, the system when activated will shut down "quickly" when it senses that the flow is too great. The trip point would be set by prior calibration.

The flow could be sensed by ∆P across a flow restriction, venturi tube or whatever, or by some actual flowmeter such as a spinning magnet like those in water softeners.

A low-pressure shut-off is an alternative. It's really the same as measuring ∆P as above, except the second pressure is just atmospheric. If adequate pressure is not reached within some time of turning on the water, the system could shut itself down.

Either method might struggle with air in the system. As #12 noted also, detecting a lower pressure would be tough if all the normal ∆P is across the heads, and the supply pressure doesn't care. Most of the systems in my neighborhood would suffer this problem I think - plenty of pressure in the system whether a head is missing or not.

 

detecting a lower pressure would be tough if all the normal ∆P is across the heads, and the supply pressure doesn't care. Most of the systems in my neighborhood would suffer this problem I think - plenty of pressure in the system whether a head is missing or not.

An orifice and pressure switch would be part of the calibration.

Just like a low value resistor to sense current.

Calibration to pressure difference of losing one head out of ten or so should be easy. The more heads in the system, the more accuracy required.

I'm thinking an inline device on each "at risk" head.

 

Just a passing thought...if water is shooting 10 or 20 feet up, that is 1/3 to 2/3 of an atmosphere, 5 psi to 10 psi. You all know, if only intuitively, that 5 or 10 psi is NOT the standard for a well pump or city water, but that is what is left available to the other sprinkler heads when one pipe has its head chopped off.

And don't forget that pressure drop in a water pipe (or any other restriction to the flow) goes up by velocity cubed. That makes the sensing easier.

 

I was just finalizing the mechanical design in my head. It was so simple that I though of pursuing it myself. (and deleted some posts)

Did another search using the correct term and my dreams were dashed.

"excess flow shut off water valve"

The one design followed my thoughts exactly. Even the dashpot, which is the term in my drawings.

Now the question. Why aren't these common on sprinkler systems?

It's just a simple, adjustable, inline valve, that shuts off if preset flow is exceeded.

"A built-in dashpot feature absorbs transient pressure surges of substantially greater magnitude. In the event of excessive flow, the valve closes instantly - - stopping flow and/or escaping line fluid."

 

Now the question. Why aren't these common on sprinkler systems?

Because most people want to use an Arduino

This is hydraulics, like what goes on in an automatic transmission. Very few people are good at that.

 

In my opinion the only viable solution is not electrical, and puts one of those hydraulic devices at each head. The million dollar idea here would be to redesign the shut-off valve to be cheap enough and effective enough that it can become a standard feature of every premium sprinkler head.

 

I'm thinking about a ball that will not be pushed against the seal at the top of its tube if the flow rate is in the correct range, but an open pipe would allow enough flow to jam the ball against its seat. After that, the pressure will keep it sealed.

Simple enough?
Cheap enough?
Will it work?

 

It would! That would also allow air to pass but jam shut when the water comes along. (Same as a scupper valve on a boat, BTW.) A metal ball has a fairly well defined and predictable terminal velocity in flowing water.

 

All that is left is to go to the store and read the labels for what, "normal" flow range is and start measuring stainless steel balls in tubes with a flow meter.

 

That seems to be the most common design.

I was going to jam an outlet pipe in one of these, until I saw they were available.

There may be no low cost ones out there.

If you can get around patents, it may be a money maker.

ps.
If you were serious about making one I'd send you this. #12
Not much lawn watering around here.

 

I'm not the one with the goal here. Offer it to Rosum2?

ps, I don't think you can patent a ball in a tube, it's too obvious. It meets the criteria, "something any first year college student would naturally think of and could probably do".

This might even turn out as nothing but a stainless steel ball that you drop into the water pipe before you screw the head on. Imagine trying to patent dropping a ball into a pipe.

 

All that is left is to go to the store and read the labels for what, "normal" flow range is and start measuring stainless steel balls in tubes with a flow meter.

If you know the diameter and composition, the rest is "known" (can be calculated). The effect of the surrounding tube on the flow will complicate things, but it's been done.

 

Imagine trying to patent dropping a ball into a pipe.

Take a look at this one. Moral: You can patent anything. Reality: Good luck defending it.

 

LOL!!! Try to stop some 9 year old girl from infringing on that patent and you'll find yourself jailed as a sex offender.

 

Patent Application:
Method for dropping a ball down a piece of pipe.

The used places the ball between his (or her) thumb and forefinger.
The used moves the ball over the pipe.
The user moves his forefinger away from his thumb.
The ball drops into the pipe.

Pay me.