Flow Meters

[Maple Man 85]

Flow meters are a great way to measure sap but I'm finding mixed reviews on accuracy of the devices. Is anyone else using a flow meter and have they noticed variance from the volume expected to be in a tank versus what the meter reads and what device are you using?

[S.S.S]

As long as the line is full there very accurate. We use one.

[Maple Man 85]

As long as the line is full there very accurate. We use one.
Which one are you using?

[maple flats]

One thing about them, they are not very accurate if there is an elbow within 2' before or after. Turbulence affects the reading.

[S.S.S]

Which one are you using?The one we use is a 2" meter in the pump line right before it enters sap tank. Its a raven flow meter.

[penfrydd]

Home Depot is selling a cheap flow meter for less than $20.

They're accurate enough. I use one on my diesel tank and have checked it with a 5 gallon can. Good enough for me.

[Lloyd'sMapleSyrupandSap]

Are you talking about a flow meter or a water meter to measure gallons? Flow meters are generally used to measure cfm, cubic feet minute or other cubic measurements. Water meters are a great way to measure gallons of sap, like if you are buying sap.

[sapman]

I do find mine in the woods pumphouse sometimes the the spinner in the middle flutters instead of spins, not registering. Then next time works fine. But amounts seem to be pretty close to correct overall.

[bill m]

Either one ( flow meter or water meter ) will work just as good. 1 gallon is 231 cu. in. and 1 cu. ft. is 7.48 gallons.

[DrTimPerkins]

Flowmeters (or water meters...they are basically the same thing) tend to have a pretty narrow range for good measurements. Getting them sized just right can be problematic. Too big a pipe and they won't register a trickle flow. It takes a certain minimum flow to get them going (wind anemometers have the same issue). Too small a meter and you may not get enough flow (especially if there is not a pump behind it). If the spinner is just fluttering or the meter doesn't go up when liquid is going through, there isn't enough flow to turn the impeller/turbine wheel and register flow.

In any case, for good indication, meters should be:
1) sized properly for expected flow rate
2) installed in proper direction (typically there is an arrow indicating direction flow should go) and orientation (some will only read when installed flat, they don't measure well in a downward direction).
3) have no obstructions (fittings, elbows, turns, probes) for 10X the diameter of the pipe on both the upstream and downstream side of flow (reduces turbulence)
4) used for the liquid intended
5) calibrated (in place if possible)
6) only be used for "clean" fluids (stuff in unfiltered sap will clog the impellers over time and result in erroneous readings)
7) only be used on pipes that are full of liquid. They don't work well if air is in the pipe or mixed in the liquid.

[Zucker Lager]

If I may add just a little to Dr. Tim's explanation.
For a very accurate reading you need a "positive displacement" meter. Its not just a spinning wheel or fan it actually takes an accurate measure of liquid and allows it to move from inlet to outlet of the meter. Then more accuracy is gained by spending $$$$ on temperature and viscosity auto calibration. We added air scrubbers and filters up stream from meters as Dr. Tim suggests. You will find very accurate meters typically in situations were the product being measured is expensive like petroleum products. Jay