Funkenjaeger

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So today I've been trying to brainstorm a way to implement a proportional electronic valve for flow control at the outlet of my march pump (to automate matching flow rates for the brutus 20 style CRDFM method), and it just occurred to me that it may make sense to throttle the pump itself via electronic means (something like a router speed control, but with electronic input rather than a knob)

I am sure you would not get a nice simple linear response, but I wonder if it would be good enough to be useful... For something like matching flow rates, you don't need control of the full range from 0-100% of max output - a significantly smaller portion of that range could be good enough.

I wish I had a router speed control lying around to test the idea. I'd go grab a lamp dimmer if I didn't think it would be likely to go up in smoke when used with a motor...

Anyone ever try anything like this?

LooyvilleLarry

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Funkenjager - I wouldn't do that unless you are using a DC motor. These motors (i.e. March 809) are meant to run at full voltage and it will violate the warranty.

They can actually run significantly hotter on less voltage. The proper way would be to control the volume on the outflow.

Also, there was another post on this recently.
Oh yeah, and a motorized proportional valve would be great

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Orange Cascade Pale Ale -

Secondary

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Funkenjaeger

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Exactly the kind of practical info I needed, thanks...

Oh well, I'll continue my search for a motorized proportional valve, or a way to build one

LooyvilleLarry

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well, building one is not all that hard, once the math is done

So, you need to figure out how much force is required to move it (while under pressure )> Then you get a servo that will drive that , then some kind of majic connector (lovejoy) that mounts to the valve, then some jerry riggin to get it all together.

__________________
Primary
Orange Cascade Pale Ale -

Secondary

Kegged
BeeCave Haus Ale - 6%
Bells Two Hearted, round 2- 6.1%
SNPA Clone (Chilled )
Hard Lemonade

Shiraz - 6 gal

CodeRage

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If you want proportional you need a needle valve with a V profile. It's going to have to be fairly large too. Then some kind of stepper motor to position it. At least this is how I have been thinking about skinning this beast.

The most practical option though is probably to ditch the march pump and go with a peristaltic pump with multiple head plumbed in parallel to each other. This will get you the flow rates you may be looking for and speed control of the pumps will give you very precise flow and volume control.

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Fletch

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Motorized proportional valves are not hard to come by, just not cheap. I have a few hundred Belimo proportional valves in my buildings, both two-way and three-way, controlling hydronic heating coils. And of course you have to have a controller with a 0-10v or 4-20 ma proportional output.

Funkenjaeger

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So far I had been looking at butterfly valves, which seem to be suitable for flow control, and seem to be commercially available in motorized versions (to the tune of $400+).

Of course it's far from impossible to rig a standard butterfly valve with a motor, slap on a feedback pot and set up servo control. But assembling it all so it's sturdy and preferably enclosed and splash-proof isn't trivial - especially if, like me, you don't have access to a machine shop to make the ideal parts.

kladue

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It would be easier to use a proportional valve like a Belimo, which can be found on ebay for under $100 on a regular basis. Without flow metering you will have fun trying to set and maintain flow rate.

Funkenjaeger

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Well with the application I mentioned (matching flow into/out of MLT) the real goal is to maintain MLT liquid level, which I have the capability to measure, so I don't need to measure the actual flow rate.

PaulB

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The best way to do it with the pump is to get the 12 or 24 VDC March pumps and then use a VFD (variable frequency drive). You are talking a few hundred bucks. Easier ways to accomplish the same thing might be to incorperate float switches and have the pump come on when needed. A ball valve could get you close and the float switch could be your safe guard so that you can totally walk away from the system.