Measuring evaporation rate

[RileySugarbush]

Last year (The first for this rig) we averaged about 30gph on the 2x6 with hood, preheater and blower. This year I added this flow meter to the inlet to my preheater. It measures flow continuously in GPH. It is showing 37GPH in this photo. Another change is I tightened up the spacing around the flues.

On our first boil of the year this meter was very interesting:

Once stabilized with everything heated up, the reading was rarely under 30 GPH and often above 40 and pretty stable. Strangely, if we missed a firing and lost the hard boil, the inlet flow would spike to above 60. I think this was because without a boil, the level in the sap pan would suddenly drop because of the lack of bubble volume. Firing back up, would drop the inlet rate below 20gph momentarily, and would shortly return to above 30.

Our session on the night averaged above 35 gph. Just one more fun thing to watch and distract me as we run the evaporator!

[Justin Turco]

That's pretty good performance from a 2X6! Where did you get that flow meter? I like it!

[RileySugarbush]

Thanks, it really seems to be running well.

I really like the flow meter. It gives a better indication to how things are going than just looking in the float box. It's strange how the indication of a low fire is a big gulp of sap being sucked in, but it really seems to be the case. Has anyone else noticed this?

I got the flow meter from McMasterCarr. Here is a rather long link right to the catalog page:

http://www.mcmaster.com/nav/enter.asp?pagetype=itmlookupctlg&reqtyp=catalog&CtlgPgNbr=523&sesnextrep=610351150974958&CtlgEdition=114&k1=8051K18&t1=PN&search=8051k18&resultsQueryStr=sesnextrep%3D610351150974958%26sea rchstring%3D8051k18%26tab%3Dfind%26FastTrack%3DFal se%26ftctlgpg%3D%26FlCntxt%3D%26newfrmwk%3Dtrue


One down side to these is the flow has to be from bottom to top. That puts a little loop in your sap feed line, but it hasn't been a problem for me and should be ok if you have your feed tank elevated.

Here is another link, to some photos of our first nights boil:

http://FloMan.smugmug.com/gallery/4585120_NoNMp

[Amber Gold]

Great idea. I'll be sure to add one to next years setup. Thanks for the link.

[Mark-NH]

We experience the same with our 2 1/2 x 6 1/2 drop flue. You were correct when you thought the lack of a rolling boil drops the level of sap and consequently the float, causing the pans to take on more sap.

I don't think this improves overall evaporation rate, just creates a false reading in your meter when viewed as a snapshot. I do like the flow meter though.

[RileySugarbush]

Mark, I'm sure it's a bad thing for the overall evaporation rate, even though the inlet flow spikes way up. When that happens, the preheater is less effective and the sap is cooler coming in The response to stoking the fire is a sudden decrease in flow in, and the average over that event has to be a reduction in rate. It just reinforces the need to keep a steady firing pattern so you never have those hiccups. Maybe that is the key for maximum production.

This flow meter is measuring sap in, not vapor out, and it is a pretty sensitive indicator of changes in conditions. I wonder how it would work on a more traditional lever float? My home made float is direct acting on a vertical pipe that never really shuts off the flow completely.