Evaporator feed pipe?

[palmer4th]

How do you figure out how large of a feed pipe you need to supply the float box? I have a leader 2x8 wse, 6ft drop flue pan.

[maple flats]

I use a 1" feed on my 3x8. However to know what is officially recommended, just look at the float box inlet. Whatever size the fitting is, is the right size. You can get away with smaller but you rish having issues if you need lots of sap in a hurry because of a problem. I like to match the fitting size.

[Tappy Sap Master]

I use a 3/4" feed pipe on my 2x6 with no issues, just wish i had a bigger feed tank. My neighbor uses a 3/4" as well on his 2x8.

[BreezyHill]

I run a 1 1/4 to the preheater and a 1" to the float box from the preheater. Next season will be 1.5" SS from the feeder tank to the float box as it is readily available. The boiling flow capacity will easily be supplied by a 3/4" but the issue you run into is if something goes wrong and you need to flood the pans, 3/4 is to small. 1" should give a nice security blanket. 3/4" capacity is around 190 gallons/Hr and 1" is around 300 G/Hr and then factor in how much head pressure from the tank and adjust the capacity up.
Now that you are likely totally confused. Think about how fast a draw off is and that you will need to have capacity to replenish the flue pan quickly when the flue starts to refill the finish pan. Fast boiling rates are accomplished by shallow flue depths, so one must have enough capacity to replenish the pan quickly to avoid a burned pan.

Good Luck!
Ben

[palmer4th]

How do you know the proper amount of head pressure

[Sunday Rock Maple]

Consistency is what is important for head pressure. We use a 180 gallon regulator tank for that reason with a float switch that keeps it to within an inch. That way the only time we have to deal with pressure variations is at the end of the boil when the 2600 gallon concentrate tank that feeds the regulator is empty and the level starts to drop. We watch it closely then and shut down with about 4 inches in the regulator.

[BreezyHill]

That depends on how high your tank is above the float box. Mine is about 12" above the box and has about 30" of depth. The feed line is about 30' with 20' of that in a steam box. That is plenty of head.

Ben

[maple flats]

Mine is about 26" above the float box and the head tank is 30" tall. It seems to work good.

[rayi]

So if you have a preheater then you should have the head tank 30 inches above the entrance to the preheater entrance

[BreezyHill]

No, that is not necessary as long as the preheater is not going to reduce the flow a lot. If a system is built with a manifold that goes into multiple small heat exchange tubes then there needs to be more square inches of exchange tubes than manifold tubes. This is due to the friction loss in the small tubes.
Use R squared times 3.1416 to get the area of the feed tube to the manifold. And do the same for the exchange tubes to be certain that you have at least 25% more than the feed tube. This will provide ample flow to the recieveing manifold and to the float box.

Or the way I build is a 1.5" tube thru a plywood square tunnel. The tunnel is 8" square with the feeder tube suspended in the center. The steam goes out the hood into the tunnel down the tunnel to the left, up to a second tunnel, back to the right, and the end has a 6" Stack connect to vent the steam out of the sugar house. The riser is about 12' with a tee on top to stop down pressure on windy days. The end toward the prevailing wind has a 6x4 reducer that was laying around and acts like a venture and sucks the steam out on windy days.
The sap comes into the float box at 190 to 195.
The new design will have the tunnel lines with some SS flashing that was given to me in an attempt to get more than 10 years out of the tunnel and to make collection of condensation easier. Paint the tunnel or it will last maybe two seasons due to the saturation of the steam destroys the plywood.

Do not use pvc it will warp due to the heat. Rubber hose is needed for the connections due to the expansion and contraction. Double clamp. There is a lot of force when you have a batch draw off and the cold, 35 degree sap hits the hot exchanger pipes.

If doing this method you will need to install a sight tube that is vented to well above the feeder tank's top. You will get gas releasing in the heat exchanger and the bubbles will case a vapor lock. The pitching of the feeder tube and exchanger is important for a nice even flow of sap. I run 4% on mine and all the bubbles go to and out the sight tube. Our original system used a float box to vent the bubbles but it broke last season in the middle of boiling and I had to throw together a pvc emergency fix. That's how I found out that pvc is not usable and silver soldering is really hard on lines that have had sap in them.

Great Question!

Ben

[rayi]

OK my preheater feeds at the bottom of the hood and comes out at the float box. The SS tubing that goes from the top to the float box has two arms on it. One is horizontal and I assume that is for the theometer The other one is at the top and is verticle. What goes on that. I know it's to release pressure or steam but what keeps the sap from running out?

[BreezyHill]

Rayi, Great question...this is a guess as I am not looking at the setup but you could do a couple of things here.

1 option is a sight tube that would go past the top of your feeder tank. Place a valve on top of a short nipple. On to the valve attach a hose barb adapter and attach a piece of clear tubing that is rated for the temps we are working with. Get a few sip ties, two reds, one black and one green, and a plastic ball that will fight in the clear tube. Red balls work best. a stainless spring from the hardware store that will stop the ball from passing the valve.
Drop the ball in the sight tube and you have a floating tank level added to your evaporator, while venting any steam that may build in the system. Ties are to mark when to stop adding wood to the evap...black, red for tank full and empty. Green when to start boiling.

Option 2 would be valve on a nipple of maybe 8 to 12 inches. This will allow steam to not block the tubing and you will need to check occasionally. There are air vents for heating systems but they are not food grade so that could be an issue.

A $20 noncontact infrared temp gun is cheaper than the gauge that will screw into the fitting and can be used to check your vacuum pump, the temp that is lost from your float box,( you may not want to see that reading), and a number of other uses.

Send a pic of the fittings if you can.

Ben

[maple flats]

Just after my feed line enters the sugarhouse (the tank is tight against the sugarhouse and the tank valve is exposed in the sugarhouse) I have a T with a 3/8" vinyl tube that goes stright up, out thru the wall well above the head tank and dumps on ground. Sometimes when the feed line is empty and I open the valve a little sap actually shoots up and out, but it only amounts to a few drops. I used to have it about 3' above the feed tank but it shot out and landed on my bench at the moment I opened the valve. After that it shows the elevation of concentrate (or sap)in the head tank.