using pneumatic valves for low-pressure water

Other Hardware Motors, Mechanics, Power and CNC
1

Hi all,

I'm starting to think about an automated watering system for growing veggies in the yard and am looking at valves. Solenoid valves for water can be had cheap, but I'd like to have a fair number of different watering zones, which would require either a multiway valve (which I haven't found for cheap) or many single valves.

I've found some rather nice multiway pneumatic valves (Matrix 750 series) at the surplus store; so, I thought I'd ask: has anyone used industrial pneumatic valves not specified for liquids for low-pressure water applications? Is it likely this sort of use will destroy the valve? I am planning to have the system empty in between uses, so there won't be water sitting around.

Thanks for any thoughts!

2

Can you post a link to the datasheet for the pneumatic valves?

I would not assume that draining the system offers an advantage - it would allow scope for deposits to crystalize.

...R

3

This is the sheet; from the 40 micron filter requirement I guess it probably won't be too happy with unfiltered water...

4

I'm no expert but my guess is that those valves are completely unsuitable for liquids.

If your water pressure is low maybe you could make "valves" by squeezing flexible tube. A servo might be sufficient to squeeze the tube shut. If squeezing the tube is insufficient to shut off the flow completely maybe you could have one proper master valve at the inlet to the system.

...R

5

dfuruta:
This is the sheet; from the 40 micron filter requirement I guess it probably won't be too happy with unfiltered water...

Not when the specs require non-lubricated dry air or neutral gasses.

Paul

6

Pinch valves would work, yes, but I'm not certain they'd be cheaper to do than conventional solenoids. I guess I could do something with cams to control multiple tubes with one motor, but it'd be a lot of thinking & work to implement effectively.

I'm sorry if this is too basic of a question, but I've been looking around and haven't found the answer: is the concern that the water/stuff in the water will abrade or corrode the valve mechanism? It seems intuitively that something airtight made from metal and plastic should also be watertight under low pressure; perhaps that's a bad assumption?

7

dfuruta:
Pinch valves would work, yes, but I'm not certain they'd be cheaper to do than conventional solenoids. I guess I could do something with cams to control multiple tubes with one motor, but it'd be a lot of thinking & work to implement effectively.

I'm sorry if this is too basic of a question, but I've been looking around and haven't found the answer: is the concern that the water/stuff in the water will abrade or corrode the valve mechanism? It seems intuitively that something airtight made from metal and plastic should also be watertight under low pressure; perhaps that's a bad assumption?

The fact that air and other gasses are compressible while water is not may have something to do with the operation of the valves.

Paul

8

You haven't said anything about flowrate or pipe size but for very low pressure a motorized ball valve might be what you need.

9

Paul_KD7HB:
The fact that air and other gasses are compressible while water is not may have something to do with the operation of the valves.

Paul

That makes sense, thanks!

outsider, thanks for the suggestion.

10

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